Methicillin-resistant Staphylococcus aureus in the community: new battlefronts, or are the battles lost?

Assessing the potential for raw meat to influence human colonization with Staphylococcus aureus

The role of household meat handling and consumption in the transfer of Staphylococcus aureus (S. aureus) from livestock to consumers is not well understood. Examining the similarity of S. aureus colonizing humans and S. aureus in meat from the stores in which those individuals shop can provide insight into the role of meat in human S. aureus colonization. S. aureus isolates were collected from individuals in rural and urban communities in Iowa (n = 3347) and contemporaneously from meat products in stores where participants report purchasing meat (n = 913). The staphylococcal protein A (spa) gene was sequenced for all isolates to determine a spa type. Morisita indices and Permutational Multivariate Analysis of Variance Using Distance Matrices (PERMANOVA) were used to determine the relationship between spa type composition among human samples and meat samples. spa type composition was significantly different between households and meat sampled from their associated grocery stores. spa types found in meat were not significantly different regardless of the store or county in which they were sampled. spa types in people also exhibit high similarity regardless of residential location in urban or rural counties. Such findings suggest meat is not an important source of S. aureus colonization in shoppers.

Healthcare-associated Pneumonia: Clinical Features and Retrospective Analysis Over 10 Years

Background:

Healthcare-associated pneumonia (HCAP) is associated with drug-resistant pathogens and high mortality, and there is no clear evidence that this is due to inappropriate antibiotic therapy. This study was to elucidate the clinical features, pathogens, therapy, and outcomes of HCAP, and to clarify the risk factors for drug-resistant pathogens and prognosis.

Methods:

Retrospective observational study among hospitalized patients with HCAP over 10 years. The primary outcome was 30-day all-cause hospital mortality after admission. Demographics (age, gender, clinical features, and comorbidities), dates of admission, discharge and/or death, hospitalization costs, microbiological results, chest imaging studies, and CURB-65 were analyzed. Antibiotics, admission to Intensive Care Unit (ICU), mechanical ventilation, and pneumonia prognosis were recorded. Patients were dichotomized based on CURB-65 (low- vs. high-risk).

Results:

Among 612 patients (mean age of 70.7 years), 88.4% had at least one comorbidity. Commonly detected pathogens were Acinetobacter baumannii, Pseudomonas aeruginosa, and coagulase-negative staphylococci. Initial monotherapy with β-lactam antibiotics was the most common initial therapy (50%). Mean age, length of stay, hospitalization expenses, ICU admission, mechanical ventilation use, malignancies, and detection rate for P. aeruginosa, and Staphylococcus aureus were higher in the high-risk group compared with the low-risk group. CURB-65 ≥3, malignancies, and mechanical ventilation were associated with an increased mortality. Logistic regression analysis showed that cerebrovascular diseases and being bedridden were independent risk factors for HCAP.

Conclusion:

Initial treatment of HCAP with broad-spectrum antibiotics could be an appropriate approach. CURB-65 ≥3, malignancies, and mechanical ventilation may result in an increased mortality.

Transmission of Staphylococcus aureus between health-care workers, the environment, and patients in an intensive care unit: a longitudinal cohort study based on whole-genome sequencing

Background

Health-care workers have been implicated in nosocomial outbreaks of Staphylococcus aureus, but the dearth of evidence from non-outbreak situations means that routine health-care worker screening and S aureus eradication are controversial. We aimed to determine how often S aureus is transmitted from health-care workers or the environment to patients in an intensive care unit (ICU) and a high-dependency unit (HDU) where standard infection control measures were in place.

Methods

In this longitudinal cohort study, we systematically sampled health-care workers, the environment, and patients over 14 months at the ICU and HDU of the Royal Sussex County Hospital, Brighton, England. Nasal swabs were taken from health-care workers every 4 weeks, bed spaces were sampled monthly, and screening swabs were obtained from patients at admission to the ICU or HDU, weekly thereafter, and at discharge. Isolates were cultured and their whole genome sequenced, and we used the threshold of 40 single-nucleotide variants (SNVs) or fewer to define subtypes and infer recent transmission.

Findings

Between Oct 31, 2011, and Dec 23, 2012, we sampled 198 health-care workers, 40 environmental locations, and 1854 patients; 1819 isolates were sequenced. Median nasal carriage rate of S aureus in health-care workers at 4-weekly timepoints was 36·9% (IQR 35·7–37·3), and 115 (58%) health-care workers had S aureus detected at least once during the study. S aureus was identified in 8–50% of environmental samples. 605 genetically distinct subtypes were identified (median SNV difference 273, IQR 162–399) at a rate of 38 (IQR 34–42) per 4-weekly cycle. Only 25 instances of transmission to patients (seven from health-care workers, two from the environment, and 16 from other patients) were detected.

Interpretation

In the presence of standard infection control measures, health-care workers were infrequently sources of transmission to patients. S aureus epidemiology in the ICU and HDU is characterised by continuous ingress of distinct subtypes rather than transmission of genetically related strains.

Funding

UK Medical Research Council, Wellcome Trust, Biotechnology and Biological Sciences Research Council, UK National Institute for Health Research, and Public Health England.

Molecular characterization of Staphylococcus aureus isolates from various healthcare institutions in Nairobi, Kenya: a cross sectional study

Background

Staphylococcus aureus (S. aureus) has established itself over the years as a major cause of morbidity and mortality both within the community and in healthcare settings. Methicillin resistant S. aureus (MRSA) in particular has been a major cause of nosocomial infections resulting in significant increase in healthcare costs. In Africa, the MRSA prevalence has been shown to vary across different countries. In order to better understand the epidemiology of MRSA in a setting, it is important to define its population structure using molecular tools as different clones have been found to predominate in certain geographical locations.

Methods

We carried out PFGE, MLST, SCCmec and spa typing of selected S. aureus isolates from a private and public referral hospital in Nairobi, Kenya.

Results

A total of 93 S. aureus isolates were grouped into 19 PFGE clonal complexes (A–S) and 12 singletons. From these, 55 (32 MRSA and 23 MSSA) representative isolates from each PFGE clonal complex and all singletons were spa typed. There were 18 different MRSA spa types and 22 MSSA spa types. The predominant MRSA spa type was t037 comprising 40.6 % (13/32) of all MRSA. In contrast, the MSSA were quite heterogeneous, only 2 out of 23 MSSA shared the same spa type. Two new MRSA spa types (t13149 and t13150) and 3 new MSSA spa types (t13182, t13193 and t13194) were identified. The predominant clonal complex was CC 5 which included multi-locus sequence types 1, 8 and 241.

Conclusion

In contrast to previous studies published from Kenya, there’s marked genetic diversity amongst clinical MRSA isolates in Nairobi including the presence of well-known epidemic MRSA clones. Given that these clones are resident within our referral hospitals, adherence to strict infection control measures needs to be ensured to reduce morbidity and mortality associated with hospital acquired MRSA infections.

Modeling Transmission of Methicillin-ResistantStaphylococcus AureusAmong Patients Admitted to a Hospital

Objective:

To determine the impact of the screening test, nursing workload, handwashing rates, and dependence of handwashing on risk level of patient visit on methicillin-resistantStaphylococcus aureus(MRSA) transmission among hospitalized patients.

Setting:

General medical ward.

Methods:

Monte Carlo simulation was used to model MRSA transmission (median rate per 1,000 patient-days). Visits by healthcare workers (HCWs) to patients were simulated, and MRSA was assumed to be transmitted among patients via HCWs.

Results:

The transmission rate was reduced from 0.89 to 0.56 by the combination of increasing the sensitivity of the screening test from 80% to 99% and being able to report results in 1 day instead of 4 days. Reducing the patient-to-nurse ratio from 4.3 in the day and 6.8 at night to 3.8 and 5.7, respectively, reduced the number of nosocomial infections from 0.89 to 0.85; reducing the ratio to 1 and 1, respectively, further reduced the number of nosocomial infections to 0.32. Increases in handwashing rates by 0%, 10%, and 20% for high-risk visits yielded reductions in nosocomial infections similar to those yielded by increases in handwashing rates for all visits (0.89, 0.36, and 0.24, respectively). Screening all patients for MRSA at admission reduced the transmission rate to 0.81 per 1,000 patient-days from 1.37 if no patients were screened.

Conclusion:

Within the ranges of parameters studied, the most effective strategies for reducing the rate of MRSA transmission were increasing the handwashing rates for visits involving contact with skin or bodily fluid and screening patients for MRSA at admission. (Infect Control Hosp Epidemiol 2005;26:607- 615)

A predictive rule for mortality of inpatients with Staphylococcus aureus bacteraemia: A classification and regression tree analysis

OBJECTIVE

To create a predictive rule to identify risk factors for mortality among patients with Staphylococcus aureus bacteraemia (SAB).

DESIGN, SETTING AND PATIENTS

This was a retrospective cohort study of all adult patients with SAB at a large community hospital in Tokyo, Japan, from April 1, 2004 to March 31, 2011. Baseline data and clinically relevant factors were collected from electronic charts. The primary outcome was in-hospital mortality. All candidate predictors were included in a classification and regression tree (CART) analysis. A receiver operating characteristic (ROC) curve was drawn, and the area under the curve (AUC) was obtained. A cross-validation analysis was performed.

MEASUREMENTS AND MAIN RESULTS

A total of 340 patients had SAB during the study period. Of these, 118 (34.7%) patients died in hospital. Among 41 potential variables, the CART analysis revealed that underlying malignancy, serum blood glucose level, methicillin resistance, and low serum albumin were predictors of mortality. The AUC was 0.73 (95% CI: 0.67-0.79). For validation, the estimated risk was 0.26 (± SE: 0.02) in the resubstitution analysis and 0.33 (± SE: 0.03) in the cross-validation analysis.

CONCLUSION

We propose a predictive model for the mortality of patients with SAB consisting of four predictors: underlying malignancy, low serum albumin, high glucose, and methicillin resistance. This model may facilitate appropriate preventative management for patients with SAB who are at high risk of mortality.

PHMB: an effective antimicrobial in wound bioburden management

The effective management of bacterial bioburden is an essential element of wound care. Recent years have seen the increased use of topical antimicrobial dressings to control colonisation and infection, yet there is concern that some may inhibit wound healing and may have systemic sequelae (World Union of Wound Healing Societies (WUWHS), 2008). This article focuses on the safety and effectiveness of PHMB, an antimicrobial compound that is relatively underused in the UK, and argues that it is an effective option for the management of bacterial colonisation and infection.

Proteome analyses of cellular proteins in methicillin-resistant Staphylococcus aureus treated with rhodomyrtone, a novel antibiotic candidate

The ethanolic extract from Rhodomyrtus tomentosa leaf exhibited good antibacterial activities against both methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus ATCC 29213. Its minimal inhibitory concentration (MIC) values ranged from 31.25–62.5 µg/ml, and the minimal bactericidal concentration (MBC) was 250 µg/ml. Rhodomyrtone, an acylphloroglucinol derivative, was 62.5–125 times more potent at inhibiting the bacteria than the ethanolic extract, the MIC and MBC values were 0.5 µg/ml and 2 µg/ml, respectively. To provide insights into antibacterial mechanisms involved, the effects of rhodomyrtone on cellular protein expression of MRSA have been investigated using proteomic approaches. Proteome analyses revealed that rhodomyrtone at subinhibitory concentration (0.174 µg/ml) affected the expression of several major functional classes of whole cell proteins in MRSA. The identified proteins involve in cell wall biosynthesis and cell division, protein degradation, stress response and oxidative stress, cell surface antigen and virulence factor, and various metabolic pathways such as amino acid, carbohydrate, energy, lipid, and nucleotide metabolism. Transmission electron micrographs confirmed the effects of rhodomyrtone on morphological and ultrastructural alterations in the treated bacterial cells. Biological processes in cell wall biosynthesis and cell division were interrupted. Prominent changes including alterations in cell wall, abnormal septum formation, cellular disintegration, and cell lysis were observed. Unusual size and shape of staphylococcal cells were obviously noted in the treated MRSA. These pioneer findings on proteomic profiling and phenotypic features of rhodomyrtone-treated MRSA may resolve its antimicrobial mechanisms which could lead to the development of a new effective regimen for the treatment of MRSA infections.

Surmounting antimicrobial resistance in the Millennium Superbug: Staphylococcus aureus

Staphylococcus aureus is the third most dreaded pathogen posing a severe threat due to its refractory behavior against the current armamentarium of antimicrobial drugs. This is attributed to the evolution of an array of resistance mechanisms responsible for morbidity and mortality globally. Local and international travel has resulted in the movement of drug resistant S. aureus clones from hospitals into communities and further into different geographical areas where they have been responsible for epidemic outbreaks. Thus, there is a dire necessity to refrain further cross movement of these multidrug resistant clones across the globe. The plausible alternative to prevent this situation is by thorough implementation of regulatory aspects of sanitation, formulary usage and development of new therapeutic interventions. Various strategies like exploring novel antibacterial targets, high throughput screening of microbes, combinatorial and synthetic chemistry, combinatorial biosynthesis and vaccine development are being extensively sought to overcome multidrug resistant chronic Staphylococcal infections. The majority of the antibacterial drugs are of microbial origin and are prone to being resisted. Anti-staphylococcal plant natural products that may provide a new alternative to overcome the refractory S.aureus under clinical settings have grossly been unnoticed. The present communication highlights the new chemical entities and therapeutic modalities that are entering the pharmaceutical market or are in the late stages of clinical evaluation to overcome multidrug resistant Staphylococcal infections. The review also explores the possibility of immunity and enzyme-based interventions as new therapeutic modalities and highlights the regulatory concerns on the prescription, usage and formulary development in the developed and developing world to keep the new chemical entities and therapeutic modalities viable to overcome antimicrobial resistance in S. aureus.

Current knowledge of methicillin-resistant Staphylococcus aureus and community-associated methicillin-resistant Staphylococcus aureus

BACKGROUND

Bacterial strains that are oxacillin and methicillin-resistant, historically termed methicillin-resistant Staphylococcus aureus (MRSA) are resistant to all beta-lactam agents, including cephalosporins and carbapenems. MRSA are pathogenic and have a number of virulence factors that enable them to result in disease. They are transmissible and important causes of nosocomial infections worldwide. An MRSA outbreak can occur when one strain is transmitted to other patients or through close contacts of infected persons in the community. Hospital-associated MRSA (HA-MRSA) isolates are also frequent causes of healthcare-associated bloodstream and catheter-related infections. Community-associated MRSA (CA-MRSA) isolates are often only resistant to beta-lactam agents and erythromycin but they are an emerging cause of community-associated infections, especially skin and soft tissue infections (SSTI) and necrotizing pneumonia.

METHODS

Current possibilities for detecting MRSA strains in the laboratory are reviewed and discussed in the context of the recent literature.

RESULTS AND CONCLUSION

The active surveillance and prevention of MRSA occurrence and spreading in hospitals are discussed in the context of recent literature.

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

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.

Synthesis and biological evaluation of new N-linked 5-triazolylmethyl oxazolidinones

A new series of oxazolidinones bearing N-linked 5-triazolylmethyl group have been synthesized and their in vitro antibacterial activities (MIC) were evaluated against a spectrum of resistant and susceptible Gram-positive organisms. Some of the analogues in this series displayed activity superior to linezolid and vancomycin. Furthermore, in vivo efficacies and pharmacokinetic properties of the selected compounds were also disclosed herein; the selected compounds showed reasonable bioavailability as well as in vivo efficacy comparable to that of linezolid.

A comparison of costs and hospital length of stay associated with intravenous/oral linezolid or intravenous vancomycin treatment of complicated skin and soft-tissue infections caused by suspected or confirmed methicillin-resistant Staphylococcus aureus in elderly US patients

OBJECTIVES

This study compared the costs and hospital length of stay (LOS) and duration of intravenous therapy associated with intravenous/oral linezolid or intravenous vancomycin treatment of complicated skin and soft-tissue infections (cSSTIs) caused by suspected or confirmed methicillin-resistant Staphylococcus aureus (MRSA) in elderly US patients.

METHODS

Data were obtained from elderly (>or=65 years) US patients participating in a multinational randomized trial of hospitalized cSSTI patients treated with linezolid or vancomycin. Costs (hospital and total) from the provider perspective were estimated for intent-to-treat (ITT) patients (ie, all those receiving >or=1 dose) using national 2003 costs (ward, medication, intravenous administration). LOS for inpatient care, duration of intravenous linezolid and vancomycin therapy (ITT and MRSA groups), and cure rates were evaluated.

RESULTS

Of 717 enrolled subjects, 163 (23%) were elderly (87 linezolid, 76 vancomycin), with no significant differences in demographic characteristics between the linezolid and vancomycin groups. Mean hospitalization and total costs were lower with linezolid compared with vancomycin (hospitalization: US $4510 vs US $6478, P<0.001; total: US $6009 vs US $7329, P=0.03). Linezolid was associated with a 3.5-day reduction in LOS and a 9.5-day reduction in the duration of intravenous therapy compared with vancomycin in the ITT group (both, P<0.001). Cure rates were comparable between linezolid and vancomycin in both the ITT group (88.7% vs 81.4%, respectively) and the MRSA group (80.0% vs 71.4%). In multivariate analyses of the ITT group, linezolid patients were 57% less likely than vancomycin patients to have a LOS >7 days (odds ratio = 0.43; 95% CI, 0.21-0.87). Chronic renal failure, malnutrition, and a diagnosis of infected ulcer predicted an LOS >7 days.

CONCLUSIONS

In this analysis of data from elderly patients with cSSTI caused by suspected or confirmed MRSA, linezolid treatment was associated with reductions in the costs of care, LOS, and duration of intravenous treatment without affecting the clinical outcomes. Although the use of a subset of patients from a larger trial that did not focus on the elderly can be seen as a study limitation, the elderly represent an important population when evaluating health care resource use and costs.

Synthesis and antibacterial activity of oxazolidinones containing triazolyl group

A new series of oxazolidinones containing triazolyl group has been synthesized and tested for in vitro antibacterial activity by MIC determination against a panel of resistant and susceptible Gram-positive organisms. Most of the analogs in this series displayed activity superior to linezolid and vancomycin in vitro. Further, in vivo efficacies of the selected oxazolidinones were also disclosed herein.

Non-multiresistant methicillin-resistant Staphylococcus aureus bacteraemia in Sydney, Australia: emergence of EMRSA-15, Oceania, Queensland and Western Australian MRSA strains

AIMS

To describe clinical features and molecular epidemiology of non-multiresistant methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia.

METHODS

Patients with non-multiresistant MRSA isolated from blood at South Western Area Pathology Service from 1 January 1999 to 31 December 2001 were enrolled. Pulsed field gel electrophoresis, phage typing, and (selected instances) multilocus sequence and staphylococcal cassette chromosome typing was performed. PCR was used to detect Panton-Valentine leukocidin (PVL), toxic shock syndrome toxin-1 (TSST-1), and enterotoxin genes.

RESULTS

Sixteen patients were detected: eight with UK EMRSA-15 (ST22-MRSA-IV), three with Oceania (South-West Pacific/Western Samoan phage pattern) (ST30-MRSA-IV), two with WA MRSA-5 (ST8-MRSA-IV), and one each with WA MRSA-1 (ST1-MRSA-IV), Queensland strain (ST93-MRSA-IV), and WA MRSA-15 (ST59-MRSA-IV). Prior hospital admissions occurred with six of the eight patients with UK EMRSA-15, none of the three with Oceania, and three of the five with other strains. Thirteen of 16 patients had underlying disease. Three of the three patients with Oceania strain bacteraemia were Polynesians; 11 of 13 of the others were Caucasians. PVL genes were detected in four of 16 isolates (all Oceania and Queensland strains). entC was detected in two EMRSA-15 strains; entA in one Oceania, two WA MRSA-5 and the WA MRSA-1 strain, with entA and entB in the WA MRSA-15 strain. tst was not detected.

CONCLUSIONS

Multiple epidemic strains cause non-multiresistant MRSA bacteraemia. Most patients had risk factors. Oceania and Queensland strains possess the PVL gene.

Staphylococcus aureus bacteraemia: incidence, risk factors and predictors for death in a Brazilian teaching hospital

The aim of this study was to evaluate the incidence of bloodstream infection due to Staphylococcus aureus and the risk factors for mortality. The design was a two-year retrospective cohort of patients more than one year of age with clinically significant and microbiologically documented bloodstream infection due to S. aureus between January 2000 and December 2001 in a tertiary teaching hospital in midwest Brazil. One hundred and eleven patients were identified with clinically significant and microbiologically confirmed bacteraemia due to S. aureus, accounting for an infection rate of five per 1000 admissions. Nosocomial infections represented 83.8% of cases and meticillin-resistant Staphylococcus aureus (MRSA) accounted for 60.2% of cases. Overall mortality due to S. aureus bacteraemia was 35.1%. Infection due to MRSA, severity of clinical status (severe sepsis or septic shock) and inadequate initial antimicrobial therapy were identified by univariate analysis as predictors of mortality. After Cox regression analysis, severity of clinical manifestations [hazard ratio (HR) 6.86, 95% confidence interval (CI) 3.05-15.43] and inadequacy of antimicrobial therapy (HR 2.27, 95%CI 1.02-5.09) remained as risk factors for mortality. Early diagnosis of bacteraemia should be sought in order to implement adequate treatment before the onset of severe sepsis and septic shock, thus reducing the mortality rate.

Molecular characterization of methicillin-resistant Staphylococcus aureus spread by neonates transferred from primary obstetrics clinics to a tertiary care hospital in Korea

OBJECTIVE

To investigate the characteristics and origins of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from neonatal patients admitted to a tertiary care hospital from local and primary care obstetrics clinics.

DESIGN

Molecular typing study.

SETTING

A 1,278-bed tertiary care hospital (Samsung Medical Center) and 2 primary obstetrics clinics in Seoul, Korea.

PATIENTS

The genotypic characteristics of 12 MRSA samples isolated from 11 neonatal patients transferred from 2 primary care obstetrics clinics to a tertiary care hospital were investigated by means of multilocus sequence typing, spa (staphylococcal protein A) typing, and SCCmec typing. Ten MRSA strains isolated from workers and environments in the associated obstetrics clinics were also investigated.

RESULTS

Although the antibiograms of isolates from 2 obstetrics clinics differed, no strain showed multidrug resistance to antimicrobials. Multilocus sequence typing analysis showed that all 22 MRSA isolates analyzed in this study had sequence type 1 (with the allelic profile 1-1-1-1-1-1-1), sequence type 493 (62-1-1-1-1-1-1), or a novel sequence type (25-1-1-1-1-1-1) and that all belonged to a single clonal complex (clonal complex 1). Moreover, they all contained SCCmec type IVA and the identical spa type (UJEBKBP). These genotypic characteristics are similar to those of typical community-associated MRSA strains rather than the hospital-acquired MRSA strains common in Korea.

CONCLUSION

The findings of this study suggest that community-acquired MRSA strains can spread in primary care clinics and be imported into tertiary care settings.

Synthesis and antibacterial activity of novel oxazolidinones bearing N-hydroxyacetamidine substituent

Novel oxazolidinone antibacterials containing N-hydroxyacetamidine moiety are synthesized with the diversity at C-5 terminus. These compounds have been evaluated against a panel of clinically relevant gram-positive and gram-negative pathogens. Most of the analogs in this series displayed activity superior to Linezolid and in vivo efficacies of selected oxazolidinones are also disclosed herein.

Methicillin‐resistant Staphylococcus aureus in the Australian community: an evolving epidemic

OBJECTIVE

To describe antimicrobial resistance and molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) isolated in community settings in Australia.

DESIGN AND SETTING

Survey of S. aureus isolates collected prospectively Australia-wide between July 2004 and February 2005; results were compared with those of similar surveys conducted in 2000 and 2002.

MAIN OUTCOME MEASURES

Up to 100 consecutive, unique clinical isolates of S. aureus from outpatient settings were collected at each of 22 teaching hospital and five private laboratories from cities in all Australian states and territories. They were characterised by antimicrobial susceptibilities (by agar dilution methods), coagulase gene typing, pulsed-field gel electrophoresis, multilocus sequence typing, SCCmec typing and polymerase chain reaction tests for Panton-Valentine leukocidin (PVL) gene.

RESULTS

2652 S. aureus isolates were collected, of which 395 (14.9%) were MRSA. The number of community-associated MRSA (CA-MRSA) isolates rose from 4.7% (118/2498) of S. aureus isolates in 2000 to 7.3% (194/2652) in 2004 (P = 0.001). Of the three major CA-MRSA strains, WA-1 constituted 45/257 (18%) of MRSA in 2000 and 64/395 (16%) in 2004 (P = 0.89), while the Queensland (QLD) strain increased from 13/257 (5%) to 58/395 (15%) (P = 0.0004), and the south-west Pacific (SWP) strain decreased from 33/257 (13%) to 26/395 (7%) (P = 0.01). PVL genes were detected in 90/195 (46%) of CA-MRSA strains, including 5/64 (8%) of WA-1, 56/58 (97%) of QLD, and 25/26 (96%) of SWP strains. Among health care-associated MRSA strains, all AUS-2 and AUS-3 isolates were multidrug-resistant, and UK EMRSA-15 isolates were resistant to ciprofloxacin and erythromycin (50%) or to ciprofloxacin alone (44%). Almost all (98%) of CA-MRSA strains were non-multiresistant.

CONCLUSIONS

Community-onset MRSA continues to spread throughout Australia. The hypervirulence determinant PVL is often found in two of the most common CA-MRSA strains. The rapid changes in prevalence emphasise the importance of ongoing surveillance.

Methicillin-resistant Staphylococcus aureus in elderly care facilities

Among multidrug-resistant bacteria, methicillin-resistant Staphylococcus aureus (MRSA) is of immediate concern, given its potential for pathogenicity and widespread presence in geriatric hospitals. Epidemiological surveys indicate that rates of MRSA cross-transmission are increasing in elderly care facilities. MRSA carriage is far more frequent than MRSA-positive clinical specimens in this setting, and the consequences of these epidemics in terms of morbidity, remain limited within these facilities. However, given that patients are continually transferred between long-term and acute-care facilities, it is reasonable to consider these units together with all other care units and to measure the effect of MRSA on a regional healthcare network, rather than on the scale of a given ward or hospital. With regard to the worldwide increase in morbidity associated with MRSA, the emergence of a community-based disease linked to these strains and the emergence of glycopeptide-resistant strains, the application of a voluntary strategy including screening, isolation and eventually, topical decolonization in elderly care facilities, appears to be an urgent matter of priority, even if this strategy will be expensive.

Epidemiology and outcomes of health-care-associated pneumonia: results from a large US database of culture-positive pneumonia

CONTEXT

Traditionally, pneumonia developing in patients outside the hospital is categorized as community acquired, even if these patients have been receiving health care in an outpatient facility. Accumulating evidence suggests that health-care-associated infections are distinct from those that are truly community acquired.

OBJECTIVE

To characterize the microbiology and outcomes among patients with culture-positive community-acquired pneumonia (CAP), health-care-associated pneumonia (HCAP), hospital-acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP).

DESIGN AND SETTING

A retrospective cohort study based on a large US inpatient database.

PATIENTS

A total of 4,543 patients with culture-positive pneumonia admitted into 59 US hospitals between January 1, 2002, and December 31, 2003, and recorded in a large, multi-institutional database of US acute-care hospitals (Cardinal Health-Atlas Research Database; Cardinal Health Clinical Knowledge Services; Marlborough, MA).

MAIN MEASURES

Culture data (respiratory and blood), in-hospital mortality, length of hospital stay (LOS), and billed hospital charges.

RESULTS

Approximately one half of hospitalized patients with pneumonia had CAP, and > 20% had HCAP. Staphylococcus aureus was a major pathogen in all pneumonia types, with its occurrence markedly higher in the non-CAP groups than in the CAP group. Mortality rates associated with HCAP (19.8%) and HAP (18.8%) were comparable (p > 0.05), and both were significantly higher than that for CAP (10%, all p < 0.0001) and lower than that for VAP (29.3%, all p < 0.0001). Mean LOS varied significantly with pneumonia category (in order of ascending values: CAP, HCAP, HAP, and VAP; all p < 0.0001). Similarly, mean hospital charge varied significantly with pneumonia category (in order of ascending value: CAP, HCAP, HAP, and VAP; all p < 0.0001).

CONCLUSIONS

The present analysis justified HCAP as a new category of pneumonia. S aureus was a major pathogen of all pneumonias with higher rates in non-CAP pneumonias. Compared with CAP, non-CAP was associated with more severe disease, higher mortality rate, greater LOS, and increased cost.

Geographic information system localization of community-acquired MRSA soft tissue abscesses

BACKGROUND

Soft tissue infections with methicillin-resistant Staphylococcus aureus (MRSA) pose an ever-increasing risk to children in the community. Although historically these infections were limited to children with prolonged hospitalization, the authors have seen an increase in community-acquired infections in children without identifiable risk factors. The goal of this study is to determine the incidence of truly community-acquired MRSA soft tissue infections in our community and geographically map regions of increased risk.

METHODS

After obtaining the institutional review board's approval, a retrospective chart review was conducted on 195 patients records who underwent an incision and drainage of soft tissue infections from January 1, 2000, to December 31, 2003. Thirteen patients were excluded from the study because no cultures were taken at the time of incision and drainage.

RESULTS

The most common organism isolated from wound culture was S aureus , 40% (73/182), of which 45% (33/73) were MRSA. Eighty-one percent (27/33) of MRSA infections were in Springfield, 1 of 18 towns represented in the patient population. Geographic information system analysis identified a significant MRSA cluster 1.96 km in diameter within the city of Springfield.

CONCLUSIONS

Geography proved to be a significant risk factor for presenting with MRSA infection. Geographic maps of antibiotic resistance can be used to guide physician antibiotic selection before culture results are available. This has significant implications for the health care provider in proper antibiotic selection within the community.

Emergence of rifampicin resistance in methicillin-resistant Staphylococcus aureus isolated at a Turkish university hospital

Twenty-three rifampicin-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolated in three wards at a university hospital in Turkey between June, 2000, and February, 2001, were studied for their genetic relatedness using a combination of antibiogram, coagulase serotyping, coagulase gene polymorphism (coa-RFLP), and pulsed-field gel electrophoresis (PFGE). They all expressed high-level rifampicin resistance (MIC, >256 mg/L) and were resistant to gentamicin, kanamycin, amikacin, ciprofloxacin, tetracycline, and cadmium acetate and were susceptible to fusidic acid, vancomycin, trimethoprim, and mupirocin. They belonged to the same coagulase serotype (serotype IV) and had identical coa-RFLP patterns. In contrast, PFGE generated nine banding patterns designated type A, types A1-A5, B, C, and D. The most common PFGE pattern (type A) and its subtypes (types A1-A5) were seen in 20 (87%) of the 23 isolates in the three wards. The results demonstrated the acquisition of rifampicin resistance by different MRSA clones and the spread of one clone among patients in the three wards.

Staphylococcus aureus bacteremia, Australia

S. aureus bacteremia in Australia is increasingly caused by MRSA, which is likely to affect empiric prescribing of antimicrobial drugs in suspected cases.

Staphylococcus aureus bacteremia (SAB) is common and increasing worldwide. A retrospective review was undertaken to quantify the number of cases, their place of acquisition, and the proportions caused by methicillin-resistant S. aureus (MRSA) in 17 hospitals in Australia. Of 3,192 episodes, 1,571 (49%) were community onset. MRSA caused 40% of hospital-onset episodes and 12% of community-onset episodes. The median rate of SAB was 1.48/1,000 admissions (range 0.61–3.24; median rate for hospital-onset SAB was 0.7/1,000 and for community onset 0.8/1,000 admissions). Using these rates, we estimate that ≈6,900 episodes of SAB occur annually in Australia (35/100,000 population). SAB is common, and a substantial proportion of cases may be preventable. The epidemiology is evolving, with >10% of community-onset SAB now caused by MRSA. This is an emerging infectious disease concern and is likely to impact on empiric antimicrobial drug prescribing in suspected cases of SAB.

Staphylococcus aureus carriage among participants at the 13th European Congress of Clinical Microbiology and Infectious Diseases

The aim of this study was to measure the rate of Staphylococcus aureus nasal colonization among attendees of the 13th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), particularly with regard to methicillin-resistant (MRSA) strains. The 31.4% rate of Staphylococcus aureus colonization detected among the participants was in line with colonization rates reported previously for healthcare workers. A statistical difference was found between the rates of Staphylococcus aureus carriage in physicians (37.4%) and non-physicians (21.7%) but not between males (35.0%) and females (28.9%). Only one participant (a Belgian physician) was found to carry MRSA. Surprisingly, the rate of methicillin-susceptible Staphylococcus aureus carriage was significantly higher among participants from countries with a low prevalence of MRSA.

[Methicillin-resistant Staphylococcus aureus (MRSA) in rehabilitation and chronic-care-facilities: what is the best strategy?]

BACKGROUND

The risk associated with methicillin-resistant Staphylococcus aureus (MRSA) has been decreasing for several years in intensive care departments, but is now increasing in rehabilitation and chronic-care-facilities (R-CCF). The aim of this study was to use published data and our own experience to discuss the roles of screening for MRSA carriers, the type of isolation to be implemented and the efficiency of chemical decontamination.

DISCUSSION

Screening identifies over 90% of patients colonized with MRSA upon admission to R-CCF versus only 50% for intensive care units. Only totally dependent patients acquire MRSA. Thus, strict geographical isolation, as opposed to "social reinsertion", is clearly of no value. However, this should not lead to the abandoning of isolation, which remains essential during the administration of care. The use of chemicals to decolonize the nose and healthy skin appeared to be of some value and the application of this procedure could make technical isolation unnecessary in a non-negligible proportion of cases.

SUMMARY

Given the increase in morbidity associated with MRSA observed in numerous hospitals, the emergence of a community-acquired disease associated with these strains and the evolution of glycopeptide-resistant strains, the voluntary application of a strategy combining screening, technical isolation and chemical decolonization in R-CCF appears to be an urgent matter of priority.

Community-Associated Methicillin-ResistantStaphylococcus aureus: A Review

Methicillin-resistant Staphylococcus aureus (MRSA) is a common bacterial pathogen responsible for a variety of infections in both children and adults. Treatment of infections caused by this organism is problematic due to its resistance to many drugs. Recent reports of community-associated MRSA (CA-MRSA) infections in patients with no known risk factors have serious public health implications. Therapeutic options for these infections are untested; therefore, the potential exists for high morbidity and mortality. Recently, clinical definitions have been established, and new molecular approaches have allowed investigators to distinguish CA-MRSA more easily from traditional nosocomial-derived MRSA strains. Identifying potential risk factors for CA-MRSA acquisition and fully characterizing the epidemiologic, clinical, and molecular properties of these strains are necessary to provide effective therapeutic guidelines.

Genetic diversity among community methicillin-resistant Staphylococcus aureus strains causing outpatient infections in Australia

Increasing reports of the appearance of novel nonmultiresistant methicillin-resistant Staphylococcus aureus MRSA (MRSA) strains in the community and of the spread of hospital MRSA strains into the community are cause for public health concern. We conducted two national surveys of unique isolates of S. aureus from clinical specimens collected from nonhospitalized patients commencing in 2000 and 2002, respectively. A total of 11.7% of 2,498 isolates from 2000 and 15.4% of 2,486 isolates from 2002 were MRSA. Approximately 54% of the MRSA isolates were nonmultiresistant (resistant to less than three of nine antibiotics) in both surveys. The majority of multiresistant MRSA isolates in both surveys belonged to two strains (strains AUS-2 and AUS-3), as determined by pulsed-field gel electrophoresis (PFGE) and resistogram typing. The 3 AUS-2 isolates and 10 of the 11 AUS-3 isolates selected for multilocus sequence typing (MLST) and staphylococcal chromosomal cassette mec (SCCmec) analysis were ST239-MRSA-III (where ST is the sequence type) and thus belonged to the same clone as the eastern Australian MRSA strain of the 1980s, which spread internationally. Four predominant clones of novel nonmultiresistant MRSA were identified by PFGE, MLST, and SCCmec analysis: ST22-MRSA-IV (strain EMRSA-15), ST1-MRSA-IV (strain WA-1), ST30-MRSA-IV (strain SWP), and ST93-MRSA-IV (strain Queensland). The last three clones are associated with community acquisition. A total of 14 STs were identified in the surveys, including six unique clones of novel nonmultiresistant MRSA, namely, STs 73, 93, 129, 75, and 80slv and a new ST. SCCmec types IV and V were present in diverse genetic backgrounds. These findings provide support for the acquisition of SCCmec by multiple lineages of S. aureus. They also confirm that both hospital and community strains of MRSA are now common in nonhospitalized patients throughout Australia.

Changing epidemiology of methicillin-resistant Staphylococcus aureus in Finland

Data on methicillin-resistant Staphylococcus aureus (MRSA) cases notified to the National Infectious Disease Register (NIDR) and antibiotic resistance profiles of MRSA isolates sent to the national reference laboratory between 1997 and 2002 were analysed. In addition, the diagnostic methods used for MRSA identification in Finnish microbiology laboratories, the number of MRSA screening specimens studied, and the MRSA situation in long-term care facilities in 2001 were reviewed. MRSA cases notified to the NIDR rose from 120 in 1997 to 597 in 2002 (from 2.3 to 11.5 cases per 100,000 population). The increase was greatest in elderly people and outside Helsinki metropolitan area, in the districts where the proportion of non-multiresistant strains was most prominent. The National Committee for Clinical Laboratory Standard's guidelines for the oxacillin disk diffusion test were followed, except for the incubation temperature and time, which may have hindered detection of some MRSA strains. There was a wide geographic variation in the rates of MRSA, but this was not related to screening activity. MRSA isolates from long-term facilities accounted for more than half of the notifications to the NIDR in 2001.

The community prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in older people living in their own homes: implications for treatment, screening and surveillance in the UK

Methicillin-resistant Staphylococcus aureus (MRSA) predominantly affects those over 65 years old. There may be a substantial pool of older people with MRSA in the community. We studied the prevalence in one London general practice, screening 258 older people living in their own home. MRSA (E-MRSA 15) was found in two participants (0.78%). Past history of MRSA was the only significant risk factor. The results of this and other studies suggest that national guidelines recommending early discharge for MRSA carriers have not resulted in widespread community acquisition amongst elderly people living in their own home. Community antibiotic policies for skin and soft-tissue infection do not require amendment. Patients with previous MRSA should be isolated and screened on admission especially to high-risk units.

Natural history of community-acquired methicillin-resistant Staphylococcus aureus colonization and infection in soldiers

BACKGROUND

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging pathogen for which the prevalence, risk factors, and natural history are incompletely understood.

METHODS

In this prospective observational study, we evaluated 812 US Army soldiers to determine the prevalence of and risk factors for CA-MRSA colonization and the changes in colonization rate over time, as well as to determine the clinical significance of CA-MRSA colonization. Demographic data and swab samples from the nares for S. aureus cultures were obtained from participants at the start of their training and 8-10 weeks later. Over this time period, participants were observed prospectively to monitor for soft-tissue infections. S. aureus isolates were characterized by in vitro examination of antibiotic susceptibilities, mecA confirmation, pulsed-field gel electrophoresis, and Panton-Valentine leukocidin (PVL) gene testing.

RESULTS

At the initial sampling, 24 of the participants (3%) were colonized with CA-MRSA, 9 of whom (38%) developed soft-tissue infections during the study period. In contrast, 229 participants (28%) were colonized with methicillin-susceptible S. aureus (MSSA), 8 (3%) of whom developed clinical infections during the same period (relative risk, 10.7; 95% confidence interval, 4.6-25.2; P<.001). At follow-up culture, the CA-MRSA colonization rate dropped to 1.6% without eradication efforts. Previous antibiotic use was a risk factor for CA-MRSA colonization at the initial sampling (P=.03). PVL genes were detected in 66% of 45 recovered CA-MRSA isolates, including all 9 clinical isolates available for analysis. Of subjects hospitalized, 5 of 6 had PVL-positive CA-MRSA infections.

CONCLUSIONS

CA-MRSA colonization with PVL-positive strains was associated with a significant risk of soft-tissue infection, suggesting that CA-MRSA may be more virulent than MSSA. Previous antibiotic use may play a role in CA-MRSA colonization.

Diversity among community isolates of methicillin-resistant Staphylococcus aureus in Australia

Community methicillin-resistant Staphylococcus aureus (CMRSA) strains are being isolated with increasing frequency around the world. In Western Australia CMRSA are endemic in geographically remote communities and have been found to belong to five different contour-clamped homogeneous electric field (CHEF) electrophoretic patterns. Representatives of each of these CHEF patterns have been compared to CMRSA representative of CHEF patterns from other Australian states and New Zealand. With one exception, all of the isolates were nonmultiresistant and were not resistant to many antimicrobial agents other than the beta-lactams. With one exception, which is not believed to be a CMRSA, all of the isolates harbored a beta-lactamase plasmid. Erythromycin resistance was associated with a 2-kb plasmid. One of the beta-lactamase plasmids was found to be able to acquire additional resistance determinants to become a multiple resistance plasmid. There were 10 multilocus sequence types belonging to eight distantly related clonal complexes of S. aureus. One new sequence type was found. Although most of the CMRSA harbored the type IVa SCCmec, a type IV structural variant was found and two new SCCmec types were identified. Protein A gene (spa) typing revealed two new spa types and, with two exceptions, corresponded to multilocus sequence typing. In contrast to other reports on CMRSA, most of the CMRSA strains studied here did not contain the Panton-Valentine leukocidin genes. The results also demonstrate that nonmultiresistant hospital strains such as UK EMRSA-15 may be able to circulate in the community and could be mistaken for CMRSA based on their resistance profiles.

Methicillin-resistant Staphylococcus aureus in community-acquired pyoderma

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen. It can also cause community-acquired infections. Indian reports about MRSA in community-acquired infections are rare.

AIM

To evaluate the rate of MRSA in community-acquired pyoderma and the nasal colonisation with S. aureus in such patients.

METHODS

Two hundred and fifty patients with community-acquired pyoderma, who attended outreach camps around Mangalore, south India between January 2000 and July 2001, were studied. Swabs collected from the skin lesions and anterior nares were inoculated onto blood agar and MacConkey's agar. Antimicrobial sensitivity testing was performed using Kirby-Bauer disk diffusion, agar dilution, and agar screen.

RESULTS

Of 250 pyoderma cases, S. aureus was isolated from 202 (80.8%) patients. Twenty-two (10.9%) S. aureus isolates were methicillin resistant, 179 (88.6%) were resistant to penicillin, and 114 (56.4%) were resistant to erythromycin. S. aureus colonization in the anterior nares was observed in 136 (54.4%) cases, 11.8% of which were MRSA. Antibiograms of clinical isolates of S. aureus matched with nasal isolates in 99 (49%) cases.

CONCLUSION

The emergence of MRSA in the community is a warning. A high nasal carriage rate may contribute to recurrent pyoderma. A correct antimicrobial policy and the avoidance of inappropriate antimicrobial usage are mandatory to reduce the spread of MRSA in the community.

Microbiologic evaluation of skin wounds: alarming trend toward antibiotic resistance in an inpatient dermatology service during a 10-year period

BACKGROUND

Increasing resistance to commonly used antibiotics has been seen for patients with superficial skin wounds and leg ulcers.

OBJECTIVES

We sought to evaluate bacterial isolates from leg ulcers and superficial wounds for resistance to commonly used antibiotics and to compare current data with previous data.

METHODS

We performed a chart review for patients admitted to a tertiary care dermatology inpatient unit from January to December 2001. Comparison was made with 2 previous surveys of the same inpatient service from 1992 and 1996.

RESULTS

Bacterial isolates were cultured from 148 patients, 84% (72 of 86) with leg ulcers and 38% (76 of 202) with superficial wounds. Staphylococcus aureus and Pseudomonas aeruginosa were the most common bacterial isolates in both groups. For patients with leg ulcers, S aureus grew in 67% of isolates (48/72) of which 75% (36/48) were methicillin-resistant (MRSA). Of leg ulcers, 35% (25/72) grew P aeruginosa, which was resistant to quinolones in 56% of cultures (14/25). For patients with superficial wounds, S aureus was isolated in 75% (57/76) and 44% were MRSA (25/57). P aeruginosa grew in 17% of isolates (13/76) and was resistant to quinolones in 18%. We found a marked increase in antibiotic resistance for both leg ulcers and superficial wounds. Over time, MRSA increased in leg ulcers from 26% in 1992 to 75% in 2001. For superficial wounds, MRSA increased from 7% in 1992 to 44% in 2001. P aeruginosa resistance to quinolones in leg ulcers increased from 19% in 1992 to 56% in 2001, whereas for superficial wounds there was no resistance in 1992 and 18% resistance in 2001.

CONCLUSION

Rapid emergence of antibiotic-resistant bacteria continues and is a problem of increasing significance in dermatology. Common pathogenic bacteria, S aureus and P aeruginosa, showed increased resistance to commonly used antibiotics. Selection of antibiotics should be on the basis of local surveillance programs.

Methicillin-Resistant Staphylococcus aureus Infection in the Texas Prison System

Recent reports indicate that correctional facility inmates may be at elevated risk for contracting methicillin-resistant Staphylococcus aureus (MRSA) infection because of overcrowding, poor hygiene, and high rates of diseases causing immunosuppression. The present study of 299,179 Texas inmates who were incarcerated between 1999-2001 indicated an incidence of 12 MRSA infections/1000 person-years. Inmates with circulatory disease, cardiovascular disease, diabetes, end-stage liver disease, end-stage renal disease, human immunodeficiency virus infection or acquired immunodeficiency syndrome, and skin diseases all exhibited elevated rates of MRSA infection.

Carriage of methicillin-resistant Staphylococcus aureus among hospital employees: prevalence, duration, and transmission to households

OBJECTIVE

To assess the prevalence and duration of methicillin-resistant Staphylococcus aureus (MRSA) carriage among hospital employees and transmission to their households.

DESIGN

A point-prevalence survey of MRSA carriage (nasal swabbing) of staff and patients throughout the hospital; a prevalence survey of MRSA carriage in 2 medical wards, with carriers observed to estimate carriage duration; and evaluation of transmission to MRSA-positive workers' families. All MRSA isolates were analyzed by pulsed-field gel electrophoresis. During the study, no MRSA outbreak was detected among hospitalized patients.

SETTING

A 600-bed, public tertiary-care teaching hospital near Paris.

RESULTS

Sixty MRSA carriers were identified among 965 healthcare providers (prevalence, 6.2%; CI95, 4.7%-7.7%). Prevalence was higher in staff from clinical wards than from elsewhere (9.0% vs 2.1%; P < .0001). Identity of isolates from employees and patients varied from 25% in medical wards to 100% in the long-term-care facility. MRSA carriage was identified in 14 employees from 2 medical wards (prevalence, 19.4%; CI95, 10.3%-28.5%). Prevalence depended on the length of service in these wards. Transmission to households was investigated in 10 MRSA-positive workers' families and was found in 4. All isolates from each family were identical.

CONCLUSIONS

Few data are available concerning the prevalence of MRSA carriers among hospital employees in the absence of an outbreak among patients. MRSA transmission between patients and employees likely depends on the frequency and duration of exposure to MRSA-positive patients and infection control measures employed. Frequent transmission of MRSA from colonized healthcare workers to their households was documented.