Yonago Acta medica 1996;38:1-8

Molecular Epidemiologic Study on Nosocomial Infection of Inpatients with Methicillin-Resistant Staphylococcus aureus during the Hospital Stay

Atsushi Ashimoto, Yoshinori Tanaka*, Akiko Adachi* and Takeshi Hamada

Department of Oral and Maxillofacial Surgery, and *Department of Bacteriology, Faculty of Medicine, Tottori University, Yonago 683, Japan

Staphylococcus aureus was isolated from the anterior nares of 58 inpatients at the Department of Oral and Maxillofacial Surgery of Tottori University Hospital from January to June, 1993. The methicillin-resistant S. aureus (MRSA) isolated was compared by antibiogram, coagulase typing,enterotoxin typing and DNA finger printing. S. aureus and MRSA were isolated from 16 (26.7%) and 4 patients (6.7%),respectively. Four strains of MRSA were resistant to 7 antibiotics, methicillin (DMPPC), oxacillin (MPIPC), ceftizoxime (CZX), ampicillin (ABPC), cefazolin (CEZ), clindamycin (CLDM) and lomefloxacin (LFLX), and one strain each was resistant to cefmetazole (CMZ) or gentamicin (GM), while six strains and one strain out of 12 methicillin-sensitive S. aureus (MSSA) were only resistant to ABPC and GM, respectively, and these MSSA were sensitive to 11 other antibiotics tested. Of the 4 inpatients, from whom MRSA was isolated, one patient with sialolithiasis had MRSA at admission, and the other three with malignant tumors were infected with MRSA after admission. Six strains of MRSA from 4 patients all showed the same patterns of coagulase typing (type ll), enterotoxin typing (type C), toxic shock syndrome toxin production and DNA restriction phenotype. Although there was a slight difference in antibiotic susceptibility testing among these six strains, these six strains of MRSA should be considered to have originated in the same source. These findings indicate that nosocomial infections with MRSA had occurred within a short term in a limited part of the ward.

Key words: molecular epidemiology; methicillin-resistant Staphylococcus aureus (MRSA); nosocomial infection

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