Jpn. J. Infect. Dis., 57, 88-90, 2004
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Laboratory and Epidemiology Communications
Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in a Sendai Hospital in 2003
Tsukasa Asagi*, Yoshihiro Kikuchi, Yoshiharu Sakurai, Tomoko Fujinol, Jun-ichiro Sekiguchil, Katsutoshi Sarutal, Tadatoshi Kuratsujil and Teruo Kirikael
National Hospital Organization, Sendai National Hospital, Miyagi 983-8520 and 1International Medical Center of Japan, Tokyo 162-8655
Communicated by Hiroshi Yoshikura
(Accepted March 25, 2004)
*Corresponding author: Mailing address: National Hospital Oraganization, Sendai National Hospital, Miyagino 2-8-8, Miyagino-ku, Miyagi 983-8520, Japan. Tel: +81-22-293-1111, Fax: +81-22-293-1172, E-mail: asagit@sendai.hosp.go.jp
Methicillin-resistant Staphylococcus aureus (MRSA) is a major hospital-acquired pathogen. Molecular epidemiological is essential for assessing hospital infection control measures (1-7).
Forty-five MRSA isolates were obtained from 24 inpatients during October 2003 in a hospital with 15 wards and 650 beds in Sendai city. Of these, 22 isolates, each derived from a single patient, were analyzed in terms of the following: chromosomal DNA typing with a contour-clamped homogeneous electric field system (CHEF MapperTM: Bio-Rad Laboratories, Hercules, Calif., USA), antibiotic resistance (disk diffusion tests by the National Committee for Clinical Laboratory standards method), enterotoxin serotyping (SET-RPLATM: Denka Seiken Co., Tokyo), toxic shock syndrome toxin-1 (TSST-1) production (TST-RPLATM: Denka Seiken), and coagulase serotyping (Denka Seiken).
Thirteen different pulsed-field gel electrophoresis (PFGE) patterns of SmaI DNA digests were detected (Fig. 1). A band-based cluster analysis (Molecular AnalystTM: Bio-Rad), in which PFGE-band similarity exceeding 70% was used as the criterion of cluster formation, revealed the three following clusters, A, AV/AU, and BH (Fig. 2A). The frequency distribution of the PFGE patterns is shown in Fig. 2B. Pattern AV5 was shared by 6 isolates, pattern A3 by four, and pattern A4 by two. The other 10 PFGE patterns appeared in only a single isolate.
As shown in Table 1, pattern AV5 was spread over five wards (e6, w2, w3, w4, and w6). Three isolates from the neonatal intensive care unit (NICU) were of pattern A3, and two from wards e6 and s6 were of pattern A4. Other patterns were unique to each ward.
The isolates showed a wide spectrum of drug resistance, with a total of 12 different patterns (Table 2). The isolates were resistant to 7 - 12 of 15 tested drugs. All of the isolates were sensitive to sulfametoxazole/trimethoprim and vancomycin. No antibiotic resistance pattern was found to be specific to a particular ward. No correlation was found between antibiotic patterns and PFGE patterns (data not shown).
Among 22 MRSA isolates, 21 produced coagulase type II, and the remaining isolate produced coagulase type I. Eleven isolates produced enterotoxin type C, nine isolates enterotoxin type B, one isolate enterotoxin type D, and one isolate produced no enterotoxins. Twelve isolates produced TSST-1. Eleven isolates produced coagulase type II, enterotoxin type C, and TSST-1; their PFGE patterns were A3, A4, A40, A42, AU7, AV6, or AV7. Nine isolates produced coagulase type II, enterotoxin type B, but not TSST-1; their PFGE patterns were AV5, AV8, AV9, or AV10.
The PFGE patterns obtained in this study were compared with those identified in Tokyo in October 2003 (Fig. 3) (4). Patterns A3 and A4 were detected in both instances. Eleven patterns were unique to Sendai, and 36 were unique to Tokyo. Previous studies conducted in 2000 - 2003 in Tokyo (1-4) and in 2001 - 2003 in Kumamoto (5-7) indicated a clone propagation of the pattern A1 MRSA in both hospitals. In a Sendai hospital, a different clone with a PFGE pattern of AV5 was found to have spread (Table 1). Thus, it was determined that nosocomial infections in a hospital in Tokyo shared common clones with those in Sendai and those in Kumamoto. However, infections in hospitals in Sendai and in Kumamoto, which are geographically separated from each other, did not share clones. Considering the fact that patients, as well as doctors, nurses, and other health care workers are frequently sent to or visit large medical facilities in Tokyo, this data may help account for how MRSA spreads nationwide in Japan.
REFERENCES
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