Prevalence and clonality of methicillin-resistant Staphylococcus aureus (MRSA) in the Atlantic Azores islands: predominance of SCCmec types IV, V and VI

Prevalence and Molecular Characterization of Methicillin-Resistant Staphylococci Recovered from Public Shared Bicycles in China

Millions of public shared bicycles (PSBs) have been launched in China, and PSBs are a potential reservoir of antimicrobial-resistant staphylococci. However, no national data to elucidate the dissemination, antimicrobial resistance and genotypes of staphylococci has been recovered from public shared bicycles located in different cities in China. Antimicrobial susceptibility, SCCmec types and sequence types of staphylococci were determined. A total of 146 staphylococci were recovered in this study, and 87% staphylococcal isolates were resistant to at least one antibiotic. In total, 29 (20%) staphylococcal isolates harbored mecA gene, and SCCmec types were determined as follows: SCCmec type II (n = 1), IV(n = 3), V (n = 4), VI (n = 1), VIII (n = 2), A/1 (n = 6), A/5 (n = 2), C/1 (n = 2), C/2 (n = 1), C/3 (n = 1), (n = 5) and Pseudo (ψ)-SCCmec (n = 1). Sequence types of 16 Staphylococcus epidermidis were determined, including ST10, ST17, ST59, ST60, ST65, ST130, ST184, ST262, ST283, ST337, ST360, ST454, ST567, ST820, ST878 and ST934. PSBs are a reservoir of diverse antimicrobial-resistant staphylococci, and staphylococcal species differences were observed in isolates that were recovered from public shared bicycles in the south and north of China. PSBs are a source of antimicrobial resistance and genetic diverse staphylococci.

Emergence of novel methicillin-resistant Staphylococcus aureus strains in a tertiary care facility in Riyadh, Saudi Arabia

PURPOSE

There is a need for continuous surveillance of methicillin-resistant Staphylococcus aureus (MRSA) to identify emergence of new strains. We hypothesize that MRSA strains are evolving with ongoing acquisition of SCCmec elements. This study was carried out to evaluate the evolution of MRSA at a tertiary care facility in Saudi Arabia.

METHODS

MRSA isolates associated with invasive clinical infection, which were identified in 2017 at the microbiology laboratory, King Khalid University Hospital (KKUH) in Riyadh, Saudi Arabia, were studied. The molecular characterization of isolates was carried out using StaphyType DNA microarray (Alere Technologies GmbH/Abbott, Jena, Germany).

RESULTS

The 125 MRSA isolates studied belonged to 18 clonal complexes (CC) which were distributed into 32 strain assignments. The predominant CC were CC5 (n=30), CC6 (n=17), CC80 (n=13), CC22 (n=12), CC361 (n=12). The findings demonstrated the first identification of CC152, CC361 and CC1153 MRSA as well as ST5-MRSA-[I+fus], "Geraldine Clone", CC6-MRSA-IV (PVL+) and CC88-MRSA-V (PVL+), WA MRSA-117 in Saudi Arabia. Four novel variants were identified: CC5-MRSA-[VI+fus+tirS], CC22-MRSA-[V/VT+fus](PVL+), CC152-MRSA-[V+fus](PVL+) and CC361-MRSA-[VT+fus]. Fifty-four isolates (n/N=54/125; 43.2%) including the novel strains carried the Q6GD50 SCCfusC gene while the Panton-Valentine leukocidin genes were present in 30.4% (n/N=38/125).

CONCLUSION

The findings demonstrate an expanding MRSA repertoire in our setting including emergence of previously unreported clonal complexes and novel strains. The high carriage of fusC gene suggests a role for fusidic acid misuse in driving the evolution of the MRSA genome and underscores the need for increased monitoring of antibiotic use.

Increase in antimicrobial resistance and emergence of major international high-risk clonal lineages in dogs and cats with urinary tract infection: 16 year retrospective study

Objectives

To evaluate temporal trends in antimicrobial resistance, over 16 years, in bacteria isolated from dogs and cats with urinary tract infection (UTI) and the clonal lineages of bacteria harbouring critical antimicrobial resistance mechanisms.

Methods

Antimicrobial susceptibility testing was conducted for 948 bacteria isolated from dogs and cats with UTI (1999-2014). Resistance mechanisms were detected by PCR, namely ESBL/AmpC in third-generation cephalosporin (3GC)-resistant Escherichia coli and Proteus mirabilis, mecA in methicillin-resistant staphylococci, and aac(6')-Ieaph(2″)-Ia and aph(2″)-1d in high-level gentamicin-resistant (HLGR) enterococci. Resistant bacteria were typed by MLST, and temporal trends in E. coli and Enterobacteriaceae antimicrobial resistance were determined by logistic regression.

Results

Enterobacteriaceae had a significant temporal increase in resistance to amoxicillin/clavulanate, 3GCs, trimethoprim/sulfamethoxazole, fluoroquinolones, gentamicin and tetracycline (P < 0.001). An increase in MDR was also detected (P < 0.0001). 3GC resistance was mainly caused by the presence of blaCTX-M-15 and blaCMY-2 in E. coli and the presence of blaCMY-2 in P. mirabilis. Two major 3GC-resistant E. coli clonal lineages were detected: O25b:H4-B2-ST131 and ST648. The mecA gene was detected in 9.2% (n = 11/119) of Staphylococcus spp., including MRSA clonal complex (CC) 5 (n = 2) and methicillin-resistant Staphylococcus epidermidis CC5 (n = 4). A temporal increase in MDR methicillin-resistant Staphylococcus pseudintermedius was detected (P = 0.0069). Some ampicillin-resistant and/or HLGR Enterococcus spp. were found to belong to hospital-adapted CCs, namely Enterococcus faecalis ST6-CC6 (n = 1) and Enterococcus faecium CC17 (n = 8).

Conclusions

The temporal increase in antimicrobial resistance and in MDR bacteria causing UTI in dogs and cats creates important therapeutic limitations in veterinary medicine. Furthermore, the detection of MDR high-risk clonal lineages raises public health concerns since companion animals with UTI may contribute to the spread of such bacteria.

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.

Staphylococcal chromosomal cassettes mec (SCCmec): A mobile genetic element in methicillin-resistant Staphylococcus aureus

Considered to be a potential "superbug", methicillin-resistant Staphylococcus aureus (MRSA) has been one of the major recent infectious pathogens and thus poses a challenge to hospital infection control. The mobile genetic element staphylococcal chromosomal cassette mec (SCCmec) carries both the mecA or mecC gene, encoding for a novel specific penicillin-binding protein (PBP2a), and site-specific recombinase genes ccrAB or/and ccrC. In MRSA, the acquisition of SCCmec leads to the resistance to the β-lactam antibiotics. As SCCmec plays a core role in the antimicrobial resistance characteristics, molecular epidemiology and evolution of MRSA, a thorough summary and comprehensive understanding of the prevalence and structural characteristics of SCCmec may aid in global surveillance, implementation and investigation on MRSA isolates, as well as further development of preventive and therapeutic approaches. Consequently, this review is aimed at describing the history, prevalence, types and subtypes, and current typing methods of SCCmec, with the focus on the typical structures of the SCCmec cassette.

Molecular characterization of methicillin-resistant Staphylococcus aureus in nosocomial infections in a tertiary-care facility: emergence of new clonal complexes in Saudi Arabia

Changes in the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) continue to be reported. This study was carried out to characterize MRSA isolates in Saudi Arabia. MRSA isolates causing nosocomial infections (n = 117) obtained from 2009–2015 at a tertiary-care facility in Riyadh, Saudi Arabia, were studied. Molecular characterization of isolates was carried out using the StaphyType DNA microarray (Alere Technologies, Jena, Germany). Fourteen clonal complexes (CC) were identified, with the most common being CC80 (n = 35), CC6 (n = 15), CC5 (n = 13) and CC22 (n = 12). With the exception of nine ST239 MRSA-III isolates, all others were of community-associated MRSA lineages. The following strains are identified for the first time in Saudi Arabia: ST8-MRSA-IV [PVL⁺/ACME⁺], USA300 (n = 1); ST72-MRSA-IV USA700 (n = 1); CC5-MRSA-IV, [PVL⁺/edinA⁺], WA MRSA-121 (n = 1); CC5-MRSA-V+SCCfus, WA MRSA-14/109 (n = 2), CC97-MRSA-IV, WA MRSA-54/63; CC2250/2277-MRSA-IV and WA MRSA-114. CC15-MRSA (n = 3) was identified for the first time in clinical infection in Saudi Arabia. None of the isolates harboured vancomycin resistance genes, while genes for resistance to mupirocin and quaternary ammonium compounds were found in one and nine isolates respectively. Fifty-seven isolates (48.7%) were positive for Panton-Valentine leukocidin genes. While the staphylokinase (sak) and staphylococcal complement inhibitor (scn) genes were present in over 95% of the isolates, only 37.6% had the chemotaxis-inhibiting protein (chp) gene. Increasing occurrence of community-acquired MRSA lineages plus emergence of pandemic and rare MRSA strains is occurring in our setting. Strict infection control practices are important to limit the dissemination of these MRSA strains.

Prevalence of Staphylococcus aureus from nares and hands on health care professionals in a Portuguese Hospital

AIMS

The main goal was to estimate the prevalence of methicillin-resistant Staphylococcus aureus on hands and in nose of health care professionals.

METHODS AND RESULTS

Detection of Staph. aureus on hands or in the nose of 169 individuals was performed. Nasal and hand carriage was found in 39·6 and in 8·9% respectively. About 17·2% of the individuals were carriers of methicillin-resistant Staph. aureus (MRSA) in the nose and 4·7% on hands. The majority of nasal MRSA were resistant to β-lactams, erythromycin and ciprofloxacin. All nasal MRSA were SCCmec type IV and Panton-Valentine leukocidin (PVL) negative. One MRSA isolated from hand was SCCmec type V. About 75·6% of MRSA isolates presented the same or closely related restriction patterns. Sixty per cent of Staph. aureus from hands and from noses from the same individual were the same strain.

CONCLUSIONS

MRSA nasal carriage was high considering healthy health care professionals but in accordance with high level of MRSA infection in Portugal. Isolates recovered in this study seemed to be different from major clones previously isolated in other Portuguese hospitals.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings may have implications on the knowledge of healthy health care workers as vehicles of MRSA infections among the community. Presence of several virulence factors may contribute to increased pathogenesis in case of infection.

Molecular Characterization of Community- and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Isolates in Southern Taiwan

A growing tendency for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) to be involved in nosocomial infections was reported. The predominance of SCCmec type IV or V CA-MRSA in soft tissue infection has also been indicated in Northern Taiwan. To establish basic information about the molecular characteristics of MRSA in our region, a total of 102 MRSA isolates were collected and characterized by an array of typing methods. Healthcare-associated MRSA (HA-MRSA) were found to be more resistant to levofloxacin (p=0.016) and moxifloxacin (p=0.015) than CA-MRSA. However, no difference was found in each and overall SCCmec type distribution between the two MRSA groups. Type I (8.7% vs. 2.6%) was more frequently found in CA-MRSA, whereas type V was more often observed in HA-MRSA (24.4% vs. 8.7%). No difference was found in the dichotomous group of PVL, SCCmec type IV, V, and IV/V between the two MRSA groups. Twenty-seven distinct spa types were identified; t437 and t1081 were the predominant types in our isolates. Moreover, 12 novel spa types with extremely low global frequency were detected in our isolates. SCCmec type III and IV were the major subtypes in the MRSA we collected. The t1081 clones all belonged to HA-MRSA and mostly to SCCmec type V (71.4%). CA-MRSA t437 clones were mostly SCCmec type IV strains (71.4%), but HA-MRSA t437 clones were predominantly SCCmec type IV (42.1%) and III (36.8%). Our findings support a difference in the molecular characteristics of CA-MRSA and HA-MRSA that may reflect various clonal origins in our isolates.

Methicillin-resistant Staphylococcus aureus in HIV patients: risk factors associated with colonization and/or infection and methods for characterization of isolates - a systematic review

Staphylococcus aureus is an important cause of infections and HIV-infected individuals are frequently susceptible to this pathogen. The aim of this study was to perform a systematic review to identify both the risk factors associated with colonization/infection by methicillin-resistant S. aureus in HIV patients and the methods used for characterization of isolates. An electronic search of articles published between January 2001 and December 2013 was first conducted. Among 116 studies categorized as being at a quality level of A, B or C, only 9 studies were considered to have high methodological quality (level A). The majority of these studies were retrospective (4/9 studies). The risk factors associated with colonization/infection by S. aureus were use of antimicrobials (4/9 studies), previous hospitalization (4/9 studies) and low CD4+ T lymphocyte counts (<200 cells/μl) (3/9 studies). Culture in mannitol salt agar (3/9 studies) and the latex agglutination test (5/9 studies) were the main methods used for bacterial phenotypic identification. Genotypic profiles were accessed by pulsed-field gel electrophoresis (6/9 studies) and USA300 was the most prevalent lineage (5/9 studies). Most isolates were resistant to erythromycin (3/9 studies) and susceptible to vancomycin (4/9 studies). Ultimately, use of antimicrobials and previous hospitalization were the main risk factors for colonization/infection by methicillin-resistant S. aureus in HIV-infected individuals. However, the numbers of evaluated patients, the exclusion and inclusion criteria and the characterization of the S. aureus isolates were not uniform, which made it difficult to establish the characteristics associated with HIV patients who are colonized/infected by S. aureus.

Insights into alpha-hemolysin (Hla) evolution and expression among Staphylococcus aureus clones with hospital and community origin

Background

Alpha-hemolysin (Hla) is a major virulence factor in the pathogenesis of Staphylococcus aureus infection, being active against a wide range of host cells. Although hla is ubiquitous in S. aureus, its genetic diversity and variation in expression in different genetic backgrounds is not known. We evaluated nucleotide sequence variation and gene expression profiles of hla among representatives of hospital (HA) and community-associated (CA) S. aureus clones.

Methods

51 methicillin-resistant S. aureus and 22 methicillin-susceptible S. aureus were characterized by PFGE, spa typing, MLST and SCCmec typing. The internal regions of hla and the hla promoter were sequenced and gene expression was assessed by RT-PCR.

Results

Alpha-hemolysin encoding- and promoter sequences were diverse, with 12 and 23 different alleles, respectively. Based on phylogenetic analysis, we suggest that hla may have evolved together with the S. aureus genetic background, except for ST22, ST121, ST59 and ST93. Conversely, the promoter region showed lack of co-evolution with the genetic backgrounds. Four non-synonymous amino acid changes were identified close to important regions of hla activity. Amino acid changes in the RNAIII binding site were not associated to hla expression. Although expression rates of hla were in general strain-specific, we observed CA clones showed significantly higher hla expression (p = 0.003) when compared with HA clones.

Conclusion

We propose that the hla gene has evolved together with the genetic background. Overall, CA genetic backgrounds showed higher levels of hla expression than HA, and a high strain-to-strain variation of gene expression was detected in closely related strains.

Contribution of peptidoglycan amidation to beta-lactam and lysozyme resistance in different genetic lineages of Staphylococcus aureus

The enzymes responsible for peptidoglycan amidation in Staphylococcus aureus, MurT and GatD, were recently identified and shown to be required for optimal expression of resistance to beta-lactams, bacterial growth, and resistance to lysozyme. In this study, we analyzed the impact of peptidoglycan amidation in representative strains of the most widespread clones of methicillin resistant S. aureus (MRSA). The inhibition of the expression of murT-gatD operon resulted in different phenotypes of resistance to beta-lactams and lysozyme according to the different genetic backgrounds. Further, clonal lineages CC1 and CC398 (community-acquired MRSA [CA-MRSA]) showed a stronger dependency on MurT-GatD for resistance to beta-lactams, when compared to the impact of the impairment of the cell wall step catalyzed by MurF. In the remaining backgrounds similar phenotypes of beta-lactam resistance were observed upon the impairment of both cell-wall-related genes. Therefore, for CA-related backgrounds, the predominant beta-lactam resistance mechanism seems to involve genes associated with secondary modifications of peptidoglycan. On the other hand, the lack of glutamic acid amidation had a more substantial impact on lysozyme resistance for cells of CA-MRSA backgrounds, than for hospital-acquired MRSA (HA-MRSA). However, no significant differences were found in the resistance level of the respective peptidoglycan structure, suggesting that the lysozyme resistance mechanism involves other factors. Taken together, these results suggested that the different genetic lineages of MRSA were able to develop different molecular strategies to overcome the selective pressures experienced during evolution.

Contamination of public buses with MRSA in Lisbon, Portugal: a possible transmission route of major MRSA clones within the community

In a previous study we have shown that public buses in Oporto, the second largest city in Portugal, were highly contaminated with MRSA. Here we describe the results of a similar study performed in another urban area of Portugal–Lisbon, the capital. Between May 2011 and May 2012, hand touched surfaces of 199 public buses in Lisbon were screened for MRSA contamination. Subsequently, the hands of 575 passengers who frequently use these bus lines were also screened. All hand carriers of MRSA were further screened for nasal carriage. The isolates were characterized by PFGE, staphylococcal cassette chromosome (SCC) mec typing, spa typing, MLST and were tested for the presence of mecA, Panton-Valentine leukocidin and arginine catabolic mobile element genes. MRSA contamination was shown in 72 buses (36.2%). The majority of the isolates belonged to three major clones: Clone A was identified as EMRSA-15 defined by pattern PFGE A, spa types t2357/t747/t025/t379/t910, ST22, and SCCmec IVh (n = 21; 29%). Clone B was the New York/Japan clone characterized by PFGE B-t002/t10682-ST5-II (n = 15; 21%). Clone C included isolates with characteristics of the international community-acquired USA300 or related clones, PFGE C-t008-ST8-IVa/IVc/IVg/IVnt/VI (n = 19; 26%). The first two clones are currently the two major lineages circulating in Portuguese hospitals. The hands of 15 individuals were contaminated with MRSA belonging to the nosocomial clones A or B. Eleven of these individuals were not nasal carriers of MRSA and all but one had travelled by public transportation, namely by bus, prior to sampling. In conclusion, public buses in two major cities in Portugal are often contaminated with MRSA representing clones dominant in hospitals in the particular geographic area. MRSA contamination of public transport and the transfer of the bacteria to the hands of passengers may represent a route through which hospital-acquired MRSA clones may spread to the community.

Methicillin resistant and susceptible Staphylococcus aureus: Appraising therapeutic approaches in the Northwest of Iran

BACKGROUND AND OBJECTIVES

Staphylococcus aureus is a versatile organism causing mild to life threatening infections. The major threat of this organism is its multidrug resistance. The present study was carried out to investigate in - vitro activity of conventional antibiotics routinely prescribed for methicillin resistant S. aureus (MRSA) and methicillin sensitive S. aureus (MSSA) infections in the Northwest of Iran and other alternating therapeutic agents which are recommended for Gram positive organisms.

MATERIALS AND METHODS

Clinical isolates of S. aureus were subjected to multiplex PCR for simultaneous speciation and detection of methicillin resistance. Antibacterial susceptibility pattern was determined using disk diffusion. The Minimum Inhibitory Concentrations (MICs) were determined using E-test strips.

RESULTS

The results revealed presence of nuc gene in all S. aureus isolates detected phenotypically earlier whereas, mecA gene was observed in 54% of strains. On disk diffusion and MIC determination assay, all MRSA and MSSA strains were susceptible to mupirocin (except one MRSA strain), linezolid and teicoplanin. Six vancomycin intermediate S. aureus strains were detected (VISA) with MIC= 4µg/mL, 5 of them being MRSA. In disk diffusion assay, 17.3% and 3.7% of isolates showed resistance to rifampin and fusidic acid, respectively. However, MIC50 and MIC90 tests shows promising in - vitro impact.

CONCLUSION

In - vitro mupirocin was found as an effective prophylactic ointment for nasal S. aureus eradication. Our data emphasize the performance of surveillance exercises to outline the existing antibiotics prescription policies and to slow down the emergence of multidrug resistant strains.

Methicillin-resistant Staphylococcus aureus in Rio de Janeiro hospitals: dissemination of the USA400/ST1 and USA800/ST5 SCCmec type IV and USA100/ST5 SCCmec type II lineages in a public institution and polyclonal presence in a private one

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) infections have changed since certain non-multiresistant MRSA lineages have emerged in hospitals. In this study, 99 MRSA isolates, 77 from a public and 22 from a private hospital, were characterized.

METHODS

Isolates were tested for antimicrobial susceptibility, whereas staphylococcal chromosomal cassette mec (SCCmec) typing and Panton-Valentine leukocidin genes were assessed by polymerase chain reaction. Pulsed-field gel electrophoresis and multilocus sequence typing analyses were carried out to determine the MRSA lineages.

RESULTS

High rates of resistance were found to erythromycin (96%), ciprofloxacin (93%), and clindamycin (90%). The SCCmec types found were as follows: type II (14.2%), III (62.6%), and IV (23.2%). Approximately 85% of type III isolates was related to the Brazilian epidemic clone in both hospitals. For type IV isolates, 94.4% were related to both USA400/ sequence type (ST) 1 and USA800/ST5 lineages in the public hospital, whereas the USA400/ST1, USA800/ST5, USA1100/ST30, and EMRSA (Epidemic MRSA)-15/ST22 lineages were detected in the private hospital. Among the SCCmec II isolates, approximately 85% were related to the USA100/ST5 lineage. Three MRSA isolates were positive to Panton-Valentine leukocidin genes.

CONCLUSION

The study showed that there was an emergence of USA400/ST1, USA800/ST5 SCCmec IV, and USA100/ST5 SCCmec II MRSA lineages in both hospitals. There was a dissemination of them in the public hospital and a polyclonal presence of the MRSA isolates in the private hospital. The spread of these lineages can be facilitated by the characteristics of the health institution.

Characterisation of MRSA strains isolated from patients in a hospital in Riyadh, Kingdom of Saudi Arabia

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is spreading worldwide and poses a serious public health problem, being present in hospital settings and communities. However, from the Middle East and the Arabian Peninsula few molecular typing data on MRSA strains are currently available. In order to obtain data on the population structure of MRSA in Riyadh, Saudi Arabia, 107 clinical and environmental MRSA isolates were genotyped using a microarray-based assay.

Results

Five major MRSA strains from four clonal complexes were identified CC8/ST239-III (20.75%), PVL-positive as well as -negative CC22-IV (18.87% and 9.43%, respectively), PVL-positive CC30-IV (12.26%) and PVL-positive CC80-IV (17.92%). Minor strains, which accounted for less than 3% each, included CC1-IV/SCCfus, PVL-positive CC1/ST772-V, PVL-positive as well as- negative CC5-IV, CC5-IV/SCCfus, CC5-V, CC6-IV, CC45-IV, PVL-negative CC80-IV, PVL-positive CC88-IV, CC97-V and a CC9/ST834-MRSA strain.

Conclusions

Typing of MRSA strains from Riyadh revealed a high diversity of clonal complexes. The prevalence of the genes encoding the Panton-Valentine leukocidin was surprisingly high (54.21%), and a significant rate of resistance markers was detected also in strains considered as community-associated.

Clonal replacement of epidemic methicillin-resistant Staphylococcus aureus strains in a German university hospital over a period of eleven years

Worldwide, methicillin-resistant Staphylococcus aureus (MRSA) pose an increased risk for healthcare- and community-associated infections. Since the first report of MRSA in England in 1961, several distinct clones or strains have emerged. Changes within the MRSA population of whole countries, small regions or of single hospitals have been observed with some clones replacing others. In this study, the clonal replacement of MRSA isolates in a South-eastern German tertiary care hospital between 2000 and 2010 is described based on microarray analyses of 778 isolates and at least 50 MRSA per year. Within these eleven years, four common epidemic strains, CC22-MRSA-IV, CC45-MRSA-IV, CC5/ST228-MRSA-I (including a variant with a truncated SCCmec element) and CC5-MRSA-II were identified. The PVL-negative CC22-MRSA-IV strain (Barnim Epidemic Strain, UK-EMRSA-15) was detected for the first time in 2001 and its abundance increased since then to 58.6% in 2010. CC5-MRSA-II increased from 2% (2000) to about 30% (2003), and since then it fluctuates between 23 and 37% of isolates. CC5/ST228-MRSA-I decreased from about the half of tested isolates (2000) to 2.3% (2010). A similar trend was observed for CC45-MRSA-IV, which decreased drastically down to 3.4% in 2010 after reaching a maximum of 62.0% in 2002. Seventeen other PVL-negative MRSA strains were identified sporadically with no significant trend being observed. Seven PVL-positive MRSA strains were found, but they remained rare during the study period accounting together for 2.7% of isolates.

A field guide to pandemic, epidemic and sporadic clones of methicillin-resistant Staphylococcus aureus

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) have become a truly global challenge. In addition to the long-known healthcare-associated clones, novel strains have also emerged outside of the hospital settings, in the community as well as in livestock. The emergence and spread of virulent clones expressing Panton-Valentine leukocidin (PVL) is an additional cause for concern. In order to provide an overview of pandemic, epidemic and sporadic strains, more than 3,000 clinical and veterinary isolates of MRSA mainly from Germany, the United Kingdom, Ireland, France, Malta, Abu Dhabi, Hong Kong, Australia, Trinidad & Tobago as well as some reference strains from the United States have been genotyped by DNA microarray analysis. This technique allowed the assignment of the MRSA isolates to 34 distinct lineages which can be clearly defined based on non-mobile genes. The results were in accordance with data from multilocus sequence typing. More than 100 different strains were distinguished based on affiliation to these lineages, SCCmec type and the presence or absence of PVL. These strains are described here mainly with regard to clinically relevant antimicrobial resistance- and virulence-associated markers, but also in relation to epidemiology and geographic distribution. The findings of the study show a high level of biodiversity among MRSA, especially among strains harbouring SCCmec IV and V elements. The data also indicate a high rate of genetic recombination in MRSA involving SCC elements, bacteriophages or other mobile genetic elements and large-scale chromosomal replacements.

High prevalence of EMRSA-15 in Portuguese public buses: a worrisome finding

BACKGROUND

The nosocomial prevalence of methicillin resistant Staphylococcus aureus (MRSA) in Portugal remains one of the highest in Europe and is currently around 50%. Transmission of S. aureus, including MRSA, occurs principally by direct human-to-human skin contact. However, S. aureus can survive for long periods on inanimate objects, which may represent an important reservoir for dissemination as well.

METHODOLOGY/PRINCIPAL FINDINGS

Between May 2009 and February 2010, handrails of 85 public urban buses circulating in Oporto, Portugal, were screened for the occurrence of MRSA. Twenty-two (26%) buses showed MRSA contamination. The molecular characterization of a total of 55 MRSA, by pulsed-field gel electrophoresis (PFGE), staphylococcal cassette chromosome (SCC) mec typing, spa typing, and multilocus sequence typing (MLST), clustered the isolates into three clonal types. However, the overwhelming majority (n = 50; 91%) of the isolates belonged to a single clone (PFGE A, spa types t747, t032, t025 or t020, ST22, SCCmec type IVh) that exhibits the characteristics of the pandemic EMRSA-15, currently the major lineage circulating in Portuguese hospitals, namely in the Oporto region. Two additional clones were found but in much lower numbers: (i) PFGE B, ST5, spa type t002, SCCmec IVa (n = 3), and (ii) PFGE C, spa type t008, ST8, SCCmec IVa (n = 2). None of the 55 isolates was PVL positive.

CONCLUSIONS/SIGNIFICANCE

Public buses in Oporto seem to be an important reservoir of MRSA of nosocomial origin, providing evidence that the major hospital-associated MRSA clone in Portugal is escaping from the primary ecological niche of hospitals to the community environment. Infection control measures are urgently warranted to limit the spread of EMRSA-15 to the general population and future studies are required to assess the eventual increase of MRSA in the Portuguese community, which so far remains low.

Molecular detection and characterization of methicillin-resistant Staphylococcus aureus (MRSA) isolates from dogs in Portugal

Fifty-four healthy dogs were screened in Portugal for the presence of nasal methicillin-resistant Staphylococcus aureus (MRSA) carriage. Sixteen MRSA isolates (one/sample) were recovered from nasal samples of dogs, and they were typed by molecular methods (S. aureus protein A [spa]-, multilocus sequence typing-, staphylococcal cassette chromosome mec-typing). MRSA isolates were investigated for their susceptibility to antimicrobial agents by disk-diffusion test. The presence of resistance genes and of the Panton-Valentine leukocidin gene (lukF-lukS) was analyzed by PCR. Four different spa-types were identified among our MRSA isolates (t032, t432, t747, and t4726), with t032 as the most frequently detected. The sequence-type ST22 was identified in four tested MRSA isolates with different spa-types. All 16 isolates presented the staphylococcal cassette chromosome mec type IV. Most of MRSA isolates were resistant to ciprofloxacin, erythromycin, and clindamycin (94%-100%), and no resistance was identified to chloramphenicol, mupirocin, and trimethoprim-sulfametoxazole. The ermC and tetM resistance genes were detected in all MRSA isolates. The amino acid changes Ser84Leu in GyrA protein and Ser80Phe in GrlA protein were the most prevalent ones in our MRSA isolates. None of the MRSA strains carried the lukF-lukS genes. The results presented in this study indicate that healthy dogs may be a reservoir of MRSA that could be transmitted to humans by direct contact.

Non-Instrumented Nucleic Acid Amplification (NINA) for Rapid Detection of Ralstonia solanacearum Race 3 Biovar 2

We report on the use of a non-instrumented device for the implementation of a loop-mediated amplification (LAMP) based assay for the select-agent bacterial-wilt pathogen Ralstonia solanacearum race 3 biovar 2. Heat energy is generated within the device by the exothermic hydration of calcium oxide, and the reaction temperature is regulated by storing latent energy at the melting temperature of a renewable lipid-based engineered phase-change material. Endpoint detection of the LAMP reaction is achieved without opening the reaction tube by observing the fluorescence of an innovative FRET-based hybridization probe with a simple custom fluorometer. Non-instrumented devices could maintain reactions near the design temperature of 63°C for at least an hour. Using this approach DNA extracted from the pathogen could be detected at fewer than ten copies within a 25 μL reaction mix, illustrating the potential of these technologies for simple, powerful agricultural diagnostics in the field. Furthermore, the assay was just as reliable when implemented in a tropical environment at 31°C as it was when implemented in an air-conditioned lab maintained at 22°C, illustrating the potential value of the technology for field conditions in the tropics and subtropics.

The need for continued monitoring of antibiotic resistance patterns in clinical isolates of Staphylococcus aureus from London and Malta

BACKGROUND

Antibiotic resistance is an increasing problem in isolates of Staphylococcus aureus (S. aureus) worldwide. In 2001 The National Health Service in the UK introduced a mandatory bacteraemia surveillance scheme for the reporting of S. aureus and methicillin-resistant S. aureus (MRSA). This surveillance initiative reports on the percentage of isolates that are methicillin resistant. However, resistance to other antibiotics is not currently reported and therefore the scale of emerging resistance is currently unclear in the UK. In this study, multiple antibiotic resistance (MAR) profiles against fourteen antimicrobial drugs were investigated for 705 isolates of S. aureus collected from two European study sites in the UK (London) and Malta.

RESULTS

All isolates were susceptible to linezolid, teicoplanin and vancomycin. Multiple antibiotic resistance profiles from both countries were determined, a total of forty-two and forty-five profiles were seen in the UK cohort (MRSA and MSSA respectively) and comparatively, sixty-two and fifty-two profiles were shown in the Maltese group. The largest MAR profile contained six antibiotics (penicillin G, methicillin, erythromycin, ciprofloxacin, clindamycin and clarithromycin) and was observed in the MRSA isolates in both the UK and Maltese cohorts.

CONCLUSION

The data presented here suggests that the monitoring of changing resistance profiles locally in maintaining treatment efficacy to resistant pathogens.