Prevalence of rectal carriage of extended-spectrum beta-lactamase-producing Escherichia coli among elderly people in community settings in China.

The importance of community-acquired infections due to extended-spectrum beta-lactamase-producing (ESBL) Escherichia coli has been increasingly recognized in recent years. No comprehensive data are available on the prevalence, risk factors, and genotypes of ESBL production in community residents in China. Rectal samples from 270 elderly people were collected in four communities in Shenyang (China). Colonies were screened by double-disk synergy test for ESBL production and then, ESBLs were characterized by PCR and sequencing. The clonal relatedness of all ESBL-producing isolates was determined by pulsed-field gel electrophoresis. Potential risk factors for rectal carriage of ESBL producers were examined by multivariate analysis. The prevalence of rectal carriage of ESBL-producing E. coli was 7.0%. All 19 ESBL-producing isolates produced CTX-M-type ESBLs, including CTX-M-14 (11 strains), CTX-M-22 (3 strains), CTX-M-79 (3 strains), CTX-M-24 (1 strain), and CTX-M-24 and CTX-M-79 together (1 strain). CTX-M-79 ESBL was first detected worldwide. ESBL-producing strains were clonally unrelated. Appearance of ESBL producers is strongly associated with the use of antibiotics in the past 3 months (odds ratio 3.2, 95% CI 1.1-9.0, P = 0.03). Our results show the importance of the intestinal tract as a reservoir for ESBL-producing isolates in community settings in China and that the use of antibiotics in the past 3 months is clearly linked to rectal carriage of ESBL producers.