High Prevalence of CTX-M Beta-Lactamases in Enterobacteriaceae from Healthy Individuals in Guangzhou,China

Abstract

This study aimed to determine the prevalence of extended-spectrum beta-lactamases (ESBLs) in Enterobacteriaceae and to characterize the genetic composition of ESBL determinants among Enterobacteriaceae isolates from healthy people in Guangzhou, China. A total of 200 rectal swab samples were collected from healthy asymptomatic individuals and tested for ESBL production using ChromID ESBL agar. Phenotypic ESBL producers were screened for bla_CTX-M, bla_TEM, and bla_SHV genes using PCR and DNA sequencing. The prevalence of ESBL-producing Enterobacteriaceae among rectal swab samples was 69.5%. All ESBL-producing isolates harbored bla_CTX-M genes (n=138) except for one isolate that harbored bla_SHV-2a. Eleven CTX-M ESBL genes were detected. The most predominant CTX-M-type genes were bla_CTX-M-14 (n=82), followed by bla_CTX-M-55 (n=19), bla_CTX-M-65 (n=10), and bla_CTX-M-27 (n=9). Isolates carrying bla_CTX-M-38,_-3,_-15,_-14b,_-98,_-121 and _-123 were also identified. Molecular homology analysis of the selected isolates was performed by phylogenetic grouping and multilocus sequence typing and indicated that the predominant clone belonged to A-CC10. This study showed a high rate of CTX-M-type ESBL genes among Enterobacteriaceae isolates from healthy individuals in China.