MULTIFACTORIAL ANALYSIS OF THE PHENOTYPES FOR BETA-LACTAMS OF 1044 ESCHERICHIA-COLI STRAINS

1 044 E. coli strains were randomly collected by the begining of 1992. Their susceptibility for seven betalactam antibiotics : amoxycillin a ugmentin, ticarcillin, claventin, cephalothin; cefoxitin and cefotaxim e, was studied routinely by the agar diffusion method. The datas were analyzed by the CERIB multifactorial analysis package which yields to homogeneous populations. This analysis showed four well defined popula tions : I) 588 strains (56.4 %) susceptible to all antibiotics ; 2) 41 0 strains (39.3 %) present a penicillinase phenotype ; 3) 11 strains ( 1.05 %) are cephalosporinase producer ; 4) 7 strains (0.67 %) were ide ntified as producing an extended-spectrum betalactamase. The remaining strains : 28 (2.68 %) had a reduced susceptibility to all antibiotics , which suggests the combination of few resistance mechanisms or other hypothesis.