Emergence of virulent methicillin-resistant Staphylococcus aureus strains carrying Panton-Valentine leucocidin genes in The Netherlands

Antimicrobial Resistance and the Prevalence of the Panton-Valentine Leukocidin Gene among Clinical Isolates of Staphylococcus aureus in Lithuania

This study aimed to determine resistance to antimicrobials of Staphylococcus aureus strains isolated from clinical specimens in Lithuanian hospitals and to identify the genes conferring resistance and virulence. The study was carried out from June 2019 to September 2021. S. aureus strains were isolated from skin, soft tissues, blood, lower respiratory tract, urine and other specimens. Antibiotic susceptibility testing was performed using the disc diffusion method according to EUCAST guidelines. All isolates were analyzed for detection of the ermA, ermC, mecA, mecC, tetK, tetM, and lukF-PV genes by multiplex real-time PCR. The 16S rRNA coding sequence was applied as an internal PCR control. Altogether, 745 S. aureus strains were analyzed. Antimicrobial susceptibility testing revealed that all isolates were susceptible to rifampin and vancomycin. Of the 745 strains, 94.8% were susceptible to tetracycline, 94.5% to clindamycin, and 88.3% to erythromycin. The lowest susceptibility rate was found for penicillin (25.8%). Six percent of the tested strains were methicillin-resistant S. aureus (MRSA). The majority of methicillin-resistant strains were isolated from skin and soft tissues (73.3%), with a smaller portion isolated from blood (17.8%) and respiratory tract (8.9%). The ermC gene was detected in 41.1% of erythromycin-resistant S. aureus strains, whereas ermA was detected in 32.2% of erythromycin-resistant S. aureus strains. 69.2% of tetracycline-resistant S. aureus strains had tetK gene, and 28.2% had tetM gene. 7.3% of S. aureus isolates harbored lukF-PV gene. The frequency of the pvl gene detection was significantly higher in MRSA isolates than in methicillin-susceptible S. aureus isolates (p < 0.0001).

Efficacy and clinical potential of phage therapy in treating methicillin-resistant Staphylococcus aureus (MRSA) infections: A review

Staphylococcus aureus infections have already presented a substantial public health challenge, encompassing different clinical manifestations, ranging from bacteremia to sepsis and multi-organ failures. Among these infections, methicillin-resistant S. aureus (MRSA) is particularly alarming due to its well-documented resistance to multiple classes of antibiotics, contributing significantly to global mortality rates. Consequently, the urgent need for effective treatment options has prompted a growing interest in exploring phage therapy as a potential non-antibiotic treatment against MRSA infections. Phages represent a class of highly specific bacterial viruses known for their ability to infect certain bacterial strains. This review paper explores the clinical potential of phages as a treatment for MRSA infections due to their low toxicity and auto-dosing capabilities. The paper also discusses the synergistic effect of phage-antibiotic combination (PAC) and the promising results from in vitro and animal model studies, which could lead to extensive human clinical trials. However, clinicians need to establish and adhere to standard protocols governing phage administration and implementation. Prominent clinical trials are needed to develop and advance phage therapy as a non-antibiotic therapy intervention, meeting regulatory guidelines, logistical requirements, and ethical considerations, potentially revolutionizing the treatment of MRSA infections.

Examining the Prevalence and Antibiotic Susceptibility of S. aureus Strains in Hospitals: An Analysis of the pvl Gene and Its Co-Occurrence with Other Virulence Factors

S. aureus is a pathogenic bacterium that causesinfections. Its virulence is due to surface components, proteins, virulence genes, SCCmec, pvl, agr, and SEs, which are low molecular weight superantigens. SEs are usually encoded by mobile genetic elements, and horizontal gene transfer accounts for their widespread presence in S. aureus. This study analyzed the prevalence of MRSA and MSSA strains of S. aureus in two hospitals in Greece between 2020–2022 and their susceptibility to antibiotics. Specimens collected were tested using the VITEK 2 system and the PCR technique to detect SCCmec types, agr types, pvl genes, and sem and seg genes. Antibiotics from various classes were also tested. This study examined the prevalence and resistance of S. aureus strains in hospitals. It found a high prevalence of MRSA and that the MRSA strains were more resistant to antibiotics. The study also identified the genotypes of the S. aureus isolates and the associated antibiotic resistances. This highlights the need for continued surveillance and effective strategies to combat the spread of MRSA in hospitals. This study examined the prevalence of the pvl gene and its co-occurrence with other genes in S. aureus strains, as well as their antibiotic susceptibility. The results showed that 19.15% of the isolates were pvl-positive and 80.85% were pvl-negative. The pvl gene co-existed with other genes, such as the agr and enterotoxin genes. The results could inform treatment strategies for S. aureus infections.

Molecular analysis of Panton-Valentine Leucocidin (pvl) gene among MRSA and MSSA isolates

The present study was conducted in order to determine the frequency of pvl gene among the pathogenic and healthy population isolates of Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus (MSSA). For this purpose, nasal swab samples were collected from the healthy individuals (to be used as controls, all the samples were collected irrespective of the sex and age factors), the pathogenic samples were collected from different patients suffering from skin &soft tissue infections caused by S. aureus (to be used as test samples).Both of these population samples were analyzed for the presence of pvl gene. S.aureus were identified through conventional microbiological identification procedures. In the case of normal samples, 70 nasal swabs were collected and only 33 (47%) proved to be S. aureus while 20 pathogenic samples were collected and all (100%) were cleared as S. aureus. For further distribution of samples into MRSA and MSSA, antibiotic susceptibility pattern was checked by using the standard protocols of Kirby-Bauer disc diffusion method. Two antibiotic discs Oxacillin (OX: 1ug) and cefoxitin (FOX: 30ug) were used. Among healthy population, MRSA was found to be 79% (n=26) and MSSA were present as 21% (n= 7). Among pathogenic strains 100% MRSA was detected where n= 20. Detection of pvl gene among the MRSA and MSSA isolates was done by using the uniplex PCR followed by gel electrophoresis. MRSA and MSSA of normal healthy population carried 49% and 7% pvl gene respectively. While, pathogenic MRSA samples carried 46% pvl gene among them. Potentially alarming percentage of pvl gene is present among the normal healthy individuals which indicates a future threat and a major health concern.

Escalation of antimicrobial resistance among MRSA part 1: focus on global spread

INTRODUCTION

Staphylococcus aureus produce numerous virulence factors that influence tissue invasion, cytotoxicity, membrane damage, and intracellular persistence allowing them to be very common human pathogens. S. aureus isolates exhibit considerable diversity though specific genotypes have been associated with antimicrobial resistance (AMR) and toxin gene profiles. MRSA is an important pathogen causing both community-acquired (CA) and healthcare-acquired (HCA) infections. Importantly, over the past several decades, both HCA-MRSA and CA-MRSA have spread all over the globe. Even more concerning is that CA-MRSA clones have disseminated into hospitals and HCA-MRSA have entered the community. Factors that enhance spread of MRSA include: poor antimicrobial stewardship and inadequate infection control. The emergence and spread of multidrug resistant (MDR) MRSA has limited therapeutic options.

AREAS COVERED

The authors discuss the escalation of MRSA, both HCA-MRSA and CA-MRSA across the globe. A literature search of MRSA was performed via PubMed (up to September 2022), using the key words: antimicrobial resistance; β-lactams; community-associated MRSA; epidemiology; infection; multidrug resistance; Staphylococcus aureus.

EXPERT OPINION

Over the past several decades, MRSA has spread all over the globe. We encourage the judicious use of antimicrobials in accordance with antimicrobial stewardship programs along with infection control measures to minimize the spread of MRSA.

Lateral Flow Immunoassay for the Detection of Panton-Valentine Leukocidin in Staphylococcus aureus From Skin and Soft Tissue Infections in the United Arab Emirates

Introduction

Panton Valentine leukocidin (PVL) is a virulence factor which is associated with methicillin sensitive and resistant Staphylococcus aureus (MSSA/MRSA) causing skin and soft tissue infections (SSTI). This study aimed to evaluate a novel lateral flow immunoassay (LFI) for PVL detection in S. aureus cultures and to describe their genotypic characterization.

Methods

The study was carried out from January-August 2020 in Dubai, United Arab Emirates. S. aureus isolates associated with SSTI were tested for PVL detection using LFI. DNA microarray-based assays were used for molecular characterization including detection of pvl genes.

Results

One-hundred thirty-five patients with a clinical diagnosis of SSTIs were recruited. Sixty-six patients received antibiotics, mostly beta lactams (n=36) and topical fusidic acid (n=15). One-hundred twenty-nine isolates (MRSA: n=43; MSSA: n=86) were tested by LFI and DNA microarrays. All 76 (58.9%) isolates which were unambiguously negative for the PVL in LFI were negative for pvl genes using the DNA microarray. All the LFI PVL positive isolates (n=53) had pvl genes detected. This translates into 100% each for sensitivity, specificity, positive and negative predictive values for the LFI. The LFI typically takes about 15 min inclusive of a 10 min incubation period. Predominant S. aureus clonal complexes (CC) were CC30 (n=18), CC22 (n=13), CC5 (n=12), CC1 (n=11), CC152 (n=8), CC15 (n=7); CC97 (n=7); CC8 and CC20 (n=6 each). Among MRSA, the proportion of pvl-positives (35/43; 81%) was higher than among MSSA (n/N=18/86; 21%). The fusidic acid resistance gene fusC was detected in 14 MRSA (33%) compared to 8 MSSA (9%). A co-carriage of fusC and pvl genes was present in 7 MRSA and in one MSSA.

Conclusion

LFI shows excellent diagnostic accuracy indices for rapid identification of PVL in MSSA/MRSA in a setting with high prevalence of pvl^+ve strains. The high occurrence of pvl and fusC genes in MRSA strains causing SSTI is of concern and needs constant surveillance.

Prevalence and association of Panton-Valentine Leukocidin gene with the risk of sepsis in patients infected with Methicillin Resistant Staphylococcus aureus

BACKGROUND

Panton-Valentine Leukocidin (PVL), is one of the virulence gene expressed by Methicillin Resistant Staphylococcus aureus (MRSA) and is known to be associated with severe form of community acquired MRSA infection. The aim of this study is to investigate its prevalence in our setting and patient's clinical outcome.

METHODS

A cross sectional study involve retrospective record review were done involving 90 MRSA positive isolates between November 2016 and October 2017. Multiplex PCR was performed to detect femA, mecA and PVL genes. Clinical presentation and outcomes of patients were reviewed and presented as descriptive analysis.

RESULTS

All of the 90 MRSA isolates included in this study were positive for femA and mecA genes following PCR. PVL gene was detected in 20% (n = 18) of the isolates of which 61.1% (n = 11) were community acquired infections and 38.8% (n = 7) were hospital acquired. Case distribution from community acquired infections include patients with skin and soft tissue infections (33.3%, n = 6), infected diabetic foot ulcers (16.7%, n = 3), and one patient each (5.5%, n = 1) for community acquired pneumonia and meningitis. Half of the PVL positive MRSA cases (50%, n = 9) were having sepsis and four of them succumbed to death due to severe infection.

CONCLUSION

This study shows a high prevalence of PVL positive MRSA infection in our population. Skin and soft tissue infections accounting for the major sources. In addition, the presence of the PVL gene is associated with increased risk for developing sepsis.

Molecular Characterization and Pathogenicity of Staphylococcus aureus Isolated from Benin-City, Nigeria

While numerous studies examine the epidemiology and molecular characterization of Staphylococcus aureus in most developed countries, the detailed molecular characterization and molecular epidemiology of S. aureus strains and clones in Africa is lacking. We determined the molecular epidemiology and virulence of 81 non-duplicate isolates of S. aureus from Benin-City, Nigeria, collected during January–July 2016, and compared with global strains. Forty-seven isolates (58.0%) were found to be methicillin-sensitive Staphylococcus aureus (MSSA), while 34 (42.0%) were methicillin-resistant Staphylococcus aureus (MRSA). ST152-MSSA (24.7%) and ST7-MRSA-V (19.8%) were the dominant groups identified, which were not genetically related to global predominant strains, but rather exhibited regional dominance. An interesting finding of the study was the presence of highly related strains in the region, which differed primarily in their methicillin resistance gene carriage, staphylococcal cassette chromosome mec (SCCmec), with 99.4–99.7% relatedness between the genomes of the strains within the MRSA–MSSA pairs. This suggests that the strains within a pair are experiencing gain or loss of SCCmec within local conditions, with evolution continuing to diversify the strains to a small degree. This study represents the most comprehensive genetic and virulence study of S. aureus in Nigeria.

Methicillin-Resistant Staphylococcus aureus ST80 Clone: A Systematic Review

This review assessed the molecular characterization of the methicillin-resistant Staphylococcus aureus (MRSA)-ST80 clone with an emphasis on its proportion of total MRSA strains isolated, PVL production, spa-typing, antibiotic resistance, and virulence. A systematic review of the literature was conducted on MRSA-ST80 clone published between 1 January 2000 and 31 August 2019. Citations were chosen for a review of the full text if we found evidence that MRSA-ST80 clone was reported in the study. For each isolate, the country of isolation, the sampling period, the source of isolation (the type of infection, nasal swabs, or extra-human), the total number of MRSA strains isolated, number of MRSA-ST80 strains, antibiotic resistance patterns, PVL production, virulence genes, and spa type were recorded. The data from 103 articles were abstracted into an Excel database. Analysis of the data showed that the overall proportion of MRSA-ST80 has been decreasing in many countries in recent years. The majority of MRSA-ST80 were PVL positive with spa-type t044. Only six reports of MRSA-ST80 in extra-human niches were found. This review summarizes the rise of MRSA-ST80 and the evidence that suggests that it could be in decline in many countries.

A genomic infection control study for Staphylococcus aureus in two Ghanaian hospitals

Background

Whole genome sequencing analysis (WGSA) provides the best resolution for typing of bacterial isolates and has the potential for identification of transmission pathways. The aim of the study was to apply WGSA to elucidate the possible transmission events involved in two suspected Staphylococcus aureus hospital outbreaks in Ghana and describe genomic features of the S. aureus isolates sampled in the outbreaks.

Methods

The study was carried out at Korle-Bu Teaching Hospital and Lekma Hospital where the suspected outbreaks occurred in 2012 and 2015, respectively. The S. aureus isolates collected from the two hospitals were from three sources including carriage, invasive disease, and the environment. Whole genome sequencing of the S. aureus isolates was performed and the sequence reads were mapped to the S. aureus reference genome of strain USA300_FPR3757. A maximum-likelihood phylogenetic tree was reconstructed. Multilocus sequence typing together with the analysis of antimicrobial resistance and virulence genes were performed by short read mapping using the SRST2.

Results

The S. aureus isolates belonged to diverse sequence types (STs) with ST15 and ST152 most common. All isolates carried the blaZ gene, with low prevalence of tetK and dfrG genes also observed. All isolates were mecA negative. The pvl genes were common and observed in distinct lineages that revealed diverse Sa2int phages. At Korle-Bu Teaching Hospital, the genomics data indicated several transmission events of S. aureus ST15 involving contamination of various surfaces in the pediatric emergency ward where the outbreak occurred.

Conclusion

The pattern of dissemination of the ST15 clone in the emergency ward of Korle-Bu Teaching Hospital highlights a basic problem with disinfection of environmental surfaces at the hospital. Diverse phage population rather than a single highly transmissible phage type likely mediates the high prevalence of pvl genes among the S. aureus isolates.

Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

Antibiotic Resistance Trends in Methicillin-Resistant Staphylococcus aureus Isolated in Kuwait Hospitals: 2011-2015

OBJECTIVE

The aim of this study was to determine antibiotic resistance trends and carriage of staphylococcal cassette chromosome mec (SCCmec) genetic elements in methicillin-resistant Staphylococcus aureus (MRSA) isolated in Kuwait hospitals to ascertain whether they were healthcare associated (HA-MRSA) or community associated (CA-MRSA).

MATERIALS AND METHODS

In total, 6,922 MRSA isolates obtained from different clinical samples were tested for resistance to antibiotics, urease production, and carriage of SCCmec elements.

RESULTS

All MRSA isolates were susceptible to linezolid, vancomycin, and teicoplanin. However, some isolates were resistant to kanamycin (2,979; 43%), ciprofloxacin (2,955; 42.7%), erythromycin and clindamycin (2,935; 42.4%), fusidic acid (2,858; 41.2%), gentamicin (2,665; 38.5%), tetracycline (2,652; 38.3%), and trimethoprim (2,324; 33.5%). Whereas the prevalence of resistance to most antibiotics showed annual variations, those resistant to chloramphenicol and rifampicin increased from 2.6 and 0.1% to 9.6 and 1.6%, respectively, and high-level mupirocin resistance declined from 9.3% in 2011 to 3.6% in 2015. In total, 3,244 (53.9%) of the isolates carried SCCmec IV followed by SCCmec III (1,737; 28.8%) and SCCmec V (890; 14.8%). SCCmec I (21; 0.3%) and II (79; 0.8%) occurred sporadically. A total of 3,651 (60.7%) of the isolates belonged to the CA-MRSA genotype and 2,290 isolates (38.1%) were identified as HA-MRSA.

CONCLUSION

This study demonstrates changes in antibiotic resistance patterns of MRSA over time and reinforces the value of surveillance in detecting such changes for the benefit of infection control and patient management.

Antimicrobial Resistance and Molecular Characterization of Staphylococcus aureus Causing Childhood Pneumonia in Shanghai

Staphylococcus aureus or methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen causing pneumonia among children. To estimate the prevalence and molecular properties of S. aureus in children pneumonia in Shanghai, China, 107 hospitalized children with S. aureus pneumonia from two children's hospitals from January 2014 through June 2015 were studied. S. aureus isolates from the respiratory specimens were characterized by antimicrobial susceptibility, agr typing, toxin genes, multilocus sequence typing (MLST), spa, and SCCmec typing. Fifty-eight (54.2%, 58/107) were MSSA (methicillin-susceptible Staphylococcus aureus) and 49 (45.8%, 49/107) were MRSA. No isolates were found resistant to teicoplanin, sulfamethoxazole/trimethoprim, rifampicin, quinupristin/dalfopristin, linezolid, or vancomycin. However, these isolates showed high resistant rates to erythromycin, fosfomycin-trometamol and clindamycin. The agrI (87/107, 81.3%) was the most common agr allele, followed by agrIII(10/107, 9.3%), agrII(9/107, 8.4%), and agrIV(1/107, 0.9%). Six pvl-positive isolates (3 MRSA and 3 MSSA) and 7 isolates of livestock associated clone ST398 (4 MRSA, 3 MSSA) were identified. CC59 was found in 35 isolates (33 MRSA and 2 MSSA), constituting majority of MRSA (33/49, 67.35%). The dominant CC were CC59 (32.7%), CC188 (13.1%), CC7 (12.1%) and CC398 (9.3%) while t172 (16.8%), t189 (12.1%), t437 (9.3%), and t091 (9.3%) were the most common spa types. In conclusion, more particular concern should appeal to ST59-SCCmecIV-t172/t437 as it is the most common epidemic clone causing pneumonia among children in Shanghai.

Genomic insights into the emergence and spread of international clones of healthcare-, community- and livestock-associated meticillin-resistant Staphylococcus aureus: Blurring of the traditional definitions

The evolution of meticillin-resistant Staphylococcus aureus (MRSA) from meticillin-susceptible S. aureus has been a result of the accumulation of genetic elements under selection pressure from antibiotics. The traditional classification of MRSA into healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA) is no longer relevant as there is significant overlap of identical clones between these groups, with an increasing recognition of human infection caused by livestock-associated MRSA (LA-MRSA). Genomic studies have enabled us to model the epidemiology of MRSA along these lines. In this review, we discuss the clinical relevance of genomic studies, particularly whole-genome sequencing, in the investigation of outbreaks. We also discuss the blurring of each of the three epidemiological groups (HA-MRSA, CA-MRSA and LA-MRSA), demonstrating the limited relevance of this classification.

Comparison of an ST80 MRSA strain from the USA with European ST80 strains

OBJECTIVES

A number of community-acquired MRSA (CA-MRSA) clonal lineages dominate worldwide. ST80 was dominant in Europe and has increasingly been described from the Middle East. Here we report the whole genome sequence of the first ST80 CA-MRSA from the USA.

METHODS

CA-MRSA isolate S0924 was obtained from a patient admitted to Cook County Hospital (Chicago, IL, USA) who came from Syria; the isolate belonged to spa type t044 and ST80. The whole genome sequence of S0924 was determined and compared with three previously published whole genome sequences of ST80 CA-MRSA from Europe and a newly sequenced ST80 CA-MRSA from the Netherlands (S1475).

RESULTS

Based on spa typing, SCCmec type and virulence gene profile, this US ST80 isolate is indistinguishable from the European CA-MRSA ST80 clone. SNP analysis within the conserved core genome showed clear differences between the strains with up to 144 SNPs differing between S0924 and strain S1800, an ST80 MRSA from Greece. The gene content showed 21 regions of difference between the US and European isolates, although these were largely restricted to mobile genetic elements. Phylogenetic reconstruction indicated that the European strains were more closely related to each other than to the US strain. The SNP data suggest that a common ancestor existed around two decades ago, indicating that the US and European ST80 strains are clonally linked.

CONCLUSIONS

These data combined with the country of origin of the patient suggest that ST80 S0924 was probably relatively recently introduced into the USA from Syria.

Insights into nasal carriage of Staphylococcus aureus in an urban and a rural community in Ghana

The epidemiology of Staphylococcus aureus in the community in Ghana was never investigated prior to this study. The aims of the study were: i) to assess prevalence of nasal S. aureus carriage in Ghanaian people living in an urban and a rural area, and ii) to identify phenotypic and genotypic traits of strains isolated from the two communities. Nasal swabs were collected from healthy individuals living in an urban community situated in the suburb of the capital city, Accra (n = 353) and in a rural community situated in the Dangme-West district (n = 234). The overall prevalence of nasal carriage was 21% with a significantly higher prevalence in the urban (28%) than in the rural community (11%) (p<0.0001). The levels of antimicrobial resistance were generally low (<5%) except for penicillin (91%) and tetracycline (25%). The only two (0.3%) MRSA carriers were individuals living in the urban area and had been exposed to hospitals within the last 12 months prior to sampling. Resistance to tetracycline (p = 0.0009) and presence of Panton-Valentine leukocidin (PVL) gene (p = 0.02) were significantly higher among isolates from the rural community compared to isolates from the urban community. Eleven MLST clonal complexes (CC) were detected based on spa typing of the 124 S. aureus isolates from the two communities: CC8 (n = 36), CC152 (n = 21), CC45 (n = 21), CC15 (n = 18), CC121 (n = 6), CC97 (n = 6), CC30 (n = 5), CC5 (n = 5), CC508 (n = 4), CC9 (n = 1), and CC707 (n = 1). CC8 and CC45 were less frequent in the rural area than in the urban area (p = 0.02). These results reveal remarkable differences regarding carriage prevalence, tetracycline resistance, PVL content and clonal distribution of S. aureus in the two study populations. Future research may be required to establish whether such differences in nasal S. aureus carriage are linked to socio-economic differences between urban and rural communities in this African country.

Staphylococcal bicomponent pore-forming toxins: targets for prophylaxis and immunotherapy

Staphylococccus aureus represents one of the most challenging human pathogens as well as a common colonizer of human skin and mucosal surfaces. S. aureus causes a wide range of diseases from skin and soft tissue infection (SSTI) to debilitating and life-threatening conditions such as osteomyelitis, endocarditis, and necrotizing pneumonia. The range of diseases reflects the remarkable diversity of the virulence factors produced by this pathogen, including surface antigens involved in the establishment of infection and a large number of toxins that mediate a vast array of cellular responses. The staphylococcal toxins are generally believed to have evolved to disarm the innate immune system, the first line of defense against this pathogen. This review focuses on recent advances on elucidating the biological functions of S. aureus bicomponent pore-forming toxins (BCPFTs) and their utility as targets for preventive and therapeutic intervention. These toxins are cytolytic to a variety of immune cells, primarily neutrophils, as well as cells with a critical barrier function. The lytic activity of BCPFTs towards immune cells implies a critical role in immune evasion, and a number of epidemiological studies and animal experiments relate these toxins to clinical disease, particularly SSTI and necrotizing pneumonia. Antibody-mediated neutralization of this lytic activity may provide a strategy for development of toxoid-based vaccines or immunotherapeutics for prevention or mitigation of clinical diseases. However, certain BCPFTs have been proposed to act as danger signals that may alert the immune system through an inflammatory response. The utility of a neutralizing vaccination strategy must be weighed against such immune-activating potential.

Recurrent furunculosis - challenges and management: a review

Furunculosis is a deep infection of the hair follicle leading to abscess formation with accumulation of pus and necrotic tissue. Furuncles appear as red, swollen, and tender nodules on hair-bearing parts of the body, and the most common infectious agent is Staphylococcus aureus, but other bacteria may also be causative. In some countries, methicillin resistant S. aureus is the most common pathogen in skin and soft tissue infections which is problematic since treatment is difficult. Furunculosis often tends to be recurrent and may spread among family members. Some patients are carriers of S. aureus and eradication should be considered in recurrent cases. Solitary lesions should be incised when fluctuant, whereas patients with multiple lesions or signs of systemic disease or immunosuppression should be treated with relevant antibiotics. The diagnostic and therapeutic approach to a patient suspected of staphylococcosis should include a thorough medical history, clinical examination, and specific microbiological and biochemical investigations. This is particularly important in recurrent cases where culture swabs from the patient, family members, and close contacts are mandatory to identify and ultimately control the chain of infection. Focus on personal, interpersonal, and environmental hygiene issues is crucial to reduce the risk of contamination and recurrences.

Spread of Community-Acquired Methicillin-ResistantStaphylococcus aureus(MRSA) in Hospitals in Taipei, Taiwan in 2005, and Comparison of Its Drug Resistance with Previous Hospital-Acquired MRSA

Panton-Valentine leucocidin (PVL)-positive methicillin-resistant Staphylococcus aureus (PVL+ MRSA) is an emerging pathogen in the community worldwide. The incidence of PVL+ MRSA in Taipei, Taiwan was 23.3% for hospital MRSA. PVL+ MRSA was isolated from both outpatients and inpatients. Some PVL+ (mecA+) strains (36.8%) showed low MIC values (<or=2 microg/ml) to oxacillin. A major PVL+ MRSA resistance pattern was oxacillin and clindamycin resistance (81%). There was no multidrug resistance over three drugs, in contrast to patient PVL- MRSA with resistance to five drugs as a major resistance pattern. The majority of PVL+ MRSA belonged to multilocus sequence (ST) type 59, while PVL+ MRSA belonged to ST239, ST59 and ST5. The data suggests that although PVL+ CA-MRSA is isolated at a high incidence from hospitals in Taipei, the drug resistance is mostly selected in the community and less prominent compared with previous PVL- hospital-acquired MRSA.

Characterization and comparison of 2 distinct epidemic community-associated methicillin-resistant Staphylococcus aureus clones of ST59 lineage

Sequence type (ST) 59 is an epidemic lineage of community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) isolates. Taiwanese CA-MRSA isolates belong to ST59 and can be grouped into 2 distinct clones, a virulent Taiwan clone and a commensal Asian-Pacific clone. The Taiwan clone carries the Panton–Valentine leukocidin (PVL) genes and the staphylococcal chromosomal cassette mec (SCCmec) V_T, and is frequently isolated from patients with severe disease. The Asian-Pacific clone is PVL-negative, carries SCCmec IV, and a frequent colonizer of healthy children. Isolates of both clones were characterized by their ability to adhere to respiratory A549 cells, cytotoxicity to human neutrophils, and nasal colonization of a murine and murine sepsis models. Genome variation was determined by polymerase chain reaction of selected virulence factors and by multi-strain whole genome microarray. Additionally, the expression of selected factors was compared between the 2 clones. The Taiwan clone showed a much higher cytotoxicity to the human neutrophils and caused more severe septic infections with a high mortality rate in the murine model. The clones were indistinguishable in their adhesion to A549 cells and persistence of murine nasal colonization. The microarray data revealed that the Taiwan clone had lost the ø3-prophage that integrates into the β-hemolysin gene and includes staphylokinase- and enterotoxin P-encoding genes, but had retained the genes for human immune evasion, scn and chps. Production of the virulence factors did not differ significantly in the 2 clonal groups, although more α-toxin was expressed in Taiwan clone isolates from pneumonia patients. In conclusion, the Taiwan CA-MRSA clone was distinguished by enhanced virulence in both humans and an animal infection model. The evolutionary acquisition of PVL, the higher expression of α-toxin, and possibly the loss of a large portion of the β-hemolysin-converting prophage likely contribute to its higher pathogenic potential than the Asian-Pacific clone.

Molecular epidemiology of community-associated meticillin-resistant Staphylococcus aureus in Asia

In Asia, most reports on the epidemiology of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) are from developed countries, with few data from resource-limited countries, not because of low actual prevalence, but probably because of scarce diagnostic facilities. The rate of MRSA in all community-associated S. aureus infections in Asian countries ranges from 2·5% to 39%. Unlike the predominance of USA300-sequence type (ST) 8 staphylococcal cassette chromosome mec (SCCmec) type IV in the USA, the molecular epidemiology of CA-MRSA in Asia is characterised by clonal heterogeneity, similar to that in Europe. The emergence of CA-MRSA is a threat in both community and hospital settings because such strains are now more prevalent than are health-care-associated MRSA (HA-MRSA) strains. Many epidemic clones are in circulation in Asia and with scarce data available, concern has arisen that CA-MRSA could have devastating results if it becomes epidemic in resource-poor regions. The epidemiology of CA-MRSA in Asia is closely linked with the health of both developing and developed countries. The present situation of CA-MRSA in Asia is important not only for local public health, but also to provide a better understanding of the successful epidemic clones of this global pathogen.

Use of Triplex PCR for Rapid Detection of PVL and Differentiation of MRSA from Methicillin Resistant Coagulase Negative Staphylococci

INTRODUCTION

Methicillin-Resistant Staphylococcus aureus (MRSA) has become a major public health problem in both hospitals and communities. Panton - Valentine Leucocidin (PVL) has been reported to be an important marker for the highly pathogenic community acquired S. aureus infections. A rapid detection of these MRSA is very important for its treatment. The specific detection of MRSA is always a problem due to the prevalence of methicillin resistance among the coagulase negative Staphylococci. Hence, this study was done to develop a rapid triplex PCR for the detection of PVL positive MRSA and for the simultaneous differentiation of MRSA from Coagulase Negative Staphylococci (CoNS).

MATERIALS AND METHODS

We developed a triplex PCR for the specific detection of PVL positive Community Acquired (CA) - MRSA and for its simultaneous differentiation from the coagulase negative Staphylococci. We used PCR for targeting the fem A gene which is specific for S. aureus, mecA which is specific for methicillin-resistance and luk - PV which is specific for the PVL toxin. The method was evaluated with a total of 100 clinical isolates of Staphylococcus spp.

RESULTS

The triplex PCR was successfully standardized by using the reference strains and it was evaluated by using clinical strains. The method was found to be rapid, highly sensitive (100%), specific (99%) and cost effective.

CONCLUSION

Triplex PCR can be used as a diagnostic tool for the detection of the highly pathogenic strains of CA-MRSA.

Community-acquired methicillin-resistant Staphylococcus aureus: the new face of an old foe?

The burden of infections caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is increasing among different patient populations globally. As CA-MRSA has become established in healthcare facilities, the range of infections caused by them has also increased. Molecular characterization of CA-MRSA isolates obtained from different centers has revealed significant diversity in their genetic backgrounds. Although many CA-MRSA strains are still susceptible to non-β-lactam antibiotics, multiresistance to non-β-lactam agents has emerged in some clones, posing substantial problems for empirical and directed therapy of infections caused by these strains. Some CA-MRSA clones have acquired the capacity to spread locally and internationally. CA-MRSA belonging to ST80-MRSA-IV and ST30-MRSA-IV appear to be the dominant clones in the countries of the Gulf Cooperation Council (GCC). The emergence of pandemic CA-MRSA clones not only limits therapeutic options but also presents significant challenges for infection control. Continued monitoring of global epidemiology and emerging drug resistance data is critical for the effective management of these infections.

Community-associated methicillin-resistant Staphylococcus aureus necrotizing pneumonia in a healthy neonate

The number of cases of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) pneumonia has increased since the late 1990s, with skin and soft tissue infections predominant among neonates. Herein, we present a rare case of CA-MRSA necrotizing pneumonia with empyema following respiratory syncytial virus (RSV) infection in a healthy neonate. Despite prompt vancomycin treatment, the disease worsened and finally we had to perform pneumonectomy. This case highlights the possibility of emerging CA-MRSA-related invasive disease among neonates.

Frequency and clinical association of Panton-Valentine leukocidin-positive Staphylococcus aureus isolates: a study from Kuwait

OBJECTIVE

This study was undertaken to determine the frequency of Panton-Valentine leukocidin (PVL)-producing Staphylococcus aureus among strains isolated in our laboratory and to study the association of PVL-positive strains with clinical disease.

MATERIALS AND METHODS

A total of 291 S. aureus isolates obtained from different clinical specimens from June 1, 2009, to March 31, 2010, at the Farwania Hospital Laboratory were investigated for antimicrobial susceptibility, carriage of genes for PVL, and SCCmec elements. Antimicrobial susceptibility testing was performed by standard methods. The presence of mecA genes for PVL SCCmec typing was determined by PCR.

RESULTS

Of the 291 S. aureus isolates, 89 (30.6%) were methicillin-resistant S. aureus (MRSA), whereas 202 (69.4%) were methicillin susceptible (MSSA). Genes for PVL were detected in 13 (14.6%) and 24 (12.0%) of the MRSA and MSSA isolates, respectively. The majority of the PVL-producing MRSA and MSSA were isolated from 12 (30.7%) and 19 (21.8%) cases of skin and soft tissue infections (SSTI), respectively. Although both MSSA and MRSA strains were uniformly susceptible to rifampicin, teicoplanin, and vancomycin, multidrug resistance was observed among PVL-producing and nonproducing MRSA isolates. Both MRSA types carried SCCmec type III, IV, IVc, and V genetic elements.

CONCLUSION

This study revealed the presence of genes for PVL in both MSSA and MRSA, associated mostly with SSTI and respiratory tract infections, supporting previous observations that PVL production is widespread among S. aureus strains obtained from different clinical sources.

Prevalence of community-associated meticillin-resistant Staphylococcus aureus and Panton-Valentine leucocidin-positive S. aureus in general practice patients with skin and soft tissue infections in the northern and southern regions of The Netherlands

The purpose of this investigation was to determine the prevalence of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) and Panton-Valentine leucocidin (PVL)-positive S. aureus in general practice (GP) patients with skin and soft tissue infections (SSTI) in the northern (Groningen and Drenthe) and southern (Limburg) regions of The Netherlands. Secondary objectives were to assess the possible risk factors for patients with SSTI caused by S. aureus and PVL-positive S. aureus using a questionnaire-based survey. From 2007 to 2008, wound and nose cultures were obtained from patients with SSTI in general practice. These swabs were analysed for the presence of S. aureus and the antibiotic susceptibility was determined. The presence of the PVL toxin gene was determined by polymerase chain reaction (PCR) and the genetic background with the use of spa typing. A survey was performed to detect risk factors for S. aureus infection and for the presence of PVL toxin.S. aureus was isolated from 219 out of 314 (70%) patients with SSTI, of which two (0.9%) patients were MRSA-positive. In 25 (11%) patients, the PVL toxin gene was found. A higher prevalence of PVL-positive S. aureus of patients with SSTI was found in the northern region compared to the south (p < 0.05). Regional differences were found in the spa types of PVL-positive S. aureus isolates, and for PVL-negative S. aureus isolates, the genetic background was similar in both regions. The prevalence of CA-MRSA in GP patients with SSTI in The Netherlands is low. Regional differences were found in the prevalence of PVL-positive S. aureus isolates from GP patients with SSTI. Household contacts having similar symptoms were found to be a risk factor for SSTI with S. aureus.

Panton-Valentine leukocidin associated staphylococcal disease: a cross-sectional study at a London hospital, England

Recently, there has been international concern at the rapid emergence of highly pathogenic strains of Staphylococcus aureus associated with a toxin called Panton-Valentine leukocidin (PVL). In the UK, these strains are considered to be rare and mainly severe. We estimate the proportion of staphylococcal infections that are caused by strains containing the PVL genes, and describe risk factors for these infections. Three hundred and ninety consecutive S. aureus clinical isolates, submitted for routine diagnostic purposes were screened for PVL genes. Risk factors for infection were identified from the patient medical record. 9.7% (95% CI 7.0-13.1%) of clinical isolates and 20.8% of skin and soft tissue specimens contained the genes for PVL. Methicillin-resistant S. aureus with PVL was rare (0.8% of all isolates) but PVL with methicillin-sensitive S. aureus was common (9.0% of all specimens). PVL infection was more frequent in males (OR 3.0, 95% CI 1.3-7.0), and in young adults aged 20-39 years (OR 3.7, 95% CI 1.3-10.4). Over half of PVL positive S. aureus infections originated in patients based in the community. Community-onset PVL-associated disease is common in the UK and mainly causes skin and soft tissue infections that do not require admission to hospital. Consideration should be given to current infection control strategy, which advocates household contact screening and decolonization on the assumption that PVL-associated disease is rare.

Community-associated meticillin-resistant Staphylococcus aureus in children in Taiwan, 2000s

Meticillin-resistant Staphylococcus aureus (MRSA) has been increasingly identified as the major cause of community-associated (CA) infections in previously healthy hosts since the late 1990s. CA-MRSA strains were recognised as a novel pathogen that is genetically different from healthcare-associated MRSA, and five major epidemic clones have been identified worldwide. In Taiwan, a significantly increasing rate of MRSA carriage and infection amongst healthy subjects was observed in the past decade. Up to 9.5% of healthy Taiwanese children carried MRSA in the nares and >50% of paediatric CA S. aureus infections were MRSA. The adult population was also affected, but this was relatively limited. The majority of CA-MRSA isolates in Taiwan belonged to the sequence type (ST) 59 lineage, defined by multilocus sequence typing, and were multiresistant to non-β-lactams. The clone of ST59 lineage can be further classified into at least two major clones by pulsed-field gel electrophoresis (PFGE) typing, staphylococcal chromosomal cassette mec (SCCmec) elements and Panton-Valentine leukocidin (PVL) genes. The clone characterised as ST59/PFGE type C/SCCmec IV/PVL-negative was prevalent amongst the colonising isolates, whereas ST59/PFGE type D/SCCmec V(T)/PVL-positive was prevalent amongst the clinical isolates. Evidence suggested that the ST59 CA-MRSA clone was not only circulating in Taiwan but also in other areas of the world. In this article, the current status of CA-MRSA in Taiwan was extensively reviewed. The information provided here is not only important for local public health but can also enhance a general understanding of the successful epidemic clones of CA-MRSA worldwide.

Fusidic acid and clindamycin resistance in community-associated, methicillin-resistant Staphylococcus aureus infections in children of Central Greece

Introduction

In Greece, fusidic acid and clindamycin are commonly used for the empiric therapy of suspected staphylococcal infections.

Methods

The medical records of children examined at the outpatient clinics or admitted to the pediatric wards of the University General Hospital of Larissa, Central Greece, with community-associated staphylococcal infections from January 2003 to December 2009 were reviewed.

Results

Of 309 children (0-14 years old), 21 (6.8%) had invasive infections and 288 (93.2%) skin and soft tissue infections (SSTIs). Thirty-five patients were ≤30 days of age. The proportion of staphylococcal infections caused by a community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) isolate increased from 51.5% (69 of 134) in 2003-2006 to 63.4% (111 of 175) in 2007-2009 (P = 0.037). Among the CA-MRSA isolates, 88.9% were resistant to fusidic acid, 77.6% to tetracycline, and 21.1% to clindamycin. Clindamycin resistance increased from 0% (2003) to 31.2% (2009) among the CA-MRSA isolates (P = 0.011). Over the 7-year period, an increase in multidrug-resistant CA-MRSA isolates was observed (P = 0.004). One hundred and thirty-one (93.6%) of the 140 tested MRSA isolates were Panton-Valentine leukocidin-positive. Multilocus sequence typing of 72 CA-MRSA isolates revealed that they belonged to ST80 (n = 61), ST30 (n = 6), ST377 (n = 3), ST22 (n = 1), and ST152 (n = 1). Resistance to fusidic acid was observed in ST80 (58/61), ST30 (1/6), and ST22 (1/1) isolates.

Conclusion

In areas with high rate of infections caused by multidrug-resistant CA-MRSA isolates, predominantly belonging to the European ST80 clone, fusidic acid and clindamycin should be used cautiously as empiric therapy in patients with suspected severe staphylococcal infections.

Investigation of Panton-Valentine leukocidin expressing Staphylococcus aureus colonization among children in a child care center

The presence of Panton-Valentine leukocidin expressing Staphylococcus aureus colonization was investigated with a qualitative nucleic acid hybridization assay among 122 children and 19 staff in a child care center. Genotyping of 5 Panton-Valentine leukocidin-positive isolates by pulsed-field gel electrophoresis revealed that one child and a teacher from the same class were colonized with the clonally related strains. This finding allowed us to suggest that close contact with colonized people is a risk factor for being colonized.

Community-acquired methicillin-resistant Staphylococcus aureus: community transmission, pathogenesis, and drug resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is able to persist not only in hospitals (with a high level of antimicrobial agent use) but also in the community (with a low level of antimicrobial agent use). The former is called hospital-acquired MRSA (HA-MRSA) and the latter community-acquired MRSA (CA-MRSA). It is believed MRSA clones are generated from S. aureus through insertion of the staphylococcal cassette chromosome mec (SCCmec), and outbreaks occur as they spread. Several worldwide and regional clones have been identified, and their epidemiological, clinical, and genetic characteristics have been described. CA-MRSA is likely able to survive in the community because of suitable SCCmec types (type IV or V), a clone-specific colonization/infection nature, toxin profiles (including Pantone-Valentine leucocidin, PVL), and narrow drug resistance patterns. CA-MRSA infections are generally seen in healthy children or young athletes, with unexpected cases of diseases, and also in elderly inpatients, occasionally surprising clinicians used to HA-MRSA infections. CA-MRSA spreads within families and close-contact groups or even through public transport, demonstrating transmission cores. Re-infection (including multifocal infection) frequently occurs, if the cores are not sought out and properly eradicated. Recently, attention has been given to CA-MRSA (USA300), which originated in the US, and is growing as HA-MRSA and also as a worldwide clone. CA-MRSA infection in influenza season has increasingly been noted as well. MRSA is also found in farm and companion animals, and has occasionally transferred to humans. As such, the epidemiological, clinical, and genetic behavior of CA-MRSA, a growing threat, is focused on in this study.

Emergence of SCCmec type IV and SCCmec type V methicillin-resistant Staphylococcus aureus containing the Panton-Valentine leukocidin genes in a large academic teaching hospital in central Switzerland: external invaders or persisting circulators?

The hospital epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) has changed in the past few years due to the encroachment of community-associated MRSA (CA-MRSA) strains into health care settings. MRSA strains that were isolated during a 2-year period from patients of the Luzerner Kantonsspital were analyzed to elucidate their epidemiology. Moreover, extended surveillance of individuals who were contacts of those patients was carried out for 6 months to identify the routes of spread and to assess the quality of the infection control measures used in our setting. Patient data were collected to distinguish CA-MRSA strains from health care-associated MRSA (HA-MRSA) strains by epidemiological criteria, as defined by the Centers for Disease Control and Prevention (CDC). On the basis of the CDC definition, the majority of the strains were considered to be HA-MRSA. However, 87% of them belonged to staphylococcal cassette chromosome mec (SCCmec) types IV and V, which are traditionally associated with CA-MRSA. Surprisingly, classical nosocomial SCCmec types I and II represented a minority, whereas SCCmec type III was completely absent. By PFGE analysis, four predominant clonal lineages and 21 highly variable sporadic genotypes were detected. Twenty-eight percent of the MRSA strains studied carried the genes encoding the Panton-Valentine leukocidin (PVL), of which 21% and 83% were associated with SCCmec types IV and V, respectively. Among 289 contact individuals screened for MRSA carriage throughout the extended surveillance, a single secondary patient was discovered. The possibility of nosocomial transmission could be excluded. The high proportions of SCCmec type IV and V strains as well as PVL-positive strains suggest strong infiltration of CA-MRSA into our institution. Moreover, the low endemic prevalence of MRSA demonstrates that current infection control measures are sufficient to limit its spreading and the emergence of large epidemic outbreaks.

Panton-Valentine leukocidin (PVL)-positive methicillin-susceptible and resistant Staphylococcus aureus in Taiwan: identification of oxacillin-susceptible mecA-positive methicillin-resistant S. aureus

Methicillin-resistant Staphylococcus aureus (MRSA) arises when methicillin-susceptible S. aureus (MSSA) acquires the staphylococcal cassette chromosome mec (SCCmec). Most pvl-positive MRSA in Taiwan belong to ST59 lineage and carry SCCmec V. The genetic profiles of 51 MSSA were compared with those of 80 MRSA from the same hospitals. Nine pvl-positive MSSA (oxacillin MIC < or = 2 microg/mL) shared >80% similarity in pulsed field gel electrophoresis pattern with 17 pvl-positive SCCmec V MRSA. Further investigation found that 5 of these 9 isolates were MRSA by cefoxitin and carried SCCmec V. All 26 pvl-positive isolates had very similar genetic profile (ST59, protein A clonal complex [spa-CC] c2:441/437, and agr group I). The success of the ST59:SCCmec V MRSA may be due in part to its heterogeneous and borderline resistance to methicillin, which may be missed by testing only oxacillin, with subsequent exposure to beta-lactams causing the emergence of more resistant subpopulations.

Waves of resistance: Staphylococcus aureus in the antibiotic era

Staphylococcus aureus is notorious for its ability to become resistant to antibiotics. Infections that are caused by antibiotic-resistant strains often occur in epidemic waves that are initiated by one or a few successful clones. Methicillin-resistant S. aureus (MRSA) features prominently in these epidemics. Historically associated with hospitals and other health care settings, MRSA has now emerged as a widespread cause of community infections. Community or community-associated MRSA (CA-MRSA) can spread rapidly among healthy individuals. Outbreaks of CA-MRSA infections have been reported worldwide, and CA-MRSA strains are now epidemic in the United States. Here, we review the molecular epidemiology of the epidemic waves of penicillin- and methicillin-resistant strains of S. aureus that have occurred since 1940, with a focus on the clinical and molecular epidemiology of CA-MRSA.

Cooccurrence of predominant Panton-Valentine leukocidin-positive sequence type (ST) 152 and multidrug-resistant ST 241 Staphylococcus aureus clones in Nigerian hospitals

Ninety-six clinical isolates of Staphylococcus aureus from Nigeria were characterized phenotypically and genetically. Twelve multidrug-resistant methicillin (meticillin)-resistant S. aureus (MRSA) isolates carrying a new staphylococcal cassette chromosome mec element and a high proportion of Panton-Valentine leukocidin (PVL)-positive methicillin-susceptible S. aureus (MSSA) isolates were observed. The cooccurrence of multidrug-resistant MRSA and PVL-positive MSSA isolates entails the risk of emergence of a multidrug-resistant PVL-positive MRSA clone.

Cross-border dissemination of methicillin-resistant Staphylococcus aureus, Euregio Meuse-Rhin region

MRSA clones were associated with hospital-associated clonal complexes and with Panton-Valentine leukocidin–positive community-associated MRSA.

Because the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) differs among the 3 countries forming the Euregio Meuse-Rhin (EMR) region (Belgium, Germany, and the Netherlands), cross-border healthcare requires information about the spread of MRSA in the EMR. We investigated the emergence, dissemination, and diversity of MRSA clones in the EMR by using several typing methods. MRSA associated with clonal complexes 5, 8, 30, and 45 was disseminated throughout the EMR. Dutch isolates, mainly associated with sequence types (ST) ST5-MRSA-II, ST5-MRSA-IV, ST8-MRSA-IV, and ST45-MSRA-IV had a more diverse genetic background than the isolates from Belgium and Germany, associated with ST45-MRSA-IV and ST5-MRSA-II, respectively. MRSA associated with pigs (ST398-MRSA-IV/V) was found in the Dutch area of the EMR. Five percent of the MRSA isolates harbored Panton-Valentine leukocidin and were classified as community-associated MRSA associated with ST1, 8, 30, 80, and 89.

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.

Staphylococci in primary skin and soft tissue infections in a Swedish county

Patients with skin and soft tissue infections (SSTI) are frequently encountered in primary health care. The majority are uncomplicated and treated empirically by surgical incision and drainage and/or antibiotics. This strategy may risk delaying the detection of methicillin-resistant Staphylococcus aureus (MRSA), which, although still rare in Sweden, is increasingly being found in patients with SSTI. To avoid 'late detection' of MRSA, primary health care physicians in Kronoberg county, Sweden, were asked to perform a culture as soon as the patient's first visit. Samples from 175 patients with primary SSTI confirmed that S. aureus is the dominant pathogen. Two cases of MRSA were detected. Furthermore, isolates of S. aureus producing the Panton-Valentine leukocidin (PVL) toxin were more common among isolates from SSTI than among S. aureus from secondary infections. Finally, we confirmed the importance of the coagulase-negative staphylococcal species S. lugdunensis as a pathogen as it was isolated as the only pathogen in 10% of the skin and soft tissue samples.