Antimicrobial resistance and genotypies of plasmidmediated AmpC βlactamasesproducing and extendedspectrum βlactamasesproducing strains in respiratory intensive care units

Abstract:

ObjectiveTo investigate antimicrobial resistance,genotypies and the prevalence of AmpC βlactamasesproducing and extendedspectrum βlactamases (ESBLs)producing gramnegative strains from specimens of respiratory intensive care units(RICUs) in 2 hospitals of Shenzhen.MethodsA total of 96 multidrugresistant Escherichia coli and Klebsiella pneumoniae strains were detected by threedimensional test for AmpC βlactamases and phenotypic confirmatory test based on Clinical and Laboratory Standard Institute (CLSI) criteria for ESBLs.Antimicrobial susceptibility of AmpC βlactamases and ESBLsproducing strains was detected by KirbyBauer and Etest methods.Universal primer PCR for AmpC βlactamases and ESBLs gene amplification and DNA sequencing were carried out for genotyping of these βlactamases.ResultsAmpC βlactamases, ESBLs and AmpC βlactamases combined with ESBLsproducing strains were found in 9(9.38%), 52(54.17%)and 10 (10.42%) strains,respectively.AmpC βlactamases producing strains were more susceptible to cefepime and imipenem, the resistant rate being 33.33% and 0.00% respectively. ESBLsproducing strains were more susceptible to imipenem，piperacillin/tazobactam and cefoperazone/sulbactam , the resistant rate being 0.00%, 34.62% and 19.23% respectively. AmpC βlactamases combined with ESBLsproducing strains were only sensitive to imipenem and no imipenemresistant one was found. The genotypes of AmpC βlactamases were DHA1and ACT1, the incidence being 76.92% and 26.08% respectively. ESBLs genotypes were CTXM series and SHV5, the incidence being 96.77% and 3.23% respectively.ConclusionThere are epidemic strains of plasmidmediated DHA1,ACT1 type AmpC βlactamases and CTXM,SHV type ESBLsproducing gramnegative strains in RICUs in two hospitals, they are resistant to  most  new broadspectrum βlactam antibiotics, but sensitive to imipenem.