Tuesday, December 30, 2008

Methicillin-resistant Staphylococcus aureus (MRSA) among dental patients: a problem for infection control in dentistry?

Methicillin-resistant Staphylococcus aureus (MRSA) among dental patients: a problem for infection control in dentistry?
Clin Oral Investig. 2008 Dec 23

Zimmerli M, Widmer AF, Dangel M, Filippi A, Frei R, Meyer J.
Department of Oral Surgery, Oral Radiology and Oral Medicine, School of Dental Medicine, University of Basel, Basel, Switzerland.

We assessed the frequency of carriers of methicillin-resistant Staphylococcus aureus (MRSA) among 500 dental patients of a university clinic. From each participant, two specimens were taken from the anterior nares and the pharynx and analysed by culture. The participants completed a questionnaire on possible risk factors of MRSA infection. Two hundred ten individuals carried S. aureus, 90 in the nares only, 51 in the throat only and 69 in nares and throat. Isolates of 208 patients were methicillin-sensitive; two isolates were methicillin-resistant, both carried in the throat exclusively. In conclusion, the frequency of nasal and/or throat carriers of MRSA among dental patients was low and suggests few opportunities of exposure in the dental clinic assessed.


Methicillin-Resistant Staphylococcus aureau Infections

Methicillin-Resistant Staphylococcus aureau Infections
Top HIV Med. 2008 Dec-2009

Bartlett JG.
The Johns Hopkins University School of Medicine, Baltimore, MD, USA.

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection is epidemic in the community, differs from nosocomial MRSA in virulence, mechanisms, and antibiotic susceptibility, and exhibits diverse and often unique pathologic characteristics. The community-acquired MRSA USA 300 strains are transmitted largely by person-to-person contact and cause characteristic soft-tissue abscesses and, less commonly, other sometimes unusual and serious infections including a necrotizing pneumonia, and other necrotic infections such as necrotizing fasciitis, pelvic thrombophlebitis, and septic phlebitis. This MRSA 300 family remains susceptible to drugs active against nosocomial MRSA (ie, vancomycin, linezolid, daptomycin) and is often susceptible to trimethoprim-sulfamethoxazole, doxycycline, and clindamycin. Recent epidemiologic data indicate that nosocomial MRSA (eg, mainly USA 100) strains are also present in the community and that MRSA USA 300 strains are present in hospital settings, with both families found in intermediate frequency in health care-associated settings (eg, nursing homes, dialysis centers). More work is needed to identify effective barrier precautions to limit their spread. This article summarizes a presentation on MRSA made by John G. Bartlett, MD, at the 11th Annual Clinical Update for the Ryan White HIV/AIDS Program Clinicians held in August 2008 in Washington, DC. The original presentation is available as a Webcast at

Topics in HIV Medicine

Daptomycin for methicillin-resistant Staphylococcus aureus infections of the spine

Daptomycin for methicillin-resistant Staphylococcus aureus infections of the spine
Spine J. 2008 Dec 26

Burdette SD.
Department of Medicine, Wright State University Boonshoft School of Medicine, Dayton, OH 45409, USA.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) infection is increasingly common. Treatment with vancomycin-based therapy is often unsuccessful. Daptomycin is a relatively new lipopeptide antibiotic with potent activity against MRSA.

PURPOSE: To describe the successful management of MRSA infection involving the spine.

STUDY DESIGN: Two case reports of MRSA infection, one involving epidural and lumbar subdural abscesses, the other with osteomyelitis and discitis.

METHODS: Two cases are described, one with lumbar epidural and subdural abscesses and the other with osteomyelitis and discitis of the spine. Switching from vancomycin to daptomycin plus rifampin-based therapy resulted in patient improvement that allowed discharge from the hospital.

RESULTS: Both patients recovered fully from their infection.

CONCLUSIONS: Daptomycin is a safe and effective option for the treatment of MRSA infection involving the spine.

PMID: 19112049 [PubMed - as supplied by publisher]

Monday, November 24, 2008

The prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in skin abscesses presenting to the pediatric emergency dep

The prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in skin abscesses presenting to the pediatric emergency department.
N C Med J. 2008

Magilner D, Byerly MM, Cline DM.
Wake Forest University-School of Medicine, USA.

BACKGROUND: Community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) infections have been increasing. The most common of these infections present as skin abscesses. The objectives of this study were to prospectively determine the prevalence of CA-MRSA in abscesses in the population of a pediatric emergency department, to determine antibiotic sensitivity patterns of the CA-MRSA isolates, and to describe the patient population that presented with skin abscesses.

METHODS: We conducted a prospective study of children under the age of 18 years who presented to our pediatric emergency department with a skin abscess that required incision and drainage. Pus from these abscesses was sent for culture to determine the causative agent, and antibiotic sensitivities were reported. Characteristics of the patient population that presented with these abscesses were examined.

RESULTS: Sixty-eight patients were enrolled over an 18-month period. Of these, 60 (88%) had cultures positive for Staphylococcus aureus (S. Aureus). Of these 60 patients, 51 (85%) were identified as CA-MRSA by their resistance patterns. All of the CA-MRSA isolates were sensitive to trimethoprim/sulfamethoxisole; 6 (10%) were either resistant or intermittently resistant to clindamycin.

LIMITATIONS: The study was conducted on a convenience sample of patients and enrolled a relatively small number of patients.

CONCLUSIONS: CA-MRSA is responsible for the vast majority of skin abscesses presenting to the pediatric emergency department. CA-MRSA isolates are likely to be sensitive to trimethoprim/sulfamethoxisole or clindamycin, although there is some resistance to clindamycin.


Wednesday, November 12, 2008

First report of methicillin-resistant Staphylococcus aureus septic arthritis complicating acupuncture

First report of methicillin-resistant Staphylococcus aureus septic arthritis complicating acupuncture: simple procedure resulting in most devastating outcome.

Diagn Microbiol Infect Dis. 2008 Nov 4

Woo PC, Lau SK, Yuen KY.
State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong; Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong; Department of Microbiology, The University of Hong Kong, Hong Kong.

We report the 1st case of methicillin-resistant Staphylococcus aureus (MRSA) septic arthritis after acupuncture, with articular cartilage destruction and chronic osteomyelitis. The patient responded to arthrotomy, synovectomy, and 6 months of antibiotics. The emergence of community-associated MRSA infections would further aggravate the problem. Strict adherence to proper infection control guidelines is mandatory.


Tuesday, November 4, 2008

Methicillin-resistant Staphylococcus aureus in orthopaedic surgery.

Methicillin-resistant Staphylococcus aureus in orthopaedic surgery.
J Bone Joint Surg Br. 2008 Nov

Patel A, Calfee RP, Plante M, Fischer SA, Arcand N, Born C.
Department of Orthopaedic Surgery, Brown University, Providence, Rhode Island 02903, USA.

Methicillin-resistant Staphylococcus aureus (MRSA) has become a ubiquitous bacterium in both the hospital and community setting. There are two major subclassifications of MRSA, community-acquired and healthcare-acquired, each with differing pathogenicity and management. MRSA is increasingly responsible for infections in otherwise healthy, active adults. Local outbreaks affect both professional and amateur athletes and there is increasing public awareness of the issue. Health-acquired MRSA has major cost and outcome implications for patients and hospitals. The increasing prevalence and severity of MRSA means that the orthopaedic community should have a basic knowledge of the bacterium, its presentation and options for treatment. This paper examines the evolution of MRSA, analyses the spectrum of diseases produced by this bacterium and presents current prevention and treatment strategies for orthopaedic infections from MRSA.

PMID: 18978255 [PubMed - in process]

Maternal-Infant Perinatal Transmission of Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus.

Maternal-Infant Perinatal Transmission of Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus.
Am J Perinatol. 2008 Oct 31

Pinter DM, Mandel J, Hulten KG, Minkoff H, Tosi MF.
Department of Pediatrics, Maimonides Medical Center, Brooklyn, New York.
Because of the increasing importance of STAPHYLOCOCCUS AUREUS (SA), including methicillin-resistant SA (MRSA) in serious neonatal infections, we studied the contribution of perinatal maternal-infant transmission of SA to the colonization and infection of newborn infants. Cultures for SA, including MRSA, were obtained from nares and vagina of women in labor at term. Each mother's infant, if delivered vaginally, was cultured from nares and skin at delivery and again after 48 hours (at discharge). All MRSA and selected SA isolates were studied by pulsed field gel electrophoresis (PFGE). Infants were monitored after discharge for staphylococcal infection for 4 weeks. Of 304 women completing the study, 43 were colonized with SA, and 9/43 had MRSA. Of 252 evaluable infants, 25 were colonized with SA, and 9/25 had MRSA. Six of 252 mother-infant pairs were concordant for SA colonization, and one of these for MRSA. Isolates from five of these six infants were indistinguishable from their mother's isolates by PFGE, including the pair with MRSA. One SA-colonized infant and four noncolonized infants subsequently developed staphylococcal infections during the monitoring period. About 20% of SA isolates in this maternal population were MRSA. Perinatal maternal-infant transmission accounted for 20% of instances of perinatal colonization of infants with SA. Molecular confirmation of perinatal maternal-infant transmission of MRSA was first documented. In this population of term infants, most SA infections in the first 4 weeks of life appeared to result from colonization that occurred after discharge from the nursery.

[PubMed - as supplied by publisher]

Sunday, October 26, 2008

Community acquired infections with methicillin resistant strains of Staphylococcus aureus: Report of five cases

Community acquired infections with methicillin resistant strains of Staphylococcus aureus: Report of five cases
Rev Med Chil. 2008 Jul

Luis Miguel Noriega1,3, Patricia González2,3, Juan Carlos Hormazábal4, Consuelo Pinto3a, Magdalena Canals3a, José Manuel Munita1,3,5, Luis Thompson1,3, Alejandra Marcotti1,3, Jorge Pérez1,3,5, Daniel Ibáñez4, Pamela Araya4, Claudio Canals1,3, Pablo Vial1,2,3.
1Unidad de Infectología y Departamento de Medicina, Clínica Alemana, Santiago de Chile; 2Laboratorio Clínico, Clínica Alemana; 3Facultad de Medicina Clínica Alemana, Universidad del Desarrollo; 4Subdepartamento de Microbiología Clínica, Instituto de Salud Pública, Chile; 5Servicio Medicina, Hospital Padre Hurtado. Santiago de Chile. aEstudiantes de Medicina, Facultad de Medicina, Clínica Alemana, Universidad del Desarrollo

Community acquired infections with methicillin resistant strains of Staphylococcus aureus (MRSA) infections have a more aggresive clinical course and involve mostly skin and lungs. These infections appear as outbreaks among prisoners, spoñsmen, men having sex with men and military personnel. The higher aggressiveness of these strains is due to the production of several toxins, mainly Panton- Valentine leukocidine. The detection of the gene that codes for this toxin is a distinctive feature ofthese strains. We report five patients with community acquired MRSA infections. The clinicalpresentation was a skin infection in all. One patient had a pleuropneumonia in addition. Apart for resistance to beta-lactam antimicrobials, the strains were resistant to erythromycin and ciprofloxacin. Patients were treated with vancomycin, clotrimoxazole or intravenous clindamycin with a good evolution. An epidemiológical surveillance for community acquired MRSA strain infections should be started and measures to adequately treat infected patients and avoid dissemination should be implemented.

Complete Text in Spanish


Tuesday, August 12, 2008

MRSA Associated with Acupuncture and Joint Injection

Outbreak of Invasive Methicillin-Resistant Staphylococcus aureus Infection Associated With Acupuncture and Joint Injection.
August 2008

Murray RJ, Pearson JC, Coombs GW, Flexman JP, Golledge CL, Speers DJ, Dyer JR, McLellan DG, Reilly M, Bell JM, Bowen SF, Christiansen KJ.

From the Department of Microbiology and Infectious Diseases, PathWest Laboratory Medicine WA-Royal Perth Hospital (R.J.M., J.C.P., G.W.C, J.P.F., K.J.C.), the Division of Microbiology and Infectious Diseases, PathWest Laboratory Medicine WA-Queen Elizabeth II Medical Centre (C.L.G., D.J.S.), the Infectious Diseases Department (J.R.D., D.G.M.) and the Communicable Diseases Control Directorate, Western Australian Department of Health (S.F.B), Western Diagnostic Pathology (D.G.M), and Hands-On Infection Control (M.R.), West Perth, Perth, Western Australia , and the Department of Microbiology and Infectious Diseases, Women's and Children's Hospital, Adelaide, South Australia (J.M.B) , Australia . (Present affiliation: Clinical Services, Fremantle Hospital and Health Services, Perth, Western Australia, Australia [S.F.B.].).

Objective. To describe an outbreak of invasive methicillin-resistant Staphylococcus aureus (MRSA) infection after percutaneous needle procedures (acupuncture and joint injection) performed by a single medical practitioner.

Setting. A medical practitioner's office and 4 hospitals in Perth, Western Australia.

Patients. Eight individuals who developed invasive MRSA infection after acupuncture or joint injection performed by the medical practitioner.

Methods. We performed a prospective and retrospective outbreak investigation, including MRSA colonization surveillance, environmental sampling for MRSA, and detailed molecular typing of MRSA isolates. We performed an infection control audit of the medical practitioner's premises and practices and administered MRSA decolonization therapy to the medical practitioner.

Results. Eight cases of invasive MRSA infection were identified. Seven cases occurred as a cluster in May 2004; another case (identified retrospectively) occurred approximately 15 months earlier in February 2003. The primary sites of infection were the neck, shoulder, lower back, and hip: 5 patients had septic arthritis and bursitis, and 3 had pyomyositis; 3 patients had bacteremia, including 1 patient with possible endocarditis. The medical practitioner was found to be colonized with the same MRSA clone [ST22-MRSA-IV (EMRSA-15)] at 2 time points: shortly after the first case of infection in March 2003 and again in May 2004. After the medical practitioner's premises and practices were audited and he himself received MRSA decolonization therapy, no further cases were identified.

Conclusions. This outbreak most likely resulted from a breakdown in sterile technique during percutaneous needle procedures, resulting in the transmission of MRSA from the medical practitioner to the patients. This report demonstrates the importance of surveillance and molecular typing in the identification and control of outbreaks of MRSA infection.

Infection Control & Hospital Epidemiology

Monday, August 4, 2008

Prevention of MRSA: what hygienic measures are meaningful?]

Prevention of MRSA: what hygienic measures are meaningful?
Anasthesiol Intensivmed Notfallmed Schmerzther. 2008 Jul
Kerwat K, Wulf H.
Klinik für Anästhesie und Intensivtherapie/Universitätsklinikum Giessen und Marburg.

MRSA has become a major challenge for the health system. The proportion of MRSA in the total collective of Staphylococcus aureus cases in Germany amounts to about 35 %. The further spread of MRSA must be prevented or at least slowed down. There is controversial discussion about which hygienic measures are meaningful. In Germany most people and institutions attempt to follow the recommendations of the Robert Koch Institute. These recommendations include, among others, the isolation of MRSA patients. However, this measure can only be achieved with difficulty and has limited efficacy. It may even happen that MRSA patients are treated less effectively just on account of the isolation and the other extensive measures and may more frequently experience complications. Thus it must be considered whether or not better results would be obtained without isolation when the standard hygienic protocols are strictly observed.

Thieme Connect

Sunday, July 13, 2008

Methicillin-Resistant Staphylococcus aureus Infections in Collegiate Football Players.

Methicillin-Resistant Staphylococcus aureus Infections in Collegiate Football Players.
Med Sci Sports Exerc. 2008 Jul 8

Bowers AL, Huffman GR, Sennett BJ.
Department of Orthopaedic Surgery, Hospital of the University of Pennsylvania, Philadelphia, PA.

PURPOSE: Methicillin-resistant Staphylococcus aureus (MRSA) has been recognized as a serious skin infection in the athletic population. Literature in reference to football players has been sparse. We sought to better elucidate circumstances surrounding such infections in collegiate football players.

METHODS: Data from three Division-I collegiate football programs were consolidated and analyzed. Variables included presence of MRSA infection, timing of occurrence, body location involved, lesion morphology, need for surgical treatment, and antibiotic route. Data were analyzed statistically to evaluate player position, body location, and timing of occurrences.

RESULTS: Of the 491 collegiate football players, 33(6.7%) were diagnosed with MRSA infections. Cutaneous manifestations included abscess (70%), cellulitis (16%), folliculitis, impetigo, and necrotizing fasciitis. Of the infections, 90% underwent surgical drainage, whereas 27% received intravenous antibiotics. Extremity infections (n = 30) greatly exceeded truncal infections (n = 7); the most common locations were the elbow(n = 11), knee (n = 6), leg (n = 4), and forearm (n = 4). There was no difference in occurrence by player position. Infectionsoccurred predominantly in the first third of the season (P less than 0.001, chi-square test) and significantly decreased as the season progressed.

CONCLUSION: MRSA infections involving football players are becoming more common. This study documents player positions involved, timing of occurrence in the season, location and type of infections, and required treatment. Exposed extremities may predispose to infection due to risk for minor trauma and direct contact with bacteria. As infection risk seems to be independent of position, all players should observe protective measures. Although most infections occur earlier in the season, physicians should remain alert for infection occurrences throughout the season.


Sunday, June 29, 2008

Treatment of infective endocarditis caused by methicillin-resistant Staphylococcus aureus: Teicoplanin versus vancomycin in a retrospective study.

Treatment of infective endocarditis caused by methicillin-resistant Staphylococcus aureus: Teicoplanin versus vancomycin in a retrospective study.

Scand J Infect Dis. 2008

Huang JH, Hsu RB.
From the Department of Surgery, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, ROC, Taiwan.

Infective endocarditis caused by methicillin-resistant Staphylococcus aureus (MRSA) is increasing. Vancomycin and teicoplanin are 2 intravenous glycopeptides appropriate for its treatment. There is no human study comparing teicoplanin and vancomycin for the treatment of MRSA endocarditis. Between 1996 and 2006, 51 MRSA endocarditis patients were treated at the authors' hospital. There were 29 patients with nosocomial infection; 15 were treated with teicoplanin. Teicoplanin was used as the first therapeutic agent in 3 patients because of renal insufficiency. Vancomycin was used as the first therapeutic agent in 12 patients. Treatment was changed to teicoplanin because of adverse reactions in 10 and persistent bacteremia in 2 patients. Early operation was performed in 2 patients because of persistent MRSA bacteremia. Overall, 7 patients died in hospital. There was no statistically significant difference in hospital mortality rate (42% vs 47%) and bacteriologic failure rate (34% vs 40%) between 36 patients treated with vancomycin and 15 patients treated with teicoplanin. Teicoplanin can be an alternative therapy of MRSA infective endocarditis.


Friday, June 27, 2008

A computational model of antibiotic-resistance mechanisms in Methicillin-Resistant Staphylococcus aureus (MRSA

A computational model of antibiotic-resistance mechanisms in Methicillin-Resistant Staphylococcus aureus (MRSA
J Theor Biol. 2008 Jun 4

Murphy JT, Walshe R, Devocelle M.
Modelling and Scientific Computing Group, School of Computing, Faculty of Engineering and Computing, Dublin City University, Glasnevin, Dublin 9, Ireland; Centre for Synthesis and Chemical Biology, Department of Pharmaceutical and Medicinal Chemistry, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland.

An agent-based model of bacteria-antibiotic interactions has been developed that incorporates the antibiotic-resistance mechanisms of Methicillin-Resistant Staphylococcus aureus (MRSA). The model, called the Micro-Gen Bacterial Simulator, uses information about the cell biology of bacteria to produce global information about population growth in different environmental conditions. It facilitates a detailed systems-level investigation of the dynamics involved in bacteria-antibiotic interactions and a means to relate this information to traditional high-level properties such as the Minimum Inhibitory Concentration (MIC) of an antibiotic. The two main resistance strategies against beta-lactam antibiotics employed by MRSA were incorporated into the model: beta-lactamase enzymes, which hydrolytically cleave antibiotic molecules, and penicillin-binding proteins (PBP2a) with reduced binding affinities for antibiotics. Initial tests with three common antibiotics (penicillin, ampicillin and cephalothin) indicate that the model can be used to generate quantitatively accurate predictions of MICs for antibiotics against different strains of MRSA from basic cellular and biochemical information. Furthermore, by varying key parameters in the model, the relative impact of different kinetic parameters associated with the two resistance mechanisms to beta-lactam antibiotics on cell survival in the presence of antibiotics was investigated.

Elsevier Science Direct

Tuesday, June 10, 2008

Risk of Infection and Death due to Methicillin-Resistant Staphylococcus aureus in Long-term Carriers.

Risk of Infection and Death due to Methicillin-Resistant Staphylococcus aureus in Long-term Carriers.

Clin Infect Dis. 2008 Jun

Datta R, Huang SS.
1Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, and 2Channing Laboratory, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts; 3Division of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut; and 4Division of Infectious Diseases, University of California Irvine School of Medicine, Irvine.

Background: Patients with newly acquired methicillin-resistant Staphylococcus aureus (MRSA) have significant risks of short-term morbidity and mortality due to this pathogen. We were interested in assessing whether long-term carriers have persistent risks of disease and whether all carriers, regardless of the duration of carriage, should be considered to be reasonable candidates for interventions to reduce the risk of infection. Methods. We conducted a single-center retrospective cohort study to evaluate the risk of subsequent MRSA infection and death among patients known to have harbored MRSA for at least 1 year (i.e., prevalent carriers).

Results: Among 281 prevalent carriers, 65 (23%) developed a total of 96 discrete and unrelated MRSA infections in the year after their identification as prevalent carriers. The most common infections were pneumonia (accounting for 39% of MRSA infections), soft-tissue infection (14%), and central venous catheter infection (14%). Twenty-four percent of all infections involved bacteremia. Thirty-eight MRSA infections occurred during a new hospitalization, and 32 (84%) of these infections were the reason for admission to the hospital. MRSA contributed to 14 deaths, with 6 of these deaths deemed to be attributable to MRSA. Harboring MRSA for less then 2 and MRSA colonization at the time of detection as a prevalent carrier were predictive of subsequent infection with MRSA.

Conclusions: Individuals who are known to have harbored MRSA for greater 1 year are at high risk for subsequent MRSA morbidity and mortality and should be considered to be targets for intervention, in addition to individuals who have newly acquired this pathogen.

PMID: 18532892 [PubMed - as supplied by publisher]

Wednesday, May 14, 2008

Health-care workers: source, vector, or victim of MRSA?

Health-care workers: source, vector, or victim of MRSA?
Lancet Infect Dis. 2008 May
Albrich WC, Harbarth S.
Respiratory and Meningeal Pathogens Research Unit, Chris Hani Baragwanath Hospital, University of the Witwatersrand, Johannesburg, South Africa; Institute for Infectious Diseases, University Hospital Bern, Bern, Switzerland.

There is ongoing controversy about the role of health-care workers in transmission of meticillin-resistant Staphylococcus aureus (MRSA). We did a search of the literature from January, 1980, to March, 2006, to determine the likelihood of MRSA colonisation and infection in health-care workers and to assess their role in MRSA transmission. In 127 investigations, the average MRSA carriage rate among 33 318 screened health-care workers was 4.6%; 5.1% had clinical infections.

Risk factors included chronic skin diseases, poor hygiene practices, and having worked in countries with endemic MRSA. Both transiently and persistently colonised health-care workers were responsible for several MRSA clusters. Transmission from personnel to patients was likely in 63 (93%) of 68 studies that undertook genotyping. MRSA eradication was achieved in 449 (88%) of 510 health-care workers. Subclinical infections and colonisation of extranasal sites were associated with persistent carriage. We discuss advantages and disadvantages of screening and eradication policies for MRSA control and give recommendations for the management of colonised health-care workers in different settings.

PMID: 18471774 [PubMed - in process]

Tuesday, April 22, 2008

Real-time optical detection of methicillin-resistant Staphylococcus aureus using lytic phage probes.

Real-time optical detection of methicillin-resistant Staphylococcus aureus using lytic phage probes.

Biosens Bioelectron. 2008 Mar 18

Guntupalli R, Sorokulova I, Krumnow A, Pustovyy O, Olsen E, Vodyanoy V.
Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, 109 Greene Hall, Auburn, AL 36849, United States.

Staphylococcus aureus (S. aureus)-specific bacteriophage was used as a probe for detection of methicillin-resistant S. aureus (MRSA) in aqueous solution using a novel optical method. Biorecognition phage monolayers transferred to glass substrates using Langmuir-Blodgett (LB) technique were exposed individually to MRSA in solution at logarithmic concentrations ranging from 10(6) to 10(9)cfu/ml, and observed for real-time binding using a CytoVivatrade mark optical light microscope system. Results indicate that LB monolayers possessed high levels of elasticity (K), measuring 22 and 29mN/m for 10(9) and 10(11)pfu/ml phage concentrations, respectively. Near-instantaneous MRSA-phage binding produced 33+/-5%, 10+/-1%, 1.1+/-0.1%, and 0.09+/-0.01% coverage of the substrate that directly correlated to a decrease in MRSA concentrations of 10(9), 10(8), 10(7), and 10(6)cfu/ml. The exclusive selectivity of phage monolayers was verified with Salmonella enterica subsp. enterica serovar typhimurium (S. typhimurium) and Bacillus subtilis.


Thursday, March 27, 2008

The Emergence of Mupirocin Resistance among Clinical Isolates of Methicillin-Resistant Staphylococcus aureus in Trinidad: a First Report.

The Emergence of Mupirocin Resistance among Clinical Isolates of Methicillin-Resistant Staphylococcus aureus in Trinidad: a First Report.

Jpn J Infect Dis. 2008 Mar

Orrett FA.
Unit of Pathology and Microbiology, Faculty of Medical Sciences, The University of the West Indies, St. Augustine, Trinidad and Tobago, West Indies.

The objective of the study was to investigate the trend of mupirocin resistance among methicillin-resistant Staphylococcus aureus (MRSA) in Trinidad. No premarketing susceptibility surveillance was ever done following the introduction of mupirocin in 1986. A total of 188 MRSA strains recovered over a 2-year period from various body sites were tested for mupirocin resistance via the disc diffusion method. The major sources of MRSA were surgical site infections (74.0%) and bloodstream infections (8.0%). High-level and low-level mupirocin resistance were detected in 26.1 and 44.1% of MRSA stains, respectively. Resistances to other non-beta-lactam antibiotics were also high. Ninety-eight percent of all MRSA were resistant to erythromycin. This was followed by resistance rates of 96.8, 95.2, 94.1, 93.6, and 93.1%, for gentamicin, ciprofloxacin, amikacin and tobramycin, co-trimoxazole, and tetracycline, respectively. No MRSA strains were found to be resistant to vancomycin, linezolid, and quinupristin-dalfopristin. The study showed that mupirocin resistance among Trinidadian MRSA strains was relatively high compared to that seen in other countries. Because of the increasing prevalence of MRSA at the San Fernando General Hospital (SFGH) and the apparently increasing resistance to mupirocin, frequent monitoring of MRSA susceptibility patterns and infection control initiatives may be helpful in reducing the incidence of MRSA with a concomitant decrease in mupirocin resistance. This report is the first after 20 years of continuous use of the drug at the SFGH.

Japanese Journal of Infectious Disease

Sunday, March 23, 2008

Long-term outcomes following infection with meticillin-resistant or meticillin-susceptible Staphylococcus aureus.

Long-term outcomes following infection with meticillin-resistant or meticillin-susceptible Staphylococcus aureus.
J Hosp Infect. 2008 Mar

Haessler S, Mackenzie T, Kirkland KB.
Dartmouth–Hitchcock Medical Center, Dartmouth Medical School, Lebanon, New Hampshire, USA.

Staphylococcus aureus (SA) is becoming increasingly resistant to antibiotics in hospitals and the community. Long-term outcomes following susceptible and resistant SA infection have not been studied. We performed a retrospective matched pair analysis of all patients with positive culture for meticillin-resistant SA (MRSA) or meticillin-susceptible SA (MSSA) from any site to assess the outcomes of infection. Data were collected for length of hospitalisation and in-hospital mortality, as well as longer-term outcomes including all-cause mortality, number of rehospitalisations and subsequent cultures for SA during the year following infection. Twelve months after their initial SA infection, 42% of patients were dead. There were no differences between the groups in short-term mortality, length of hospitalisation, number of subsequent hospitalisations and cultures for SA during the year following infection.

Following discharge, however, MRSA infection was associated with higher mortality than MSSA at three months (32% vs 18% P=0.02), six months (42% vs 22% P=0.002) and 12 months (51% vs 32% P=0.005). In conclusion, SA infection is associated with a high one-year all-cause mortality. Most deaths occur after discharge. The likelihood of dying during the year following infection is higher for patients with MRSA infection than for those with MSSA infection.


Thursday, March 20, 2008

A model for surveillance of methicillin-resistant Staphylococcus aureus

A model for surveillance of methicillin-resistant Staphylococcus aureus

Public Health Rep. 2008 Jan-Feb

Simons H, Alcabes P.
Hunter College, City University of New York, School of Health Sciences, New York, NY 10010, USA.

It is well recognized that methicillin-resistant Staphylococcus aureus (MRSA) has become a community pathogen. Several key differences between community-associated and hospital-associated MRSA strains exist, including distinct methicillin resistance genes and genetic backgrounds and differing susceptibility to antibiotics. Recent studies have demonstrated that typical hospital and community strains easily move between hospital and community environments. Despite evidence of MRSA's expanding reach in the community, the best methods for population-level detection and containment have not been established. In an effort to determine effective methods for monitoring the spread of MRSA, we reviewed the literature on hospital-associated and community-associated MRSA (CA-MRSA) in the community and proposed a model for enhanced surveillance. By linking epidemiologic and molecular techniques within a surveillance system that coordinates activities in the community and health-care setting, scientists and public health officials can begin to measure the true extent of CA-MRSA in communities and hospitals.


Friday, March 14, 2008

Methicillin-Resistant Staphylococcus aureus in a Family and Its Pet Cat

Methicillin-Resistant Staphylococcus aureus in a Family and Its Pet Cat

NEJM Mar 13, 2008

To the Editor: Many isolates of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) produce Panton–Valentine leukocidin (PVL), increasing the virulence of the bacteria, which can cause disseminated deep abscesses and necrotizing pneumonia.1 We report the transmission of PVL-positive MRSA between a symptomatic woman and both her asymptomatic family and their healthy pet cat.

An otherwise healthy woman presented with recurrent multiple deep abscesses. Swabs from several abscesses and nasal cultures grew MRSA that was resistant to both beta-lactam and fusidic acid antibiotics. Polymerase-chain-reaction assays for the PVL genes lukS-PV and lukF-PV were positive. The genotype of the staphylococcal chromosomal cassette was SCCmec type IV. Nasal, axillary, and inguinal cultures from her husband and their two children yielded MRSA on several occasions. Mupirocin nasal ointment and antiseptic washes were recommended for all family members. Although the patient's husband and children became MRSA-negative, the patient remained MRSA-positive. Therefore, her three apparently healthy cats were screened. Pharyngeal culture from one cat grew MRSA with the same antimicrobial resistance pattern as that of the human isolates. The clonal identity of the isolates from the family and the cats was found by typing of the spa gene repeat region and multilocus sequence typing,2,3 which showed spa-type t131 and ST80 in all isolates. This sequence combination does not correspond with that of clone USA300 (reference)

A veterinarian recommended topical decolonization of the MRSA-positive cat with ciprofloxacin and rifampin. Four weeks after the cat's treatment, screening tests of the family were negative for MRSA. Moreover, the patient's deep abscesses completely resolved. Further MRSA screening of the asymptomatic cat was declined by the family.

There is evidence that companion animals, mainly dogs, harbor MRSA,4 and interspecies MRSA transmission has been shown in the members of a family and their dog.5 This case illustrates that MRSA transmission also occurs between humans and cats. The abscesses in our patient cleared only after antibiotic treatment of the cat. It remains unclear whether the cat was the source of the patient's infection or vice versa, although spa-type t131 is extremely rare in humans.2 We conclude that pets should be considered as possible household reservoirs of MRSA that can cause infection or reinfection in humans.

Andreas Sing, M.D. Christian Tuschak, Ph.D. Stefan Hörmansdorfer, Vet.D. Bavarian Food and Health Safety Authority 85764 Oberschleißheim, Germany

New England Journal of Medicine

Woman and Cat Shared 'Super Bug'

By Serena GordonHealthDay Reporter Wed Mar 12, 11:47 PM ET
WEDNESDAY, March 12 (HealthDay News) -- People share their homes, their food and more with their pets, but one thing you probably never thought you could share with your animals is a drug-resistant staph infection.

However, according to a letter in the March 13 issue of the New England Journal of Medicine, a German family appears to have done just that. Doctors were puzzled when a woman was repeatedly treated for methicillin-resistant Staphylococcus aureus (MRSA), yet still kept coming back with the infection.

Eventually, they discovered that the family cat was harboring the dangerous bacteria, sometimes called a "super bug."

"Animals and especially pets or companion animals might serve as reservoirs for human-pathogenic bacteria," said Dr. Andreas Sing, head of the department of infectiology at the Bavarian Food and Health Safety Authority in Germany.

Before you give puss the boot, know that researchers believe it was the woman who probably initially transmitted the bacteria to the cat, not the other way around.

About 25 percent to 30 percent of Americans are colonized with staph bacteria, but only about 1 percent are colonized with MRSA, according to the U.S. Centers for Disease Control and Prevention. Most MRSA infections occur in health-care settings, such as hospitals or nursing homes, but the number of community-acquired infections is growing. According to the CDC, about 12 percent of all MRSA infections are now acquired in the community.

MRSA spreads through skin-to-skin contact with an infected person, but its transmission has also been associated with contaminated surfaces, crowded living conditions and poor hygiene, according to the CDC.

MRSA infections often look like a boil or an inflamed pimple, and may be red, swollen and draining pus, the CDC said.

The German woman was otherwise healthy, but kept getting multiple, deep abscesses. Both the abscesses and nasal swabs tested positive for MRSA. Her family members -- a husband and two children -- were also tested, and they tested positive on several occasions. Nasal ointments and antiseptic washes were prescribed for the family to "decolonize" them.

The family members then tested negative for MRSA, but the woman kept testing positive. Doctors then tested the woman's three cats, and found that one, despite having no symptoms, was carrying the same strain of MRSA. Once the cat was decolonized and both the cat and woman were retreated with antibiotics, all family members -- human and feline -- tested negative for the bacteria.

Sing and his colleagues pointed out that this is the first documented MRSA infection in a cat, although there have been reports of other animals, including dogs, harboring MRSA.

Because this infection is generally community-acquired, Sing thinks it's more likely that the woman initially transmitted the bacteria to her pet, and then the animal passed the infection back to her.

"Cats are social. They like to rub up against people and it's the skin-to-skin contact that passes MRSA," explained Dr. Matthew Sims, director of the infectious disease research program at Beaumont Hospital in Royal Oak, Mich.

But, he added, "People shouldn't start worrying about having pets. They can carry all sorts of things which we've known about forever, but you don't need to get rid of your cats or other animals."

Sims said that if you suspect you might have a MRSA infection, go to your doctor for treatment and let your doctor know if you have other people or pets in your household so your doctor can recommend appropriate treatment or prevention steps for them.

The best way to prevent these infections, Sims said, is to practice good hygiene and wash your hands frequently. If you know you have a MRSA infection, avoid direct contact with other people and animals until you've been treated.
More information

To learn more about MRSA, visit the U.S. Centers for Disease Control and Prevention.

Yahoo News

Wednesday, March 5, 2008

Community-associated methicillin-resistant Staphylococcus aureus skin infections: advances toward identifying the key virulence factors.

Community-associated methicillin-resistant Staphylococcus aureus skin infections: advances toward identifying the key virulence factors.

Curr Opin Infect Dis. 2008 Apr

Nygaard TK, Deleo FR, Voyich JM.
aDepartment of Veterinary Molecular Biology, Montana State University, Bozeman, USA bLaboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, Montana, USA.

PURPOSE OF REVIEW: In recent years there has been an increase in the incidence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections in healthy individuals, the cause of which is largely unknown. CA-MRSA primarily causes skin and soft-tissue infections but certain strains are also associated with unusually severe pathology. The purpose of this review is to provide a critical analysis of our current knowledge of virulence factors contributing to skin and soft-tissue infections caused by CA-MRSA.

RECENT FINDINGS: Isolates classified as pulsed-field gel electrophoresis type USA300 have emerged as the predominant CA-MRSA genotype and in most geographic areas account for 97% or more of CA-MRSA infections. Recent key studies, such as those reporting the complete genome sequence of USA300, and the discovery of cytolytic peptides that contribute significantly to CA-MRSA virulence, lead the way for future investigations.

SUMMARY: Although we have only a cursory understanding of the molecular mechanisms of CA-MRSA virulence, studies using clinically relevant CA-MRSA isolates are beginning to identify virulence determinants specific to this pathogen. Identifying CA-MRSA virulence determinants and the concerted regulation of these factors will foster development of vaccines and therapeutics designed to control CA-MRSA skin infections.

Lippincott, Williams & Wilkins

Sunday, March 2, 2008

Methicillin-Resistant and -Susceptible Staphylococcus aureus Sequence Type 398 in Pigs and Humans

Methicillin-Resistant and Susceptible Staphylococcus aureus Sequence Type 398 in Pigs and Humans

EID - Volume 14, Number 3–March 2008

Alex van Belkum,* Damian C. Melles,* Justine K. Peeters,* Willem B. van Leeuwen,* Engeline van Duijkeren,† Xander W. Huijsdens,‡ Emile Spalburg,‡ Albert J. de Neeling,‡ and Henri A. Verbrugh,* on behalf of the Dutch Working Party on Surveillance and Research of MRSA (SOM)1*University Medical Center Rotterdam, Rotterdam, the Netherlands; †University of Utrecht, Utrecht, the Netherlands; and ‡National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands

Nasal Staphylococcus aureus carriage has increased in pig farmers, and specific lineages of S. aureus are shared by farmers and their animals (1,2). In addition, rates of nasal carriage of methicillin-resistant S. aureus (MRSA) by veterinary personnel working with pigs is high (3–5). The pig-related MRSA appears to be clonal and was identified by multilocus sequence typing (MLST) as sequence type 398 (2,6,7). Such resistant bacterial strains can spread from animals to the environment, which may facilitate the colonization of persons who are not involved in animal husbandry (8). The porcine MRSA strain has been isolated from humans with invasive and superficial infections, and familial outbreaks of colonization and cross-colonization have been documented (2,6,7).

We sought to determine whether the clinical effect of the porcine ST398 MRSA strain can be substantiated by the existence of genetically homologous, methicillin-susceptible S. aureus (MSSA) strains among healthy or infected persons. The international MLST database (www.mlst.net) (9) listed only 1 ST398 MSSA nasal carriage isolate from a patient in Cape Verde. In addition, 1 ST398 MRSA strain was isolated from a woman living in Groningen, the Netherlands, without further clinical and epidemiologic data available. ST398 MSSA nasal carriage isolates were also identified in several pig farmers in a study by Armand-Lefevre et al. (1). We describe the population genetic analysis of Dutch community-based and nosocomial MSSA isolates in comparison with pig- and pig farmer–derived ST398 MRSA isolates, performed by spa-sequencing and amplified fragment length polymorphism (AFLP) analysis (10,11).

The Study

Most of the ST398 MRSA strains studied were collected at the Dutch Institute for Public Health and the Environment (RIVM, Bilthoven, the Netherlands). A total of 20 strains were isolated from the nares of pigs in several slaughterhouses (RIVM 21–40) (
12), whereas 18 additional strains were detected during in-hospital screenings for MRSA carriage among Dutch farmers from independent farms (RIVM 1–8, 10–12 and 14–20). In addition, 8 clinical and carriage isolates were obtained from the Veterinary Medical Diagnostic Centre in Utrecht (Table).

Amplified fragment length polymorphism (AFLP) analysis was performed as described previously (
10). A total of 147 marker fragments per strain were scored, and a binary table with marker absence [0] or presence [1] was constructed. A total of 30 fragments with differential occurrence, when genetically heterogeneous MSSA and ST398 MRSA fingerprints were compared, were reamplified and sequenced (Applied Biosystems, Foster City, CA, USA). Fragments were sequenced for 3 independent strains, and the consensus was analyzed by using BLAST . Typing of the staphylococcal chromosome cassette (SCCmec) and the presence of the Panton-Valentine leukocidin (PVL) genes was performed by PCR.

We embedded the genetic fingerprints of the 46 pig-related MRSA isolates in the population structure of S. aureus as obtained before (
10,11). These studies include high throughput AFLP fingerprints of 829 nonclinical S. aureus human carriage isolates and 146 and 77 (including 2 MRSA isolates) clinical isolates of human and animal origin, respectively. All carriage strains were isolated from volunteers living in the Rotterdam region, where pig farms are absent.

Sequencing of the repetitive region of the protein A gene spa was performed for all ST398 MRSA isolates
13). Data were analyzed by using the Ridom Staphtype software version 1.4 .

Analysis of the AFLP data was performed as described previously (
10). Both hierarchical cluster analysis and principle component analysis were performed with Spotfire Decision Site 7.2 software. We used the Fisher exact test to compare the distribution of strain categories in different phylogenetic lineages. A 2-sided p value <0.05>

The AFLP analysis of the ST398 MRSA strains derived from human and animal sources (n = 46) indicated that these strains are highly clonal. When the AFLP patterns for the ST398 strains were included in the overall population analysis for Dutch MSSA strains from carriage and infection, the distinct cluster was still observed (Figure 1). Few Dutch MSSA strains from the Rotterdam region coclustered with the ST398 pig-related MRSA isolates (Figure 1, panel B). In total, 6 (0.6%) MSSA isolates coclustered with the ST398 MRSA isolates, of which 2 were nasal carriage isolates from healthy persons (Table). Of the 6 strains, 3 were blood culture isolates taken from 3 elderly patients. All 3 patients had nosocomial bacteremia: 1 after inflammatory aneurism of the aorta, 1 during Fournier gangrene, and the last 1 after primary ventricular fibrillation. Epidemiologic data exclude a cluster of nosocomial infections; patients were not in direct contact (data not shown).

After principle component analysis , the ST398 MRSA strains still clustered as a separate group (Figure 2). The AFLP analysis did not distinguish strains from pigs or pig farmers, and only a limited number of polymorphic AFLP fragments were seen. AFLP markers that were positive for the ST398 MRSAs and absent from the other strains, or vice versa, were sequenced. Of 30 fragments analyzed, 9 were ≈100% specific for the pig-associated strains. Another 3 fragments were present in a subset of the pig-associated strains only. Of these 12 fragments, 4 were not homologous with current entries in the GenBank database, including the 10 S. aureus full-genome sequences. Of the 12 pig-specific markers, 8 were homologous with known sequences, which suggests that these markers become pig-specific by point mutations in the AFLP primer annealing site(s) rather than by genomic rearrangement. Several of the sequences encode factors were associated with membranes or transport.

The preponderance of types t011 and t108 was confirmed by spa sequencing (12). These made up >75% of all cases. However, the other types all belonged to the same family of spa types, which suggests recent drift in the sequence motifs. The t011 types are primarily associated with SCCmec IV and IVa, whereas the t108 type is nearly fully associated with SCCmec V. This finding suggests that ST398 MRSA has arisen independently on at least 2 occasions. Finally, SCCmec III is found in association with t108, t898, t567, t034, and t571. This finding suggests promiscuous dissemination of this cassette among the ST398 MRSA. Strain RIVM-17 harbored the PVL genes. Apparently, the bacteriophage carrying these genes found its way into the porcine ST398 MRSA lineage.


The massive colonization of Dutch pigs with a single sequence type of MRSA was unexpected (
12). Molecular strain typing was initially compromised because PFGE failed (14). Spa gene sequencing (13) showed heterogeneity in the ST398 MRSA lineage with types t011 and t108, which are closely related, covering >75% of all isolates. Hence, 1 or 2 new MRSA lineages had been discovered. We found a degree of genetic association between spa types and the presence of certain SCCmec cassettes, which suggests bacterial evolution and horizontal DNA exchange in the zoonotic reservoir.

We found that ST398 is rare among Dutch MSSA strains colonizing healthy persons (2 [0.2%] of 829 strains). However, a relatively high number of MSSA isolates homologous to the ST398 MRSA were derived from bacteremic patients (3 [2.1%] of 146; p = 0.026). These 3 bacteremia isolates were not related epidemiologically; they were isolated from different patients in different medical departments over an extended period. This finding suggests that these MSSA strains are quite virulent. The strict segregation of ST398 strains (
Figure 1, panel A; Figure 2) corroborates that the strains belong to a separate biotype associated with pigs (15).

Our findings pose a warning to public health surveillance: if the ST398 MSSA virulence toward humans would be maintained within the ST398 MRSA lineage from pigs, care should be taken not to introduce this strain into humans. We consider it to be likely that ST398 MRSA from pigs is capable of causing serious infection in humans even though its primary host seems to be pigs.

Dr van Belkum is with the Department of Medical Microbiology and Infectious Diseases, University Medical Center Rotterdam, Rotterdam, the Netherlands. His research interests include MRSA.


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