title: Evolution of CTX-M-type beta-lactamases in isolates of Escherichia coli infecting hospital and community patients.
abstract: Escherichia coli isolates collected at our Institution from 1999 to 2003 (n=20,258) were studied to evaluate the production of CTX-M-type extended-spectrum beta-lactamases (ESBL). Isolates suspected of producing CTX-M enzymes were analyzed by the double-disk synergy test, hybridization with specific probes, PCR and direct DNA sequencing. Overall, 53 ESBL-positive isolates were found to carry CTX-M-type genes (blaCTX-M-1, n=51; blaCTX-M-15, n=2). The isolation of CTX-M-positive strains increased from 1 per year (1999) to 26 per year (2003). The first isolate carrying the blaCTX-M-15 gene appeared in 2003 and was obtained from a patient previously treated with ceftazidime. CTX-M-positive isolates were characterized by multi-drug resistance and were obtained both from inpatients (n=29) and outpatients (n=24). Most patients were over 60-year-old (n=45), had underlying chronic diseases (n=32), and had been hospitalized more than once (n=33). Strains were frequently isolated from the urinary tract, often after recurrent infections. Our study demonstrates that CTX-M-producing isolates are increasing among E. coli strains. Adequate laboratory detection may help in choosing appropriate treatment and in limiting the spread of this resistance trait.
authors.affiliation: Laboratory of Medical Microbiology, Ospedale di Circolo and University of Insubria, Viale Borri 57, 21100 Varese, Italy.
authors.forename: Gioconda
authors.initials: G
authors.lastname: Brigante
authors.forename: Francesco
authors.initials: F
authors.lastname: Luzzaro
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Perilli
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Lombardi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Colì
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Rossolini
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Amicosante
authors.forename: Antonio
authors.initials: A
authors.lastname: Toniolo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D014552:Urinary Tract Infections / Q000453:epidemiology / Q000382:microbiology; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; C473109:beta-lactamase CTX-M-15; C055184:beta-lactamase TEM-3; D001618:beta-Lactamases