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.
Khalil
S B
SB
Research Sciences Department, U.S. Naval Medical Research Unit No. 3, Cairo, Egypt.
Cassels
F J
FJ
Shaheen
H I
HI
Pannell
L K
LK
El-Ghorab
N
N
Kamal
K
K
Mansour
M
M
Savarino
S J
SJ
Peruski
L F
LF
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