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

Laboratory and Epidemiology Communications

EpidemiologlCal Analysis Of a Methicillin‑Resistant Staphylococcus aureus
Ou他reak in a Neonatal Intensive Care Unit a洗er Cleanlng Of

Environmental Surfaces in the Unit by Genomic DNA Fingerprlntlng
Using Pulsed‑Field Gel Electrophoresis
Aki Kaneko, Hirofumi Miyazawa, Fumiko Kirikae, Masahito Hashimoto, Kiminori Toyooka,
Yumiko Ishii, Toshiko Suzuki, MitsuharuHasegawa, Tadatoshi Kuratsuji, Morito Sumlyq,
Koichiro Kudo, Oichirou Kobori, Yoshio Yazaki and Teruo Kirikae*International Medical Center ofJapan,
Toyama I‑21‑1, Shinjuku‑ku, Tokyo 162‑8655
Communicated by Hiroshi Yoshikura(Accepted June 23, 2000)

Nosocomial infection caused by methicillin‑resistant

M

1

2

Staphylococcu乍aureus (MRSA) is a serious problem in

34n■l窟塵轟浄療帝普憲驚牽5MI

nePnatal intensIVe Care units (NICUs) (I)･ Genome typing
uslng Pulsed‑field gel electrophoresis (PFGE) is a powerfultool for investlgatlng the source, transmission, and spread ofMRSA.
An MRSA outbreak occurred in an NICU right afterintensive cleanlng Of the environmental surfaces in the unit
and this ou他reak continued f♭r 5 moれ血s. The hospital had

925 beds and the NICU had 5 beds. MRSA outbreaks had
occumd in the NICU twice successively wi仇an inteⅣal of

7 months. PFGE analysts revealed that these two outbreaks
were due to a single strain (2). A触r仇ese outbreaks, envi‑

ronmental surfaces in the NICU were intensively cleaned

with a hospital‑grade disinfectant‑detergent (0.2%
alkyldiaminoethylglycine hydrochloride) ･Thirty‑seven isolates from 31 patients affected by theou他reaks were tested fわr chromosomal DNA typing by using

a contour‑clamped homogeneous electric field system (CHEF

MapperTM: Bio‑Rad Laboratories, Hercules, Calif1, USA),antibiotic resistance (WalkAwayTM, Dade Behring, Deerfield,Ill. , USA), enterotoxin serotyping (SETIRPLA: Denka Seiken
Fig. I. Pulsed一名eld gel electrophoresis ofSmaI‑digested genomic DNA

C0., Tbkyo), toxic shock syn血ome toxin‑ 1 (TSSTL 1) produc‑&om MRSA isolates.
Lane 1: PFGEpatternA, lane 2: H, lane 3: I‑I, lane 4:I‑2, lane 5:F,M: low range PFG Markertion (TST‑RPLA: Denka Seiken), and coagulase serotyping(Denka Seiken).
Five different PFGE pattems of SmaI DNA digests weredetected (Fig. 1). A band‑based cluster analysis of thesepattems (Molecular Analyst'M: Bio‑Rad) revealed that these
five PFGE pattems were more than 95 % similarity(Fig. 2).
Sensitivityto antibiotics is shown in Table 1 ; there were four
different patterns. All isolates except No. 150 produced96979899100%

AH ト ト Fenterotoxin type C (Table 2). No. 150 did not produce any
type of enterotoxin. All isolates tested produced TSST‑ 1 and1 2type u coagulase (Table 2).

The PFGE pattem, antibiotic pattem, and enterotoxin

serotypeTere identical for 28 isolates (Table 2) and 9 isolates

Fig. 2. Cluster analysts OfMRSA isolates based on PFGE pattems.

from prevlOuS Outbreaksinthe NICU ( 1 ). TYle dates of isolation

ofMRSA are illustrated in Fig. 3. Two different strains ofThese results indicated that this outbreak in the NICU wasMRSA were iso】atedfrom the same patients at different periods.

dominated by a slngle strain.
*Co汀eSpOnding author: Fax: +81 ‑3‑3202‑7364, E‑mail: tkirikae@ ri.imcj.go.jp
130Jpn. J. Infect. Dig., 53, 2000
Table 1. Antibiotic pattem classified by MIC pattem of 1 5 antibiotics agalnSt MRSA
Antibiodc Antibiodcs 1 isted

a‑1

MIC of≧nr

C LDM

pattem in footnote#
氏良氏氏

氏礼良s

0M

C MZ

GMM N0VC M

STRR良s氏氏s氏sss氏I S I‑TlSSSSSSSS

H日日a‑2a‑3b#Listcdantibiotics are benzyl‑penicillin, oxacillin, ampicillin, piperacillin, cefazolin, cefotiam, erythromycin

and imipenem/cilastatin. CLDM: clindamycin, FOM: fosfomycin, CMZ: Cehetazole, GM: gentamicin,
MINO: minocycline, VCM: Vancomysin, ST: streptomycin, R: resistant, S: susceptible, I: intermediate

Table 2. Phenotypicand genotypic characterization of the S. aurleZJS isolates
p FG E Antibiotic Enterotoxin

Isolate No.

Pattern

AHHFAHAH

Dominant strains書

pattem

山山がb 3:山山山‑ 一A
十++一++++lIl135

一一 一 l1Coagul ase

Br 一 i 一 F 一一一C

D

type++十十++++1 1 1 1 1 1 ‑1 1 Il ‑1 T‑▲ l ■‑▲ l‑ 1

J I L

136
150192
214, 293
241
290●tsolateNo. ordominant strains: 94, 98, 103, 107, 114, 127, 140, 144, 147, 165, 182, 195, 203,209, 215, 218, 222, 225, 231, 233, 235, 239, 245, 251, 261, 273, 278, 28l and 292.

△

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

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Nov.1999

REFERENCES｡ .+ . ･T

U:…享;:●

Dcc.

Jan.2000

Semin. Perinato1., 22, 25‑32.

Feb

2. Kaneko, A., Miyazawa, H., Kirikae, F., Toyooka, K.,Hashimoto, M., Yamasaki, S., Hasegawa, M., Takeuchi,C., Kuratsuji, T., Sumlya, M., Kobori, 0., Yazaki, Y.

Mar.

and Kirikae, T. (2000): EpidemiOlogical analysis of(Month/Year)methicillin‑resistant Staphylococcus aureus outbreaks inFig. 3. Dates orisolation ofMRSA.

a neonatal intensive care unit by genomiC DNA finger‑

Each symbol represents PFGE pattern of each isolate. closed circle

printing uslng Pulsed‑fie)d gel electrophoresis･ Jpn. J･
Infect. Dis., 53, 82‑84.

stands for PFGE pattem A, open circle designated pattem F, open
square designates pattem H, open triangle refers to patternト1 , andopen diamond refers to pattem I‑2. MRSAsisolated from the same
patient are connected by a line.

131