Hospital Dissemination of tst-1-Positive Clonal Complex 5 (CC5) Methicillin-Resistant Staphylococcus aureus

Nasal Staphylococcus aureus Carriage and Antimicrobial Resistance Profiles Among Community-Dwelling Adults in Jiangsu, China

INTRODUCTION

Persistent nasal carriage has been associated with Staphylococcus aureus infection. Previous S. aureus studies in Asia have primarily focused on clinical patients, providing limited information on persistent nasal carriage among the general adult population.

METHODS

This study examined 143 healthy adults in a community in Jiangsu, China. Nasal swab samples were collected 10 times. The colonization status was identified using SPA typing. We also determined antimicrobial susceptibility, genotype, and genomic characteristics of S. aureus.

RESULTS

The prevalence of S. aureus nasal carriage among the community individuals was on average 16.78%. The carriage rates of methicillin-resistant S. aureus and multidrug-resistant S. aureus were 6.29% and 7.69%, respectively. We identified 8.39% persistent carriers, 39.16% intermittent carriers, and 52.45% noncarriers. Furthermore, family members displayed concordance in terms of genotype and genomic characteristics.

CONCLUSION

Persistent nasal sampling captured intermittent carriers that were missed during short-term sampling, thus highlighting the necessity for regular community testing. SPA typing can serve as a rapid method for determining S. aureus colonization. The potential for intrafamilial transmission of S. aureus is evident, with persistent carriers being the most probable source of infection.

Virulence attributes of successful methicillin-resistant Staphylococcus aureus lineages

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of severe and often fatal infections. MRSA epidemics have occurred in waves, whereby a previously successful lineage has been replaced by a more fit and better adapted lineage. Selection pressures in both hospital and community settings are not uniform across the globe, which has resulted in geographically distinct epidemiology. This review focuses on the mechanisms that trigger the establishment and maintenance of current, dominant MRSA lineages across the globe. While the important role of antibiotic resistance will be mentioned throughout, factors which influence the capacity of S. aureus to colonize and cause disease within a host will be the primary focus of this review. We show that while MRSA possesses a diverse arsenal of toxins including alpha-toxin, the success of a lineage involves more than just producing toxins that damage the host. Success is often attributed to the acquisition or loss of genetic elements involved in colonization and niche adaptation such as the arginine catabolic mobile element, as well as the activity of regulatory systems, and shift metabolism accordingly (e.g., the accessory genome regulator, agr). Understanding exactly how specific MRSA clones cause prolonged epidemics may reveal targets for therapies, whereby both core (e.g., the alpha toxin) and acquired virulence factors (e.g., the Panton-Valentine leukocidin) may be nullified using anti-virulence strategies.

TSST-1 protein exerts indirect effect on platelet activation and apoptosis

Thrombocytopenia or platelet dysfunction is a risk factor for severe infection. Staphylococcus aureus (S. aureus) releases a variety of virulence factors especially toxic shock syndrome toxin 1 (TSST-1), which may cause toxic shock syndrome. S. aureus, when carrying the tst gene, is more prone to cause toxic shock syndrome and is responsible for an especially high rate of mortality. However, the effect of TSST-1 protein on platelets is unknown. Patients with the tst gene positive S. aureus bacteremia showed more serious infection, higher mortality and lower platelet count. The tst gene positive S. aureus strains induce more platelet apoptosis and activation and corresponding up-regulation of Bak and down-regulation of Bcl-XL in addition to the activation of Caspase-3. C57BL/6 mice infected with the tst gene positive strains resulted in both a decrease in platelet count and an increase in platelet apoptosis and/or activation events and mortality. Moreover, TSST-1 protein, encoded by tst gene, caused the decrease of platelet count, the increase of platelet apoptosis and activation events and the level of inflammatory cytokines in vivo. However, TSST-1 protein was unable to induce traditional activation and apoptosis on human platelets in vitro. These results suggested that TSST-1 protein may exert indirect effects on platelet activation and apoptosis in vivo.

Methicillin-resistant Staphylococcus aureus in China: a multicentre longitudinal study and whole-genome sequencing

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we conducted whole-genome sequencing on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing, SCCmec typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%) and ST5-t2460-II (6.0%), respectively. Of note, CC8, the predominant lineage in 2014–2015, was replaced by CC59 after 2016. Interestingly, the extension and unstable structure of the CC5 population was observed, with ST5-t311-II, ST764-t1084-II, ST5-t2460-II and ST764-t002-II existing complex competition. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA was less resistant to most tested antimicrobials and carried fewer resistance determinants. But rifampicin resistance and mupirocin resistance were closely linked with CC8 and CC5, respectively. MRSA isolates conservatively carried multiple virulence genes involved in various functions. PVL encoding genes were more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China to monitor changes in MRSA epidemiology.

Emergence of Methicillin-Resistant Staphylococcus aureus ST239/241 SCCmec-III Mercury in Eastern Algeria

In this paper, we investigate the epidemiology of infections-associated Staphylococcusaureus (S. aureus) from the Medical Intensive Care Unit (MICU) at University Hospital Center of Constantine (UHCC) in Algeria, with a special emphasis on methicillin-resistant strains (MRSA) revealed by cefoxitin disks (30 μg), then confirmed by penicillin-binding protein (PBP2a) agglutination and real-time polymerase chain reaction (RT-PCR) targeting mecA and mecC genes. Staphylococcal Cassette Chromosome mec (SCCmec type), staphylococcal protein A (spa-type), multilocus sequence type (MLST), Panton-Valentine Leucocidin (PVL), and toxic shock syndrome toxin-1 (TSST-1) were further investigated in all isolates, and whole genome sequencing was performed for a selected subset of three hospital-acquired MRSA (HA-MRSA) isolates. A measurement of 80% out of the 50 S. aureus isolates were identified as HA-MRSA harbouring the mecA gene, and 72.5% of them were multidrug resistant (MDR). Twelve STs, four different SCCmec cassettes, fourteen spa types, ten isolates Panton-Valentine Leukocidin (PVL)-positive, and three isolates TSST-1 were identified. Interestingly, there was a high prevalence (n = 29; 72.5%) of a worrisome emerging clone: the HA-MRSA ST239/241 SCCmec-III mercury with PVL negative, resistant to β-lactams, aminoglycosides, quinolones, and tetracyclines. Other clones of HA-MRSA isolates were also identified, including PVL-positive ST80 SCCmec-IV/SCCmec-unknown (22.5%), ST34 SCCmec-V with TSST-1 positive (2.5%), and PVL-negative ST72 SCCmec-II (2.5%). Genome analysis enables us to describe the first detection of both PVL-negative HA-MRSA ST239/241 SCCmec-III mercury carrying ccrC, as well as SCCmec-V cassette, which dramatically changes the epidemiology of S. aureus infections in one of the hospitals in eastern Algeria.

Characterisation of Staphylococcus aureus isolates from bovine mastitis in Ningxia, Western China

OBJECTIVES

The aim of this study was to explore the antimicrobial resistance, virulence genes and molecular characteristics of Staphylococcus aureus from bovine mastitis cases.

METHODS

A total of 125 non-duplicate S. aureus isolates from bovine mastitis cases in Ningxia, China, were characterised by antimicrobial susceptibility and molecular testing to determine the antimicrobial resistance, virulence genes and molecular characteristics.

RESULTS

All methicillin-resistant S. aureus (MRSA) isolates were resistant to ampicillin, oxacillin, ceftiofur, erythromycin, gentamicin and clindamycin, with resistance to nine different categories of antibiotics observed amongst the MRSA isolates. Of the methicillin-susceptible S. aureus (MSSA) isolates, 62.1% were resistant to ampicillin and sulfisoxazole. Nine clonal complexes (CCs) and 16 spa types were identified by multilocus sequence typing (MLST) and spa typing. The dominant CCs were CC97 (51.2%) and CC50 (30.4%), while t224 (30.4%), t518 (20.0%) and t359 (16.8%) were the most common spa types. A relatively high proportion (27.2%) of the S. aureus isolates belonged to ST4053, a novel sequence type identified in this study. In addition, two CC30 MSSA isolates and two CC59 MRSA isolates were positive for Panton-Valentine leukocidin, while one CC239 MRSA isolate and three CC5 MSSA isolates were positive for TSST-1. All MRSA isolates carried the immune evasion cluster (IEC) genes, including scn (100%; 9/9) and sak (100%; 9/9), which were classified into type E.

CONCLUSION

Our study indicates severe antibiotic resistance and complicated molecular characterisation of S. aureus causing bovine mastitis. Additional studies should be conducted to monitor infection and transmission of S. aureus.

The prevalence of drug-resistant and virulent Staphylococcus spp. in a municipal wastewater treatment plant and their spread in the environment

Drug-resistant and pathogenic Staphylococcus spp. strains can reach surface waters and air with wastewater evacuated to the environment. These strains increase the environmental pool of genetic determinants conferring antibiotic resistance and virulence, and constitute a health risk for the employees of wastewater treatment plants (WWTP) who come into daily contact with bioaerosols. The aim of this study was to identify the genetic determinants of drug resistance and virulence in Staphylococcus spp. strains isolated from untreated (UWW) and treated wastewater (TWW), an activated sludge (AS) bioreactor, river water collected upstream and downstream from the wastewater discharge point (URW and DRW), and WWTP employees. All isolates were analysed for the presence of the rpoB gene, and were subjected to clonal analysis by ERIC fingerprinting. As a result, 249 of the 455 analysed isolates were selected for PCR. The presence of the gene encoding nuclease activity in S. aureus (nuc), the methicillin resistance gene (mecA), vancomycin resistance gene (vanA), antiseptic resistance gene (qacA/B) and virulence genes (sasX, pvl, tst1, hla, sec) was determined. The prevalence of nuc, mecA, vanA and qacA/B genes in wastewater and river water was determined by quantitative PCR (qPCR). In the group of strains isolated from wastewater and water samples, 63% were identified as S. aureus, and 20% of the strains carried the vanA gene. The hla virulence gene was present in 80% of the isolates, and the pvl gene was detected in 27% of the isolates. In the group of strains isolated from the employees, 82% were identified as S. aureus, and the presence of vanA and mecA genes was confirmed in 14% and 16% of the isolates, respectively. The most prevalent virulence gene was hla (74%), whereas pvl was observed in 43% of the isolates. The quantitative analysis revealed the highest concentrations of the studied genes in UWW samples, at 2.56x10⁴ gene copies/ml for nuc, 1.18x10³ gene copies /ml for mecA, 8.28x10⁵ gene copies /ml for vanA and 3.83x10⁵ gene copies /ml for qacA/B. Some of analysed genes were identified in the isolates from both URW and DRW samples, as well as in genomic DNA of these samples. These results indicate that wastewater is not effectively treated in the analysed WWTP, which could contribute to the dissemination of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) to the environment. An analysis of the genetic relatedness of selected isolates revealed clusters of strains originating from UWW samples, AS samples and the employees. These observations suggest that ARGs and ARB are transmitted by wastewater bioaerosols to the upper respiratory tract mucosa of the plant's employees, thus increasing their exposure to infectious factors.

Environmental Contamination Prevalence, Antimicrobial Resistance and Molecular Characteristics of Methicillin-Resistant Staphylococcus Aureus and Staphylococcus Epidermidis Isolated from Secondary Schools in Guangzhou, China

Background: Methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE), the most prevalent causes of hospital-associated and community-associated infections, could exist on frequently touched surfaces. This study aims to determine the contamination prevalence and the characteristics of MRSA and MRSE isolated from secondary school environments. Methods: We collected environmental samples from ten secondary schools in Guangzhou city between October 2016 and January 2017. The samples were confirmed for MRSA and MRSE isolates by using biochemical tests and polymerase chain reactions. Antimicrobial susceptibility testing was performed by the Kirby-Bauer disk diffusion method. Staphylococcal cassette chromosome mec (SCCmec) typing, toxin gene screening, and multilocus sequence typing (MLST) were performed to further characterize the isolates. Data were analyzed by two-sample proportion tests. Results: A total of 1830 environmental samples were collected. The prevalence of MRSA and MRSE contamination were 1.86% (34/1830) and 5.14% (94/1830), respectively. The proportions of multidrug resistance in both MRSA (58.82%) and MRSE (63.83%) isolates were high. Seven clonal complexes (CC) and 12 sequence types (ST) were identified, with the CC5 (35.29%) and ST45 (25.53%) being the most prevalent. We found that 44.12% of the MRSA isolates were community-acquired and the main type was ST45-SCCmec IV. We found that 5.88% and 32.35% of MRSA isolates were positive to Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin-1 (tst) gene, respectively. No MRSE isolate was positive to the toxin genes. Conclusion: Our findings raise potential public health concerns for environmental contamination of MRSA and MRSE in school environments. Surfaces of school environments may potentially provide a source for cross-contamination with these bacteria into the wider community.

Fatality of Staphylococcus aureus infections in a Greek university hospital: role of inappropriate empiric treatment, methicillin resistance, and toxin genes' presence

The aim of the present study was to identify predictors of fatality among patients with S. aureus infections requiring hospitalization. Cases hospitalized with S. aureus infections at the University General Hospital of Patras, Greece, during a 4-year period (2013-2016) were studied. mecA, lukS/lukF-PV (Panton-Valentine leukocidin, PVL), tst (toxic shock syndrome toxin), fnbA (fibronectin-binding protein A), eta, and etb (epidermolytic toxins) genes' carriage was detected by PCR in 149 selected patients. Among 464 patients, 346 were included (118 with missing data). Primary bacteremia predominated (44.2%), followed by lower respiratory tract infections (13.6%), deep seated infections (9.8%), osteoarticular (9.5%), and catheter-related bloodstream infections (6.1%). Methicillin-resistant S. aureus (MRSA) represented 33.8% of infections and were less likely to receive appropriate empiric treatment (79.5% versus 97.4%; P < 0.001). Thirty-day fatality was 14.5%. Multivariate analysis revealed that development of septic shock, Charlson Comorbidity Index, lower respiratory tract infection, bacteremia (primary or secondary), MRSA, and CRP was significantly associated with fatality. Appropriate empiric treatment was a predictor of good prognosis. Thirty-two out of 149 S. aureus (21.5%) carried lukS/lukF-PV genes, whereas, 14 (9.4%), 133 (78.7%), four (2.7%), and one (0.7%) carried tst, fnbA, eta, and etb genes, respectively. No difference was found among toxin genes' presence and mortality. PVL was significantly more frequently found among MRSA as compared to MSSA (45.1% versus 9.2%; P < 0.001). MRSA represented one third of the infections requiring hospitalization and were independently associated with fatality, probably since were more likely to receive inappropriate antibiotic treatment as compared to MSSA.

Carriage of the Toxic Shock Syndrome Toxin Gene by Contemporary Community-Associated Staphylococcus aureus Isolates

We report here the prevalence of the tst-1 gene among 252 methicillin-susceptible Staphylococcus aureus (MSSA) isolates and 458 methicillin-resistant S aureus (MRSA) isolates collected from 531 subjects between 2008 and 2017, one of which was recovered from a child with MRSA toxic shock syndrome. tst-1 was encoded by 43 (6%) S aureus isolates overall: 42 (16.7%) MSSA isolates and 1 (0.2%) MRSA isolate (P < .001).

The tst gene associated Staphylococcus aureus pathogenicity island facilitates its pathogenesis by promoting the secretion of inflammatory cytokines and inducing immune suppression

Staphylococcus aureus (S. aureus) is an important pathogen causing various limited or systemic infections. Methicillin resistant S. aureus (MRSA) in particular presents a major clinical and public health problem. Toxic shock syndrome toxin-1 (TSST-1) encoded by the gene tst is an important virulence factor of tst positive S. aureus, leading to multi-organ malfunction. However, the mechanism of TSST-1 in pathogenesis is only partly clear. In this study, we investigated the prevalence of the tst gene in clinical isolates of S. aureus. Then, animal experiments were performed to further evaluate the influence of the presence of the tst gene associated Staphylococcus aureus Pathogenicity Island (SaPI) on body weight, serum cytokine concentrations and the bacterial load in different organs. In addition, macrophages were used to analyze the secretion of cytokines in vitro and bacterial survival in the cytoplasm. Finally, pathological analysis was carried out to evaluate organ tissue impairment. The results demonstrated that the prevalence of tst gene was approximately 17.8% of the bacterial strains examined. BALB/c mice infected with tst gene associated SaPI positive isolates exhibited a severe loss of body weight and a high bacterial load in the liver, heart, kidney and spleen. Pathological analysis demonstrated that tissue impairment was more severe after infection with tst gene associated SaPI positive isolates. Moreover, the secretion of IL-6, IL-2 and IL17A by macrophages infected with tst gene associated SaPI positive isolates clearly increased. Notably, IL-6 secretion in BALB/c mice infected with tst gene associated SaPI positive isolates was higher than that in BALB/c mice infected with negative ones. Together, these results indicated that the tst gene associated SaPI may play a critical role in the pathological process of infection via a direct and persistent toxic function, and by promoting the secretion of inflammatory cytokines that indirectly induce immune suppression.

Molecular Typing and Variations in Amount of tst Gene Expression of TSST-1-Producing Clinical Staphylococcus aureus Isolates

The toxic shock syndrome toxin-1 (TSST-1), encoded by tst gene, has been proposed to cause staphylococcal toxic shock syndrome (TSS) in a susceptible host, which highlights the need to evaluate the level of tst gene expression and molecular genetic characteristics of the tst-positive isolates. A total of 916 S. aureus isolates collected from seven hospitals in China were screened for the tst gene. The tst positive isolates were characterized by spa, SCCmec, PFGE, and agr typing. Representative strains were also subjected to MLST typing. qRT-PCR was used to quantify tst and major virulence regulator genes expression. We also sequenced the regions of promoter and open reading frame (ORF) of tst to investigate whether they correlate with the variation in tst expression. We found 208 (22.7%) of surveyed isolates including 198 (29.8%) of MRSA and 10 (4.0%) of MSSA isolates harbored the tst gene. The most common clone among tst positive MRSA isolates belonged to ST5 (CC5)-agr2-t002-SCCmecII. The amount of tst mRNA varied 8.4-folds among clinical S. aureus isolates. Sequencing the tst promoter revealed a base T deletion in tst high expressed isolates. As for major virulence regulators, srrA, sarT, RNAIII, and ccpA in four tst differentially expressed strains were detected to be highly expressed, respectively. Our study revealed high prevalence of ST5 (CC5)-agr2-t002-SCCmecII clone among tst positive MRSA in hospitals from China. The levels of tst expression among clinical S. aureus isolates varied, which may be associated with tst promoter and variations in specific virulence regulators.

Molecular Characterization of Methicillin Resistant Staphylococcus aureus in West Bank-Palestine

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a public health threat and a major cause of hospital-acquired and community-acquired infections. This study aimed to investigate the genetic diversity of MRSA isolates from 2015 to 2017 and to characterize the major MRSA clones and anti-biogram trends in Palestine.

Methodology: Isolates were obtained from 112 patients admitted to different hospitals of West Bank and East Jerusalem, originating from different clinical sources. Antibiotic susceptibility patterns, staphylococcal chromosomal cassette mec (SCCmec) typing, and Staphylococcus aureus protein A (spa) typing were determined. Also, a panel of toxin genes and virulence factors was studied, including: Panton-Valentine Leukocidin (PVL), ACME-arcA, Toxic Shock Syndrome Toxin-1 (TSST-1), and Exfoliative Toxin A (ETA).

Results: Of the 112 confirmed MRSA isolates, 100% were resistant to all β-lactam antibiotics. Resistance rates to other non- β-lactam classes were as the following: 18.8% were resistant to trimethoprim-sulfamethoxazole, 23.2% were resistant to gentamicin, 34.8% to clindamycin, 39.3% to ciprofloxacin, and 63.4% to erythromycin. All MRSA isolates were susceptible to vancomycin (100%). Of all isolates, 32 isolates (28.6%) were multidrug- resistant (MDR). The majority of the isolates were identified as SCCmec type IV (86.6%). The molecular typing identified 29 spa types representing 12 MLST-clonal complexes (CC). The most prevalent spa types were: spa type t386 (CC1)/(12.5%), spa type t044 (CC80)/(10.7%), spa type t008 (CC8)/(10.7%), and spa type t223 (CC22)/(9.8%). PVL toxin gene was detected in (29.5%) of all isolates, while ACME-arcA gene was present in 18.8% of all isolates and 23.2% had the TSST-1 gene. The two most common spa types among the TSST-1positive isolates were the spa type t223 (CC22)/(Gaza clone) and the spa type t021 (CC30)/(South West Pacific clone). All isolates with the spa type t991 were ETA positive (5.4%). USA-300 clone (spa type t008, positive for PVL toxin gene and ACME-arcA genes) was found in nine isolates (8.0%).

Conclusions: Our results provide insights into the epidemiology of MRSA strains in Palestine. We report a high diversity of MRSA strains among hospitals in Palestine, with frequent SCCmec type IV carriage. The four prominent clones detected were: t386-IV/ CC1, the European clone (t044/CC80), Gaza clone (t223/CC22), and the USA-300 clone (t008/CC8).

Comparison of community- and healthcare-associated methicillin-resistant Staphylococcus aureus isolates at a Chinese tertiary hospital, 2012-2017

The transmission between community-associated (CA-) and healthcare-associated (HA-) methicillin-resistant Staphylococcus aureus (MRSA) has increased the challenge of infection control. To understand the clonal evolution and transmission of MRSA isolates, we compared the characteristics of 175 CA-MRSA and 660 HA-MRSA strains at a Chinese tertiary hospital in 2012–2017. Antibiotic susceptibility was performed on VITEK system, the genetic background of the isolates was characterized by SCCmec, spa, and MLST typing, while virulence determinants were screened using conventional PCR. Although more than 70% of the CA-MRSA isolates were erythromycin and clindamycin resistant, CA-MRSA was more susceptible than HA-MRSA to most of the antibiotics tested. ST239-MRSA-III-t030 (30%) was the most prevalent clone among HA-MRSA, while ST59-MRSA-IVa-t437 (28.8%) was the major clone among CA-MRSA. Notably, ST59-MRSA-IVa-t437 accounted for 6.7% of the chosen HA-MRSA isolates. Additionally, difference in virulence gene content was found between the CA- and HA-MRSA strains. In conclusion, epidemiological characteristics were largely different between CA- and HA-MRSA. Although ST239-MRSA-III-t030 is still the predominant clone among HA-MRSA, the community clone ST59-MRSA-IVa-t437 has the potential of becoming an essential part of HA-MRSA in the region tested.

Disseminated Clonal Complex 5 (CC5) methicillin-resistant Staphylococcus aureus SCCmec type II in a tertiary hospital of Southern Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of human infections worldwide, with major dominant lineage circulating in particular geographical regions. The Brazilian Epidemic Clone (BEC, SCCmec III, ST 239) has been predominant in most Brazilian hospitals. Here, we report the prevalence of MRSA SCCmec type II exhibiting different STs, most of them belonging to CC5 in a tertiary hospital in Southern Brazil.

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.

Spread of Tst-Positive Staphylococcus aureus Strains Belonging to ST30 Clone among Patients and Healthcare Workers in Two Intensive Care Units

Staphylococcus aureus is a major cause of infections. Toxic shock syndrome toxin (TSST-1) and Panton–Valentine leukocidin (PVL) are associated with severe clinical syndromes. S. aureus colonizing isolates recovered from healthcare workers and patients in the intensive care unit (ICU) of a university hospital comprising Group A were compared with those from adult non-ICU carriers (Group B). mecA, lukS/lukF-PV (Panton–Valentine leukocidin, PVL), and tst (toxic shock syndrome toxin) gene carriage was detected by PCR. Clones were identified in all methicillin-resistant S. aureus (MRSA) and toxin-positive methicillin-susceptible strains (MSSA) by pulsed-field gel electrophoresis (PFGE), agr groups, and multi locus sequencing typing (MLST). Group A included 90 S. aureus isolates, whereas Group B 53. PVL was more frequently found among MRSA vs. MSSA (p < 0.001) and in strains of Group B as compared to Group A (p < 0.001), consistent with the spread of ST80-IV. Higher incidence of tst gene carriage was identified among MSSA vs. MRSA (P 0.005) belonging mainly to ST30, and Group A vs. Group B (P 0.002). The wide dissemination of ST80-IV mainly in the community is responsible for a high percentage of PVL-positive MRSA, while silent spread of tst-positive S. aureus clones among ICU patients and personnel poses a threat of hospital transmission and possible severe infections.