Characterization of an enterotoxigenic Escherichia coli strain from Africa expressing a putative colonization factor.
An enterotoxigenic Escherichia coli (ETEC) strain of serotype O114:H- that expressed both heat-labile and heat-stable enterotoxins and tested negative for colonization factors (CF) was isolated from a child with diarrhea in Egypt. This strain, WS0115A, induced hemagglutination of bovine erythrocytes and adhered to the enterocyte-like cell line Caco-2, suggesting that it may elaborate novel fimbriae. Surface-expressed antigen purified by differential ammonium sulfate precipitation and column chromatography yielded a single protein band with M(r) 14,800 when resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (16% polyacrylamide). A monoclonal antibody against this putative fimbrial antigen was generated and reacted with strain WS0115A and also with CS1-, CS17-, and CS19-positive strains in a dot blot assay. Reactivity was temperature dependent, with cells displaying reactivity when grown at 37 degrees C but not when grown at 22 degrees C. Immunoblot analysis of a fimbrial preparation from strain WS0115A showed that the monoclonal antibody reacted with a single protein band. Electron microscopy and immunoelectron microscopy revealed fimbria-like structures on the surface of strain WS0115A. These structures were rigid and measured 6.8 to 7.4 nm in diameter. Electrospray mass-spectrometric analysis showed that the mass of the purified fimbria was 14,965 Da. The N-terminal sequence of the fimbria established that it was a member of the CFA/I family, with sequence identity to the amino terminus of CS19, a new CF recently identified in India. Cumulatively, our results suggest that this fimbria is CS19. Screening of a collection of ETEC strains isolated from children with diarrhea in Egypt found that 4.2% of strains originally reported as CF negative were positive for this CF, suggesting that it is biologically relevant in the pathogenesis of ETEC.
Research Sciences Department, U.S. Naval Medical Research Unit No. 3, Cairo, Egypt.
S B
SB
Khalil
F J
FJ
Cassels
H I
HI
Shaheen
L K
LK
Pannell
N
N
El-Ghorab
K
K
Kamal
M
M
Mansour
S J
SJ
Savarino
L F
LF
Peruski
D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000302:isolation & purification*; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000302:isolation & purification*; D002417:Cattle; D003967:Diarrhea / Q000209:etiology; D004926:Escherichia coli / Q000276:immunology* / Q000472:pathogenicity; D005260:Female; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000648:ultrastructure; D006801:Humans; D007223:Infant; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D008970:Molecular Weight
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C022924:colonization factor antigens; D036781:Fimbriae Proteins