Isolation of R Factors Conferring Kanamycin Resistance from Tuberculous Patients Treated with Kanamycin

Abstract

In a survey of 228 tuberculous patients who had received kanamycin (KM) treatment, KM‐resistant Escherichia coli or Escherichia freundii were isolated from 29. From the patients who had not received KM‐therapy, KM‐resistant strains were not isolated. Of the 29 KM‐resistant strains isolated, 5 E. coli strains were also resistant to other aminoglycoside antibiotics, i.e., paromomycin, fradiomycin and streptomycin. They were also resistant to chloramphenicol and sulfanilamide and all of these resistances could be transferred to E. coli strains by conjugation. The resistance was considered to be conferred by an R factor. The remaining 24 KM‐resistant strains were identified as E. freundii. In these level of KM‐resistance was rather low and conjugal transfer was not observed. All were resistant to paromomycin but sensitive to fradiomycin. When 381 KM‐sensitive strains were plated on an agar plate containing 25 μg of KM/ml, 23 KM‐resistant strains were isolated. The mutants thus obtained were similar to the second type of 24 KM‐resistant strains isolated from patients. Thus it was strongly suggested that the 24 strains carrying low levels of KM‐ and paromomycin‐resistance, that is, conjugally nontransmissible, appeared by spontaneous mutation in the intestines of patients who had received KM‐treatment. © jointly owned by author and Igakushoin (Publisher)