Jpn. J. Infect. Dis., 53, 2000

Laboratory and Epidemiology Communications

EpidemiologlCal Analysts Of Methicillin‑Resistant Staphylococcus aureus
Ou他reaks in a Neonatal Intensive Care Unit by Genomic DNA

Fingerprlntlng Using Pulsed‑Field Gel Electrophoresis
Aki Kaneko, Hirofumi Miyazawa, Fumiko Kirikae, Kiminori Toyooka, Masahito Hashimoto,Shinji Yamasaki, MitsuharuHasegawa, Chiaki Takeuchi, Tadatoshi Kuratsuji, Morito Sumlya,
Oichirou Kobori, Yoshio Yazaki and Teruo Kirikae*Internalional Medical Center ofJapan,
Toyama 1‑21‑1, Shinjuku, TobJo 162‑8655
Communicated by Hiroshi Yoshikura(Accepted May 26, 2000)

Nosocomial infection caused by methicillin‑resistantinvestlgatlng the source, transmission, and spread orMRSA

Staphy/ococcus. aureus (MRSA) is a critical problem. in
nePnatal intensive Care units (NICUs) (1)･ Genome typlng

infection (2).

An MRSA outbreak, though with no clinical manifesta‑

uslng Pulsed‑rIeld gel electrophoresis (PFGE) is useful fortions, occu汀ed in NICU twice successively with an interval*Co汀eSpOnding author: Fax: +81‑3‑3202‑7364, E‑mail: tkirikae

NICU had five beds. Isolates from individual patients affectedof7 months. The hospitalhad total of about 900 beds and the@ri.imcj.go.jp

by the two outbreaks and those from other wards during the82Jpn. J. Infect. Dis., 53, 2000
M

1

2

3

4

5

6

7

8

9

second outbreak were tested for chromosomal DNA typeM

(contour‑clamped homogeneous electric field system, CHEF

MapperTM: Bio‑Rad Laboratories, Hercules, Calif･, USA),antibiotic resistance (WalkAwayTM, Dade Behring, Deerfield,Ill., USA), enterotoxin serotype (SET‑RPLA: Denka SeikenCo., Tokyo), toxic shock syndrome toxinl1 (TSST‑1)
production (TST‑RPLA: Denka Seiken), and coagulase

serotype (Denka Seiken).
Eight different PFGE pattems of SmaI DNA digests weredetected (Fig. I). Band‑based cluster analysis (MolecularAnalystTM: Bio‑Rad) revealed that these eight PFGE pattents
shared more than 93 % similarity伊ig. 2). Sensitivityto antl‑

biotics is shown in Table 1 ; there were five different pattems.
All isolates except No. 27 produced enterotoxintype C (Table9496

10 0 %98ABBCDEFG
l'一Fig. 1. Pulsed‑field electrophoresis of SmaI‑digested genomic DNA

kom MRSA isolates.
Lane 1: isolate No.9 (pattemA), lane 2: No. 27 (F), lane 3: Nol 28(A), lane4: No. 50 (Bl), lane 5: No. 43 (D), lane 6: Nol 44 (G), lane

7: No. 45 (E), lane 8: No. 49 (B2), lane9: No. 52 (C), M: lowrange
Fig. 2. Cluster analysis of MRSA isolates based on PFGE pattems･PFG Marker.

Table 1. Antibiotic pattem classified by MIC pattem of I 6 antibiotics agalnSt MRSA

Antibi.ticMIC(LLg/ml)

of:pattem PCG MPIPC ABPC PIPC CEZ CMZ CTM IPM EM GM OFLX MINO VCM CLDM
abCd

良R良R氏

RR良RR

良R良良氏

氏R氏R臥R氏RR氏

氏氏氏氏RR良R氏良氏臥礼礼氏

良氏RRR

ss氏氏良ISIIS

R良R礼R

SSSSS

良R氏良S

STF 0M

SSSSS

臥良氏IS

PCG: benzyl‑penicillin, MPIPC: oxacillin, ABPC: ampicillin, PIPC: piperacillin, CEZ: cefazolin, CMZ: ce血etaZOle, CTM: cefotiam,

IPM: imipenem/cilastatin, EM: erythromycin, GM: gentamicin, OFLX: onoxacin, MINO: minocycline, VCM: vancomysin, CLDM: clindamycin,
ST: streptomycin, FOM: fosfomycin, R: resistant, S: susceptible, I: intermediate

Table 2. Phenotypicand genotypic characterization of the S･ auyleuS isolates
I solati on

Ward monthNo.

pattem

1 2 5 0ノ 0ノ

AAAAA

pattem(1 999)NICUEnterotoxin

I solate PFG E AntibioticFeゎ.

TSST‑I CoagulaseAII

一一一一一LlIIL

1 一一一 l1

一一一一一一l + lILI

Ctype

D

+++++

l 一一一一+++十十ⅡⅡⅡⅡⅡ

一++++

LlIII

+++++

ⅡⅡⅡⅡⅡ

++++十十LLIl 一 l++++++ⅡⅡⅡⅡⅡⅡaCaalO O 8 0 ′▲U 51NNNsss

2 2 2 つJ 4 7 c 9 1 0FAAAAeaaaa

43叫45495 05

D G E配B 1 cd a C a a.D183[1 ‑ 1Jpn. J. Infect. Dis., 53, 2000

2). In addition, No. 44 producedtype B enterotoxin. No. 27 did

REFERENCES

not produce any type of enterotoxin. All the isolates produced

TSST‑1 and coagulasetype II (Table 2).
PFGE pattem, antibiotic pattem and enteterotoxin serotype

1. Baltimore, R. S.(1998): Neonatal nosocomial infections.

were identical for all the 5 isolates from the first outbreak in

2. Ichiyama, S., Ohta, M., Shimokata, K., Kato, N. andSemin. Perinato1., 22, 25‑32.

the NICU and for 4 in 5 isolates from the second outbreak

Takeuchi, J. (1991): Genomic DNA fingerprintings by(Table 2), while isolates from other wards showed larger
diversity. These results indicated that, though there was anpulsed‑rleld gel electrophoresis as an epidemiologlCal
marker for study of nosocomial infections caused byinteⅣal of7 months, the two MRSA ou他reaks in the NICU

methicillin‑resistant Staphylococcus aureus. J. Clin.

was due to a slngle strain.

Microbio1., 29, 2690‑2695.

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