Energy-Dependent Accumulation of Norfloxacin and Porin Expression in Clinical Isolates of Klebsiella pneumoniae and Relationship to Extended-Spectrum β-Lactamase Production

Abstract

The relationships between porin deficiency, active efflux of fluoroquinolones, and extended-spectrum ␤-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 ESBLnegative 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.

Epidemiology and Clinical Features of Infections Caused by Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in Nonhospitalized Patients

“…These antimicrobials may select for ESBLEC in previously colonized patients, since ESBL production and resistance to these antimicrobials are linked. The plasmids encoding ESBLs also frequently encode the genetic determinants of trimethoprim-sulfamethoxazole resistance; the association between ESBL production and quinolone resistance is more complex (17,25). The prevalence of ESBLEC colonization in the community is not known.…”

The porin and the permeating antibiotic: a selective diffusion barrier in Gram-negative bacteria

“…several studies have observed that there is a relationship between the balance of porin expression and β-lactam susceptibility in clinical K. pneumoniae isolates [24][25][26][27][28][29][30] . a similar phenomenon has been reported in a patient infected with Salmonella enterica subsp.…”

The Challenge of Efflux-Mediated Antibiotic Resistance in Gram-Negative Bacteria

“…In an important study of ESBL-producing strains from outbreaks of nosocomial infections (294), ciprofloxacin resistance (caused in part by AcrB overproduction) was strongly correlated with cefoxitin resistance, suggesting that for ␤-lactam resistance, not only the ␤-lactamases and porin depletion but also efflux may make a significant contribution. Similarly, ESBL-producing strains often lack porins and show a stronger efflux of fluoroquinolones (295). The significance of efflux in ␤-lactam resistance was pursued later by the Pagès group (296), who examined cefoxitin-resistant but ceftazidime-susceptible clinical isolates.…”