title: CTX-M type beta-lactamases among fecal Escherichia coli and Klebsiella pneumoniae isolates in non-hospitalized children and adults.
abstract: 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 bla(CTX-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 bla(CTX-M) determinants and underscores the role that commensals could play as a reservoir for their dissemination.
authors.affiliation: Division of Infectious Diseases, Department of Microbiology and Centre of Infection, University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong. plho@hkucc.hku.hk
authors.forename: Pak-Leung
authors.initials: PL
authors.lastname: Ho
authors.forename: River Chun-Wai
authors.initials: RC
authors.lastname: Wong
authors.forename: Kin-Hung
authors.initials: KH
authors.lastname: Chow
authors.forename: Kenneth
authors.initials: K
authors.lastname: Yip
authors.forename: Samson Sai-Yin
authors.initials: SS
authors.lastname: Wong
authors.forename: Tak-Lun
authors.initials: TL
authors.lastname: Que
mesh_terms: D018550:Cephalosporin Resistance / Q000235:genetics*; D002510:Cephalosporinase / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D006801:Humans; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D002510:Cephalosporinase; D001618:beta-Lactamases