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Superoxide-mediated protection of Escherichia coli from antimicrobials.

ABSTRACT: Antimicrobial lethality is promoted by reactive oxygen species (ROS), such as superoxide, peroxide, and hydroxyl radical. Pretreatment with subinhibitory concentrations of plumbagin or paraquat, metabolic generators of superoxide, paradoxically reduced killing for oxolinic acid, kanamycin, and ampicillin. These pretreatments also reduced an oxolinic acid-mediated ROS surge. Defects in SoxS MarA or AcrB eliminated plumbagin- and paraquat-mediated MIC increases but maintained protection from killing. Thus, superoxide has both protective and detrimental roles in response to antimicrobial stress.

SUBMITTER: Mosel M

PROVIDER: S-EPMC3811261 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Superoxide-mediated protection of Escherichia coli from antimicrobials.

Mosel Michael M Li Liping L Drlica Karl K Zhao Xilin X

Antimicrobial agents and chemotherapy 20130826 11

Antimicrobial lethality is promoted by reactive oxygen species (ROS), such as superoxide, peroxide, and hydroxyl radical. Pretreatment with subinhibitory concentrations of plumbagin or paraquat, metabolic generators of superoxide, paradoxically reduced killing for oxolinic acid, kanamycin, and ampicillin. These pretreatments also reduced an oxolinic acid-mediated ROS surge. Defects in SoxS MarA or AcrB eliminated plumbagin- and paraquat-mediated MIC increases but maintained protection from killi ...[more]

PMID: 23979754

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Project description:Adherence of bacteria to the human intestinal mucosa can facilitate their internalization and the development of pathological processes. Escherichia coli O104:H4 is considered a hybrid strain (enteroaggregative hemorrhagic E. coli [EAHEC]), sharing virulence factors found in enterohemorrhagic (EHEC), and enteroaggregative (EAEC) E. coli pathotypes. The objective of this study was to analyze the effects of natural and synthetic antimicrobials (carvacrol, oregano extract, brazilin, palo de Brasil extract, and rifaximin) on the adherence of EHEC O157:H7, EAEC 042, and EAHEC O104:H4 to HEp-2 cells and to assess the expression of various genes involved in this process. Two concentrations of each antimicrobial that did not affect (p≤0.05) bacterial viability or damage the bacterial membrane integrity were used. Assays were conducted to determine whether the antimicrobials alter adhesion by affecting bacteria and/or alter adhesion by affecting the HEp-2 cells, whether the antimicrobials could detach bacteria previously adhered to HEp-2 cells, and whether the antimicrobials could modify the adherence ability exhibited by the bacteria for several cycles of adhesion assays. Giemsa stain and qPCR were used to assess the adhesion pattern and gene expression, respectively. The results showed that the antimicrobials affected the adherence abilities of the bacteria, with carvacrol, oregano extract, and rifaximin reducing up to 65% (p≤0.05) of E. coli adhered to HEp-2 cells. Carvacrol (10 mg/ml) was the most active compound against EHAEC O104:H4, even altering its aggregative adhesion pattern. There were changes in the expression of adhesion-related genes (aggR, pic, aap, aggA, and eae) in the bacteria and oxidative stress-related genes (SOD1, SOD2, CAT, and GPx) in the HEp-2 cells. In general, we demonstrated that carvacrol, oregano extract, and rifaximin at sub-minimal bactericidal concentrations interfere with target sites in E. coli, reducing the adhesion efficiency.

Project description:BACKGROUND: Feedlot cattle in North America are routinely fed subtherapeutic levels of antimicrobials to prevent disease and improve the efficiency of growth. This practice has been shown to promote antimicrobial resistance (AMR) in subpopulations of intestinal microflora including Escherichia coli. To date, studies of AMR in feedlot production settings have rarely employed selective isolation, therefore yielding too few AMR isolates to enable characterization of the emergence and nature of AMR in E. coli as an indicator bacterium. E. coli isolates (n = 531) were recovered from 140 cattle that were housed (10 animals/pen) in 14 pens and received no dietary antimicrobials (control--5 pens, CON), or were intermittently administered subtherapeutic levels of chlortetracycline (5 pens-T), chlortetracycline + sulfamethazine (4 pens-TS), or virginiamycin (5 pens-V) for two separate periods over a 9-month feeding period. Phenotype and genotype of the isolates were determined by susceptibility testing and pulsed field gel electrophoresis and distribution of characterized isolates among housed cattle reported. It was hypothesized that the feeding of subtherapeutic antibiotics would increase the isolation of distinct genotypes of AMR E. coli from cattle. RESULTS: Overall, patterns of antimicrobial resistance expressed by E. coli isolates did not change among diet groups (CON vs. antibiotic treatments), however; isolates obtained on selective plates (i.e., M(A),M(T)), exhibited multi-resistance to sulfamethoxazole and chloramphenicol more frequently when obtained from TS-fed steers than from other treatments. Antibiograms and PFGE patterns suggested that AMR E. coli were readily transferred among steers within pens. Most M(T) isolates possessed the tet(B) efflux gene (58.2, 53.5, 40.8, and 50.6% of isolates from CON, T, TS, and V steers, respectively) whereas among the M(A) (ampicillin-resistant) isolates, the tem1-like determinant was predominant (occurring in 50, 66.7, 80.3, and 100% of isolates from CON, T, TS, and V steers, respectively). CONCLUSIONS: Factors other than, or in addition to subtherapeutic administration of antibiotics influence the establishment and transmission of AMR E. coli among feedlot cattle.

Dataset Information

Superoxide-mediated protection of Escherichia coli from antimicrobials.

Publications

Superoxide-mediated protection of Escherichia coli from antimicrobials.

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