Jpn. J. Infect. Dis., 54, 2001

Laboratory and Epidemiology Communications

Molecular Epidemiology of Methicillin‑Resistant Staphylococcus aureus
Infections in a Newbom Nursery, a Neonatal Intensive Care Unit,

and a General Pediatrics Ward
Namiko Mori, Tomoko Fujino, Hiroshi Uchida, Hirofumi Miyazawa, Shigeki Minoura,Akihiko Kawana, Hisashi Kawahata, Michiko Gotoh, Tatsumi Yonamine,
Fumiko Yamanishi, Tadatoshi Kuratsuji, Koichiro Kudo, Oichirou Kobori,
Yoshio Yazaki and Teruo Kirikae*International Medical Center of Japan,Toyama 1‑21‑1, Shinjuku‑ku, Tokyo 162‑8655

Communicated by Hiroshi Yoshikura(Accepted October 10, 2001)

Nosocomial infection caused by methicillin‑resistantM 1 2M

3456789101112M

Staphylococcus aureus (MRSA) is a serious problem. inperinatal, neonatal, and pediatric medicine. Genome typlng
using pulsed‑field gel electrophoresis (PFGE) is a powerfultool fわr investlgatlng the source, transmission, and spread ofMRSA.
In June 2001, an MRSA outbreak occurred involving aneonatal intensiv.e care unit (NICU)･ a newbom nursery, anda general pediatncs ward in a hospital with 925 beds. Thesethree wards are on the same floor. The NICU had five beds
and the pediatric ward had 27 beds. One baby each in thenewbom (B3) and in the NICU (Nl) had conjunctivitis. Onebaby (N3) in the NICU had pneumonia. Two children (C2and C3) in the general pediatrics ward had sepsis and otitis

media. MRSA was isolated from eye mucus (from B3 andNl), the pharynx (from N3 and C2), and otorrhea (from C3)of these children. MRSA was also isolated from umbilical(from Bl), vaginal (fTrom B2), pharynx (from N2) and nasal(from Cl) swabs, and the tip ofa stomach tube (from N4)･ AFig. 1. Pulsed‑field gel electrophoresis ofSmaI‑digested genomic DNA

total often isolates were obtained and co°ed as an isolate

from MRSA isolates.

group 4N4SO60 1. Six MRSA isolateswith two different PFGE

PFGE analysis orHOSP1200 isolates orNos. 719 (lane 1) and 592

pattems (pattems A4 and B) had been obtained from the same(lane 2), and 4N4SO601 isolates ofNos. 856 (lane 3), 858 (lane 4),

wards in December 2000 (isolate group HOSP1200) (1).

862 (lane 5), 861 (lane 6), 866 (lane 7), 867 (1ane 8), 860 (lane 9),

The all isolates 4N4SO60l were tested f♭r chromosomal

863 (lane IO), 864 (lane ll) and 859 (lane 12). M: Iowrangc PFG

DNA typing (PFGE) by using a contour‑clamped homogenPPus

Marker.

electric field system (CHEF MapperTM: Bio‑Rad Laboratones,Hercules, Calif., USA). They were also tested for antibioticresistance (WalkAwayTM : Dade Behring, Deerfield, Ill., USA),enterotoxin serotyping (SET‑RPLA: Denka Seiken Co.,

405060708090100(%)

Tokyo), toxic shock syndrome toxinl 1 (TSST‑ 1 ) production

A4(TST‑RPLA: Denka Seiken), and coagulase serotypingAlュ(Denka Seiken).
PFGE pattems ofSmaI DNA digests for isolate 4N4SO60l

B

are shown in Fig.1. Band‑based cluster analysts Of theseLpattems (Molecular AnalystTM: BioIRad) revealed five PFGE,pattemsA4,A13, B, L, and K. A4,A13, and B shared a simi‑
larity of more than 75% (Fig. 2). Sensitivity to antibiotics isshown in Table 1. There were four different pattems. Pattems
a and a'were different only in the level ofminocycline (MINO)
sensitivlty. All isolates except No. 859 produced enterotoxin

KFig. 2. Band‑based cluster analysis of PFGE patterns ofthcsc outbreakisolates and the isolation dates ofMRSAwith each PFGE patterns.

type C and TSSTl1. All except Nos. 859 and 864 produced*Corres.ponding author: Fax: +8 1 ‑3‑3202‑7364, E‑mail: tkirikae@

type II coagulase (Table 2).

All three MRSA isolates aom the newbornnursery (Nos.

ri,imq.go,Jp189

Jpn. J. Infect. Dis., 54, 2001
Table L Antibiotic pattem classfied by antibiotic pattern of 1 8 antibiotics agalnSt MRSA
Antibioticpattem

戸OM

aabC

氏良良s

Antibiotics
LVFX

GM良良良IABKM

INO

SSSSss良良ST

Tl S S 1

VCM

SSSS

TEIC

SSSS

SSSS

All isolates were resistant to PCG, MPIPC, ABPC, CEZ, CTM, CFDN, FMOX, lPM,EM, CLDM.
PCG: benzyl‑penicillin, MPIPC: oxacillin, ABPC: ampicillin, CEZ: cefazolin, CTM:cefotiarn, CFDN: cefdinir, FMOX: nomoxef, lPM: imipenem/cilastatin, EM: erythromycin,

CLDM: clindamycin, FOM: fosfomycin, LVFX: lcvofloxacin, GM: gentamicin, MINO:minocycline, ASK: arbckacin, ST: streptomycin, VCM: vancomycin, TEIC: teicoplanin,
R: resistant, S: susceptible, 1: intcrmcdiatc.

Table 2･ Phenotypic and genotypic characterization ofS. aureus isolates in June 2001 (4N4SO601)
ward

Child

newborn nursery

Xs:二atea1

source

856

B2
B3

N

86

N4C3

1cye
63866
867

pediatrics
C2cye

8N3

general8862

1C,pap.G.mEumbilicus

85N2sy‑plo‑

camCrvaglna
mucus

mucus

1864

A4A4

unctiviti

conJunCtivitis

pharynx

pharymx

camer

859
pharymx

B

carriernasal
sepsisoto汀heaasA4A4aCoagulasc

C+

C+

11C+

IlC

十一C+

1111ⅠⅠ

A4aC+

IlaC+

ⅠⅠI

otitis

TSST‑IA4

cavltyAaa'pneumonia

tube

Enterotoxin

a'Came一conJ

stomach860

lan..ttbiotic

carrler

3

media

KaCbC

LcB

VIIl856, 858, and 862) and three offour isolatesfrom the NICU

Outbreak in 2000. Babies in the newborn nursery and the(Nos･ 861 , 866, and 867) had almost the same character (Table2)･ They all produced enterotoxin type C, TSST‑1, and typell coagulase, and had the same PFGE pattem ofSmaI DNANICU were examined by doctors in one team but cared forby nurses belonglng tO two different teams. Children in thegeneral pediatrics ward were examined by doctors of anotherdigests and almost the same spectnlm Of antibiotics susceptトdifferent team and cared for by nurses belonglng tO the teambility･ These isolates were identical in PFGE pattem to anisolate in the previous outbreak, HOSP 1200 isolate No. 592.
Another isolate, No. 863, from the NICU had a pattern
identical to an isolate ofHOSP1 200 (No. 7 19) in the previous

taking care of the NICU. The MRSA in the newbom nursery
and the NICU, therefわre, appeared to be transmitted by doctors

but not by nurses.

outbreak･ Three isolates fTrom the general pediatrics ward had

REFERENCE

characters different from other MRSAs isolated from thenewbom nursery or NICU. These results indicate the outbreak1. Fujino, T., Mori, N., Kawana, A., Kawabata, H.,

in the newbom nursery and the NICU was brought about by

Kuratsuji, T., Kudo, K., Kobori, 0., Yazaki, Y. andclonal expansion ofMRSA which had caused an outbreak inthe same wards in December 2000. The MRSA infections inresistant Staphylococcus aureus in a Tokyo hospital in

the general pediatrics ward were probably unrelated to the2000. Jpn. J. infect. Dis., 54, 91‑93.

Kirikae, T. (2001 ): Molecular epidemiology ofmethicillin‑lワo