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Journal of Clinical Microbiology, May 2000, p. 1767-1771, Vol. 38, No. 5
Centro de Investigaciones en Ciencias
Microbiológicas, Instituto de Ciencias, Benemérita
Universidad Autónoma de Puebla, Puebla,
México,1 and International Centre
for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), Dhaka-1000,
Bangladesh2
Received 9 November 1999/Returned for modification 20 December
1999/Accepted 11 February 2000
DNA amplification of lngA, the structural gene of
longus type IV pilus produced by human enterotoxigenic
Escherichia coli (ETEC) was achieved by the use of specific
oligonucleotide primers designed from the nucleotide sequence of
lngA. A 630-bp fragment representing the entire
lngA gene was amplified in eight prototype strains
previously characterized as longus positive. Five ETEC strains
producing colonization factor antigen III (CFA III) (also a type IV
pilus) were also positive by PCR, confirming the DNA homology between
CFA III and longus. None of the non-ETEC and non-E. coli
enteropathogens studied showed the 0.63-kbp amplicon. The procedure
thus detected only ETEC strains harboring type IV pili genes with or
without other colonization factors. Except for five lngA
PCR-positive, probe-positive strains, all lngA PCR-positive strains produced the pilin as demonstrated by immunoblotting. To test
the amplification procedure in a clinical setting, a collection of 264 fresh clinical E. coli strains isolated from 88 Mexican children with diarrhea was screened by PCR. Among 82 ETEC isolates found, 30 (36.5%) were lngA PCR-positive. Twenty-seven
percent of the children shed ETEC that possessed lngA. In
parallel with DNA probes or PCR protocols to detect enterotoxin genes,
the lngA PCR method may prove useful for detection of ETEC
harboring type IV pilus genes in epidemiological studies.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Identification of Enterotoxigenic Escherichia
coli Harboring Longus Type IV Pilus Gene by DNA
Amplification
*
Corresponding author. Mailing address: Centro de
Investigaciones en Ciencias Microbiológicas, Instituto de
Ciencias, Benemérita Universidad Autónoma de Puebla,
Edificio 76, 3r Piso, 14 Sur Ave., San Claudio, Ciudad Universitaria,
C. P. 72570, Puebla, Puebla, México. Phone: (52 22) 33 20 10. Fax: (52 22) 44 45 18. E-mail: jgiron{at}siu.buap.mx.
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