A Livestock-Associated,Multidrug-Resistant,Methicillin-Resistant Staphylococcus aureus Clonal Complex 97 Lineage Spreading in Dairy Cattle and Pigs in Italy

Pandemic methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 97 (CC97) lineages originated from livestock-to-human host jumps. In recent years, CC97 has become one of the major MRSA lineages detected in Italian farmed animals. The aim of this study was to characterize and analyze differences in MRSA and methicillin-susceptible S. aureus (MSSA) mainly of swine and bovine origins. Forty-seven CC97 isolates, 35 MRSA isolates, and 6 MSSA isolates from different Italian pig and cattle holdings; 5 pig MRSA isolates from Germany; and 1 human MSSA isolate from Spain were characterized by macrorestriction pulsed-field gel electrophoresis (PFGE) analysis, multilocus sequence typing (MLST), spa typing, staphylococcal cassette chromosome mec (SCCmec) typing, and antimicrobial resistance pattern analysis. Virulence and resistance genes were investigated by PCR and microarray analysis. Most of the isolates were of SCCmec type V (SCCmec V), except for two German MRSA isolates (SCCmec III). Five main clusters were identified by PFGE, with the German isolates (clusters I and II) showing 60.5% similarity with the Italian isolates, most of which (68.1%) grouped into cluster V. All CC97 isolates were Panton-Valentine leukocidin (PVL) negative, and a few (n = 7) tested positive for sak or scn. All MRSA isolates were multidrug resistant (MDR), and the main features were erm(B)- or erm(C)-mediated (n = 18) macrolide-lincosamide-streptogramin B resistance, vga(A)-mediated (n = 37) pleuromutilin resistance, fluoroquinolone resistance (n = 33), tet(K) in 32/37 tet(M)-positive isolates, and blaZ in almost all MRSA isolates. Few host-associated differences were detected among CC97 MRSA isolates: their extensive MDR nature in both pigs and dairy cattle may be a consequence of a spillback from pigs of a MRSA lineage that originated in cattle as MSSA and needs further investigation. Measures should be implemented at the farm level to prevent spillover to humans in intensive farming areas.     

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.     

MRSA Clonal Complex 22 Strains Harboring Toxic Shock Syndrome Toxin (TSST-1) Are Endemic in the Primary Hospital in Gaza,Palestine

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in both community and healthcare-related settings worldwide. Current knowledge regarding the epidemiology of S. aureus and MRSA in Gaza is based on a single community-based carriage study. Here we describe a cross-sectional analysis of 215 clinical isolates collected from Al-Shifa Hospital in Gaza during 2008 and 2012.

Methods

All isolates were characterized by spa typing, SCCmec typing, and detection of genes encoding Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin (TSST-1). Representative genotypes were also subjected to multilocus sequence typing (MLST). Antibiotic susceptibility testing was performed using VITEK2 and MicroScan.

Results

MRSA represented 56.3% of all S. aureus strains, and increased in frequency from 2008 (54.8%) to 2012 (58.4%). Aside from beta-lactams, resistance was observed to tetracycline, erythromycin, clindamycin, gentamicin, and fluoroquinolones. Molecular typing identified 35 spa types representing 17 MLST clonal complexes (CC), with spa 998 (Ridom t223, CC22) and spa 70 (Ridom t044, CC80) being the most prevalent. SCCmec types I, III, IV, V and VI were identified among MRSA isolates, while type II was not detected. PVL genes (lukF/S-PV) were detected in 40.0% of all isolates, while the TSST-1 gene (tst) was detected in 27.4% of all isolates, with surprisingly high frequency within CC22 (70.4%). Both PVL and TSST-1 genes were found in several isolates from 2012.

Conclusions

Molecular typing of clinical isolates from Gaza hospitals revealed unusually high prevalence of TSST-1 genes among CC22 MRSA, which is noteworthy given a recent community study describing widespread carriage of a CC22 MRSA clone known as the ‘Gaza strain’. While the latter did not address TSST-1, tst-positive spa 998 (Ridom t223) has been detected in several neighboring countries, and described as endemic in an Italian NICU, suggesting international spread of a ‘Middle Eastern variant’ of pandemic CC22 strain EMRSA-15.     

Characterization of Staphylococcus aureus from Distinct Geographic Locations in China: An Increasing Prevalence of spa-t030 and SCCmec Type III

Staphylococcus aureus belongs to one of the most common bacteria causing healthcare and community associated infections in China, but their molecular characterization has not been well studied. From May 2011 to June 2012, a total of 322 non-duplicate S. aureus isolates were consecutively collected from seven tertiary care hospitals in seven cities with distinct geographical locations in China, including 171 methicillin sensitive S. aureus (MSSA) and 151 MRSA isolates. All isolates were characterized by spa typing. The presence of virulence genes was tested by PCR. MRSA were further characterized by SCCmec typing. Seventy four and 16 spa types were identified among 168 MSSA and 150 MRSA, respectively. One spa type t030 accounted for 80.1% of all MRSA isolates, which was higher than previously reported, while spa-t037 accounted for only 4.0% of all MRSA isolates. The first six spa types (t309, t189, t034, t377, t078 and t091) accounted for about one third of all MSSA isolates. 121 of 151 MRSA isolates (80.1%) were identified as SCCmec type III. pvl gene was found in 32 MSSA (18.7%) and 5 MRSA (3.3%) isolates, with ST22-MSSA-t309 as the most commonly identified strain. Compared with non-epidemic MRSA clones, epidemic MRSA clones (corresponding to ST239) exhibited a lower susceptibility to rifampin, ciprofloxacin, gentamicin and trimethoprim-sulfamethoxazole, a higher prevalence of sea gene and a lower prevalence of seb, sec, seg, sei and tst genes. The increasing prevalence of multidrug resistant spa-t030 MRSA represents a major public health problem in China.     

High genetic diversity among community-associated Staphylococcus aureus in Europe: results from a multicenter study

Background

Several studies have addressed the epidemiology of community-associated Staphylococcus aureus (CA-SA) in Europe; nonetheless, a comprehensive perspective remains unclear. In this study, we aimed to describe the population structure of CA-SA and to shed light on the origin of methicillin-resistant S. aureus (MRSA) in this continent.

Methods and Findings

A total of 568 colonization and infection isolates, comprising both MRSA and methicillin-susceptible S. aureus (MSSA), were recovered in 16 European countries, from community and community-onset infections. The genetic background of isolates was characterized by molecular typing techniques (spa typing, pulsed-field gel electrophoresis and multilocus sequence typing) and the presence of PVL and ACME was tested by PCR. MRSA were further characterized by SCCmec typing. We found that 59% of all isolates were associated with community-associated clones. Most MRSA were related with USA300 (ST8-IVa and variants) (40%), followed by the European clone (ST80-IVc and derivatives) (28%) and the Taiwan clone (ST59-IVa and related clonal types) (15%). A total of 83% of MRSA carried Panton-Valentine leukocidin (PVL) and 14% carried the arginine catabolic mobile element (ACME). Surprisingly, we found a high genetic diversity among MRSA clonal types (ST-SCCmec), Simpson’s index of diversity = 0.852 (0.788–0.916). Specifically, about half of the isolates carried novel associations between genetic background and SCCmec. Analysis by BURP showed that some CA-MSSA and CA-MRSA isolates were highly related, suggesting a probable local acquisition/loss of SCCmec.

Conclusions

Our results imply that CA-MRSA origin, epidemiology and population structure in Europe is very dissimilar from that of USA.     

Associations between dru Types and SCCmec Cassettes

Molecular typing is an important tool in the investigation of methicillin resistant Staphylococcus aureus (MRSA) outbreaks and in following the evolution of MRSA. The staphylococcal cassette chromosome mec (SCCmec) contains a hypervariable region with a variable number of 40 bp repeats named direct repeat units (dru). The dru region has been suggested as a supplementary typing method for MRSA and an international nomenclature exists. The purpose of this study was to investigate the diversity and variability of the dru region in a diverse collection of MRSA. We studied 302 MRSA isolates harbouring SCCmec types I to VI. The isolates represented a broad genetic background based on Staphylococcal protein A (spa) typing and multilocus sequence typing (MLST) and included 68 isolates (68 patients) from an outbreak with t024-ST8-IVa and 26 isolates from the same patient. Sequencing identified 53 dru types (dt) in 283 isolates, while eighteen isolates contained no dru repeats and one isolate resisted sequencing. The most common dru type, dt10a, was present in 53% of the sequenced isolates and was found in all SCCmec types, except type II. Seven (10%) of the 68 epidemiologically related patients had isolates with dru type variants indicating that dru typing is not useful as a first line epidemiological typing tool. However, MRSA isolates cultured from a single patient over a three year period exhibited a single dru type. The finding of dt10a in most SCCmec types suggests that dru and mecA originate from the same Staphylococcus species.     

Susceptibility of important Gram-negative pathogens to tigecycline and other antibiotics in Latin America between 2004 and 2010

Background

The evolving epidemiology of methicillin resistant Staphylococcus aureus (MRSA) is characterized by the emergence of infections caused by non multiresistant MRSA carrying staphylococcal chromosomal cassette (SCC)mec IV or V in the healthcare settings. A molecular epidemiological analysis of non multiresistant MRSA isolates from four acute general hospitals was performed in Palermo, Italy, during a one year period.

Methods

For the purpose of the study, MRSA isolates were defined as non multiresistant when they were susceptible to at least three classes of non ??-lactam antibiotics. Seventy-five isolates were submitted to antimicrobial susceptibility testing, multilocus sequence typing (MLST) and polymerase chain reaction (PCR) for SCCmec, accessory gene regulator (agr) groups, arginine catabolic mobile element (ACME) and Panton Valentine leukocidin (PVL) toxin genes. For epidemiological typing, Multiple-Locus Variable-Number Tandem Repeat Fingerprinting (MLVF) was performed on all isolates and pulsed field gel electrophoresis (PFGE) on ST8 isolates.

Results

Non multiresistant MRSA isolates were isolated from all hospitals. Resistances to ciprofloxacin, macrolides and tetracycline were the most prevalent. MLST attributed 46 isolates with ST22, 13 with ST8, eight with ST1, three with ST50 and three with ST398. SCCmec type IV was found in all isolates. PVL was detected in one ST22 isolate. All isolates tested negative for the ACME element. MLVF identified 31 different patterns, some subtype clusters ranging in size between two and 22 isolates. The closely related PFGE patterns of the ST8 isolates differed from USA300.

Conclusions

A polyclonal circulation of non multiresistant MRSA along with blurring of boundaries between healthcare associated (HA)-MRSA and community associated (CA)-MRSA appear to be occurring in our epidemiological setting. A better understanding of spread of MRSA with the support of molecular typing can provide invaluable information in the epidemiological, microbiological and clinical fields.     

Methicillin‐resistant Staphylococcus aureus carriage among veterinary staff and dogs in private veterinary clinics in Hokkaido,Japan

To explore the prevalence and molecular characteristics of methicillin‐resistant Staphylococcus aureus (MRSA) in veterinary medical practices, MRSA carriage was tested among 96 veterinarians (Vets), 70 veterinary technicians (VTs) and 292 dogs with which they had contact at 71 private veterinary clinics (VCs) in Hokkaido, Japan. MRSA isolates were obtained from 22 Vets [22.9%] and 7 VTs [10%]. The prevalence of MRSA among Vets was as high as that found in an academic veterinary hospital in our previous study. In contrast, only two blood donor dogs and one dog with liver disease (1.0%, 3/292) yielded MRSA. All MRSA‐positive dogs were reared or treated in different VCs, in each of which at least one veterinary staff member carrying MRSA worked. Sequence types (ST) identified by multilocus sequence typing, spa types, and SCCmec types for canine MRSA isolates (ST5‐spa t002‐SCCmec II [from two dogs] or ST30‐spa t021‐SCCmec IV [from a dog]) were concordant with those from veterinary staff members in the same clinics as the MRSA‐positive dogs, with which they had potentially had contact. Most MRSA isolates from veterinary staff were the same genotype (SCCmec type II and spa type t002) as a major hospital‐acquired MRSA clone in Japan. The remaining MRSA was the same genotypes as domestic and foreign community‐associated MRSA. Measures against MRSA infection should be provided in private VCs.     

Nasal Carriage of Methicillin-Resistant Staphylococcus aureus among Pediatricians in Taiwan

Background

Health care workers (HCWs) are at the interface between hospitals and communities. The survey for methicillin-resistant Staphylococcus aureus (MRSA) carriage among HCWs has mostly been conducted to investigate outbreaks or endemics. Community-associated MRSA are prevalent among children in Taiwan. We conducted this study to better understand the carriage rate of MRSA among pediatricians in non-outbreak situations in Taiwan,.

Methods

A total of 220 pediatricians from Taiwan who attended the annual meeting of Taiwan Pediatric Association in April, 2010 were recruited to participate in this study and were sampled from the nares for the detection of MRSA by polymerase chain reaction (PCR) and further by culture. The following molecular analyses were performed, including pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), typing of staphylococcal cassette chromosome mec (SCCmec) and the presence of Panton-Valentine leukocidin (PVL) genes.

Results

MRSA was detected from 15 attendees (6.8%) by PCR. MRSA-colonized attendees had a significantly lower rate (0.041) of working in the medical center, while borderline significantly higher rate of working in the Regional Hospital (p=0.056), than those without MRSA colonization. From those 15 samples, 12 MRSA isolates were identified by culture and molecularly characterized. Three PFGE patterns, two sequence types (ST 59, ST 508), and two SCCmec types (IV and V_T) were identified, respectively. Five isolates, including three carrying SCCmec types V_T, were PVL-positive. All 12 isolates were susceptible to vancomycin, teicoplanin, linezolid, fusidic acid, trimethoprim/sulfamethoxazole, and doxycyclin, and resistant to penicillin.

Conclusion/significance

Around seven percent of pediatricians in Taiwan harbored CA-MRSA in their nares.     

Comparison of spa Types,SCCmec Types and Antimicrobial Resistance Profiles of MRSA Isolated from Turkeys at Farm,Slaughter and from Retail Meat Indicates Transmission along the Production Chain

The prevalence of MRSA in the turkey meat production chain in Germany was estimated within the national monitoring for zoonotic agents in 2010. In total 22/112 (19.6%) dust samples from turkey farms, 235/359 (65.5%) swabs from turkey carcasses after slaughter and 147/460 (32.0%) turkey meat samples at retail were tested positive for MRSA. The specific distributions of spa types, SCCmec types and antimicrobial resistance profiles of MRSA isolated from these three different origins were compared using chi square statistics and the proportional similarity index (Czekanowski index). No significant differences between spa types, SCCmec types and antimicrobial resistance profiles of MRSA from different steps of the German turkey meat production chain were observed using Chi-Square test statistics. The Czekanowski index which can obtain values between 0 (no similarity) and 1 (perfect agreement) was consistently high (0.79–0.86) for the distribution of spa types and SCCmec types between the different processing stages indicating high degrees of similarity. The comparison of antimicrobial resistance profiles between the different process steps revealed the lowest Czekanowski index values (0.42–0.56). However, the Czekanowski index values were substantially higher than the index when isolates from the turkey meat production chain were compared to isolates from wild boar meat (0.13–0.19), an example of a separated population of MRSA used as control group. This result indicates that the proposed statistical method is valid to detect existing differences in the distribution of the tested characteristics of MRSA. The degree of similarity in the distribution of spa types, SCCmec types and antimicrobial resistance profiles between MRSA isolates from different process stages of turkey meat production may reflect MRSA transmission along the chain.     

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.     

Livestock-Associated Methicillin Resistant and Methicillin Susceptible Staphylococcus aureus Sequence Type (CC)1 in European Farmed Animals: High Genetic Relatedness of Isolates from Italian Cattle Herds and Humans

Methicillin-resistant Staphylococcus aureus (MRSA) Sequence Type (ST)1, Clonal Complex(CC)1, SCCmec V is one of the major Livestock-Associated (LA-) lineages in pig farming industry in Italy and is associated with pigs in other European countries. Recently, it has been increasingly detected in Italian dairy cattle herds. The aim of this study was to analyse the differences between ST1 MRSA and methicillin-susceptible S. aureus (MSSA) from cattle and pig herds in Italy and Europe and human isolates. Sixty-tree animal isolates from different holdings and 20 human isolates were characterized by pulsed-field gel electrophoresis (PFGE), spa-typing, SCCmec typing, and by micro-array analysis for several virulence, antimicrobial resistance, and strain/host-specific marker genes. Three major PFGE clusters were detected. The bovine isolates shared a high (≥90% to 100%) similarity with human isolates and carried the same SCCmec type IVa. They often showed genetic features typical of human adaptation or present in human-associated CC1: Immune evasion cluster (IEC) genes sak and scn, or sea; sat and aphA3-mediated aminoglycoside resistance. Contrary, typical markers of porcine origin in Italy and Spain, like erm(A) mediated macrolide-lincosamide-streptograminB, and of vga(A)-mediated pleuromutilin resistance were always absent in human and bovine isolates. Most of ST(CC)1 MRSA from dairy cattle were multidrug-resistant and contained virulence and immunomodulatory genes associated with full capability of colonizing humans. As such, these strains may represent a greater human hazard than the porcine strains. The zoonotic capacity of CC1 LA-MRSA from livestock must be taken seriously and measures should be implemented at farm-level to prevent spill-over.     

Extensive Dissemination of Methicillin-Resistant Staphylococcus aureus (MRSA) between the Hospital and the Community in a Country with a High Prevalence of Nosocomial MRSA

According to the EARS-Net surveillance data, Portugal has the highest prevalence of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) in Europe, but the information on MRSA in the community is very scarce and the links between the hospital and community are not known. In this study we aimed to understand the events associated to the recent sharp increase in MRSA frequency in Portugal and to evaluate how this has shaped MRSA epidemiology in the community. With this purpose, 180 nosocomial MRSA isolates recovered from infection in two time periods and 14 MRSA isolates recovered from 89 samples of skin and soft tissue infections (SSTI) were analyzed by pulsed-field gel electrophoresis (PFGE), staphylococcal chromosome cassette mec (SCCmec) typing, spa typing and multilocus sequence typing (MLST). All isolates were also screened for the presence of Panton Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME) by PCR. The results showed that ST22-IVh, accounting for 72% of the nosocomial isolates, was the major clone circulating in the hospital in 2010, having replaced two previous dominant clones in 1993, the Iberian (ST247-I) and Portuguese (ST239-III variant) clones. Moreover in 2010, three clones belonging to CC5 (ST105-II, ST125-IVc and ST5-IVc) accounted for 20% of the isolates and may represent the beginning of new waves of MRSA in this hospital. Interestingly, more than half of the MRSA isolates (8/14) causing SSTI in people attending healthcare centers in Portugal belonged to the most predominant clones found in the hospital, namely ST22-IVh (n = 4), ST5-IVc (n = 2) and ST105-II (n = 1). Other clones found included ST5-V (n = 6) and ST8-VI (n = 1). None of the MRSA isolates carried PVL and only five isolates (ST5-V-t179) carried ACME type II. The emergence and spread of EMRSA-15 may be associated to the observed increase in MRSA frequency in the hospital and the consequent spillover of MRSA into the community.     

Prevalence and Trends of Staphylococcus aureus Bacteraemia in Hospitalized Patients in South Africa, 2010 to 2012: Laboratory-Based Surveillance Mapping of Antimicrobial Resistance and Molecular Epidemiology

Introduction

We aimed to obtain an in-depth understanding on recent antimicrobial resistance trends and molecular epidemiology trends of S. aureus bacteraemia (SAB).

Methods

Thirteen academic centres in South Africa were included from June 2010 until July 2012. S. aureus susceptibility testing was performed on the MicroScan Walkaway. Real-time PCR using the LightCycler 480 II was done for mecA and nuc. SCCmec and spa-typing were finalized with conventional PCR. We selected one isolate per common spa type per province for multilocus sequence typing (MLST).

Results

S. aureus from 2709 patients were included, and 1231 (46%) were resistant to methicillin, with a significant decline over the three-year period (p-value = 0.003). Geographical distribution of MRSA was significantly higher in Gauteng compared to the other provinces (P<0.001). Children <5 years were significantly associated with MRSA with higher rates compared to all other age groups (P = 0.01). The most prevalent SCCmec type was SCCmec type III (531 [41%]) followed by type IV (402 [31%]). Spa-typing discovered 47 different spa-types. The five (87%) most common spa-types were t037, t1257, t045, t064 and t012. Based on MLST, the commonest was ST612 clonal complex (CC8) (n = 7) followed by ST5 (CC5) (n = 4), ST36 (CC30) (n = 4) and ST239 (CC8) (n = 3).

Conclusions

MRSA rate is high in South Africa. Majority of the isolates were classified as SCCmec type III (41%) and type IV (31%), which are typically associated with hospital and community- acquired infections, respectively. Overall, this study reveals the presence of a variety of hospital-acquired MRSA clones in South Africa dominance of few clones, spa 037 and 1257. Monitoring trends in resistance and molecular typing is recommended to detect changing epidemiological trends in AMR patterns of SAB.     

Molecular characterization of methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> nasal isolates from Turkey

Methicillin-resistant Staphylococcus aureus (MRSA) colonize most frequently in the anterior nares of the nose and cause serious infections all over the world. The aim of this study was to determine the nasal carriage rate of S. aureus and MRSA strains in Turkish elementary school children. We also analyzed molecular characterizations of MRSA strains by using pulse field gel electrophoresis (PFGE), multi locus sequence typing (MLST), staphylococcal chromosomal cassette mec (SCCmec) typing, and detection of the Panton-valentine leucocidin (PVL) gene. The nasal swabs were obtained from 4,050 children during a 4 month period in Ankara. In vitro antimicrobial susceptibility testing to 1 μg oxacillin and 30 μg cefoxitin was determined by a disk diffusion method. We found that the 1,001 of 4,050 (24.7%) children were colonized with S. aureus. Three S. aureus strains were resistant to oxacillin and cefoxitin. The rate of MRSA among all children was 0.07%. The MRSA strains revealed three different PFGE pattern. All MRSA isolates by harbored the SCCmec type IV element, but not the PVL gene. The two MRSA isolate belonged to sequence type (ST) 30, whereas the other one was a unique type. The results of this study demonstrated that S. aureus nasal carriage rate was consistent with previous studies. However, MRSA carriage rate was low. This study also indicated that the ST30-type IV without PVL gene MRSA clone may be expected to spread in Turkish community.     

High Heterogeneity within Methicillin-Resistant Staphylococcus aureus ST398 Isolates,Defined by Cfr9I Macrorestriction-Pulsed-Field Gel Electrophoresis Profiles and spa and SCCmec Types

During recent years, the animal-associated methicillin-resistant Staphylococcus aureus clone ST398 has extensively been studied. The DNA of these isolates turned out to be refractory to SmaI restriction, and consequently, SmaI is unsuitable for subtyping this clone by standard pulsed-field gel electrophoresis (PFGE). Very recently, ST398 DNA was shown to be digested by Cfr9I, a neoschizomer of SmaI. In the present study, we employed Cfr9I PFGE on 100 German and 5 Dutch ST398 isolates and compared their PFGE profiles, protein A gene variable repeat regions (spa types), and types of the staphylococcal cassette chromosome mec (SCCmec). The isolates (from healthy carrier pigs, clinical samples from pigs, dust from farms, milk, and meat) were assigned to 35 profiles, which were correlated to the SCCmec type. A dendrogram with the Cfr9I patterns assigned all profiles to two clusters. Cluster A grouped nearly all isolates with SCCmec type V, and cluster B comprised all SCCmec type IVa and V* (a type V variant first identified as III) carriers plus one isolate with SCCmec type V. Both clusters also grouped methicillin-susceptible S. aureus isolates. The association of the majority of isolates with SCCmec type V in one large cluster indicated the presence of a successful subclone within the clonal complex CC398 from pigs, which has diversified. In general, the combination of Cfr9I PFGE with spa and SCCmec typing demonstrated the heterogeneity of the series analyzed and can be further used for outbreak investigations and traceability studies of the MRSA ST398 emerging clone.Methicillin-resistant Staphylococcus aureus (MRSA) strains are an important cause of hospital-acquired infections worldwide (8). However, MRSA strains are not confined to health care settings, and during the last 10 years community-acquired MRSA has increasingly been reported (8). In 2003, a clone of MRSA associated with pig farming and not related to the traditional hospital- and community-acquired MRSA emerged in the Netherlands (37), where it now amounts to >30% of human MRSA cases (16). This clone has also been detected in healthy and sick animals, in food of animal origin, and in humans from other European countries, Canada, the United States, the Dominican Republic, and China (5, 7, 31, 38, 39). This emerging MRSA clone belongs to the multilocus sequence type ST398, which includes different spa types (mainly t011, t034, and t108). The majority of the ST398 isolates reported are MRSA, although methicillin-susceptible (MSSA) strains have been described as well (15, 34). Resistance to methicillin and other β-lactam antibiotics is caused by the mecA gene, which is located on a mobile genetic element, the staphylococcal cassette chromosome mec (SCCmec). The SCCmec cassette consists of the mec gene complex, the ccr gene complex, and the junkyard regions. Based on the variability and combinations of these genetic elements, several types of SCCmec and several variants of the types have been described (9). Three SCCmec types (III, IVa, and V) were identified in ST398 isolates (25). However, recent investigations have shown that some ST398 isolates typed as SCCmec type III using the method of Zhang et al. (40) proved to be type V after further sequencing (21, 35).For typing S. aureus, pulsed-field gel electrophoresis (PFGE) of the whole genome by macrorestriction with the SmaI endonuclease is still considered as the “gold standard” (26). However, the isolates of the ST398 clone are nontypeable (NT) by PFGE using SmaI (3, 4). Consequently, comparison between these isolates and the typeable ones from humans and animals is not possible. The nontypeability is due to the action of a novel C5-cytosine methyltransferase which modifies the consensus sequence C^mCNGG at the second cytosine (3, 4). Other enzymes with a different recognition sequence from SmaI have been used for PFGE typing of the ST398 clone, including EagI and ApaI (22, 28, 31, 38), but the patterns obtained cannot be compared to S. aureus patterns generated with SmaI. XmaI, a neoschizomer of SmaI that recognizes the same sequence cutting at a different position, only generates partial digestions (3, 4). Recently, the use of Cfr9I, another neoschizomer of SmaI whose activity is not reduced on ST398 methylated DNA, has been recommended. This enzyme had been successfully used for typing SmaI NT macrolide-resistant Streptococcus pyogenes isolates (6, 30), and now it is being applied for typing ST398 isolates, i.e., from human origin (5, 11, 36) and, to a lesser extent, from animals (3, 36). The aim of this study was to characterize a large collection of recent ST398 isolates by Cfr9I PFGE as well as other methods (spa typing, multilocus sequence typing [MLST], and SCCmec typing). Most of them were recovered in Germany from different sources, including animals and foods.     

A Typical Hospital-Acquired Methicillin-Resistant Staphylococcus aureus Clone Is Widespread in the Community in the Gaza Strip

Epidemiological data on community acquired methicillin-resistant-Staphylococcus aureus (CA-MRSA) carriage and infection in the Middle-East region is scarce with only few reports in the Israeli and Palestinian populations. As part of a Palestinian-Israeli collaborative research, we have conducted a cross-sectional survey of nasal S. aureus carriage in healthy children and their parents throughout the Gaza strip. Isolates were characterized for antibiotic susceptibility, mec gene presence, PFGE, spa type, SCCmec-type, presence of PVL genes and multi-locus-sequence-type (MLST). S. aureus was carried by 28.4% of the 379 screened children-parents pairs. MRSA was detected in 45% of S. aureus isolates, that is, in 12% of the study population. A single ST22-MRSA-IVa, spa t223, PVL-gene negative strain was detected in 64% of MRSA isolates. This strain is typically susceptible to all non-β-lactam antibiotics tested. The only predictor for MRSA carriage in children was having an MRSA carrier-parent (OR = 25.5, P = 0.0004). Carriage of the Gaza strain was not associated with prior hospitalization. The Gaza strain was closely related genetically to a local MSSA spa t223 strain and less so to EMRSA15, one of the pandemic hospital-acquired-MRSA clones, scarcely reported in the community. The rapid spread in the community may be due to population determinants or due to yet unknown advantageous features of this particular strain.     

Characterization of Methicillin-Resistant and -Susceptible Staphylococcal Isolates from Bovine Milk in Northwestern China

Emergence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) in bovine milk is a major public health concern. The primary purpose of this research was to determine molecular genetic characteristics and antibiotic resistance of staphylococcal isolates recovered from milk of mastitic cows in the Shaanxi Province in Northwestern China. One hundred and thirteen methicillin-susceptible Staphylococcus aureus (MSSA), one mecA-positive and phenotype-positive MRSA, seven mecA- and mecC- negative but phenotype-positive MRSA and two MR-CoNS including one oxacillin-susceptible mecA-positive Staphylococcus haemolyticus (OS-MRSH) and one mecA-positive and methicillin-resistant Staphylococcus epidermidis (MRSE) isolates were recovered from 214 quarter milk samples on 4 dairy farms. All above 123 isolates were subjected to antibiotic resistance profiling. S. aureus isolates were also genotyped using the spa typing and the multilocus sequence typing (MLST). Eight MRSA and 2 MR-CoNS isolates were additionally tested for SCCmec types. Resistance was common among isolates against ampicillin or penicillin (80.5%), kanamycin (68.3%), gentamicin (67.5%), tetracycline (43.9%) and chloramphenicol (30.1%). However, no isolate was resistant to vancomycin or teicoplanin. Twenty, 29 and 58 isolates showed resistance to 1, 2 or more than 2 antibiotics, respectively. The predominant multidrug resistance profile was penicillin/ampicillin/kanamycin/gentamicin/tetracycline (46 isolates). Most S. aureus isolates belonged to spa types t524 (n = 63), t11772 (a new type, n = 31) and t4207 (n = 15). At the same time, MLST types ST71 (n = 67) and ST2738 (a new type, n = 45) were identified as dominant sequence types. The mecA-positive and phenotype-positive MRSA isolate had a composite genotype t524-ST71-SCCmecIVa, while 7 mecA-negative but phenotype-positive MRSA isolates were all t524-ST71. The OS-MRSH isolate contained a type V SCCmec cassette, while the MRSE isolate possessed a non-typeable SCCmec. The spa-MLST types t11772-ST2738 (n = 27), t11807-ST2683 (n = 4) and t11771-ST2738 (n = 3) were newly identified genotypes of S. aureus. These new genotypes and multidrug-resistant staphylococci could pose additional threat to animal and human health.     

Distribution of Staphylococcal Cassette Chromosome mec Types and Correlation with Comorbidity and Infection Type in Patients with MRSA Bacteremia

Background

Molecular epidemiological definitions that are based on staphylococcal cassette chromosome mec (SCCmec) typing and phylogenetic analysis of methicillin-resistant Staphylococcus aureus (MRSA) isolates are considered a reliable way to distinguish between healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). However, there is little information regarding the clinical features and outcomes of bacteremia patients with MRSA carrying different SCCmec types.

Methods

From January 1 through December 31, 2006, we recorded the demographic data and outcomes of 159 consecutive adult MRSA bacteremia patients from whom isolates for SCCmec analysis were collected. All participants were patients at a tertiary care center in Taiwan.

Principal Findings

The following SCCmec types were identified in MRSA isolates: 30 SCCmec II (18.9%), 87 SCCmec III (54.7%), 22 SCCmec IV (13.8%), and 20 SCCmec V (12.6%). The time from admission to the first MRSA-positive blood culture for patients infected with isolates with the SCCmec III element (mean/median, 50.7/26 days) was significantly longer than for patients infected with isolates carrying SCCmec IV or V (mean/median, 6.7/3 days for SCCmec IV; 11.1/10.5 days for SCCmec V) (P<0.05). In univariate analysis, community onset, soft tissue infection, and deep-seated infection were predictors for SCCmec IV/V. In multivariate analysis, length of stay before index culture, diabetes mellitus, and being bedridden were independent risk factors associated with SCCmec II/III.

Conclusions

These findings are in agreement with previous studies of the genetic characteristics of CA-MRSA. MRSA bacteremia with SCCmec II/III isolates occurred more among patients with serious comorbidities and prolonged hospitalization. Community onset, skin and soft tissue infection, and deep-seated infection best predicted SCCmec IV/V MRSA bacteremia.