Mutants of Klebsiella pneumoniae resistant to several antibiotics

Abstract

SPONTANEOUS antibiotic-resistant mutants that arise in bacterial populations are usually only resistant to the particular antibiotic used in the culture medium used for their isolation. In the experiments described here, however, mutants of Klebsiella pneumoniae resistant to chloramphenicol, sodium nalidixate and trimethoprim, three unrelated antibiotics, were obtained by including any one of the antibiotics in the culture medium. Because these multiply resistant mutants were commonly found in the alimentary tract of animals experimentally infected with antibiotic-sensitive K. pneumoniae and then fed on antibiotic-containing diets they may be clinically important.