Mutant-prevention concentrations of enrofloxacin for Escherichia coli isolates from chickens

Li, Qianxue; Xing-ming, BI; Diao, Youjiang; Deng, Xuming

doi:10.2460/ajvr.68.8.812

Cited by 10 publications

(13 citation statements)

References 18 publications

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“…Bacteria growing in higher concentrations of enrofloxacin (0.1 mg ml À1 ) had more elongated cells and did not have mutations in gyrA, which has been shown to be the reason for decreased sensitivity of E. coli, including those exposed to low concentrations of fluoroquinolones. 39 Both inhibitors of the efflux pump, reserpine and CCCP, inhibited the growth of E. coli in the presence of enrofloxacin (data not shown), as has been shown previously for other fluoroquinolones. 32 However, in the media containing sterilized fecal extracts, no increase in sensitivity to enrofloxacin was observed in the presence of these pump inhibitors.…”

Section: Discussionsupporting

confidence: 76%

Effect of sterilized human fecal extract on the sensitivity of Escherichia coli ATCC 25922 to enrofloxacin

et al. 2012

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The ingestion of antimicrobial residues in foods of animal origin has the potential risk of exposing colonic bacteria to small concentrations of antibiotics and inducing resistance in the colonic bacteria. To investigate whether human intestinal contents would influence resistance development in bacteria, Escherichia coli ATCC 25922 (MIC of enrofloxacin <0.03 μg ml(-1)) was exposed to 0.01 to 1 μg ml(-1) of enrofloxacin in media supplemented with glucose, sucrose, sodium acetate or sterilized human fecal extract. In the first passage, only the medium containing sterilized fecal extract supported the growth of E. coli at an enrofloxacin concentration equal to the MIC. In the second and third passages following exposure to sub-inhibitory concentrations of the drug, the bacteria in media containing sterilized fecal extract grew at 0.1 μg ml(-1) of enrofloxacin. The efflux pump inhibitors, reserpine and carbonyl cyanide-m-chlorophenylhydrazone (CCCP), increased the sensitivity of bacteria to 0.1 μg ml(-1) of enrofloxacin in the medium containing sucrose, but their effect was not observed in the medium supplemented with 2.5% sterilized fecal extract. The proportions of unsaturated and saturated fatty acids in E. coli grown in the medium with 2.5% sterilized fecal extract differed from those grown in the medium alone. Fecal extract may contain unknown factors that augment the ability of E. coli to grow in concentrations of enrofloxacin higher than MIC, both in the presence and absence of efflux pump inhibitors. This is the first study showing that fecal extract affects the level of sensitivity of E. coli to antimicrobial agents.

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Section: Discussionsupporting

confidence: 76%

Effect of sterilized human fecal extract on the sensitivity of Escherichia coli ATCC 25922 to enrofloxacin

et al. 2012

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“…For most enrofloxacin-susceptible isolates, it is possible to achieve concentrations of enrofloxacin greater than their MPCs at the infection site. However, MPC values of mutant strains exceed the C max of enrofloxacin (1.88-2.44 µg/ml) in chickens [1,10,12]. APEC strains possessing at least 1 mutation in QRDRs account for 57.4% of APEC strains [16].…”

Section: Discussionmentioning

confidence: 99%

“…Li et al [12] reported that strains containing point mutations in the QRDR of gyrA with an MPC:MIC ratio of 16 showed higher mutation frequencies than did strains with MPC:MIC ratios of 2-4. Therefore, we examined the relationship between mutation frequency and MPC:MIC ratio.…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, Li et al [11] reported that the isolation frequency of O2 strains was 32.4% in the 1990s and 16. [8][9][10][11][12][13][14][15][16][17][18][19].6% in the 2000s in China. These data and our results showing that O2 strains have low MPC values, low mutation frequencies and difficulty in acquiring parC mutations suggest that the population of O2 strains has been decreased through the use of fluoroquinolones in the treatment of avian colibacillosis.…”

Section: Discussionmentioning

confidence: 99%

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Relationships between Mutant Prevention Concentrations and Mutation Frequencies against Enrofloxacin for Avian Pathogenic <i>Escherichia coli</i> Isolates

Ozawa

Asai

2013

The Journal of Veterinary Medical Science

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ABSTRACT. Clinical efficacies of mutant prevention concentration (MPC) and mutant selection window (MSW) hypotheses have been evaluated for human clinical isolates. We tested the MSW hypothesis by evaluating the relationships between MPCs and mutation frequencies against enrofloxacin for avian pathogenic Escherichia coli (APEC) isolates. Mutation frequencies of strains with MPC:MIC ratios of 8 to 16 were significantly higher than those of strains with an MPC:MIC ratio of 4. Mutation frequencies and MPCs of serogroup O2 strains were lower than those of the other strains; these results may correlate with the absence of fluoroquinolone-resistant O2 strains. Our results support the MSW hypothesis that the range of the MSW is involved in selection of resistant mutants.

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“…The fluoroquinolone MICs for Type I and II isolates were 8- to 16-fold higher than those of the wild type, and fluoroquinolone MPCs for Type I and II isolates were 32- to 256-fold higher than those of the wild type. A previous study suggested that wild-type strains had lower mutation frequencies compared with single-mutation strains [ 8 ].…”

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confidence: 99%

Fluoroquinolone Resistance Mechanism of Clinical Isolates and Selected Mutants of Pasteurella multocida from Bovine Respiratory Disease in China

Kong

Gao

et al. 2014

The Journal of Veterinary Medical Science

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The minimum inhibitory concentrations (MICs), mutation prevention concentrations (MPCs) and contribution of quinolone resistance-determining region (QRDR) mutations to fluoroquinolone (ciprofloxacin, enrofloxacin and orbifloxacin) susceptibility in 23 Pasteurella multocida (Pm) isolates were investigated. Fluoroquinolone-susceptible isolates (MICs ≤0.25 µg/ml, 9 isolates) had no QRDR mutations, and their respective MPCs were low. Fluoroquinolone-intermediate isolates (MICs=0.5 µg/ml, 14 isolates) had QRDR mutations (Asp87 to Asn or Ala84 to Pro in gyrA), and their respective MPCs were high (4–32 µg/ml). First-step mutants (n=5) and laboratory-derived highly resistant fluoroquinolone mutants (n=5) also had QRDR mutations. The MICs of fluoroquinolones for mutant-derived strains were decreased in the presence of efflux inhibitors. The results indicated that the fluoroquinolone resistance of Pm is mainly due to multiple target gene mutations in gyrA and parC and the overexpression of efflux pump genes.

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Mutant-prevention concentrations of enrofloxacin for Escherichia coli isolates from chickens

Cited by 10 publications

References 18 publications

Effect of sterilized human fecal extract on the sensitivity of Escherichia coli ATCC 25922 to enrofloxacin

Effect of sterilized human fecal extract on the sensitivity of Escherichia coli ATCC 25922 to enrofloxacin

Relationships between Mutant Prevention Concentrations and Mutation Frequencies against Enrofloxacin for Avian Pathogenic <i>Escherichia coli</i> Isolates

Fluoroquinolone Resistance Mechanism of Clinical Isolates and Selected Mutants of Pasteurella multocida from Bovine Respiratory Disease in China

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