SYNOPSIS Seventy isolates of Providence were obtained from urinary tract infections in patients from five hospitals. They were all identified as Providence B (Providencia stuartii). A typing system was devised for these organisms based on their production of and sensitivity to bacteriophage and bacteriocins. Using this system, 27 distinct strains were recognized, and it was clear that many patients had been infected with the same strain. The minimum inhibitory concentrations of six antiseptics and disinfectants for these strains were determined. Many of the strains were up to 300-fold more resistant to the cationic antiseptics chlorhexidine, cetrimide, and Resiguard than the control strain Escherichia coli NCTC 10418. The sensitivities of the Providence strains to Hycolin, glutaraldehyde, and phenyl mercuric nitrate, however, were similar to those of the control organism. There were significant correlations between the sensitivities of the strains to the three cationic antiseptics. The loss of chlorhexidine resistance from a Providence strain after exposure of the cells to Nmethyl-N' nitro N nitrosoguanidine resulted in a concomitant loss of resistance to cetrimide and Resiguard, but there was no significant increase in the sensitivity of the mutants to the other three antibacterials.

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