OBJECTIVES: To investigate the mechanisms of carbapenem resistance in the 175 Pseudomonas aeruginosa isolates (39%; 175/448) showing non-susceptibility (European Committee on Antimicrobial Susceptibility Testing breakpoints) to imipenem (35%), meropenem (33%) and/or doripenem (33%) recovered in 2008-09 from 16 Spanish hospitals during the Comparative Activity of Carbapenem Testing (COMPACT) surveillance study. METHODS: MICs (Etest), clonal relatedness (PFGE) and metallo-β-lactamase (MBL) production (Etest-MBL, PCR and sequencing) were determined. Mutation-driven resistance was studied in 60 non-MBL producers according to the doripenem MICs (15 isolates from each of four MIC groups: ≤ 1, 2-4, 8-16 and ≥ 32 mg/L). The expression of ampC, mexB, mexY, mexD and mexF was determined by real-time reverse transcription-PCR and the presence of mutations in oprD by PCR and sequencing. Isogenic mutants expressing combinations of mutation-driven carbapenem resistance were constructed. RESULTS: Twelve (6.9%) isolates were MBL (VIM-20, VIM-2 or VIM-13) producers and all showed high-level resistance (MIC 32 mg/L) to all three carbapenems. Regarding mutation-driven resistance, all but 1 of the 60 isolates were non-susceptible (MIC >32 mg/L) to imipenem, linked to oprD inactivation. In addition, 50% of the isolates overexpressed ampC, 33% mexY, 32% mexB and 15% mexF, while none overexpressed mexD. Increasing prevalence of ampC overexpression correlated with increasing doripenem MICs (≤ 1, 13%; 2-4, 53%; 8-16, 60%; and ≥ 32, 73%) while overexpression of efflux pumps correlated only with moderate resistance. Doripenem showed slightly higher activity than meropenem against isolates overexpressing ampC, especially mexB or mexY. The analysis of a collection of isogenic laboratory mutants supported this finding. CONCLUSIONS: Although the prevalence of MBL producers is increasing, mutation-driven resistance is still more frequent in Spain. Imipenem resistance was driven by OprD inactivation, while additional AmpC and particularly efflux pump hyperproduction had a lower impact on the activity of doripenem compared with meropenem.
OBJECTIVES: To investigate the mechanisms of carbapenem resistance in the 175 Pseudomonas aeruginosa isolates (39%; 175/448) showing non-susceptibility (European Committee on Antimicrobial Susceptibility Testing breakpoints) to imipenem (35%), meropenem (33%) and/or doripenem (33%) recovered in 2008-09 from 16 Spanish hospitals during the Comparative Activity of Carbapenem Testing (COMPACT) surveillance study. METHODS: MICs (Etest), clonal relatedness (PFGE) and metallo-β-lactamase (MBL) production (Etest-MBL, PCR and sequencing) were determined. Mutation-driven resistance was studied in 60 non-MBL producers according to the doripenem MICs (15 isolates from each of four MIC groups: ≤ 1, 2-4, 8-16 and ≥ 32 mg/L). The expression of ampC, mexB, mexY, mexD and mexF was determined by real-time reverse transcription-PCR and the presence of mutations in oprD by PCR and sequencing. Isogenic mutants expressing combinations of mutation-driven carbapenem resistance were constructed. RESULTS: Twelve (6.9%) isolates were MBL (VIM-20, VIM-2 or VIM-13) producers and all showed high-level resistance (MIC 32 mg/L) to all three carbapenems. Regarding mutation-driven resistance, all but 1 of the 60 isolates were non-susceptible (MIC >32 mg/L) to imipenem, linked to oprD inactivation. In addition, 50% of the isolates overexpressed ampC, 33% mexY, 32% mexB and 15% mexF, while none overexpressed mexD. Increasing prevalence of ampC overexpression correlated with increasing doripenem MICs (≤ 1, 13%; 2-4, 53%; 8-16, 60%; and ≥ 32, 73%) while overexpression of efflux pumps correlated only with moderate resistance. Doripenem showed slightly higher activity than meropenem against isolates overexpressing ampC, especially mexB or mexY. The analysis of a collection of isogenic laboratory mutants supported this finding. CONCLUSIONS: Although the prevalence of MBL producers is increasing, mutation-driven resistance is still more frequent in Spain. Imipenem resistance was driven by OprD inactivation, while additional AmpC and particularly efflux pump hyperproduction had a lower impact on the activity of doripenem compared with meropenem.
Authors: Esther Viedma; Vanesa Estepa; Carlos Juan; Jane Castillo-Vera; Beatriz Rojo-Bezares; Cristina Seral; Francisco Javier Castillo; Yolanda Sáenz; Carmen Torres; Fernando Chaves; Antonio Oliver Journal: Antimicrob Agents Chemother Date: 2014-02-03 Impact factor: 5.191
Authors: Gabriel Torrens; Gabriel Cabot; Alain A Ocampo-Sosa; M Carmen Conejo; Laura Zamorano; Ferrán Navarro; Álvaro Pascual; Luis Martínez-Martínez; Antonio Oliver Journal: Antimicrob Agents Chemother Date: 2016-09-23 Impact factor: 5.191
Authors: Mariana Castanheira; Janet C Mills; David J Farrell; Ronald N Jones Journal: Antimicrob Agents Chemother Date: 2014-09-02 Impact factor: 5.191
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Authors: S Ronkainen; Y Xie; M Battiwalla; A J Barrett; F Stock; J P Dekker; R L Danner Journal: Transpl Infect Dis Date: 2014-06-26 Impact factor: 2.228
Authors: Gabriel Cabot; Alain A Ocampo-Sosa; M Angeles Domínguez; Juan F Gago; Carlos Juan; Fe Tubau; Cristina Rodríguez; Bartolomé Moyà; Carmen Peña; Luis Martínez-Martínez; Antonio Oliver Journal: Antimicrob Agents Chemother Date: 2012-10-08 Impact factor: 5.191