Reduced susceptibility to co-amoxiclav in Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae isolated in Romania between 1985 and 1993.

By determining the beta-lactam susceptibility of Enterobacteriaceae isolated in Eastern Romania from 1985 to 1993, three Escherichia coli, three Salmonella typhimurium and one Klebsiella pneumoniae isolates with reduced susceptibility to co-amoxiclav were found. The antibiotic susceptibility of the isolates and their E. coli derivatives, and kinetic values suggested the following resistance mechanisms: hyperproduction of TEM in S. typhimurium, limited antibiotic uptake in K. pneumoniae and OXA production in one strain of E. coli. Despite a normal beta-lactamase activity, the two remaining E. coli strains and their derivatives were less susceptible to co-amoxiclav.