MOLECULAR CHARACTERIZATION OF ENTEROTOXIGENIC ESCHERICHIA-COLI (ETEC)ISOLATED IN NEW-CALEDONIA (VALUE OF POTENTIAL PROTECTIVE ANTIGENS IN ORAL VACCINE CANDIDATES)
E. Begaud et al., MOLECULAR CHARACTERIZATION OF ENTEROTOXIGENIC ESCHERICHIA-COLI (ETEC)ISOLATED IN NEW-CALEDONIA (VALUE OF POTENTIAL PROTECTIVE ANTIGENS IN ORAL VACCINE CANDIDATES), Research in microbiology, 144(9), 1993, pp. 721-728
The role of enterotoxigenic Escherichia coli (ETEC) in childhood diarr
hoea in New Caledonia was demonstrated in previous epidemiological wor
ks. This study was undertaken in order to characterize these strains a
nd to determine whether bacterial components of current vaccine candid
ates (toxin. colonization factor antigens, O:H antigens) would be usef
ul in our region. A total of 24 ETEC strains were studied: 5 strains p
roduced heat-labile enterotoxin. 17 strains produced heat-stable enter
otoxin (9 STp and 8 STh), and 2 strains produced both toxins (1 LT/STp
/STh and 1 LT/STh). E. coli strains were screened for the presence of
genes encoding for enterotoxins (DNA dot blot and Southern hybridizati
on assays); results obtained with probes were closely correlated and w
ere in agreement with biological assays. No two ETEC strains possessed
similar plasmid profiles, and DNA sequences encoding for enterotoxins
were located on plasmids ranging from 58 to 75 MDa. The O:H (01:H-,02
:H7, 06:H16, 025:H-, 027:H7, 028ab:H9, 052:H10, 064:H5, 070:H-, 078:H1
2, 088:H25, 099:H6, 0101:H-, 0126:H12, 0166:H30) serotypes are present
ed (all the strains were typable, but some ETEC serotypes were unusual
). By using antisera against colonization factor antigens (CFA) I and
It, results showed that 9 of the 24 ETEC strains expressed CFA (2 CFA/
II and 7 CFA/I). These strains possessed high bacterial surface hydrop
hobicity. Fifteen ETEC did not possess CFA; among these, 11 did not ex
hibit high hydrophobicity or show haemagglutination activity. Four of
the 15 CFA-negative strains exhibited high hydrophobicity (two 064:H45
. one 070:H- and one 088:H25) but no haemagglutination in the presence
or absence of mannose. Only 7 of 24 ETEC expressed resistance to ampi
cillin, trimethoprimsulphamethoxazole or tetracycline. Data indicate t
hat several ETEC isolates would be refractory to current Vaccine candi
dates, and that for vaccine to be effective in our region, other antig
ens must be included.