Jpn. J. Infect. Dis., 55, 210-213, 2002

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Laboratory and Epidemiology Communications

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in a Tokyo Hospital in 2002

Tomoko Fujino, Jun-ichiro Sekiguchi, Akihiko Kawana, Hisami Konosaki, Haruo Nishimura, Katsutoshi Saruta, Koichiro Kudo, Oichirou Kobori, Yoshio Yazaki, Tadatoshi Kuratsuji and Teruo Kirikae*

International Medical Center of Japan, Toyama 1-21-1, Shinjuku-ku, Tokyo 162-8655

Communicated by Hiroshi Yoshikura

(Accepted January 24, 2003)



Methicillin-resistant Staphylococcus aureus (MRSA) is a prevalent nosocomial pathogen in healthcare facilities. Epidemiological analysis of MRSA by means of restriction fragment length polymorphisms of genomic DNA using pulsed-field gel electrophoresis (PFGE) is essential for assessment of hospital infection controls (1-4).

Two hundred eighty-six MRSA isolates were obtained from 97 inpatients in October 2002 in a hospital with 24 wards and 925 beds in Tokyo. Sixty-eight of the isolates, each derived from a single patient, were analyzed for chromosomal DNA typing by using a contour-clamped homogeneous electric field system (CHEF MapperTM, Bio-Rad Laboratories, Hercules, Calif., USA), and for antibiotic resistance (WalkAwayTM, Dade Behring, Deerfield, Ill., USA), enterotoxin serotyping (SET-RPLA, Denka Seiken Co., Tokyo), toxic shock syndrome toxin-1 (TSST-1) production (TST-RPLA, Denka Seiken), and coagulase serotyping (Denka Seiken). Isolates showing the same PFGE patterns were probably of the same origin.

Thirty-two different PFGE patterns of SmaI DNA digests were detected (Fig. 1). A band-based cluster analysis of these patterns (Molecular AnalystTM, Bio-Rad), in which PFGE-band similarity exceeding 70% was used as the criterion of cluster formation, revealed that there existed 15 clusters: patterns A, X, Y, Z, G, M, AA, AB, AC, AD, AE, AF, J, R, AG (Fig. 2A). The frequency distribution of MRSA of these different PFGE patterns isolates is shown in Fig. 2B. The most frequent pattern (A1) represented 26%. The most frequent clusters of patterns (A1 to A4, A9, A15, A16, A20 to A24) made up 54% of total isolates. Distribution of MRSA isolates in the wards is shown in Table 1. The isolates belonging to PFGE pattern A were found in 17 of 24 wards; more specifically, PFGE pattern A1 was in 11 wards, patterns A4 and A16 were in three wards, respectively, and patterns A3 and A22 were in two wards, respectively. Pattern X was in three wards, and G3 and Z were in two wards, respectively.

Sensitivity to antibiotics is shown in Table 2. The MRSA isolates had a wide spectrum of drug-resistance with 21 different patterns. Those isolates were resistant to 9-14 of 17 tested drugs. No isolate was resistant to either vancomycin or sulfamethoxazole/trimenthoprim. All of the 18 isolates having PFGE pattern A1 had antibiotic patterns j, k, m, or am. No correlation was found between other antibiotic patterns and PFGE patterns (data not shown).

Among 68 MRSA isolates, 65 isolates produced coagulase type II, and the remaining three produced coagulase type III. Fifty-seven isolates produced enterotoxin type C, four isolates enterotoxin type B, three isolates enterotoxin type B and C, while the other isolates produced no enterotoxins. Forty-eight isolates produced TSST-1, and the other 10 did not. Collectively, among 68 MRSA isolates, 55 isolates produced coagulase type II, enterotoxin type C, and TSST-1.

PFGE-based MRSA surveillance was conducted in the same hospital in December 2000 (1) and October 2001 (2). PFGE patterns A1, A2(M1), A3, A4, A9, and G3, were detected in the present study and in that conducted in December 2000 and October 2001. Patterns A15, A16, M2(A18), J3, and R1(R) were detected in the present study and in that conducted in October 2001 but not in December 2000. PFGE patterns A23(B) were detected in the present study and in that conducted in December 2000 but not in October 2001. PFGE patterns A20, A21, A22, A24, X, Y, Z, M7, AA1, AA2, AB, AC1 to 3, AD, AE, AF, J5, R2, and AG were newly detected in the present study. The study suggested the persistence of some MRSA strains as well as the rapid turnover of MRSA in the hospital.

MRSA with PFGE pattern A1 expanding in the hospital was detected in other Japanese hospitals in Kumamoto (3) and in Hiroshima (4), indicating that some MRSA strains persist in healthcare facilities in Japan.

REFERENCES

  1. Fujino, T., Mori, N., Kawana, A., Kawabata, H., Kuratsuji, T., Kudo, K., Kobori, O., Yazaki, Y. and Kirikae, T. (2001): Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a Tokyo hospital in 2000. Jpn. J. Infect. Dis., 54, 91-93.
  2. Fujino, T., Mori, N., Kawana, A., Kawabata, H., Kuratsuji, T., Kudo, K., Kobori, O., Yazaki, Y. and Kirikae, T. (2001): Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a Tokyo hospital in 2001. Jpn. J. Infect. Dis., 54, 240-242.
  3. Kawano, F., Miyazaki, H., Takami, J., Fujino, T., Saruta, K. and Kirikae T. (2002): Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a Kumamoto hospital in 2001. Jpn. J. Infect. Dis., 55, 29-30.
  4. Sasaki, R., Fujino, T., Saruta, K., Kawasaki, J., Shigeto, N. and Kirikae, T. (2002): Molecular epidemiological surveillance of methicillin-resistant Staphylococcus aureus in a Hiroshima community hospital in 2002. Jpn. J. Infect. Dis., 55, 93-95.



*Corresponding author: Fax: +81-3-3202-7364, E-mail: tkirikae@ri.imcj.go.jp


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