CTX-M type beta-lactamases among fecal Escherichia coli and Klebsiella pneumoniae isolates in non-hospitalized children and adults
Pak-Leung Ho, River Chun-Wai Wong, Kin-Hung Chow, Kenneth Yip, Samson Sai-Yin Wong, Tak-Lun Que
Division of Infectious Diseases, Department of Microbiology and Centre of Infection, University of Hong Kong, Pokfulam; and Department of Clinical Pathology, Tuen Mun Hospital, Tuen Mun, Hong Kong
Received: October 9, 2007 Revised: December 1, 2007 Accepted: January 30, 2008
We investigated the occurrence and diversity of extended-spectrum beta-lactamase (ESBL) enzymes among antibiotic-resistant Escherichia coli and Klebsiella pneumoniae isolates obtained from human feces. All ESBL-positive isolates were characterized at the molecular level by polymerase chain reaction, sequencing and pulsed-field gel electrophoresis (PFGE). Eight of 46 antibiotic-resistant E. coli (6 from children and 2 from adults) and 4 of 8 K. pneumoniae (all from adults) isolates were found to be ESBL-positive by the double-disk synergy test. Seven isolates were found to have CTX-M-14, 2 each had CTX-M-24 and CTX-M-38, and 1 had CTX-M-9. In addition, 8 isolates were found to carry TEM-1b or TEM-1c. No SHV-type enzyme was found among the E. coli strains. In 9 strains, the plasmidic blaCTX-M determinants were transferable to E. coli by conjugation. Analysis by PFGE showed evidence of clonal and non-clonal spread. The present study shows fecal carriage of organisms producing blaCTX-M determinants and underscores the role that commensals could play as a reservoir for their dissemination.
beta-Lactamases; Drug resistance, microbial; Epidemiology; Escherichia coli; Feces
J Microbiol Immunol Infect. 2008;41:428-432.