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Journal of Clinical Microbiology, September 1999, p. 2974-2978, Vol. 37, No. 9
U.S. Naval Medical Research Unit No. 3, Cairo, Egypt1; Facultad de Medicina,
Universidad Nacional Autonoma de Mexico, Mexico, D.F.,
Mexico2; and National Institute of Child
Health and Human Development, Bethesda,
Maryland3; and Department of Medical
Microbiology and Immunology, Goteborg University, Goteborg,
Sweden4
Received 22 December 1998/Returned for modification 6 February
1999/Accepted 5 June 1999
No past studies of diarrhea in children of the Middle East have
examined in detail the phenotypes of enterotoxigenic Escherichia coli (ETEC) strains, which are important pathogens in this
setting. During a prospective study conducted from November 1993 to
September 1995 with 242 children under 3 years of age with diarrhea
living near Alexandria, Egypt, 125 episodes of diarrhea were positive for ETEC. ETEC strains were available for 98 of these episodes, from
which 100 ETEC strains were selected and characterized on the basis of
enterotoxins, colonization factors (CFs), and O:H serotypes. Of these
representative isolates, 57 produced heat-stable toxin (ST) only, 34 produced heat-labile toxin (LT) only, and 9 produced both LT and ST.
Twenty-three ETEC strains expressed a CF, with the specific factors
being CF antigen IV (CFA/IV; 10 of 23; 43%), CFA/II (5 of 23; 22%),
CFA/I (3 of 23; 13%), PCFO166 (3 of 23; 13%), and CS7 (2 of 23; 9%).
No ETEC strains appeared to express CFA/III, CS17, or PCFO159. Among
the 100 ETEC strains, 47 O groups and 20 H groups were represented,
with 59 O:H serotypes. The most common O serogroups were O159 (13 strains) and O43 (10 strains). O148 and O21 were each detected in five
individual strains, O7 and O56 were each detected in four individual
strains, O73, O20, O86, and O114 were each detected in three individual
strains, and O23, O78, O91, O103, O128, and O132 were each detected in two individual strains. The most common H serogroups were H4 (16 strains), 12 of which were of serogroup O159; H2 (9 strains), all of
which were O43; H18 (6 strains); H30 (6 strains); and H28 (5 strains);
strains of the last three H serogroups were all O148. Cumulatively, our
results suggest a high degree of clonal diversity of disease-associated
ETEC strains in this region. As a low percentage of these strains
expressed a CF, it remains possible that other adhesins for which we
either did not assay or that are as yet undiscovered are prevalent in
this region. Our findings point out some potential barriers to
effective immunization against ETEC diarrhea in this population and
emphasize the need to identify additional protective antigens commonly
expressed by ETEC for inclusion in future vaccine candidates.
0095-1137/99/$04.00+0
Phenotypic Diversity of Enterotoxigenic
Escherichia coli Strains from a Community-Based Study of
Pediatric Diarrhea in Periurban Egypt


*
Corresponding author. Mailing address: c/o Commanding
Officer, U.S. Naval Medical Research Unit No. 3, PSC 452, Box 5000, FPO
AE 09835-0007. Phone: 011 20/2 284 1381. Fax: 011 20/2 284 1382. E-mail: boushrah{at}namru3.navy.mil.
Present address: Division of Bacterial and Mycotic Diseases,
National Center for Infectious Diseases, Centers for Disease Control
and Prevention, Atlanta, GA 30333.
Present address: Department of Veterinary and Biomedical Sciences,
University of Nebraska, Lincoln, NE 68583.
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