title: Nasal carriage of methicillin-resistant Staphylococcus aureus among preclinical medical students: epidemiologic and molecular characteristics of methicillin-resistant S. aureus clones.
abstract: Between May 2008 and October 2009, a total of 2103 interns were randomly tested for nasal colonization of S. aureus and methicillin-resistant Staphylococcus aureus (MRSA). The prevalence of S. aureus among staphylococci specimens was 23.1%, and among the total S. aureus the MRSA prevalence was 9.4%. MRSA isolates were further subtyped using genetic element staphylococcal cassette chromosome mec (SCCmec) typing, pulsed-field gel electrophoresis (PFGE) band pattern, and multilocus sequence typing. SCCmec type IVa was the most prevalent strain, at 45.4 %. Eleven PFGE patterns were identified in MRSA strains, with 1 predominant (pulsotype A, 45.5%). Eight strains which belonged to clonal complex 78 carried type IVa SCCmec and produced type 3 coagulase. Panton-Valentine leukocidin (PVL) genes (lukS and F-PV) were identified in 10 (45.4%) MRSA strains; these predominately carried ϕSa2958type and ϕSa108PVL-like type PVL phages. After inducing prophages, 8 strains infected other S. aureus isolates and could generate novel PVL-positive strains of S. aureus. The present study demonstrates that interns can carry certain MRSA strains asymptomatically and contribute to the spread of MRSA between the community and hospital.
authors.affiliation: Department of Medical Microbiology and Parasitology, College of Basic Medical Sciences, China Medical University, Shenyang 110001, People's Republic of China. xxma@mail.cmu.edu.cn
authors.forename: Xiao Xue
authors.initials: XX
authors.lastname: Ma
authors.forename: Dan Dan
authors.initials: DD
authors.lastname: Sun
authors.forename: Si
authors.initials: S
authors.lastname: Wang
authors.forename: Mei Lian
authors.initials: ML
authors.lastname: Wang
authors.forename: Miao
authors.initials: M
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Shang
authors.forename: En Hua
authors.initials: EH
authors.lastname: Wang
authors.forename: En Jie
authors.initials: EJ
authors.lastname: Luo
mesh_terms: D001427:Bacterial Toxins / Q000235:genetics; D015373:Bacterial Typing Techniques; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D003030:Coagulase / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005098:Exotoxins / Q000235:genetics; D005260:Female; D005838:Genotype; D006801:Humans; D007956:Leukocidins / Q000235:genetics; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D058889:Molecular Typing; D058885:Multilocus Sequence Typing; D009296:Nasal Cavity / Q000382:microbiology*; D015995:Prevalence; D039002:Prophages / Q000302:isolation & purification; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013337:Students, Medical; D055815:Young Adult
chemical_list: D001427:Bacterial Toxins; D003030:Coagulase; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin