The Aminoglycosides Resistance Of Extended Spectrum β-lactamase In Enterobacteriaceae

Objective: To study the resistance of extended spectrum β -lactamaseproducing clinical isolates in Enterobacteriaceae to other antimicrobial agents, and investigate the molecular mechanisms of the aminoglycosides-resistance in ESBLs-producing Enterobacteriaceae strains.Methods: A totle of 210 strains include E. coli, K. pneumonia and E.cloacae.The Enterobacteriaceae clinical isolates were collected from West China Hospital of Sichuan University from July,2003 to January,2004,and the ESBLs-producing strains were screened and confirmed by double agar dilution method according to NCCLS Guidelines.The MICs of 11 antibacterial agents against the clinical isolates was detected by double agar dilution method.The nucleotide sequence of aminoglycoside modification genes in ESBLs-producing plus aminoglycoside-resistant strains that were amplified by PCR were detected by automatic sequencer,and compared with relative DNA sequencing reported by others in internet gene bank through Blastn searching.Results:The resistant rate of E. coli, K. pneumonia and E. cloacae in Enterobacteriaceae to ciprofloxacin was above 50%.Imipenem was activeagainst 90% of the isolates.Most of the Enterobacteriaceae were multidrug resistance.Amikacin and etilmicin were the most active against the clinical isolates in the aminoglycosides.However the resistant rates of E. cloacae to amikacin and etilmicin were 56.77% and 65.38%,respectively.The resistant rate of clinical isolates to gentamicin was above 80%.Cross-resistance to aminoglycosides exist significantly. Among 20 aminoglycoside-resistant plus ESBLs-producing strains,aminoglycoside modifying enzymes gene have been found.They were aminoglycoside acetyltransferase(3)-I gene (aac(3)-I), aminoglycoside acetyltransferase(3)-II gene (aac(3)-IT) ^ aminoglycoside acetyltransferase(6')-I gene (aac(6')-I)^ aminoglycoside acetyltransferase (6')-II gene (aac(6 ')-II) ^ aminoglycoside adenyltransferase (2")-I gene (ant(2")-I) and aminoglycoside phosphoryltransferase(3')-VI gene (aph(3')-VI).The DNA sequences of modifying enzyme gene were in concordance with other aminoglycoside modifying enzymes refer to Internet gene bank.BlarEM were detected in all 20 ESBLs-producing strains.Conclusions: The situations of multidrug resistance of ESBLs-producing strains in Enterobacteriaceae was severe and prevalent. Imipenem is still the most active antibiotic for treatment of the infections caused by these resistant strains.There were aminoglycoside modifying enzyme in ESBLs-producing strains of Enterobacteriaceae. The aminoglycosides should be prudent used empirically when combined with other antibiotics or evidence-based prescribed according to the results of in-vitro combination suscepitibility test.