Molecular epidemiology of methicillin-resistant Staphylococcus aureus in Israel: dissemination of global clones and unique features

ST913-IVa-t991 Methicillin-Resistant Staphylococcus aureus among Pediatric Patients, Israel

In Israel, prevalence of sequence type 913, staphylococcal cassette chromosome mecIVa, spa type t991 methicillin-resistant Staphylococcus aureus lineage has surged among pediatric populations, predominantly in Arab and Orthodox Jewish communities. Antimicrobial resistance patterns vary by demographics. This lineage's spread and microevolution in the Middle East underscore the need for ongoing surveillance.

A look at staphylococci from the one health perspective

Staphylococcus aureus and other staphylococcal species are resident and transient multihost colonizers as well as conditional pathogens. Especially S. aureus represents an excellent model bacterium for the "One Health" concept because of its dynamics at the human-animal interface and versatility with respect to host adaptation. The development of antimicrobial resistance plays another integral part. This overview will focus on studies at the human-animal interface with respect to livestock farming and to companion animals, as well as on staphylococci in wildlife. In this context transmissions of staphylococci and of antimicrobial resistance genes between animals and humans are of particular significance.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

The Dissemination of a Single Staphylococcusaureus Strain, Spa-t2873, as the Predominant Cause of Bovine Mastitis in Israeli Dairy Farms

Simple Summary

Staphylococcus aureus is one of the most important pathogens causing intramammary infection (IMI) in cattle. We aimed to characterize which are the specific strains that are responsible for the majority of these cases. During the one-year survey, S. aureus was identified in 152 dairy farms, with a total of 440 positive samples. One specific type (designated-spa t2873) was found in 284 isolates (64.5%). Notably, 25 cases were detected in one specific farm, all of which were found to be dominant spa t2873 type. By using genomic analysis, we were able to ascertain that most transmission events occurred within the same milking group. Our study revealed the dissemination of a single strain to the majority of Israeli dairy farms. The possibility of inter-farm transmission should be monitored and prevented.

Abstract

Staphylococcus aureus is one of the most important pathogens causing intramammary infection (IMI) in dairy herds. The goals of this study were (1) to describe the prevalence of S. aureus in Israeli dairy farms; (2) to characterize the spa-based clonal structure of mastitis-related S. aureus isolates; (3) to analyze the transmission network of a large outbreak within a single farm and (4) to characterize the virulence factors of the outbreak strain. The prevalence and the molecular survey were performed on all Israeli IMI-related isolates, 9.2019–8.2020. Molecular methods included spa-typing for the survey and whole-genome sequencing (WGS) for the investigation of the farm ‘A’ outbreak. During the one-year survey, S. aureus was identified in 152 dairy farms, with a total of 440 positive samples. The spa t2873 was found in 284 isolates (64.5%) across 112 farms (73.6%). Other common types included t529 (n = 46), t9303 (n = 34) and the methicillin-resistant S. aureus t011 (n = 11). The highest number of cases (n = 25) was detected in Farm ‘A’, all of which were found to be spa t2873. Phylogenetic analysis confirmed that most transmission events occurred within the same milking group, and inter-group transmission was due to the transfer of cows between groups or due to consecutive milking order. The spa t2873 strain contained putative virulence genes, including various intracellular and collagen adhesion proteins. Our study revealed the dissemination of the t2873 strain to the majority of Israeli dairy farms. The possibility of inter-farm transmission should be monitored and prevented.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Clinical Isolates during 7.5 Years in One Regional Hospital in Israel

Background

The clonal repertoire of community-associated Methicillin-resistant Staphylococcus aureus (CA-MRSA) strains appear to differ between hospitals and geographic locations. We aimed to study the molecular epidemiology of MRSA infections in our regional hospital in Israel.

Methods

A retrospective analysis of MRSA isolates from hospitalized patients, which underwent spa typing between 2012 and 2019. Mainly, MRSA-bloodstream isolates were typed. Isolates were grouped into healthcare-associated (HcA) or community-associated (CA). HcA were further divided into hospital-related or long-term care facility- (LTCF-) related. Several representatives underwent SCCmec typing.

Results

We analyzed 166 clinical MRSA isolates: 115 (70%) bloodstream, 42 (25%) wounds/abscesses, and 9 (5%) screening isolates. 145 (87%) were HcA, and 21 (13%) were CA. Common (72%) spa types were t002, t032, t008, t001, and t065. Eighty (55%) isolates were attributed to LTCFs and 65 isolates to our hospital, both showing similar spa types distribution. The most prevalent spa type among patients with HcA infection was t002 (50 isolates, 32%), followed by t032, t065, t578, t008, and t001. Most (88/115, 77%) bloodstream infections (BSIs) were HcA, typically occurring in the same facility in which the infection was acquired. In 27 cases (23%), the BSI developed in the community setting, and in half of these cases, a previous healthcare system exposure was evident.

Conclusions

The MRSA clonal population in this longitudinal study was stable and consisted mainly of molecular lineages widespread in Europe. SCCmec-IV strains play a major role in causing MRSA infections in the healthcare settings, especially in LTCFs. Community-acquired MRSA BSIs without any previous healthcare exposure are still relatively rare.

Distribution of the Most Prevalent Spa Types among Clinical Isolates of Methicillin-Resistant and -Susceptible Staphylococcus aureus around the World: A Review

Background:Staphylococcus aureus, a leading cause of community-acquired and nosocomial infections, remains a major health problem worldwide. Molecular typing methods, such as spa typing, are vital for the control and, when typing can be made more timely, prevention of S. aureus spread around healthcare settings. The current study aims to review the literature to report the most common clinical spa types around the world, which is important for epidemiological surveys and nosocomial infection control policies.

Methods: A search via PubMed, Google Scholar, Web of Science, Embase, the Cochrane library, and Scopus was conducted for original articles reporting the most prevalent spa types among S. aureus isolates. The search terms were “Staphylococcus aureus, spa typing.”

Results: The most prevalent spa types were t032, t008 and t002 in Europe; t037 and t002 in Asia; t008, t002, and t242 in America; t037, t084, and t064 in Africa; and t020 in Australia. In Europe, all the isolates related to spa type t032 were MRSA. In addition, spa type t037 in Africa and t037and t437 in Australia also consisted exclusively of MRSA isolates. Given the fact that more than 95% of the papers we studied originated in the past decade there was no option to study the dynamics of regional clone emergence.

Conclusion: This review documents the presence of the most prevalent spa types in countries, continents and worldwide and shows big local differences in clonal distribution.

Hospital clones of methicillin-resistant Staphylococcus aureus are carried by medical students even before healthcare exposure

Background

Methicillin-resistant Staphylococcus aureus (MRSA) strains are prevalent in healthcare and the community. Few studies have examined MRSA carriage among medical students.

The aim of this study is to examine Staphylococcus aureus (SA) carriage, and particular MRSA, over time in cohort medical students

Methods

Prospective collection of nasal swabs from medical students in Israel and assessment of SA carriage. Three samples were taken per student in preclinical and clinical parts of studies. Antibiotic susceptibilities were recorded and MRSA typing was performed by staphylococcal cassette chromosome mec (SCCmec) types, Panton Valentine Leukocidin (PVL) encoding genes, and spa types. Clonality was assessed by pulsed-field gel electrophoresis.

Results

Among 58 students, SA carriage rates increased from 33% to 38% to 41% at baseline (preclinical studies), 13 and 19 months (clinical studies), respectively (p = 0.07). Methicillin-susceptible SA (MSSA) carriage increased in the clinical studies period (22 to 41%, p = 0.01). Overall, seven students (12%) carried 13 MRSA isolates. MRSA isolates were PVL negative and were characterized as SCCmecII-t002, SCCmecIV-t032, or t12435 with untypable SCCmec. MRSA carriage during the pre-clinical studies was evident in 4/7 students. Two students carried different MRSA clones at various times and persistent MRSA carriage was noted in one student. Simultaneous carriage of MRSA and MSSA was not detected.

Conclusions

MSSA carriage increased during the clinical part of studies in Israeli medical students. Compared with previous reports, higher rates of MRSA carriage were evident. MRSA strains were genotypically similar to Israeli healthcare-associated clones; however, carriage occurred largely before healthcare exposure, implying community-acquisition of hospital strains.

Methicillin-Resistant Staphylococcus aureus spa Type t002 Outbreak in Horses and Staff at a Veterinary Teaching Hospital after Its Presumed Introduction by a Veterinarian

Methicillin-resistant Staphylococcus aureus (MRSA) infection and colonization, involving MRSA strains which differ from common human health care-associated clones, have become serious emerging conditions in equine veterinary hospitals. In 2010, MRSA spa type t535 caused an outbreak involving both horses and personnel in a veterinary teaching hospital in Israel. Since then, surveillance continued, and occasional MRSA isolation occurred. Two years later, MRSA of another spa type, t002, was isolated from a veterinarian and, 3 weeks later, from a horse. The appearance of spa type t002, a common clone in human medicine in Israel, among both personnel and horses, prompted a point-prevalence survey of hospital personnel and hospitalized horses. Fifty-nine staff members (n = 16 equine; n = 43, other) and 14 horses were screened. Ten of 59 staff members (16.9%) and 7 of 14 horses (50%) were MRSA carriers. Among the staff, 44% of large animal department (LAD) personnel, compared with only 7% of non-LAD personnel, were carriers. Isolates from all horses and from 9 of 10 personnel were found to be of MRSA spa type t002. This clone was later isolated from an infected postoperative wound in a hospitalized horse. Measures were taken to contain transmission between horses and personnel, as was done in the previous outbreak, resulting in reduction of transmission and, finally, cessation of cross-transmission between horses and personnel.

Molecular epidemiology of community-onset methicillin-resistant Staphylococcus aureus infections in Israel

Data on community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) in Israel are scarce. The objective of this study was to characterize the major CA-MRSA clones in Israel. All clinical MRSA isolates detected in the community during a period of 2.5 years (2011-2013) from individuals insured by a major health maintenance organization in Israel were collected, with additional data from medical records. Antibiotic susceptibility patterns and staphylococcal chromosomal cassette mec (SCCmec) typing were determined. SCCmec IV and V isolates were further typed by pulsed-field gel electrophoresis (PFGE), spa typing, and detection of a panel of toxin genes. MRSA were detected in 280 patients, mostly from skin infections. Patients with SCCmec IV (n = 120, 43 %) were younger (p < 0.0001) and reported less contact with healthcare facilities. Almost all isolates were trimethoprim-sulfamethoxazole susceptible (98 %). spa-CC032, a typical nosocomial MRSA clone, accounted for 28 % of SCCmec IV. The two major CA-MRSA clones were t008 USA300 (13 %) and t991 (10 %); t991 was isolated mainly from children (75 %), was Panton-Valentine leukocidin (PVL) negative but eta-positive, and was typically susceptible to most antibiotic groups. PVL-positive strains (n = 31) included mainly USA300 (52 %) and t019 (13 %). While multiple genetic lineages were evident among community-onset MRSA in Israel, approximately 20 % are typical CA-MRSA clones, mainly USA300 and a local clone, t991.

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.

Staphylococcus aureus nasal carriage among outpatients attending primary health care centers: a comparative study of two cities in Saudi Arabia and Egypt

Epidemiological and molecular data on community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) are still scarce in both Egypt and Saudi Arabia. There is almost no data regarding methicillin resistant Staphylococcus aureus (MRSA) prevalence in both countries. This study was conducted to investigate the prevalence and molecular epidemiology of S. aureus and MRSA nasal carriage among outpatients attending primary health care centers in two big cities in both countries. A total of 206 nasal swabs were obtained, 103 swabs from each country. S. aureus isolates were characterized by antibiotic susceptibility, presence of mecA and PVL genes, SCCmec-typing and spa typing, the corresponding Multi locus sequence typing clonal complex was assigned for each spa type based on Ridom StaphType database. MRSA was detected in 32% of the Egyptian outpatients while it was found in 25% of the Saudi Arabian outpatients. All MRSA isolates belonged to SCCmec type V and IVa, where some isolates in Saudi Arabia remained nontypeable. Surprisingly PVL(+) isolates were low in frequency: 15% of MRSA Egyptian isolates and 12% of MRSA isolates in Saudi Arabia. Two novel spa types were detected t11839 in Egypt, and t11841 in Saudi Arabia. We found 8 spa types among 20 isolates from Egypt, and 12 spa types out of 15 isolates from Saudi Arabia. Only two spa types t008 and t223 coexisted in both countries. Four clonal complexes (CC5, CC8, CC22, and CC80) were identified in both Egypt and Saudi Arabia. However, the data collected lacked a representation of isolates from different parts of each country as only one health center from each country was included, it still partially illustrates the CA-MRSA situation in both countries. In conclusion a set of control measures is required to prevent further increase in MRSA prevalence.

Molecular characterization of methicillin-resistant Staphylococcus aureus strains isolated from patients with hospital readmissions

It is unclear whether patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) continue to harbor the same genotype during hospital readmissions. We characterized 140 MRSA strains isolated from 33 persistent MRSA carriers with hospital readmissions. Nearly half of the patients continued to harbor the same genotype, and the rest acquired different genotypes. Among 25 patients who received eradication therapy, 16 (64%) were colonized with MRSA strains exhibiting different genotypes from the preexisting one.

Community-associated methicillin-resistant Staphylococcus aureus case studies

Over the past decade, the emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has changed the landscape of S. aureus infections around the globe. Initially recognized for its ability to cause disease in young and healthy individuals without healthcare exposures as well as for its distinct genotype and phenotype, this original description no longer fully encompasses the diversity of CA-MRSA as it continues to expand its niche. Using four case studies, we highlight a wide range of the clinical presentations and challenges of CA-MRSA. Based on these cases we further explore the globally polygenetic background of CA-MRSA with a special emphasis on generally less characterized populations.

Clonal transmission of a rare methicillin-resistant Staphylococcus aureus genotype between horses and staff at a veterinary teaching hospital

Methicillin-resistant Staphylococcus aureus (MRSA) infection or colonization has become a serious emerging condition in equine hospitals. Following the detection of MRSA in asymptomatic hospitalized horses and in two horses with post-operative wound infections, an investigation was conducted. Twelve of 84 horses (14.3%) and 16 of 139 personnel (11.5%) were MRSA carriers. The profile of the dominant MRSA strain common to horses and staff was multi-drug-resistant, spa-type t535, SCCmec type V, pvl-negative. MLST of a representative isolate yielded sequence type (ST) 5. The risk of MRSA carriage among veterinary personnel was greater in equine veterinarians and full-time technicians in comparison to part-time technicians and to other personnel not working with horses. Strict infection control measures were implemented, horses infected or colonized with MRSA were isolated and decolonization of personnel was attempted. Six months after the intervention, the large animal department personnel and hospitalized horses were all MRSA-negative and the decolonization was considered successful. This outbreak, caused by a rare MRSA strain and involving both hospitalized horses and personnel, further demonstrates the ability of MRSA to spread between animals and humans and emphasizes the importance of infection control measures to decrease the risk for MRSA colonization and infection of both horses and personnel.

Polyclonal non multiresistant methicillin resistant Staphylococcus aureus isolates from clinical cases of infection occurring in Palermo, Italy, during a one-year surveillance period

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 β-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.