The prevalence of aminoglycoside resistance and corresponding resistance genes in clinical isolates of staphylococci from 19 European hospitals

Aminoglycosides still play an important role: in antistaphylococcal therapi es, although emerging resistance amongst staphylococci is widespread. To fu rther our understanding of the prevalence of aminoglycoside resistance in E urope, we tested 699 and 249 consecutive unrelated clinical isolates of Sta phylococcus aureus and coagulase-negative staphylococci (CNS), respectively , from the SENTRY Antimicrobial Surveillance Program, for susceptibility to gentamicin, tobramycin, kanamycin and streptomycin, and examined the relat ionship between susceptibility to these antimicrobials and susceptibility t o methicillin. Three hundred and sixty-three staphylococcal isolates demons trated resistance to at least one of the aminoglycosides tested; all of the se isolates were screened for the presence of aac(6')-Ie+aph(2 "), ant(4')- Ia and aph(3')-IIIa, the genes encoding the most clinically relevant aminog lycoside-modifying enzymes. S. aureus isolates derived from hospital-acquir ed pneumonia tended to be more resistant to aminoglycosides and methicillin than isolates from blood or wound infections. In S. aureus, resistance to aminoglycosides was closely associated with methicillin resistance. Suscept ibility of S. aureus to gentamicin has decreased by 9% from previous Europe an studies to a current level of 77%, while susceptibility of CNS, currentl y at 67%, has increased by 21%. Geographical variation occurred, correlatin g with methicillin resistance, although intra-country variation was conside rable. aac(6')-Ie+aph(2 "), ant(4')-Ia and aph(3')-IIIa were found througho ut Europe in 68%, 48% and 14% respectively of staphylococci resistant to at least one aminoglycoside. aph(3')-IIIa was considerably more common in met hicillin-susceptible S. aureus and CNS isolates; the reverse was true for t he other two resistance genes. The prevalence of ant(4')-Ia and aph(3')-III a genes in aminoglycoside-resistant staphylococci was significantly greater than that reported in previous European studies.