Distribution and antimicrobial resistance genes of CTX-M extended-spectrum β-lactamase- and Klebsiella pneumoniae carbapenemasesproducing Escherichia coli isolated from patients with infection

Abstract:

ObjectiveTo investigate clinical distribution and antimicrobial resistance genes of  CTXM extendedspectrum βlactamases (ESBLs) and Klebsiella pneumoniae carbapenemases (KPCs)producing Escherichia coli (E. coli) isolated from patients with infection. MethodsMultidrugresistant E. coli (MDRE. coli) isolated from clinical specimens in a hospital in 2011-2012 were collected, minimal inhibitory concentrations (MICs) were detected by microbroth dilution method; ESBLs and KPC genes were amplified by polymerase chain reaction (PCR),  CTXM and KPC genotypes，as well as multilocus sequence types (MLST) were identified. ResultsOf 48 MDRE.coli, 45（93.75%） only produced ESBLs, 44（91.67%） carried  blaCTXM gene, 20（41.67%） of which were blaCTXM1 gene and 32（66.67%）were blaCTXM9 gene，8（16.67%）carried both genes. The following subtypes were identified through gene sequencing: CTXM14（65.91%，29/44）, CTXM55（31.82%，14/44）, CTXM15（11.36%，5/44）, CTXM3（2.27%，1/44）, CTXM24（2.27%，1/44）,and CTXM65（2.27%，1/44）. The detection rates of CTXM14+CTXM55, CTXM14+CTXM15, and CTXM55+CTXM65 were 11.36% (5/44）, 4.55%(2/44）, and 2.27%(1/44）respectively. PCR showed that 2(4.17%） ESBLs+KPCproducing strains carried blaKPC and  blaCTXM genes, sequencing analysis showed that 1 was CTXM14+KPC2，and the other was CTXM3+KPC2. ST 131 （53.66%）was the main type of MLST,  ST648, ST405, ST167, and ST1193 were also detected. ConclusionCTXM14, CTXM55 and CTXM15 are the most common genotypes of ESBLsproducing E. coli isolates, different subtypes exists, ST131 is the predominant MLST, KPC2producing  isolate of E.coli has been detected.