In Vitro Evaluation of Co- trimoxazole using some strains of Enterobacteriaceae

Abstract

This study was carried out to evaluate the efficacy of co- trimoxazole against enterobacteria. Co-trimoxazole is a combination of trimethoprim and sulfamethoxazole in a fixed 1 : 5 ratio. Fifity clinical isolates from five different genera of enterobacteria were isolated from patients suffering from abdominal disturbances, respiratory tract infections, urinary tract infections, typhoid fever and others. Ten strains from each genus were isolated. The genera were: Salmonella, Shigella, Escherichia, Proteus and Klebsiella. The species isolated were as follow: 2 species of Salmonella, 4 species of Shigella, 1 species of Escherichia , 2 species of Proteus and 2 species of Klebsiella. Also standard strains were obtained for comparison. The different strains were purified on selective media and identified by biochemical tests .All clinical isolates were subjected to two types of tests: disc diffusion method and serial dilution method in nutrient broth by using different concentrations of the drug. The results showed that: 10 strains of Salmonella were susceptible to co-trimoxazole, 9 strains of Shigella from 4 species were susceptible , while one strain of Shigella sonnei was intermediate, 8 strains of E.coli were susceptible, one strain of E.coli was intermediate and one strain was resistant. All strains of Proteus were resistant, 6 strains of Klebsiella from 2 species were susceptible, while 3 strains were intermediate and one strain of Klebsiella pneumoniae was resistant. The same results obtained by disc diffusion method were similar to those obtained by serial dilution method.