CS22, a novel human enterotoxigenic Escherichia coli adhesin, is related to CS15.
Enterotoxigenic Escherichia coli (ETEC) expresses a broad spectrum of O:H antigens. Serogroup O20 is one of the most prevalent among the ETEC strains lacking any of the defined colonization factors (CFs), in Argentina. An O20:H- strain, ARG-3, adhered to Caco-2 cells and exhibited a thermoregulated 15.7-kDa protein band upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). An antiserum against this protein inhibited ARG-3 adhesion to Caco-2 cells and bound to very thin fibrilla-like structures on the bacterial surface. A 15.7-kDa protein-defective mutant failed to adhere to Caco-2 cells and lacked immunogold-labeled surface structures. The N-terminal amino acid sequence of the structural subunit showed 95% homology to that of CS15 of ETEC (former antigen 8786) and 65% homology with fimbria SEF14 of Salmonella enterica serovar Enteritidis. Nevertheless, the molecular size of ARG-3 adhesin was different from that of CS15, as revealed by SDS-PAGE and mass spectrometry. Both proteins are immunologically related, yet not identical, since an antiserum against the 15.7-kDa protein reacted solely with ARG-3 after absorption with bacteria bearing CS15. Moreover, only under low stringency conditions could DNA from strain ARG-3 be amplified by PCR using primers derived from the nfaA sequence of CS15. Thus, from the DNA sequence obtained from the ARG-3 PCR product, it could be deduced that the subunit protein differed in 30 residues from that of CS15. ARG-3 adhesin was found in 60% of the O20:H- CF-negative ETEC strains from Argentina; however, it appeared restricted to this serotype. We propose the designation CS22 for the herein identified nonfimbrial adhesin of human ETEC.
Pichel
M
M
Departamento de Bacteriología, Instituto Nacional de Enfermedades Infecciosas-ANLIS "Carlos G. Malbrán," 1281 Capital Federal, Argentina.
Binsztein
N
N
Viboud
G
G
D018829:Adhesins, Bacterial / Q000096:biosynthesis / Q000235:genetics*; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000235:genetics*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D018938:Caco-2 Cells; D003967:Diarrhea / Q000382:microbiology; D004768:Enterotoxins; D004926:Escherichia coli / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D015964:Gene Expression Regulation, Bacterial; D006358:Hot Temperature; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D019081:O Antigens; D017386:Sequence Homology, Amino Acid
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; C409567:CS15 protein, E coli; C409566:CSEA protein, E coli; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D019081:O Antigens; C022924:colonization factor antigens; D036781:Fimbriae Proteins