Study on antimicrobial resistance and detection of AmpC and extendedspectrum βlactamasesproducing strains in a respiratory intensive care unit

Abstract:

ObjectiveTo investigate antimicrobial resistance and the prevalence of AmpC βlactamases and extendedspectrum βlactamases(ESBLs)producing gramnegative bacteria from specimens of a respiratory intensive care unit(RICU)．MethodsAmpC βlactamasesproducing and AmpC βlactamases combined with ESBLsproducing strains were detected by threedimensional test, ESBLsproducing isolates were identified with the method recommended by the National Committee for Clinical Laboratory Standard(NCCLS). Antimicrobial susceptibility of AmpC βlactamases and ESBLsproducing strains were detected by KirbyBauer and Etest methods. ResultsAmpC βlactamases, ESBLs and AmpC βlactamases combined with ESBLsproducing strains were found in 28(16.67%), 71 (42.26%)and 12(7.14%) strains respectively. The most common AmpC βlactamasesproducing strains was Enterobacter cloacae (57.14%);  Among ESBLsproducing strains, the most common isolates were Klebsiella pneumoniae (71.70%)and Escherichia coli (55.81%). The AmpC βlactamasesproducing strains were more susceptible to imipenem and cefepime, the resistant rate of which was 3.57% and 28.57% respectively. The  resistant rate of ESBLsproducing strains  to imipenem，piperacillin/tazobactam and cefoperazone/sulbactam was  2.82%, 32.39% and 25.35% respectively. AmpC βlactamases combined with ESBLsproducing strains were only sensitive to imipenem, imipenemresistant strain was not found.ConclusionAmpC βlactamases and ESBLsproducing gramnegative strains are common in clinical isolates from RICU, and resistance to the majority of  new broadspectrum βlactamas, but sensitive to imipenem.