Transferable antibiotic resistance in a general hospital: a two year survey

For two years transferable antibiotic resistance (TAR) was studied by replicator methods in strains of Enterobacteriaceae isolated in a 900-bed hospital. Transfer to an Escherichia coli recipient was demonstrated in 21% of 7,800 Enterobacteriaceae. It was most common in Klebsiella (37% of isolates) and least in Acinetobacter (6%). The mean number of phenotypic resistance markers (RMs) transferred was higher from Klebsiella pneumoniae or Enterobacter cloacae than from E. coli or P. mirabilis. K. pneumoniae and E. cloacae especially transferred 7 or more RMs much more often than other species. Some RMs were associated with a particular species, e.g. streptomycin with E. coli, kanamycin or gentamicin with E. cloacae and kanamycin with P. mirabilis. The same was true of certain patterns of resistance transfer, e.g. Ap-Km and P. mirabilis, Ap-Sm and E. coli, Ap-Km-Gm-Tm-Cm and K. pneumoniae. However, many of the commonest resistance phenotypes were transferred from several species and from several biotypes within any given species. Resistance patterns transferred from E. coli were detected sporadically throughout, whereas many of those transferred from Klebsiella, Enterobacter or Proteus were found only for a limited time.