GENOTYPIC AND PHENOTYPICAL CHARACTERIZATI ON OF POTENTIAL VIRULENCE OF BOVINE ESCHERICHIA-COLI STRAINS ISOLATED IN ALGERIA

In order to characterize pathogenic potential of Escherichia coli stra ins isolated from diarrhoeic calves in Algeria, a large range of virul ence factors and markers were researched in 51 strains via DNA-DNA hyb ridation on colonies and via phenotypical tests. The sequence research ed were those coding for adhesins F5, F41, F17, PapA, PapG, AFA and AF A, proteins involved in the effacement of the enterocyte microvilli Ea eA and EaeB, and toxins STaP, STb, LTp, SLT1, SLT2, CNF1 and CNF2. The phenotypes explored were the colicins, aerobactin, haemolysins, and h aemagglutinin production and the serum resistance. The reaction of the strains to these different tests allows to distinguish three groups o f strains: Strains with intestinal tropism sub-divided into 2 strains STaP+ F5+F41+ (ETEC), 2 strains EaeA+ EaeB+SLT1+ (EHEC-like) and 5 str ains EaeA+ (EPEC). The strains had a negative reaction to aerobactin, serum resistance, and haemolysins tests. Only EPEC and EHEC-like strai ns were colicinogenic. Potentially invading strains subdivided into 3 strains NTEC2 (CNF2+, CNF2+AFA+ and CNF2+ F17A+PapA+), 17 strains posi tive to AFA and/or F17 and/or Pap adhesins probes, and 13 strains nega tive to genetic probes. Except for one Pap+F17+ strain, all the others were positive to aerobactin production and/or serum resistance; furth ermore, some were colicinogenic. Nine strains with negative reaction t o genotypical and phenotypical tests (except for hemagglutination) can be considered as commensals or belonging to pathotypes not detected i n this study. Mannose-resistant hemagglutination test was positive for 13 strains out of 19 positive with at least one gene probe of adhesin s and for 8 strains out of 13 negative to gene probes of adhesins. A p athotype diversity exists in bovine E. coli isolated in Algeria. These pathotypes are similar to those met in Europe and America, but their relative importance is to be determined.