title: Genetic characterization of the mechanisms of resistance to amoxicillin/clavulanate and third-generation cephalosporins in Salmonella enterica from three Spanish hospitals.
abstract: The mechanisms of antimicrobial resistance were characterized in 90 Salmonella enterica isolates either resistant or with intermediate resistance to amoxicillin/clavulanate (AMC(R/I)) or resistant to third-generation cephalosporins (C3G(R)). These isolates were recovered in three Spanish hospitals during 2007-2009. The C3G(R) phenotype was expressed by three isolates that carried the following extended-spectrum β-lactamase genes: phage-associated bla(CTX M-10) in S. Virchow, bla(CTX-M-14a) surrounded by ISEcp1 and IS903 in S. Enteritidis, and bla(CTX-M-15) linked to ISEcp1 and orf477 in S. Gnesta (first description in this serotype). The AMC(R/I) phenotype was found in 87 isolates (79 S. Typhimurim, 7 S. Enteritidis, and one S. Thompson). The bla(PSE-1) gene, followed by bla(OXA-1) was mostly found among S. Typhimurim, and the bla(TEM-1) gene among S. Enteritidis. Three different gene combinations [bla(PSE-1) +floR+aadA2+sul+tet(G); bla(OXA-1) +catA+aadA1/strA-strB+sul+tet(B) and bla(TEM-1) + cmlA1+aadA/strA-strB+sul+tet(A)/tet(B) genes] were associated with the ampicillin-chloramphenicol-streptomycin-sulfonamides-tetracycline phenotype in 68 AMC(R/I) S. enterica isolates. Class 1 integrons were observed in 79% of the isolates and in most of them (45 isolates) two integrons including the aadA2 and bla(PSE-1) gene cassettes, respectively, were detected. The bla(OXA-1) +aadA1 arrangement was detected in 23 isolates, and the aac(6')-Ib-cr+bla(OXA-1) +catB3+arr3 in another one. Non-classic class 1 integrons were found in three isolates: dfrA12+orfF+aadA2+cmlA1+aadA1 (1 isolate), dfrA12+orfF+aadA2+ cmlA1+aadA1+qacH+IS440+sul3 (1 isolate) and dfrA12+orfF+aadA2+cmlA1+aadA1+qacH+IS440+ sul3+orf1+mef(B)Δ-IS26 (1 isolate). Taken together, these results underline the need for clinical concern regarding β-lactam resistance in Salmonella and thus for continuous monitoring.
authors.affiliation: Molecular Microbiology Area, Center for Biomedical Research of La Rioja-CIBIR, Logroño, Spain.
authors.forename: María
authors.initials: M
authors.lastname: de Toro
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Sáenz
authors.forename: Emilia
authors.initials: E
authors.lastname: Cercenado
authors.forename: Beatriz
authors.initials: B
authors.lastname: Rojo-Bezares
authors.forename: Marta
authors.initials: M
authors.lastname: García-Campello
authors.forename: Esther
authors.initials: E
authors.lastname: Undabeitia
authors.forename: Carmen
authors.initials: C
authors.lastname: Torres
mesh_terms: D019980:Amoxicillin-Potassium Clavulanate Combination / Q000008:administration & dosage / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use; D002511:Cephalosporins / Q000008:administration & dosage* / Q000627:therapeutic use; D019818:Clavulanic Acid / Q000008:administration & dosage* / Q000627:therapeutic use; D003428:Cross Infection / Q000188:drug therapy* / Q000382:microbiology; D016521:Electrophoresis, Gel, Pulsed-Field; D006761:Hospitals; D006801:Humans; D032023:Integrons / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012480:Salmonella Infections / Q000188:drug therapy* / Q000382:microbiology; D019779:Salmonella enterica / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D013030:Spain; D018440:beta-Lactam Resistance / Q000187:drug effects / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D019818:Clavulanic Acid; D019980:Amoxicillin-Potassium Clavulanate Combination; D001618:beta-Lactamases