[Genetic control and the mechanism of the spread of gentamycin resistance among Enterobacteriaceae strains in a hospital].

Strains of K. pneumoniae belonging to serowars K10, K3, K16 and K62 and two strains of E. coli with multiple drug resistance including newly detected resistance to gentamicin were isolated in succession within the 2-year period of microbiological survey of a hospital department for premature infants. Resistance to gentamicin in the first isolate of K. pneumoniae was due to the non-conjugated plasmid pP12140 with a molecular weight of 15 MD. This plasmid also controlled resistance to streptomycin and sulfanilamides and was physically independent of the other large (about 80 MD) conjugative R plasmid controlling resistance to kanamycin, tetracycline, chloramphenicol and ampicillin. In the strains of K. pneumoniae and E. coli isolated within the following 2 years the marker of gentamicin resistance was included into large (80-120 MD) conjugative R plasmids controlling 6-7 resistance types. DNA of such plasmids was used for transformation of the recipient strain C600 of E. coli. In addition to the transformants with the acquired R plasmids possessing all the resistance markers there were isolated transformants carrying plasmids with the molecular weight of 15 MD controlling resistance to gentamicin, streptomycin and sulfanilamides and capable of self-replication. Analysis of the plasmids with the help of endonucleases EcoR1 and Pst1 revealed complete identity of plasmid pP12140 and similar plasmids of the transformants isolated with the use of DNA of the plasmids of the other K. pneumoniae strains. Marked relation with the plasmids of the transformants isolated with the use of the plasmid DNA of E. coli was also revealed.(ABSTRACT TRUNCATED AT 250 WORDS)