Short communication: methicillin-resistant Staphylococcus aureus detection in US bulk tank milk.

Short communication: methicillin-resistant Staphylococcus aureus detection in US bulk tank milk.
J Dairy Sci. 2009 Oct

Virgin JE, Van Slyke TM, Lombard JE, Zadoks RN.
USDA, APHIS, VS, Centers for Epidemiology and Animal Health, Fort Collins, CO 80526-8117, USA.

* USDA:APHIS:VS, Centers for Epidemiology and Animal Health, 2150 Centre Ave., Bldg B, Fort Collins, CO 80526-8117 Quality Milk Production Services, College of Veterinary Medicine, Cornell University, Ithaca, NY14850-1263
1 Corresponding author: jason.e.lombard@aphis.usda.gov

Staphylococcus aureus is a major cause of mastitis in dairy cattle. This study estimated the herd prevalence of methicillin-resistant Staph. aureus (MRSA) among US dairy herds by testing bulk tank milk (BTM) samples using genotypic and phenotypic methods. A nationally representative sample of 542 operations had BTM cultured for Staph. aureus, and 218 BTM samples were positive upon initial culture. After 4 wk to 4 mo of frozen storage, 87% of 218 samples (n = 190) were still culture positive for Staph. aureus on blood agar, but none were positive for MRSA on the selective indicator medium CHROMagar MRSA. A duplex PCR was used to detect the Staph. aureus-specific nuc gene and the methicillin resistance gene, mecA, in mixed staphylococcal isolates from the 190 BTM samples that were positive for Staph. aureus after storage. Seven samples tested positive for nuc and mecA, and 2 samples tested positive for mecA only. MecA-positive Staphylococcus spp., but not MRSA, were subsequently isolated from 5 samples, whereas neither mecA-positive Staphylococcus spp. nor MRSA was isolated from the remaining 4 samples. Presence of methicillin-resistant, coagulase-negative Staphylococcus spp. may complicate the detection of MRSA by means of PCR on BTM. Bulk tank milk in the United States is not a common source of MRSA.

Journal of Dairy Science

Toward the Development of Evidence-Based Guidelines for the Management of Methicillin-Resistant Staphylococcus aureus Otitis.

Toward the Development of Evidence-Based Guidelines for the Management of Methicillin-Resistant Staphylococcus aureus Otitis.

J Otolaryngol Head Neck Surg.
Macneil SD, Westerberg BD, Romney MG.

Abstract

OBJECTIVES: (1) To determine the causative bacteriology of discharging ears in a case series from a tertiary/quaternary academic centre serving an urban population and from a review of the literature and (2) to develop treatment guidelines for methicillin-resistant Staphylococcus aureus (MRSA) otorrhea based on the best available evidence.

METHODS: A retrospective analysis of all "ear" cultures from the microbiology laboratory at St. Paul's Hospital, Vancouver, was performed to ascertain a qualitative analysis on the susceptibility and bacteriology data. A systematic review of the literature was performed for all studies examining the bacteriology, susceptibility, and treatment for any MRSA infection producing otorrhea.

RESULTS: Staphylococcus aureus and Pseudomonas aeruginosa (PA) were present in 39.7% and 13.5%, respectively, of ear cultures obtained at our institution versus 9.9 to 54.1% and 25.0 to 48.6% in identified studies in the literature. Methicillin-sensitive Staphylococcus aureus (MSSA) was present more frequently than MRSA (31.2% vs 8.5% at our institution; 16.9% vs 6.9% in the literature). MRSA isolates were often resistant to gentamicin (14.8%) and ciprofloxacin (7.7%) but susceptible to trimethoprim-sulfamethoxazole (TMP-SMX) (85.3%) and fusidic acid (96.3%), suggesting a preponderance of the "community strain" of MRSA.

CONCLUSION:The susceptibility of MRSA to antibiotics in commonly used otic drops (ie, gentamicin and ciprofloxacin) is low. Based on the available data, we suggest an evidence-based approach to the management of MRSA otorrhea considering whether the strain is community or hospital acquired and whether the tympanic membrane is intact.

PubMed

Methicillin-Resistant Staphylococcus aureus Furunculitis in the Outpatient Burn Setting

Methicillin-Resistant Staphylococcus aureus Furunculitis in the Outpatient Burn Setting

J Burn Care Res. 2009 Jun

Warner P, Neely A, Bailey JK, Yakuboff KP, Kagan RJ.
From the *Shriners Hospitals for Children, Cincinnati, Ohio; and daggerUniversity of Cincinnati, Cincinnati, Ohio.

Methicillin-resistant Staphylococcus aureus (MRSA) is becoming more predominant in the community. We have seen increasing cases of furunculitis in our outpatient burn clinic, which appear to develop weeks after the initial burn injury and in patients with limited inpatient stays. We performed a 3-year retrospective review of all outpatient burn patients who developed furunculitis. Data analyzed included length of hospital stay, type of injury sustained, culture and sensitivity results, and treatment provided. A total of 28 patients were identified with MRSA furunculitis, which presented as painful, hard, indurated boils with minimal purulent drainage. Adults had less extensive burn injuries (mean of 12% TBSA adults vs 20% TBSA children) with shorter hospital stays (mean 8 days adults vs 22 days children). Fifty-seven percent of the patients had multiple furuncules, involving both burned and nonburned areas. Patients with furunculitis had a less resistant MRSA strain than those without furunculitis. Of the 22 patients who received systemic antibiotic coverage, 14 (58%) were successfully treated with 1 antibiotic regimen, whereas 8 (33%) required multiple antibiotics. In this study, furunculitis in the outpatient setting was believed to be consistent with community-acquired MRSA. Incision and drainage was not sufficient in patients with multiple furuncles, and systemic antibiotics were administered. Through increased awareness of the prevalence of community-acquired MRSA in the community, appropriate antibiotic treatment can be initiated, and the discomfort and transmission risk associated with this disease can be minimized.

Lippincott, Williams & Wilkins

Topical Therapy for Methicillin-Resistant Staphylococcus aureus Colonization: Impact on Infection Risk.

Topical Therapy for Methicillin-Resistant Staphylococcus aureus Colonization: Impact on Infection Risk.

Infect Control Hosp Epidemiol. 2009 Jun

Robicsek A, Beaumont JL, Thomson Jr RB, Govindarajan G, Peterson LR.
From the Departments of Medicine (A.R.) and Pathology (R.B.T., L.R.P.), Feinberg School of Medicine, Northwestern University, Chicago, and the Department of Medicine (G.G.), the Division of Infectious Diseases (A.R.), the Division of Microbiology (R.B.T., L.R.P.), and the Center on Outcomes, Research, and Education (J.L.B.), NorthShore University HealthSystem, Evanston, Illinois.

Objective.

We evaluated the usefulness of topical decolonization therapy for reducing the risk of methicillin-resistant Staphylococcus aureus (MRSA) infection among MRSA-colonized inpatients.

Design.

Retrospective cohort study. Setting and intervention. Three hospitals with universal surveillance for MRSA; at their physician's discretion, colonized patients could be treated with a 5-day course of nasal mupirocin calcium 2%, twice daily, plus chlorhexidine gluconate 4% every second day. Patients and methods. MRSA carriers were later retested for colonization (407 subjects; study 1) or followed up for development of MRSA infection (933 subjects; study 2). Multivariable methods were used to determine the impact of decolonization therapy on the risks of sustained colonization (in study 1) and MRSA infection (in study 2).

Results.

Independent risk factors for sustained colonization included residence in a long-term care facility (odds ratio [OR], 1.8 [95% confidence interval {CI}, 1.1-3.2]) and a pressure ulcer (OR, 2.3 [95% CI, 1.2-4.4]). Mupirocin at any dose decreased this risk, particularly during the 30-60-day period after therapy; mupirocin resistance increased this risk (OR, 4.1 [95% CI, 1.6-10.7]). Over a median follow-up duration of 269 days, 69 (7.4%) of 933 patients developed infection. Independent risk factors for infection were length of stay (hazard ratio [HR], 1.2 per 5 additional days [95% CI, 1.0-1.4]), chronic lung disease (HR, 1.7 [95% CI, 1.0-2.8]), and receipt of non-MRSA-active systemic antimicrobial agents (HR, 1.8 [95% CI, 1.1-3.1]). Receipt of mupirocin did not affect the risk of infection, although there was a trend toward delayed infection among patients receiving mupirocin (median time to infection, 50 vs 15.5 days; [Formula: see text]).

Conclusions.

Mupirocin-based decolonization therapy temporarily reduced the risk of continued colonization but did not decrease the risk of subsequent infection.

ChicagoJournals

Activity of the anti-MRSA carbapenem razupenem (PTZ601) against Enterobacteriaceae with defined resistance mechanisms.

Activity of the anti-MRSA carbapenem razupenem (PTZ601) against Enterobacteriaceae with defined resistance mechanisms.

J Antimicrob Chemother. 2009 Jun

Livermore DM, Mushtaq S, Warner M.
Antibiotic Resistance Monitoring & Reference Laboratory, Health Protection Agency Centre for Infections, 61 Colindale Avenue, London, NW9 5EQ, UK.

Background

Razupenem (previously known as PTZ601, PZ-601, SMP-601 or SM-216601) is a novel carbapenem, active against Enterobacteriaceae as well as Gram-positive bacteria including methicillin-resistant staphylococci and enterococci.

Methods

We examined the effect of extended-spectrum beta-lactamases (ESBLs) and AmpC beta-lactamases on the activity of razupenem, using the CLSI agar dilution method to measure MICs for mutants, transconjugants and isolates with and without these enzymes.

Results

ESBLs had no effect on the activity of razupenem against Escherichia coli and Klebsiella spp., and only a small effect when coupled with outer membrane impermeability. Inducible or, more especially, derepressed AmpC enzymes gave some protection, with most AmpC-derepressed Enterobacter and Citrobacter spp. requiring MICs of approximately 8 mg/L. This relative resistance was further increased when porins were lost, restricting drug uptake. Metallo- and class A-carbapenemases conferred resistance, with MICs >/=16 mg/L.

Conclusions

Razupenem has good activity against ESBL producers, but is affected by AmpC enzymes, especially when derepressed and coupled with outer membrane impermeability; its activity is also compromised by carbapenemases.

OxfordJournals

Antimicrobial resistance profile of methicillin resistant staphylococcal aureus from skin and soft tissue isolates.

Antimicrobial resistance profile of methicillin resistant staphylococcal aureus from skin and soft tissue isolates.
J Pak Med Assoc. 2009 May

Idrees F, Jabeen K, Khan MS, Zafar A.
Department of Pathology & Microbiology, Aga Khan University Hospital, Karachi, Pakistan.

OBJECTIVES: To evaluate resistance rates in methicillin resistant Staphylococcus aureus (MRSA) against clindamycin, cotrimoxazole, tetracycline, fusidic acid, rifampicin and chloramphenicol isolated from skin and soft tissue infections (SSTI). METHODS: Descriptive analysis of SSTI samples yielding MRSA in clinical laboratory of a tertiary care center; receiving specimens across Pakistan from January 2005 to June 2007.

MICROBIOLOGICAL METHODS: MRSA were identified using standard microbiological techniques. Susceptibility testing was performed by disc diffusion according to Clinical Laboratory Standards Institute (CLSI) against fusidic acid, tetracycline, cotrimoxazole, clindamycin, rifampicin and chloramphenicol. Minimum inhibitory concentrations (MIC) of rifampicin were determined using agar dilution method according to CLSI.

RESULTS: During the study period 501 MRSA were isolated from SSTI. Overall variable susceptibility pattern with high resistance rates to tetracycline (82%), clindamycin (79%), cotrimoxazole (59%), and rifampicin (50%) were observed. Resistance to chloramphenicol (10%) and fusidic acid (9%) was low.

CONCLUSION: There is a strong need in resource limited countries to review the utility of conventional antibiotics for the management of MRSA SSTI as new agents are expensive and not available. High resistance rates were observed against cotrimoxazole, tetracycline and clindamycin. Resistance to fusidic acid, rifampicin and Chloramphenicol was low.

PubMed

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.

SpringerLink