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Title

Energy-dependent accumulation of norfloxacin and porin expression in clinical isolates of Klebsiella pneumoniae and relationship to extended-spectrum β-lactamase production

AuthorsMartínez-Martínez, Luis; Pascual, Álvaro; Conejo, María del Carmen; García, Isabel; Joyanes, Providencia; Doménech-Sánchez, Antonio; Benedí Benito, Vicente Javier
Issue Date1-Dec-2002
PublisherAmerican Society for Microbiology
CitationAntimicrobial Agents and Chemotherapy 46(12): 3926-3932 (2002)
AbstractThe relationships between porin deficiency, active efflux of fluoroquinolones, and extended-spectrum β-lactamase (ESBL) production were determined for 53 clinical isolates of Klebsiella pneumoniae. Thirty-two ESBL-positive strains (including 22 strains expressing porins and 10 strains lacking porins) and 21 ESBL-negative strains were evaluated. Active efflux of norfloxacin was defined as a ≥50% increase in the accumulation of norfloxacin in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP) in comparison with the corresponding basal value in the absence of CCCP. The quinolone resistance-determining regions of both gyrA and parC from 13 strains, representing all isolates with different porin profiles and with or without active efflux, were determined. Porin loss was significantly more common among ESBL-positive strains (10 of 32 [31.2%]) than among ESBL-negative strains (0 of 2 [0%]) (P < 0.01). Active efflux was observed in 7 of 10 (70%) strains lacking porins and in 4 of 43 (9.3%) strains producing porins (P < 0.001). The 11 strains showing active efflux corresponded to 3 of 21 (14.3%) ESBL-negative strains and 8 of 32 (25.5%) ESBL-positive strains (P > 0.05). Basal values of norfloxacin accumulation were higher in strains lacking active efflux than in those that had this mechanism (P < 0.05). In the absence of topoisomerase changes, the contribution of either porin loss or active efflux to fluoroquinolone resistance in K. pneumoniae was negligible. It is concluded that among K. pneumoniae strains of clinical origin, porin loss was observed only in those producing ESBL, and that a significant number of porin-deficient strains also expressed active efflux of norfloxacin. In terms of fluoroquinolone resistance, both mechanisms are significant only in the presence of topoisomerase modifications.
Publisher version (URL)http://dx.doi.org/10.1128/AAC.46.12.3926-3932.2002
URIhttp://hdl.handle.net/10261/123238
DOI10.1128/AAC.46.12.3926-3932.2002
Identifiersdoi: 10.1128/AAC.46.12.3926-3932.2002
issn: 0066-4804
Appears in Collections:(IMEDEA) Artículos
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