Drug-sensitivity of El Tor vibrio strains isolated in the Philippines in 1964 and 1965

About 1500 strains of El Tor vibrios, isolated in 1964 and 1965 in the Philippines, were examined for their susceptibilities to 17 drugs. All the strains tested were highly sensitive to dihydroxymethyl-furalazine, and most were highly sensitive to tetracycline hydrochloride, chloramphenicol and erythromycin, and moderately sensitive to novobiocin, dihydrostreptomycin sulfate, kanamycin and neomycin. They showed a remarkable fluctuation of sensitivity to ampicillin, cefaloridine, cefalotin and sulfafurazole, and a high resistance to benzylpenicillin sodium, oleandomycin and spiramycin.Experimental confirmation was provided of the fact that El Tor vibrios and non-agglutinable vibrios can be distinguished from classical cholera vibrios by their resistance to polymyxin B and colistin.Highly streptomycin-resistant strains, and to a lesser extent ampicillin- and sulfafurazole-resistant strains, were relatively often isolated from cholera patients who had been treated with antibiotics. One patient yielded a strain resistant to tetracycline, chloramphenicol, streptomycin and sulfafurazole.