Jpn. J. Infect. Dis., 58, 2005

Laboratory and Epidemiology Communications

An Outbreak of Diarrhea Caused by Escherichia coli Serogroup
O169:HNM Harboring a Coding Gene for Enteroaggregative
E. coli Heat-Stable Enterotoxin 1 (astA) in Fukui Prefecture
Fubito Ishiguro*, Yoshito Kyota, Michio Mochizuki and Takeo Horikawa
Fukui Prefectural Institute of Public Health and Environmental Science, Fukui 910-8551, Japan
Communicated by Haruo Watanabe(Accepted March 10, 2005)

In Japan, the first outbreak of gastroenteritis caused bya strain of Escherichia coli having a coding gene forenteroaggregative E. coli heat-stable enterotoxin 1 (astA)
occurred in Osaka Prefecture in 1996 (1). Outbreaks ofdiarrhea due to the same strain have since been reported inHiroshima city and Oita Prefecture (2,3). The strain was also
implicated in a food-poisoning outbreak that occurred in aschool dormitory in Fukui Prefecture on 19 to 22 August 2004,
in which 69 of 95 exposed individuals (82 students and 13
teaching staffs) were symptomatic. Lunches that were served
on 19 or 20 August were the only food stuffs ingested incommon by all these patients, although no portions of thelunches remained for examination. The clinical symptoms
recorded were as follows: explosive diarrhea (68 people),abdominal pain (55), fever (17), headache (12), and nausea(10).
Stool samples were collected from 15 students and 1 teaching staff of 69 patients and 3 food-handlers (1 of those foodhandlers was clinically symptomatic) during 23 - 24 August,and were examined for bacteriological inspection. E. coli
O169:HNM were isolated from all samples. A PCR-based
assay for genes encoding astA, aggR, eae, LT, ST, invE, andstx (4-6) revealed that all 19 strains were positive for astAand negative for aggR, eae, LT, ST, invE, and stx, as previously described (data not shown). When 13 of the 19 strains
were tested for their sensitivity to tetracyclin (TC), fosfomycin(FOM), ampicillin (ABPC), streptomycin (SM), ciprofloxacin(CPFX), kanamycin (KM), cefotaxime (CTX), chloramphenicol (CP), sulfamethoxazole-trimethoprim (ST), gentamycin (GM), nalidixic acid (NA), and sulfisoxazole (Su) byusing Sensi Disc (Becton Dickinson Microbiology Systems,Cockeysville, Md., USA), all were resistant to TC, andintermediately resistant to FOM and ABPC (data not shown).
These 13 isolates were also examined by pulsed-field gelelectrophoresis (PFGE) using a Gene Path Typing System(Program No. 22; Nippon Bio Rad, Tokyo, Japan). The PFGE
patterns of XbaI- (Nippon Bio Rad) or BlnI- (Roche Diagnostics, Mannheim, Germany) digested chromosomal DNAs
were identical among all the isolates examined (Fig. 1). The
plasmid profiles were also identical among these isolates (datanot shown). As referring, 1,730 strains of O-serotyped E. coli
isolates from sporadic diarrhea cases at 2 hospitals in Fukui(A)

M 1 2 3 4 5 6 M 7 8 9 10 1112 1314 1516 M

kb
533.5−
436.5−
339.5−
242.5−
145.5−
97.0−
48.5−

(B)

M 1 2 3 4 5 6 M 7 8 9 10 1112 131415 16 M

kb
533.5−
436.5−
339.5−
242.5−
145.5−
97.0−
48.5−

Fig. 1. PFGE patterns of XbaI- and BlnI-digests of chromosomal DNAof Escherichia coli O169:HNM (astA positive) isolates. (A) XbaIdigests and (B) BlnI-digests. Lane 1 - 2, Isolates from food-handler
A; Lane 3 - 4, Isolates from food-handler B; Lane 5 - 6, Isolates fromfood-handler C; Lane 7, Isolate from a staff of patient; Lane 8 - 16,Isolates from students of patient; M, λ DNA ladder.

from 1997 to 2004, only 3 strains were found to be E. coli
O169:HNM, and 2 of these were positive for astA.
We would like to express our thanks to Dr. N. Takada,
Faculty of Medical Sciences, University of Fukui, for hisreview of the manuscript.
This article appeared in the Infectious Agents Surveillance
Report, vol. 25, no. 10, p. 262-263, 2004 in Japanese.

*Corresponding author: Mailing address: Fukui Prefectural
Institute of Public Health and Environmental Science, Haramecho 39-4, Fukui 910-8551, Japan. E-mail: ishigurofubito@fklab.
fukui.fukui.jp
119Jpn. J. Infect. Dis., 58, 2005
by known gene negative E. coli (astA positive) O6:H10.
Infect. Agents Surveillance Rep., 25, 101-102 (in Japanese).
4. Yatsuyanagi, J., Kinouchi, T., Saito, S., Sato, H. andMorita, M. (1996): Enteropathogenic Escherichia colistrains harboring enteroaggregative Escherichia coli(EaggEC) heat-stable enterotoxin-1 gene isolated froma food-borne like outbreak. J. Jpn. Assoc. Infect. Dis.,70, 73-79 (in Japanese).
5. Ratchtrachenchai, O. A., Subpasu, S. and Itoh, K.
(1997): Investigation on enteroaggregative Escherichia
coli infection by multiplex PCR. Bull. Dept. Med. Sci.,
39, 211-220.
6. Itoh, F., Ogino, T., Itoh, K. and Watanabe, H. (1992):
Differentiation and detection of pathogenic determinants
among diarrheagenic Escherichia coli by polymerasechain reaction using mixed primers. Jpn. J. Clin. Med.,50, 343-347.

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