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

Laboratory and Epidemiology Communications

EpidemiologlCal Analysts Of a Methicillin‑Resistant
Staphylococcus aureus Outbreak in Surgery Wards
by Genomic DNA Polymorphisms
Aki Kaneko, Tomoko Fujino, Sosuke Kimura, Hirofumi Kuroki, Toshiko Suzuki,

MitsuharuHasegawa, Tadatoshi Kuratsuji, Morito Sumlya, Koichiro Kudo,Oichirou Kobori, Yoshio Yazaki and Teruo Kirikae*

Intemational Medical Center ofJapan,
Toyama I‑21‑1, Shinjuku‑ku, TobJo 162‑8655
Communicated by Hiroshi Yoshikura(Accepted November 2, 2000)

Hospital infection, especially postoperative infection,

DNA using pulsed‑field gel electrophoresis (PFGE) is an
essential tool for epidemiology of MRSA infection.

caused by methicillin‑resistant Staphylococcus aureus(MRSA) is a serious problem in surgical wards (1)･ Analys.is

In a cardiac surgery ward in a hospital in Tokyo, twoof restriction fragment length polymorphisms of genomlC

patients, P 1 and P2, successively contracted severe sepsis. In*Co汀eSpOnding author: Fax: +8 1 ‑3‑3202‑7364, E‑mail: tkirikae

an orthopedic ward in that hospital, One patient, P3, simulta‑
neously contracted acute arthritis at a left knee jolnt. MRSA
was isolated from the blood or the affected region Of each@ri. imcj. go.jp
207

Jpn. J. Infect. Dis., 53, 2000
patient. The isolates and isolates from carriers in the sameof β∫JX I digests (Fig. 1C) were detected. Sensitivity towards during that period were tested f♭r chromosomal DNA

antibiotics is shown in Table 1 ; three different pattems weretyping by using a contour‑clamped homogeneous electric fieldsystem (CHEF MapperTM: Bio‑Rad Laboratories, Hercules,type C, TSST‑1, and type II coagulase (Table 2). No. 374

observed. All isolates except No. 374 produced enterotoxin

Calif･, USA), antibiotic resistance (WalkAway'M, Dadeproduced neither enterotoxin nor TSST‑ 1 , but did produce
type lH coagulase (Table 2).

Behring, Deerfield, 111･, USA), enterotoxfn serotyping (SET‑RPLA: Denka Seiken Co･, Tokyo), toxIC Shock syndrome
toxhl 1 (TSST‑ 1 ) production (TST‑RPLA.I Denka Seiken), andcoagulase serotyping (Denka Seiken).
Seven different PFGE pattems ofSmaI DNA digests (Fig.

Assu…arizedinTable 2,inpatient P 1 , two different PFGE

patterns ofSmaI DNA digests were detected among twelve
MRSA isolates obtained from different sources on different
days･ ln patient P2, all eight MRSA isolates showed the samelA), six pattems orβg/I digests (Fig. 1B), and eight pattems

(A)

M

12345

67pattern(pattemA). Isolate No. 358 fTrom patient Pl, No. 357
fTrom P2, and No. 379 fTrom P3 showed the same PFGE pattemofSmaI DNA digests (patternA), the same patternofBgll
digests (pattem A), the same pattem ofBstX I digests (pattern89101112Mα ), and the same spectrum of antibiotic susceptibility (patternSmala)･ In an orthopedic surgery ward, another MRSA isolate wasobtained什om another patient (P4), in addition to P3. TheMW(Kb)

PFGE patterns of the isolate (No. 382: pattems CBt) weredifferent from those of No. 379 from P3 (pattems AAa). Ina cardiac surgery ward, 1 7 doctors and 2 1 nurses were working

291.0‑‑‑
242.5‑‑‑

during the outbreak. MRSA surveys of personnel were

1 94.0‑‑‑‑perfわrmed, and detected three ca汀iers, including a doctor(M3) and two nurses (Ml and M2). Isolate No. 375 from M2

145.5‑‑‑

showed the same PFGE pattems as those of No. 356 from Pl

97.0‑‑‑(pattems BAD ), though the antibiotic resistance patternwas
slightly different. Isolate No. 374 was different from other48.5‑‑‑MRSA isolates in PFGE pattem, antibiotic susceptibility, andother biologlCal properties. From the end of July throughAugust, four additional MRSA isolates were obtained fromthree patients (P5, P6, and P7) in the cardiac surgery ward.

(B)

The PFGE pattems were different from those of isolates fromβg/1 242.5‑‑

patients Pl, P2, and P3.

1 94.0‑‑‑

The above events could be summarized as fわllows. The

infections of patients Pl and P2 in the cardiac surgery ward

145.5‑‑‑and possibly that ofP3 in the orthopedic surgery ward werecaused by the same or closely related MRSA, given that the97.0‑‑‑‑isolates shared the same molecular markers. During the same

period, three medical staff in the cardiac surgery ward were
found to be MRSA carriers. The isolates were, however, dif‑ferent from one another and also different from the isolates(C)
β∫/X 197.0‑‑‑‑

from patients Pl, P2, and P3. Later, three more patients inthe same ward were infected by MRSA, though the strahs

48.5‑‑‑

were distinct from any of the previous isolates. This finding

suggests that new MRSAs were constantly introduced intoFig. L Pulsed‑field gel electrophoresis ofgenomic DNA from MRSA
isolates･ Upper panel: SmaI‑digested genomic DNA; Middle panel:

the ward.

βg/トdigested DNA. Lower panel: β∫/X 1‑digested. Lane 1 :MRSA

isolate No. 374, lane2: No. 375, lane 3: No. 378, 1ane4: No. 356,lane 5: No. 358, lane 6: No. 360, lane 7: No. 379, lane 8: No. 382,REFERENCE

1ane9:No.417,lane 10:No.418,lane ll:No.426,lane 12:No.465.
M: low range PFG Marker. PFGE pattems are classified asA‑G, A

1. Baltimore, R. S. (1998): Neonatal nosocomial infections.
Semin. Perinato1., 22, 25‑32.

F, and a‑77, respectively, as shown in Table 2.

Table 1 ･ Antibiotic patternclassified by MIC pattem of 1 5 antibiotics agalnSt MRSAAntibiotics listedin fbotnote#a a.a b c

良R良氏氏

EM

CLDMu/FX

GM

RR氏RS

RRRRS

良良I良s

SSS良氏

MINO
S I一l S S

ABKST

VC M

F 0M

SSSSS

SSSSS

SSSSS

SSSSS

" Listed antibiotics are benzyl‑penicillin, ampicillin, plperaCillin, cefazolin, cefotiam and imlpenem/cilastatin･

EM: erythromycln, CLDM: clindamycin, LVFX: levonoxacin, GM: gentamicin, MTNO:minocycline, ABK: arbekacin,
ST: streptomycin, VCM: vancomycin, FOM: fosfomycin, R: resistant, S: susceptible, I: intermediate208Jpn. J. Infect. Dis., 53, 2000
Table 2. Phenotypic and genotypic characterization of the MRSA isolates｡epai:dnn,'ec;a?こ, Sympto‑s lsolationNo･ i慧?.iO.fn lsoJaa;lfn source rpsaFiSaHpaBF"genE (pBPasF?G荒A,nilHioiic En,war.:et:in TSSTll C晋ePI

sepsIS

June 19

catheter

A356

June 19

sputuma359

June 19

urine

AC363

June 30

spu山m

AC+ⅠI

June 30:三:呈sepsIS｣

AaC+lI

aC+lI

α

B+H

noseA

C+

ⅠI

370

July5nose

AC+

lI

371

July5sputum

AC+II378

July7spu

A

C+ⅠI

364

P2

cardiacSu rgery

358

tum

380

July

21

sputumAC

419

July 28

blood

AC+

11420

Julysputum

A

C+

lI

421

July 31

noseB

Csputum

ACbloodA

31427

August 4

357

June 19360

June 19

surglCal wound A

361

June 19

surgical wound(1)A

362

June 19

surgical wound(2)A365

June 30

surgical wound(3)366June 30

spu山mc ardiac
S urgeryJuly 3sputumA

Julysputum

Aa.Aritis ;;; ;:i;2: o?uhrogpeeSic :::eeJOlnt;::;;

M3

sCuarrgdtai

374

JulyきAB:

AB

::≡;

5

nose

41

8426

July28Augustsputum

I

nose

209

H

ⅠⅠ+++十十++++ⅠⅠ+

IIIIlGaEFD三三; iulyp2S8t2. SCuarrgd寓::;;a+A373;言57α+lIA3723｣+l I‑ 1‑ ▼.l.1

β Fどd++++I 1 l ▼l