Aminoglycoside resistance patterns in clinical isolates of E. coli and Klebsiella sp. from Czechoslovakia and the United States.
Resistance of gram-negative bacilli to aminoglycoside antibiotics differs by region and country. Previous studies have demonstrated predominance of the nucleotidyltransferase ANL(2") as the mechanism of enzymatic resistance to gentamicin in the United States and many European countries (Federal Republic of Germany, Switzerland, Greece, Turkey) whereas the acetylating enzymes AAC(6') and AAC(3) were the principal causes of resistance to aminoglycosides in Japan and Chile. In the present comparison of 18 drug resistant isolates of E. coli and Klebsiella sp. from Czechoslovakia and the United States, with aminoglycoside-inactivating enzymes, ANT(2") characterized the most strains from both countries. In a higher number of isolates from Czechoslovakia however, the aminoglycoside resistance was mediated by AAC(3). In the majority of strains a simultaneous occurrence of two gentamicin-inactivating enzymes i.e. ANT(2"), plus AAC (2'), or AAC(6') or AAC(3) was observed. In amikacin resistant E. coli strains the mechanism of resistance was represented by production of AAC(6') or AAC*--an acetyltransferase with uncommon substrate profile. In all E. coli and K. pneumoniae strains from the United States apart from ANT(2") also AAC(2') was detected. This represents a broadening of the host range of aac(2') gene, the occurrence of which has been limited only to Providencia and Proteus strains.