title: Antimicrobial susceptibility of clinical isolates of Enterobacteriaceae producing complex beta-lactamase patterns including extended-spectrum enzymes.
abstract: The antimicrobial susceptibility of 103 clinical isolates of Enterobacteriaceae to 11 antibiotics, was investigated, using a conventional inoculum size (5 x 10(5) CFU) and a higher inoculum size (5 x 10(8) CFU). All the isolates produced complex beta-lactamase patterns, including an extended-spectrum beta-lactamase (ESBL) of the TEM- or SHV-type plus other enzymes (a TEM-type or an SHV-type non-ESBL and/or a class C enzyme). The following repertoire of ESBLs was produced by the isolates: TEM-15, TEM-19, TEM-26, TEM-52, TEM-72, TEM-87, TEM-92, SHV-2a, SHV-5 and SHV-12, as assessed by sequencing. Production of the other enzymes was showed by analytical isoelectric focusing. Overall, meropenem was the most active agent and less influenced by inoculum size, while other beta-lactams showed a lower activity and a significant inoculum size effect. In conclusion, from its in vitro performance, meropenem could be considered as the last resource drug against strains producing complex beta-lactamase patterns including an ESBL.
authors.affiliation: Sciences and Biomedical Technologies Department, University of L'Aquila, via Vetoio, Coppito, 67100 L'Aquila, Italy.
authors.forename: Bernardetta
authors.initials: B
authors.lastname: Segatore
authors.forename: Domenico
authors.initials: D
authors.lastname: Setacci
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Perilli
authors.forename: Luigi
authors.initials: L
authors.lastname: Franchino
authors.forename: Nicola
authors.initials: N
authors.lastname: Franceschini
authors.forename: Alessio
authors.initials: A
authors.lastname: Agnifili
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Rossolini
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Amicosante
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015169:Colony Count, Microbial; D003428:Cross Infection / Q000382:microbiology; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D005798:Genes, Bacterial; D006801:Humans; D007558:Italy; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D017422:Sequence Analysis, DNA; D013845:Thienamycins / Q000494:pharmacology / Q000627:therapeutic use; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D013845:Thienamycins; D047090:beta-Lactams; D001618:beta-Lactamases; D000077731:Meropenem