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Abstract Infections caused by Staphylococcus aureus remain a major global healthcare problem. We aimed to find the common lineages of S. aureus strains circulating in a burn hospital in Tehran. A total of 167 isolates of S. aureus obtained from patients, healthcare workers (HCWs) and environment in Shahid Motahari burn hospital were genotyped by using spa, agr and staphylococcal cassette chromosome mec (SCC mec) typing methods. Antimicrobial susceptibility testing was performed by using the disc diffusion method. The frequency of methicillin-resistant S. aureus (MRSA) was 64.7% (n = 108), with distribution frequencies among patient, HCW and surface isolates of 64.2% (n = 79), 50% (n = 7) and 73.3% (n = 22), respectively. SCC mec type III (75%, n = 81) was found to be the most frequent SCC mec type among MRSA isolates, followed by SCC mec type I (20.4%, n = 22) and SCC mec type IV (1.8%, n = 2). The remaining MRSA isolates (2.8%, n = 3) were nontypeable by this method. About 78.4% (n = 131), 10.2% (n = 17) and 4.8% (n = 8) of all isolates were characterized as agr types I, II and III, respectively, and the other isolates (6.6%) were nontypeable. spa types t030 and t037 constituted the first and second most predominant spa types found in 56.4% (n = 57) and 25.6% (n = 26) of isolates, respectively. We also report here a novel spa type, t16471. The most prevalent genotypes of the isolates found among patient, surface and HCW samples were SCC mec type III/t030, t037/ agr type I. Continuous tracking of epidemic isolates and better hospital infection control policies are recommended to efficiently prevent the spread of bacteria to inpatients. [ABSTRACT FROM AUTHOR]

The risk of zoonotic transmission to humans highlights the need to understand the molecular ecology of Staphylococcus aureus in foods. In this study, 142 S. aureus isolates obtained from various raw and processed foods from Shanghai, China were characterized to determine their genetic diversity and virulence gene content. A total of 16 clonal complexes (CCs), 34 staphylococcal protein A ( spa ) types, and 6 accessory gene regulator ( agr ) allelic groups were identified and analyzed among the 142 S. aureus isolates. Among these, the genotype CC188-t189- agr Ι was the most prevalent, constituting 28.2% of all isolates. The presence of virulence genes encoding 20 staphylococcal enterotoxins ( se ), toxic shock syndrome toxin ( tsst1 ), exfoliative toxins ( eta , etb , and etd ), Panton–Valentine leukocidin ( lukS -PV and lukF -PV), as well as methicillin resistance gene ( mecA ), was determined by PCR. Of these S. aureus isolates, 72.5% harbored toxin genes, in which the most frequent toxin gene was sep (43.7%), followed by sej (26.1%) and pvl (21.1%). In contrast, see , ses , set , tsst1 , etb , and etd were not found in any of the isolates tested. Eight S. aureus isolates (5.6%, 8/142), seven from raw milk and one from frozen food, were mecA positive and resistant to oxacillin, thus were MRSA. The 142 S. aureus isolates displayed 52 different toxin gene profiles. Although no direct association was found between toxin gene profile and the S. aureus genotype, the isolates belonging to CC5, CC9, CC20, CC50, and CC72 clonal lineages in general carried more toxin genes (> 5) compared with the isolates in other CCs. It was also revealed that raw milk and raw meat were the major sources of isolates containing multiple toxin genes. S. aureus isolates from food that were genetically highly related, displayed diverse toxin gene profiles, implying the significant role of horizontal gene transfer in the emergence of highly toxigenic S. aureus isolates. [ABSTRACT FROM AUTHOR]