title: Rapid dissemination and diversity of CTX-M extended-spectrum beta-lactamase genes in commensal Escherichia coli isolates from healthy children from low-resource settings in Latin America.
abstract: A survey carried out in 2005 among members of a healthy population of children living in Bolivia and Peru revealed that fecal carriage of Escherichia coli strains resistant to expanded-spectrum cephalosporins was remarkably increased compared to that observed in the same settings in 2002 (1.7% in 2005 versus 0.1% in 2002). In this work, we demonstrated that this phenomenon was mainly related to the dissemination of CTX-M-type extended-spectrum beta-lactamase (ESBL) determinants among commensal E. coli strains. Of 50 ESBL-producing isolates collected in the 2005 survey, 44 harbored a CTX-M-type and 6 an SHV-type (SHV-2 or SHV-12) ESBL. Compared to 2002 results, an increased diversity of CTX-M-type ESBLs was also observed: members of the CTX-M-1 group (CTX-M-15) emerged in Bolivia (where only CTX-M-2 was observed in 2002), while members of the CTX-M-9 group (CTX-M-14 and CTX-M-24) emerged in Peru (where only CTX-M-15 and CTX-M-2 were observed in 2002). A new CTX-M-2 variant named CTX-M-56 was also detected. Molecular characterization of the CTX-M-producing isolates and gene transfer experiments suggested that different mechanisms could be involved in the spreading of different CTX-M group determinants and revealed that additional resistance determinants for non-beta-lactam antibiotics were preferentially carried by plasmids encoding certain CTX-M variants (CTX-M-15 and variants of the CTX-M-2 group). Three CTX-M-15-encoding conjugative plasmids from Peruvian isolates carried the new fluoroquinolone resistance gene aac(6')-Ib-cr. To our best knowledge, this is the first report of the detection of aac(6')-Ib-cr in Latin America.
authors.affiliation: Dipartimento di Biologia Molecolare, Sezione di Microbiologia, Università di Siena, Policlinico Santa Maria alle Scotte, Siena, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Pallecchi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bartoloni
authors.forename: Costanza
authors.initials: C
authors.lastname: Fiorelli
authors.forename: Antonia
authors.initials: A
authors.lastname: Mantella
authors.forename: Tiziana
authors.initials: T
authors.lastname: Di Maggio
authors.forename: Herlan
authors.initials: H
authors.lastname: Gamboa
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gotuzzo
authors.forename: Göran
authors.initials: G
authors.lastname: Kronvall
authors.forename: Franco
authors.initials: F
authors.lastname: Paradisi
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Rossolini
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001838:Bolivia / Q000453:epidemiology; D002443:Ceftriaxone / Q000494:pharmacology; D018550:Cephalosporin Resistance; D002648:Child; D002675:Child, Preschool; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D006801:Humans; D007223:Infant; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010568:Peru / Q000453:epidemiology; D010957:Plasmids / Q000235:genetics; D011203:Poverty; D017422:Sequence Analysis, DNA; D013997:Time Factors; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D002443:Ceftriaxone; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases