Transmissible drug resistance in certain enteric bacilli isolated in Tehran.

A total of 284 isolates of gram-negative enteric bacilli associated with urinary tract infections or normal fecal flora were examined for resistance to antimicrobial agents and the presence of transmissible R factors. Klebsiella pneumoniae and Proteus isolates exhibited the highest frequencies of resistance to antimicrobial agents. The incidence of drug resistance among clinical isolates of Escherichia coli was considerably higher than its incidence among E. coli strains isolated from healthy individuals. Transmissible R factors mediating resistance to antimicrobial agents were demonstrated in 43% of resistant strains of E. coli isolated from urinary infections and 21 - 26% of those isolated from healthy individuals. Frequencies of R factor transfer among drug-resistant strains of K. pneumoniae and Proteus species were 26 and 28%, respectively.