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Background The most common clinical manifestations of Staphylococcus aureus strains in the community are skin and soft-tissue infections. S. aureus could colonize the body sites and complicate the pathogenesis of skin diseases. S. aureus colonization is a risk factor for severe conditions such as bone and joint infections, pneumonia, bacteremia, and endocarditis. This study aimed to investigate the prevalence of S. aureus strains in skin and soft tissue infections and other skin disorders in patients referring to dermatology clinics and to evaluate the antibiotic resistance pattern and molecular characteristics of S. aureus isolates. Methods Skin swabs were collected from the lesional sites in 234 outpatients referring to dermatology clinics in three hospitals in Tehran. Antibiotic susceptibility, biofilm formation, and hemolysis tests were performed for isolates. PCR was done for SCCmec typing, agr grouping, and virulence genes detecting. Results The prevalence of S. aureus strains among patients with skin and soft-tissue infections and other skin lesions was 44.77% (30/67) and 44.91% (75/167), respectively. Also, 59 (56.19%) isolates were MRSA, 35.57% were HA-MRSA, and 30.5% were CA-MRSA. The psmα gene was more prevalent (62.8%) among isolates, followed by hlaα (56.1%), tsst-1 (15.2%) eta (13.3%), etb (6.6%), and pvl (2.8%). The agr specificity groups I, II, III, and IV were identified in 49.5, 21.9, 11.4, and 14.2% of S. aureus isolates, respectively. Most (56%) S. aureus isolates produced a moderate biofilm, and 23.8% of them produced strong biofilms. α-hemolysin (46.6%), β-hemolysin (25.7%), γ-hemolysin (19%), and both α and β-hemolysin (5.7%) were also produced by isolates. Conclusion The present study results indicated high colonization of skin lesions by HA-MRSA and CA-MRSA clones; MRSA strains were more resistant to antibiotics, contained various toxin genes, and were able to form biofilms. Therefore, they could play a vital role in the pathogenesis of various skin diseases; also, they could spread and cause infections in other body sites. Eradication and decolonization strategies could prevent recurrent infections and the spread of resistant strains and improve skin conditions.

Context Typical opportunistic pathogens of coagulase positive Staphylococcus spp. are capable of causing a wide spectrum of different purulent and toxin-mediated diseases such as enteric infections. 1 Staphylococcus intermedius is very similar to S. aureus in phenotypic characteristics and similarly produces enterotoxins. 2-4 Pigment production, hemolysis, alkaline phosphatase and urease positive tests, mannitol and maltose fermentation and susceptibility to novobiocin and Polymyxin B are characteristics of S. intermedius. 2,5 Originally regarded as a single species, molecular characterization has placed S. intermedius in a new classification as S. intermedius group (SIG), which includes S. intermedius, S. pseudintermedius, and S. delphini. 6,7 These species cause diseases in human and animals (especially people who keep pets at home). S. aureus is a human commensal, while other coagulase positive species are present in animals. It has been revealed that S. intermedius mostly infects dogs (resides on the skin or mucosal surfaces). 8 The general transferability of these species between pets and humans has increased during recent years. 9,10 Staphylococcal species are able to express a wide spectrum of virulence factors, such as coagulase, cell wall components, hemolysins, proteases, enterotoxins, toxic-shock syndrome (TSS), and exfoliating toxins. 11 Enterotoxins produced by these species are pyrogenic components not inactivated by gastrointestinal enzymes and thermal process and lead to diarrhea. Enterotoxins are members of superantigens and more than 20 different types have been recognized, however some most important agents include SEA, SEB, SEC, SED and SEE. 12,13 On the other hand, increasing antibiotic resistance among coagulase positive staphylococci is an ongoing concern. 14 Differentiation of coagulase positive staphylococci except for S. aureus by phenotypic tests is a difficult and unreliable or insufficient process in laboratory settings. 15 Considering this, several methods have been introduced for the identification of these strains, 16 for example a molecular test including hsp60 and sodA genes could differentiate them. 17 S. intermedius is the predominant infectious agent among non-S. aureus coagulase positive species in Iran according to previous reports. The aims