Phenotypic and genotypic evaluation of aminoglycoside resistance in clinical isolates of staphylococci in Tehran, Iran.
Aminoglycosides play an important role in the treatment of staphylococcal infections, despite the emerging widespread resistance among Staphylococcus. To determine the prevalence of aminoglycoside resistance and aminoglycoside modifying enzyme (AME) genes among infected patients at a teaching hospital in Tehran, Iran, we tested 585 Staphylococcus isolates, of which 322 were Staphylococcus aureus and 263 were coagulase-negative staphylococci, as determined by the disk diffusion method and multiplex PCR. The minimum inhibitory concentration of gentamicin for each isolate was determined by microbroth dilution. All methicillin-resistant staphylococci were mecA-positive by PCR. Of the 585 isolates, 27.6% were susceptible to gentamicin and kanamicin, 27.1% to tobramicin and amikacin, and 21.3% to netilmicin. The most prevalent AME genes included aac(6')-Ie-aph(2'') (93.7%) followed by aph(3')-IIIa (84.3%) and ant (4')-Ia (28.1%). More than 90% of aminoglycoside-resistant staphylococci contained at least one AME gene. The coexistence of two or three AME genes was detected in most gentamicin-resistant isolates. These results suggest an alarming rate of aminoglycoside resistance in this test location in Tehran, Iran. Continued surveillance at the genotypic and phenotypic levels, and adherence to well-designed antibiotic and infection-control policies are necessary to limit the spread of antimicrobial resistance.
Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Mohammad
M
Emaneini
Morovat
M
Taherikalani
Mohammad-Amin
MA
Eslampour
Hossein
H
Sedaghat
Marzieh
M
Aligholi
Fereshteh
F
Jabalameli
Shadi
S
Shahsavan
Nazli
N
Sotoudeh
D000123:Acetyltransferases / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005839:Gentamicins / Q000494:pharmacology*; D006801:Humans; D007492:Iran / Q000453:epidemiology; D007612:Kanamycin / Q000494:pharmacology*; D019868:Kanamycin Kinase / Q000235:genetics; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D009713:Nucleotidyltransferases / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013210:Staphylococcus / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D005839:Gentamicins; D007612:Kanamycin; C108453:6'-aminoglycoside acetyltransferase-2''-aminoglycoside phosphotransferase; D000123:Acetyltransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); D019868:Kanamycin Kinase; C428104:Ant(4')-Ia protein, Staphylococcus aureus; D009713:Nucleotidyltransferases