Interactions of Methicillin Resistant Staphylococcus aureus USA300 and Pseudomonas aeruginosa in Polymicrobial Wound Infection.

2013

Pastar I, Nusbaum AG, Gil J, Patel SB, Chen J, Valdes J, Stojadinovic O, Plano LR, Tomic-Canic M, Davis SC.

Source

Department of Dermatology and Cutaneous Surgery, Wound Healing and Regenerative Medicine Research Program, University of Miami Miller School of Medicine, Miami, Florida, United States of America.

Abstract

Understanding the pathology resulting from and polymicrobial wound infections is of great importance due to their ubiquitous nature, increasing prevalence, growing resistance to antimicrobial agents, and ability to delay healing. Methicillin-resistantUSA300 is the leading cause of community-associated bacterial infections resulting in increased morbidity and mortality. We utilized a well-established porcine partial thickness wound healing model to study the synergistic effects of USA300 and on wound healing. Wound re-epithelialization was significantly delayed by mixed-species biofilms through suppression of keratinocyte growth factor 1. showed an inhibitory effect on USA300 growth while both species co-existed in cutaneous wounds . Polymicrobial wound infection in the presence of resulted in induced expression of USA300 virulence factors Panton-Valentine leukocidin and α-hemolysin. These results provide evidence for the interaction of bacterial species within mixed-species biofilms and for the first time, the contribution of virulence factors to the severity of polymicrobial wound infections.

PubMed

Impact of Methicillin Resistant Staphylococcus aureus Contact Isolation Units on Medical Care.

2013

Masse V, Valiquette L, Boukhoudmi S, Bonenfant F, Talab Y, Carvalho JC, Alarie I, Carrier N, Farand P.

Source

Infectious Diseases Division, Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Quebec, Canada.

Abstract

BACKGROUND:

Patient isolation using contact precautions has gained widespread use to halt MRSA transmission, however supportive data is scarce and concerns regarding patient safety and satisfaction have been raised. At our institution, MRSApatients are isolated on a dedicated ward (cohort isolation), rather than in separate rooms. Our objectives were (1) to determine the proportion of bedside medical visits to patients on an isolation ward, (2) to quantify complications in those patients and (3) to determine if those complications are related to isolation and if they can be prevented.

METHODS:

This retrospective case-control study was performed on the two sites of a tertiary teaching hospital in Sherbrooke, QC, Canada. We matched MRSA patients with an admission diagnosis of heart failure or chronic obstructive pulmonary disease to similar non-isolated controls. The proportion of bedside visits was ascertained through the number of progress notes with subjective elements or with a physical examination. Complications were sought through an extensive file review, and events were analysed according to Baker's CAES causality and preventability scales.

RESULTS:

Overall, 111 patient pairs were analysed (35 with heart failure and 76 with COPD). Isolated patients received less bedside visits (subjective notes/1,000 patient-days: 849.6 983.3, p = 0,001). Attending physicians (454.5 451.4, p = 0,02) and residents (347.0 416.9, p = 0.01) are responsible for this discrepancy, while medical students appear to visit isolated and non-isolated patients equally (116.5 114.9, p = 0.90). Isolated patients showed a tendency towards longer stay and more preventable complications, although no difference in the total number of complications was observed.

CONCLUSION:

Isolated patients have less documented care that suggests less bedside visits from the medical staff, which could hamper the therapeutical relationship. Further studies are needed to explain this finding.

PubMed

Predictive factors for early mortality among patients with methicillin-resistant Staphylococcus aureusbacteraemia.

Feb 2013

Gasch O, Camoez M, Domínguez MA, Padilla B, Pintado V, Almirante B, Lepe JA, Lagarde M, Ruiz de Gopegui E, Martínez JA, Montejo M, Torre-Cisneros J, Arnáiz A, Goenaga MA, Benito N, Rodríguez-Baño J, Pujol M; on behalf of the REIPI/GEIH Study Groups.

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Source

Hospital Universitari de Bellvitge, IDIBELL, Barcelona, Spain.

Abstract

OBJECTIVES:

A high proportion of patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia die within a few days of the onset of infection. However, predictive factors for early mortality (EM) have barely been examined. The aim of this study was to determine the predictive factors for EM in patients with MRSA bacteraemia.

METHODS:

All episodes of MRSA bacteraemia were prospectively followed in 21 Spanish hospitals from June 2008 to December 2009. Epidemiology, clinical data, therapy and outcome were recorded. All MRSA strains were analysed in a central laboratory. Mortality was defined as death from any cause occurring in the 30 days after the onset of MRSAbacteraemia. EM was defined as patients who died within the first 2 days, and late mortality (LM) for patients who died after this period. Multivariate analyses were performed by using logistic regression models.

RESULTS:

A total of 579 episodes were recorded. Mortality was observed in 179 patients (31%): it was early in 49 (8.5%) patients and late in 130 (22.5%). Independent risk factors for EM were [OR (95% CI)] initial Pitt score >3 [3.99 (1.72-3.24)], previous rapid fatal disease [3.67 (1.32-10.24)], source of infection lower respiratory tract or unknown [3.76 (1.31-10.83) and 2.83 (1.11-7.21)], non-nosocomial acquisition [2.59 (1.16-5.77)] and inappropriate initial antibiotic therapy [3.59 (1.63-7.89)]. When predictive factors for EM and LM were compared, inappropriate initial antibiotic therapy was the only distinctive predictor of EM, while endocarditis and lower respiratory tract sources both predicted LM.

CONCLUSIONS:

In our large cohort of patients several factors were related to EM, but the only distinctive predictor of EM was inappropriate initial antibiotic therapy.

Oxford - Journal of Antimicrobial Chemotherapy

Draft Genome Sequence of the Methicillin-Resistant Staphylococcus aureus Isolate MRSA-M2.

2013

Harro JM, Daugherty S, Bruno VM, Jabra-Rizk MA, Rasko DA, Shirtliff ME.

Source

Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland, USA.

Abstract

We report the draft genome sequence of a methicillin-resistant strain of Staphylococcus aureus, designated MRSA-M2. This clinical isolate was obtained from an osteomyelitis patient undergoing treatment at the University of Texas Medical Branch (Galveston, TX). This strain is an ST30, spa type T019, agr III strain and has been utilized as a model S. aureus strain in a number of proteomic, transcriptomic, and animal model studies.

PubMed

Laboratory Maintenance of Methicillin-Resistant Staphylococcus aureus (MRSA).

Feb 2013

Vitko NP, Richardson AR.

Source

Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina.

Abstract

Staphylococcus aureus is an important bacterial pathogen in the hospital and community settings, especially Staphylococcus aureus clones that exhibit methicillin-resistance (MRSA). Many strains of S. aureus are utilized in the laboratory, underscoring the genetic differences inherent in clinical isolates. S. aureus grows quickly at 37°C with aeration in rich media (e.g., BHI) and exhibits a preference for glycolytic carbon sources. Furthermore, S. aureus has a gold pigmentation, exhibits β-hemolysis, and is catalase and coagulase positive. The four basic laboratory protocols presented in this unit describe how to culture S. aureus on liquid and solid media, how to identify S. aureus strains as methicillin resistant, and how to generate a freezer stock of S. aureus for long-term storage. Curr. Protoc. Microbiol.

Full Text

Wiley Online

Predicting High Prevalence of Community Methicillin-Resistant Staphylococcus aureus Strains in Nursing Homes.

Mar 2013

Murphy CR, Hudson LO, Spratt BG, Quan V, Kim D, Peterson E, Tan G, Evans K, Meyers H, Cheung M, Lee BY, Mukamel DB, Enright MC, Whealon M, Huang SS.

Source

Division of Infectious Diseases and Health Policy Research Institute, University of California, Irvine, School of Medicine, Irvine, California.

Abstract

We assessed characteristics associated with community-associated methicillin-resistant Staphylococcus aureus(CA-MRSA) carriage among residents of 22 nursing homes. Of MRSA-positive swabs, 25% (208/824) were positive for CA-MRSA. Median facility CA-MRSA percentage was 22% (range, 0%-44%). In multivariate models, carriage was associated with age less than 65 years (odds ratio, 1.2; [Formula: see text]) and Hispanic ethnicity (odds ratio, 1.2; [Formula: see text]). Interventions are needed to target CA-MRSA.

PubMed

Controlled Multicenter Evaluation of a Bacteriophage Based Method for the Rapid Detection of Staphylococcusaureus in Positive Blood Cultures.

Feb 2013

Bhowmick T, Mirrett S, Reller LB, Price C, Qi C, Weinstein MP, Kirn TJ.

Source

UMDNJ-Robert Wood Johnson Medical School, 1 Robert Wood Johnson Place, New Brunswick, NJ 08901.

Abstract

Staphylococci are a frequent cause of bloodstream infections (BSIs). Appropriate antibiotic treatment for BSIs may be delayed because conventional laboratory testing methods take 48-72 hours to identify and characterize isolates from positive blood cultures. We evaluated a novel assay based on bacteriophage amplification that identifies S. aureus and differentiates between methicillin-susceptible and methicillin-resistant S. aureus (MSSA and MRSA, respectively) in samples taken directly from signal positive BACTEC™ blood culture bottles within 24 hours of positive signal, with results available within 5 hours. The performance of the MicroPhage KeyPath™ MRSA/MSSA Blood Culture Test was compared to conventional identification and susceptibility testing methods. At four sites, we collectively tested a total of 1165 specimens of which 1116 were included in our analysis. Compared to standard methods, the KeyPath™ MRSA/MSSA Blood Culture Test demonstrated a sensitivity, specificity, positive predictive value and negative predictive value of 91.8%, 98.3%, 96.3% and 96.1%, respectively for correctly identifying S. aureus. Of those correctly identified as S. aureus (n=334), 99.1% were correctly categorized as either MSSA or MRSA. Analysis of a subset of the data revealed that the KeyPath™ MRSA/MSSA Blood Culture Test delivered results a median of 30 hours sooner than conventional methods (a median of 46.9 hours vs a median of 16.9 hours). Although the sensitivity of the test in detecting S. aureus-positive samples is not high, its accuracy in determining methicillin resistance and susceptibility among positives is very high. These characteristics may enable earlier implementation of appropriate antibiotic treatment for many S. aureus BSI patients. (Subsets of these results were presented at the 2010 ICAAC meeting in Boston, MA and the 2011 ASM meeting in New Orleans).

PubMed