Emergence of methicillin-resistant,vancomycin-intermediate Staphylococcus aureus among patients associated with group A Streptococcal pharyngitis infection in southern India

Beyond Staphylococcus aureus being an etiological agent for several serious clinical complications, the foot prints of S. aureus in pharyngitis infection has also been recently recognized. With due response to the fact, a prospective study was conducted between 2009 and 2010 to describe the molecular epidemiology of S. aureus in throat swabs of pharyngitis patients. A total of 63 methicillin-resistant S. aureus (MRSA) and 102 methicillin-susceptible S. aureus (MSSA) isolates were recovered from 265 throat swabs, representing a community-acquired outpatient population from Tamil Nadu, India. Molecular characterization of MRSA was done by two conventional multiplex PCR assays including Panton-Valentine leukocidin (PVL), mecA and nuc genes, and staphylococcal cassette chromosome mec (SCCmec) typing. Among 165 S. aureus isolates, methicillin resistance was observed in 38.2% (n = 63), in which 69.8% (n = 44/63) of the MRSA along with 55.9% (n = 57/102) of MSSA harbored PVL toxin genes. SCCmec typing showed 50.8% of isolates as SCCmec V (n = 32), 44.4% as SCCmec III (n = 28), and 1.6% as SCCmec types I, II and IVa (n = 1). Multilocus sequence typing performed for 26 selected MRSA isolates resulted in 12 different sequence types (ST), including a novel ST2129/SCCmec III, PVL-positive. Ten MRSA isolates were categorized as ST772 (38.5%)/SCCmec V, PVL-positive, and three isolates as ST368 (11.5%)/SCCmec III, PVL-negative. Though the prominent clones of ST772/SCCmec V were multidrug-susceptible worldwide, they were highly multidrug-resistant in the current study, including four clones intermediate to vancomycin. Totally, 10 (15.9%) out of 63 MRSA isolates were documented as vancomycin-intermediate S. aureus (VISA). Collectively, the present study for the first time portrayed the high prevalence of active MRSA pharyngitis infection and also emphasizes an alarming need for discrimination of pharyngeal-asymptomatic carriers of S. aureus from those with an active S. aureus pharyngitis infection.     

Molecular analysis and the toxin,MSCRAMM, and biofilm genes of methicillin-resistant Staphylococcus aureus strains isolated from pemphigus wounds: A study based on SCCmec and dru typing

IntroductionPemphigus is a chronic autoimmune blistering disease. Pemphigus blisters can damage the natural skin barrier and increase the risk of life-threatening conditions. Colonization of pemphigus wounds with methicillin-resistant Staphylococcus aureus (MRSA) prolongs wound healing and increases mortality rate. Assessing MRSA prevalence, types, and toxin and adhesion genes can facilitate the detection of MRSA strains which cause infections, selection of appropriate treatments, and healing of pemphigus wounds. This study aimed to determine the SCCmec, the direct repeat unit (dru) types (dts), and the toxin, MSCRAMM, and biofilm genes of MRSA strains isolated from pemphigus wounds.MethodsIn this cross-sectional study, 118 S. aureus isolates were gathered from 118 patients with pemphigus. MRSA detection was performed using the mecA gene. Using the polymerase chain reaction method, all MRSA isolates were assessed for the presence of the sea, seb, sec, tst, eta, pvl, hla, hlb, MSCRAMM, and ica genes. Typing and subtyping were performed through respectively SCCmec typing and dru typing methods. The Bionumerics software was used for analyzing the data and drawing the minimum spanning tree.FindingsFrom 118 S. aureus isolates, 51 were MRSA. SCCmec typing revealed the prevalence of SCCmec II with a prevalence of 64.7% (33 out of 51 isolates) and SCCmec III with a prevalence of 35.3% (18 out of 51 isolates). Dru typing indicated seven dts, namely dts 10a, 10g, 10m, 13i, 8h, 8i, and 9ca in two main clusters. The dt9ca was a new dru type and was registered in the dru-typing database (www.dru-typing.org). The prevalence rates of the hla, sea, and sec genes in MRSA isolates were respectively 54.9%, 27.4%, and 1.9%, while the hlb, seb, eta, and pvl genes were not detected at all. Only one MRSA with SCCmec III and dt10a carried the tst encoding gene. MSCRAMM gene analysis revealed the high prevalence of the eno (31.3%) and the fib (21.5%) genes. The prevalence rates of the icaA and icaD biofilm formation genes were 3.9% and 5.8%, respectively. There were no significant differences between the two detected SCCmec types and between the two detected dts clusters respecting the prevalence of the encoding genes of virulence factors and MSCRAMMs.ConclusionThe toxin genes hla and sea are prevalent among MRSA strains with SCCmec II and III isolated from pemphigus wounds. The most prevalent dts are dt10a and dt10g among MRSA with SCCmec III and dt8h and dt8i among MRSA with SCCmec II.     

A combined multi-virulence-locus sequence typing and Staphylococcal Cassette Chromosome mec typing scheme possesses enhanced discriminatory power for genotyping MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) remains a major threat to human populations worldwide. Knowing the extent of MRSA genetic diversity within a healthcare facility may provide important insights into the epidemiology of this important pathogen. MRSA isolates recovered from nasal swabs of patients entering the Intensive Care Unit of the Penn State Milton S. Hershey Medical Center, USA, from 2008 to 2009 were genotyped using Staphylococcal Cassette Chromosome mec (SCCmec), multilocus sequence typing (MLST) and a newly developed multi-virulence-locus sequence typing (MVLST) scheme. Sequence data for seven housekeeping genes (arcC, aroE, glpF, gmk, pta, tpi and yqiL) and six virulence genes (alt, essC, geh, hlgA, htrA and sdrC) were used for MLST and MVLST analyses, respectively. MLST identified 12 sequence types (STs) within the hospital isolates. One ST designated ST5 was the most common subtype (38.8%) followed by ST105 (22.4%) and ST8 (16.4%). In contrast, MVLST identified 29 STs (Virulence Types, VTs) from the same set of isolates, with VT6 (32.8%) being the predominant subtype followed by VT9 (8.9%) and VT2 (8.9%). Subsequent analysis of 25 MRSA isolates associated with an outbreak at a Pennsylvania state prison revealed all isolates were VT2 and SCCmec type IVa. These results suggest that a combination of MVLST and SCCmec typing may clarify the epidemiology of MRSA. Additional research with a more diverse set of strains and correlation with conventional epidemiologic data are needed to validate this new subtyping strategy.     

The evolution of Staphylococcus aureus

A broad variety of infections, ranging from minor infections of the skin to post-operative wound infections can be caused by Staphylococcus aureus. The adaptive power of S. aureus to antibiotics leaded, in the early 1960s, to the emergence of methicillin-resistant S. aureus (MRSA). The cause of resistance to methicillin and all other β-lactam antibiotics is the mecA gene, which is situated on a mobile genetic element, the staphylococcal cassette chromosome mec (SCCmec). Seven major variants of SCCmec, type I to VII, are distinguished. The most important techniques used to investigate the molecular epidemiology of S. aureus are pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), S. aureus protein A (spa) typing and SCCmec typing (only for MRSA). These techniques have been used to study the evolution of the MRSA clones that have emerged since the early 1960s, and to study their subsequent worldwide dissemination. The early MRSA clones were hospital-associated (HA-MRSA). However, from the late 1990s, community-associated MRSA (CA-MRSA) clones emerged worldwide. CA-MRSA harbors SCCmec type IV, V or VII, the majority belong to other S. aureus lineages compared to HA-MRSA, and CA-MRSA is often associated with the presence of the toxin Panton-Valentine leukocidin (PVL). However, during recent years, the distinction between HA-MRSA and CA-MRSA has started to disappear, and CA-MRSA is now endemic in many US hospitals. MRSA probably originated trough the transfer of SCCmec into a limited number of methicillin-sensitive S. aureus (MSSA) lineages. This review describes the latest observations about the structure of SCCmec, the techniques used to study the molecular epidemiology and evolution of S. aureus as well as some challenges that researchers face in the future.     

Population deviation of piggery-associated methicillin-resistant Staphylococcus aureus based on mec-associated direct repeat unit analysis

Piggery-associated methicillin-resistant Staphylococcus aureus (MRSA) is a potential zoonotic pathogen. We constructed the population structure and dynamics of staphylococcal chromosome cassette mec (SCCmec) in MRSA ST9 isolates from different geographical areas of Taiwan. A total of 140 MRSA (135 piggery and 5 human clinical) isolates from three populations located in western Taiwan (n = 96 including the 5 clinical isolates), central eastern Taiwan (n = 22), and Penghu Island (n = 22) were collected and characterized by analysis of the mec-associated direct repeat unit (dru). Twenty-eight dru types (with 24 novel) and 15 dru-Clonal Complexes (CCs) were identified. The predominant novel dt12w type (48.6%) was widespread in all populations and may have a superior ability to transmit among populations. The minimum spanning network showed that at least two ancestral dru types (dt11a and dt12w) were identified, and the genetics between different populations could be differentiated. Temporal distributions of clone population dynamics estimated through the Bayesian skyline plot indicated a stable population with a long evolutionary history for MRSA ST9 in Taiwan. Findings indicating that some dru types are shared between piggery-associated and human-clinical MRSA ST9 suggest the occurrence of cross-species horizontal transmission of SCCmec.     

Clinical and molecular characteristics of nosocomial meticillin-resistant Staphylococcus aureus skin and soft tissue isolates from three Indian hospitals

We analysed risk factors for nosocomial meticillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTIs) in three Indian hospitals. We also determined antimicrobial resistance patterns and genotypic characteristics of MRSA isolates using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and staphylococcal cassette chromosome (SCCmec) typing. Medical records of 709 patients admitted to three tertiary hospitals with nosocomial S. aureus SSTIs were clinically evaluated. Antimicrobial susceptibility testing of patient isolates was performed in accordance with Clinical and Laboratory Standards Institute guidelines, with meticillin and mupirocin resistance confirmed by multiplex polymerase chain reaction. PFGE analysis of 220 MRSA isolates was performed, followed by MLST and SCCmec typing of a selected number of isolates. MRSA was associated with 41%, 31% and 7.5% of infections at the three hospitals, respectively. Multiple logistic regression analysis identified longer duration of hospitalisation [odds ratio (OR): 1.78; OR: 2.83 for ≥20 days], intra-hospital transfer (OR: 1.91), non-infectious skin conditions (3.64), osteomyelitis (2.9), neurological disorders (2.22), aminoglycoside therapy (1.74) and clindamycin therapy (4.73) as independent predictors for MRSA SSTIs. MRSA isolates from all three hospitals were multidrug resistant, with fifteen clones (I–XV) recognised. A majority of the strains possessed type III cassette. The common sequence type (ST) 239 was considered the signature MLST sequence for PFGE clone III. This major MRSA clone III was closely related to the UK EMRSA-1 and was significantly more resistant to antibiotics. Dissemination of multidrug-resistant MRSA clones warrants continuous tracking of resistant genotypes in the Indian subcontinent.     

Molecular characterization of invasive Staphylococcus aureus strains isolated from patients with diabetes in Iran: USA300 emerges as the major type

There have been few studies focused on the molecular characterization of invasive Staphylococcus aureus strains in patients with diabetes in Iran. In the present study, 20 invasive S. aureus strains recovered from the patients with diabetes characterized by the virulence and resistance analysis, biofilm formation, staphylocoagulase (SC) typing, S. aureus protein A locus (spa) typing staphylococcal cassette chromosome mec (SCCmec) typing, and multilocus sequence typing (MLST). Virulence gene detection indicated a high prevalence of strains encoding the pvl genes (50%), a low prevalence of the tst and seg gene (each of them was 5%) and a markedly high prevalence of fnbB (95%), fnbA (85%), icaD (75%), icaA (65%). A total of 3 coagulase types (III, 85%; II, 10%; V, 5%), 2 agr types (I, 90%; II 10%) and 2 SCCmec types (IV, 65%; III, 35%) and four different clones namely ST8-MRSA-IV/t008 (50%) (USA300), ST239-MRSA-III/t030 (35%), ST5-MRSA-IV/t002 (10%), and ST45-MRSA-IV/t038 (5%) were detected in this study. Eighty-five percent of the isolates were biofilm producers. All the 4 high-level mupirocin resistance (HLMUPR) strains belonged to CC/ST8-MRSA-IV/t008 clone and carried mupA gene. Fusidic acid-resistant isolate belonged to ST239-SCCmec III/t030 clone. One vancomycin-intermediate resistance isolates was detected in our study, which belonged to ST5-MRSA-IVt002. Circulating clone in MRSA strains (USA300) isolated from the patients with diabetes highlighting the possibility of transmission of these microorganisms' clones between hospital, community, and environments. However, further studies require providing critical insights into the importance of continued controlling and treatment of S. aureus infections in patients with diabetes.     

A novel multidrug-resistant PVL-negative CC1-MRSA-IV clone emerging in Ireland and Germany likely originated in South-Eastern Europe

This study investigated the recent emergence of multidrug-resistant Panton-Valentine leukocidin (PVL)-negative CC1-MRSA-IV in Ireland and Germany.Ten CC1-MSSA and 139 CC1-MRSA isolates recovered in Ireland between 2004 and 2017 were investigated. These were compared to 21 German CC1-MRSA, 10 Romanian CC1-MSSA, five Romanian CC1-MRSA and two UAE CC1-MRSA, which were selected from an extensive global database, based on similar DNA microarray profiles to the Irish isolates. All isolates subsequently underwent whole-genome sequencing, core-genome single nucleotide polymorphism (cgSNP) analysis and enhanced SCCmec subtyping.Two PVL-negative clades (A and B1) were identified among four main clades. Clade A included 20 German isolates, 119 Irish isolates, and all Romanian MRSA and MSSA isolates, the latter of which differed from clade A MRSA by 47–130 cgSNPs. Eighty-six Irish clade A isolates formed a tight subclade (A1) exhibiting 0–49 pairwise cgSNPs, 80 of which harboured a 46 kb conjugative plasmid carrying both ileS2, encoding high-level mupirocin resistance, and qacA, encoding chlorhexidine resistance. The resistance genes aadE, aphA3 and sat were detected in all clade A MRSA and the majority (8/10) of clade A MSSA isolates. None of the clade A isolates harboured any enterotoxin genes other than seh, which is universally present in CC1. Clade B1 included the remaining German isolate, 17 Irish isolates and the two UAE isolates, all of which corresponded to the Western Australia MRSA-1 (WA MRSA-1) clone based on genotypic characteristics. MRSA within clades A and B1 differed by 188 cgSNPs and clade-specific SCCmec characteristics were identified, indicating independent acquisition of the SCCmec element.This study demonstrated the existence of a European PVL-negative CC1-MRSA-IV clone that is distinctly different from the well-defined PVL-negative CC1-MRSA-IV clone, WA MRSA-1. Furthermore, cgSNP analysis revealed that this newly defined clone may have originated in South-Eastern Europe, before spreading to both Ireland and Germany.     

Methicillin-resistant Staphylococcus aureus ST30-SCCmec IVc clone as the major cause of community-acquired invasive infections in Argentina

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have become a major concern worldwide. We conducted a prospective multicenter study of invasive CA-MRSA to evaluate clinical features and genotype of strains causing invasive infections in Argentina. A total of 55 patients with invasive CA-MRSA infections were included. Most patients (60%) had bloodstream infections, 42% required admission to intensive care unit and 16% died. No CA-MRSA isolates were multiresistant (resistant ⩾3 classes of antibiotics). All isolates carried Panton-Valentine leukocidin (PVL) genes and staphylococcal cassette chromosome (SCCmec) type IV. The majority CA-MRSA strains belonged to ST30 and had identical pulsed-field gel electrophoresis (PFGE) patterns, qualifying as a clonal dissemination of a highly transmissible strain. The main clone recovered from patients with CA-MRSA invasive infections was genotyped as pulsed-field gel electrophoresis type C-ST30, SCCmec type IVc-spa type 019, PVL positive. It has become predominant and replaced the previously described CA-MRSA clone (PFGE type A, ST5, SCCmec type IV, spa type 311).     

All methicillin-resistant Staphylococcus auveus (MRSA) are not equal

New typing techniques are giving a greater understanding of the evolution and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA). A comparison of the overall genetic background of isolates is now possible using MultiLocus sequence typing (MLST). However, even isolates with the same genetic background can be different from each other because of the acquisition of antibiotic-resistance and pathogenicity determinants. Sequencing of the region involved with methicillin resistance, the mec region or staphylococcal cassette chromosome mec (SCCmec), has demonstrated that there are different SCCmecs. It has been found that strains with similar genetic backgrounds can have different SCCmecs and that strains with different genetic background can have similar SCCmecs. This, and molecular evidence, indicates that SCCmecs are mobile elements that are able to move between cells by an as yet unidentified mechanism.Typing has also demonstrated that some strains, known as epidemic MRSA (EMRSA), spread more readily in hospitals and health care institutions. However, it is not known why they have this ability. Whereas in the past MRSAs were regarded as being associated with health care institutions, strains have emerged in the community that are quite different from those associated with health care institutions. These strains are not multiply resistant to antimicrobials like most of the strains associated with health care institutions; however, there is concern that they will acquire additional resistance determinants and present problems for the treatment of staphylococcal infections. Some EMRSA are not multiply resistant and, on their resistance profiles, could be mistaken for community MRSA. This highlights the importance of typing in identifying and tracing MRSA for infection control.     

Methicillin-Resistant Staphylococcus aureus: A Growing Risk in the Hospital and in the Community

Methicillin-resistant Staphylococcus aureus is a common and continuously growing cause of nosocomial and community-acquired infections. The type, disease severity, and clinical outcomes of these infections, as well as the genotypic and susceptibility patterns of the bacteria differ according to the setting in which the infection occurs—a healthcare facility or the community setting. The incidence of these infections in the community setting has been growing consistently in the past decade or so. In addition, resistance to the many current antibiotics used to treat these infections is also growing, further complicating management. Rapid-diagnosis tests and new therapeutic agents are constantly under investigation. The authors review the current understanding of the epidemiology, clinical manifestations, and management of methicillin-resistant Staphylococcus aureus infection, including the growing problem of resistance. In addition, they discuss promising diagnostic and therapeutic alternatives, as well as new control strategies to prevent its transmission or the development of infection among carriers.Methicillin-resistant Staphylococcus aureus (MRSA) refers to isolates that are resistant to β-lactam antibiotics (including penicillins and cephalosporins).1 According to the Clinical and Laboratory Standards Institute (CLSI), MRSA is defined as isolates with a methicillin minimum inhibitory concentration (MIC) ≥4 μg/mL; however, S aureus already is considered nonsusceptible to oxacillin if the MIC is >2 μg/mL.2Methicillin resistance is mediated by the penicillin-binding protein (PBP)-2a encoded by the mecA gene. βlactam antibiotics have poor affinity for this altered PBP, and organisms are not killed when exposed to common therapeutic concentrations. The mecA gene is located on a mobile genetic element, the staphylococcal chromosome cassette (SCCmec). Sequencing SCCmec from many MRSA strains reveals that there are at least 5 SCCmec types (I-V) that vary in genetic base-pair construction and size.3     

Methicillin-Resistant Staphylococcus aureus (MRSA) Detected at Four U.S. Wastewater Treatment Plants

Background: The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal wastewater could be a reservoir of this microorganism. To date, no U.S. studies have evaluated the occurrence of MRSA in wastewater.Objective: We examined the occurrence of MRSA and methicillin-susceptible S. aureus (MSSA) at U.S. wastewater treatment plants.Methods: We collected wastewater samples from two Mid-Atlantic and two Midwest wastewater treatment plants between October 2009 and October 2010. Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® microbroth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains. Data were analyzed by two-sample proportion tests and analysis of variance.Results: We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) wastewater samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multidrug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates.Conclusions: Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater. Because of increasing use of reclaimed wastewater, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.     

Molecular epidemiology and antibiotic resistance of methicillin-resistant Staphylococcus aureus circulating in the Russian Federation

The aim of this study was to investigate the patterns of antimicrobial resistance and molecular features of methicillin-resistant Staphylococcus aureus (MRSA) isolates in Russia. Isolates recovered from hospital patients (n = 480), healthy medical personnel (n = 25), and healthy carriers (n = 13) were included in the study. Hospital-acquired MRSA (HA-MRSA) demonstrated high resistance to ciprofloxacin, gentamicin, and chloramphenicol (76%–92%), moderate – to tetracycline, erythromycin, clindamycin, and rifampicin (38%–54%), and low – to fusidic acid, co-trimoxazole, mupirocin, and daptomycin (2%–7%). Elevated MIC (2.0 μg/ml) of vancomycin was detected in 26% of isolates. All isolates were susceptible to linezolid and tigecycline. Multilocus sequence typing (MLST) revealed that CC8 isolates (ST8 + ST239) constituted 83.1% of HA-MRSA and that this genetic lineage dominated in all regions from Krasnoyarsk to Saint Petersburg. A local ST239 variant harboring the tst gene (ST239_Kras) was detected in Krasnoyarsk. The other HA-MRSA isolates belonged to clonal complex 5 (CC5) (21 isolates, 12.2%) and CC22 (2, 1.2%). The majority of CC5 isolates were affiliated with sequence type 228 (ST228) and were characterized with decreased susceptibility to ceftaroline (MIC = 2 μg/ml). We also detected, for the first time in Russia, livestock-associated MRSA (LA-MRSA) from clusters CC398 and CC97 in humans. Among the 2053 healthy persons screened for nasal carriage of S. aureus, the bacteria were isolated from 426 (21%); among them, 13 carried isolates identified as community-associated MRSA (CA-MRSA). Eleven of 13 CA-MRSA isolates belonged to ST22 (spa types t223, t3243, and t3689; SCCmec types IVa and IVc, agr type I, tst-positive) and were similar to the EMRSA-15/Middle Eastern variant (Gaza strain).     

Genotyping of community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) in a tertiary care centre in Mysore,South India: ST2371-SCCmec IV emerges as the major clone

The burden of community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) is on the rise in population and clinical settings on account of the adaptability and virulence traits of this pathogen. We characterized 45 non-duplicate CA-MRSA strains implicated mainly in skin and soft tissue infections (SSTIs) in a tertiary care hospital in Mysore, South India. All the isolates were genotyped by staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) typing, accessory gene regulator (agr) typing, and multi-locus sequence typing (MLST). Four sequence types (STs) belonging to three major clonal complexes (CCs) were identified among the isolates: CC22 (ST2371 and ST22), CC1 (ST772) and CC8 (ST8). The majority (53.3%) of the isolates was of the genotype ST2371-t852-SCCmec IV [sequence type-spa type-SCCmec type], followed by ST22-t852-SCCmec IV (22.2%), ST772-t657-SCCmec V (13.3%) and ST8-t008-SCCmec IV (11.1%). ST237I, a single locus variant of ST22 (EMRSA-15 clone), has not been reported previously from any of the Asian countries. Our study also documents for the first time, the appearance of ST8-SCCmec IV (USA300) strains in India. Representative strains of the STs were further analyzed by pulsed field gel electrophoresis (PFGE). agr typing detected type I or II alleles in the majority of the isolates. All the isolates were positive for the leukotoxin gene, pvl (Panton–Valentine leukocidin) and the staphylococcal enterotoxin gene cluster, egc. Interestingly, multidrug resistance (resistance to ⩾3 classes of non-beta-lactam antibiotics) was observed in 77.8% (n = 35) of the isolates. The highest (75.5%) resistance was recorded for ciprofloxacin, followed by erythromycin (53.3%), and quinupristin–dalfopristin (51.1%). Inducible clindamycin-resistance was identified in 37.7% of the isolates and it was attributed to the presence of erm(A), erm(C) and a combination of erm(A) and erm(C) genes. Isolates which showed a phenotypic pattern of M^R/L^S (macrolide-resistance/lincosamide-sensitivity) harbored the msr(A) gene. In conclusion, we report a high rate of multidrug resistance among Indian strains of CA-MRSA and the emergence of the lineages ST2371 and ST8 in India.     

MRSA Pediatric clone expressing ermC plus lnuA genes causing nosocomial transmission and healthcare workers colonization in a neonatal intensive care unit

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of both nosocomial and community-acquired infections. We describe an outbreak caused by the MRSA Pediatric clone expressing an unusual lincosamide resistant phenotype. Between January and May 2006, an MRSA outbreak was detected at the Neonatal Unit of Hospital Interzonal General de Agudos “Evita”, Buenos Aires Province, Argentina that affected ten patients. Seven isolates from seven patients plus five MRSA recovered from health care workers (nasal carriage) were studied. Two phenotypes were observed: (i) ELCi (10), resistance to erythromycin and lincomycin and inducible resistance to clindamycin; (ii) ELiCi (2), resistance to erythromycin and inducible resistance to lincomycin and clindamycin. All 12 MRSA were resistant to oxacillin, erythromycin and gentamicin. Isolates expressing the ELCi-phenotype showed lincomycin MIC values between 16 and 32 mg/L, while the remaining 2 isolates with ELiCi-phenotype presented a MIC value of 0.5 mg/L. No differences were observed between the clindamycin MIC values in both phenotypes, ranging 0.25–0.5 mg/L. Isolates showing ELCi-phenotype harbored ermC plus lnuA genes, and the other two only ermC gene. All 12 isolates were genetically related and belonged to the Pediatric clone (ST100) harboring a new variant of SCCmecIV. This is the first MRSA outbreak expressing an unusual ELCi phenotype due to a combination of ermC plus lnuA genes.     

Prevalence of community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) in skin and soft tissue infections among cases from Puducherry, India

Aim

Methicillin resistant Staphylococcus aureus (S. aureus) is a major human pathogen which causes a wide range of hospital and community-acquired infections worldwide. Our objective is to describe the prevalence of MRSA within Puducherry, India.

Methods

A total of 172 patients treated with incision and drainage of soft tissue infections from March 2009 to September 2010 were included in the present study. We examined the antibiotic sensitivity pattern and the distribution of genes among MRSA isolates.

Results

In total, 72 isolates were obtained of which 51 were MRSA and 21 were methicillin sensitive S. aureus (MSSA). All the isolates showed absolute resistance pattern against beta lactam antibiotics (penicillin, ampicillin, amoxicillin) and were found to be sensitive towards macrolide and lincosamide antibiotics. The gene distribution among MRSA isolates showed the presence of femA, mecA, and lukS in 100, 94.4 and 69.4?% of the isolates respectively. The antibiotic sensitivity pattern and molecular characterization showed an increased prevalence of community acquired MRSA (CA-MRSA) in the study population.

Conclusion

The MRSA isolates were found to be sensitive to macrolide and lincosamide antibiotics but MSSA showed resistance pattern to the same. In this regard these antibiotics can be used for the effective treatment of MRSA at the expense of MSSA among the study population.     

Multidrug-Resistant Methicillin-Resistant Staphylococcus aureus Associated with Bacteremia and Monocyte Evasion,Rio de Janeiro,Brazil

We typed 600 methicillin-resistant Staphylococcus aureus (MRSA) isolates collected in 51 hospitals in the Rio de Janeiro, Brazil, metropolitan area during 2014–2017. We found that multiple new clonal complex (CC) 5 sequence types had replaced previously dominant MRSA lineages in hospitals. Whole-genome analysis of 208 isolates revealed an emerging sublineage of multidrug-resistant MRSA, sequence type 105, staphylococcal cassette chromosome mec II, spa t002, which we designated the Rio de Janeiro (RdJ) clone. Using molecular clock analysis, we hypothesized that this lineage began to expand in the Rio de Janeiro metropolitan area in 2009. Multivariate analysis supported an association between bloodstream infections and the CC5 lineage that includes the RdJ clone. Compared with other closely related isolates, representative isolates of the RdJ clone more effectively evaded immune function related to monocytic cells, as evidenced by decreased phagocytosis rate and increased numbers of viable unphagocytosed (free) bacteria after in vitro exposure to monocytes.     

Bovine mastitis Staphylococcus aureus: Antibiotic susceptibility profile,resistance genes and molecular typing of methicillin-resistant and methicillin-sensitive strains in China

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) infection in dairy animals is of great concern for livestock and public health. The aim of present study was to detect new trends of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) towards antibiotic susceptibility, resistance genes and molecular typing by methods of disc diffusion, multiplex PCR assay and multilocus sequence typing (MLST). A total of 219 S. aureus strains were isolated from bovine mastitis cases from six provinces of China, including 34 MRSA strains. The results revealed that more than 70% isolated strains showed resistance to various antibiotics, and multiple-drugs resistance to more than five categories of antibiotics was found more common. The ermC was the most prevalent resistance gene, followed by other genes; however, ermA was the least frequently detected gene. Twenty-eight mecA-negative MRSA and six mecA-positive MRSA strains were detected, and in which three strains were ST97-MRSA-IV, others were ST965-MRSA-IV, ST6-MRSA-IV and ST9-MRSA-SCCmec-NT. The mecA-negative MRSA strains were found resistant to most of the antibiotics, and harbored aac(6′)/aph(2′′), aph(3′)-III and tetM genes higher than MSSA strains. The resistance to most of the antibiotics was significantly higher in MRSA than in MSSA strains. The MLST profiles showed that these strains mainly belonged to CC5, CC398, CC121 and CC50 lineage, especially within ST97 and ST398, while some novel sequence types (ST2154, ST2165 and ST2166) were identified and deposited in the MLST database. This indicates that the resistance of S. aureus is becoming more complicated by changes in multi-drug resistance mechanism and appearance of mecA-negative MRSA isolates, and importantly, MRSA-IV strains in different MLST types are emerging.     

Multiple-locus variable-number tandem-repeat analysis of meticillin-resistant Staphylococcus aureus discriminates within USA pulsed-field gel electrophoresis types

Many isolates of meticillin-resistant Staphylococcus aureus (MRSA) are indistinguishable when compared using the standard pulsed-field gel electrophoresis (PFGE) typing method. This may present a problem when investigating local outbreaks of MRSA transmission in a healthcare setting. It also impedes investigation of the widely disseminated community-acquired MRSA (USA 300-0114) in the inpatient setting, which is displacing other traditional hospital-acquired PFGE types. Combination of methods, including multiple-locus sequence typing (MLST), spa typing and staphylococcal cassette chromosome mec (SCCmec) typing, have been used with, or in place of, PFGE to characterise MRSA for epidemiological purposes. These methods are technically challenging, time-consuming and expensive and are rarely feasible except in large laboratories in tertiary care medical centres. Another method, which is simpler and with faster turnaround time, is multiple-locus variable-number tandem-repeat analysis (MLVA). We investigated the utility of MLVA to distinguish common PFGE types. The results suggest that MLVA can be used to identify unrelated strains with identical PFGE patterns or confirm close genetic composition of linked isolates. MLVA could potentially be used in conjunction with PFGE to validate relationships, but further prospective evaluation of these relationships will be required in order to define the proper role, if any, for use of this method in hospital epidemiology.