Faculty Opinions recommendation of Selection of resistant bacteria at very low antibiotic concentrations.

The emergence of antibiotic-resistant pathogens due to worldwide antibiotic use is raising concern in several settings, including aquaculture. In this work, the selection of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) was evaluated after exposure of zebrafish to oxytetracycline (OTC) for two months, followed by a recovery period. The selection of ARB in water and fish was determined using selective media. The abundance of tetA genes was estimated through qPCR. Higher prevalence of ARB was measured in all samples exposed to the antibiotic when compared to control samples, although statistical significance was only achieved five days after exposure. Isolates recovered from samples exposed to the antibiotic were affiliated with Pseudomonas and Stenotrophomonas. Various antibiotic susceptibility profiles were detected and 37% of the isolates displayed multidrug resistance (MDR). The selection of the tetA gene was confirmed by qPCR at the highest OTC concentration tested. Two MDR isolates, tested using zebrafish embryos, caused significant mortality, indicating a potential impact on fish health and survival. Overall, our work highlights the potential impact of antibiotic contamination in the selection of potential pathogenic ARB and ARGS.

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SDD and selection of antibiotk-resistant bacteria

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/26.6.854 ◽

1990 ◽

Vol 26 (6) ◽

pp. 854-855 ◽

Cited By ~ 1

Author(s):

ROLAND NAU ◽

A.B.J SPEEKENBRINK

Keyword(s):

Resistant Bacteria ◽

Selection Of

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Bacteriocins of Gram-positive bacteria having activity spectra extending beyond closely-related species

Beneficial Microbes ◽

10.3920/bm2018.0126 ◽

2019 ◽

Vol 10 (3) ◽

pp. 315-328 ◽

Cited By ~ 17

Author(s):

S.D. Todorov ◽

B.D.G. de Melo Franco ◽

J.R. Tagg

Keyword(s):

Critical Points ◽

Anticancer Agents ◽

Multidrug Resistant ◽

Food Preservation ◽

Resistant Bacteria ◽

Closely Related Species ◽

Gram Positive Bacteria ◽

Activity Spectrum ◽

Novel Applications ◽

Selection Of

Bacteriocins are bacterially-produced antimicrobial peptides that have killing activity principally against other relatively closely-related bacteria. Some bacteriocins of the lactic acid bacteria (LAB) have for many years been extensively applied in food biopreservation. However, especially during the last decade, a number of reports have appeared about unanticipated extensions to the generally rather narrow anti-bacterial activity spectrum of some of the LAB bacteriocins and novel applications have been proposed for bacteriocins ranging from controlling the growth of an increasingly-heterogeneous variety of pathogens, including Gram-negative multidrug resistant bacteria, viruses, yeasts, and in particular, difficult to control Mycobacterium spp., to their potential application as anticancer agents. How best can we assess this now rapidly-accumulating stream of reports on potential future applications of bacteriocins? Where is the line between realistic, science-based proposals and highly-speculative fiction and what are the ‘critical points’ that might help us to draw this line? In this review, we have attempted to analyse a selection of the presently-available data concerning relatively ‘unorthodox’ (i.e. beyond food preservation) applications of bacteriocins, and, by utilising our set of ‘critical points’, we endeavour to identify essential or/and missing information that appear crucial for success of the proposed applications.

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Potential risks of antibiotic resistant bacteria and genes in bioremediation of petroleum hydrocarbon contaminated soils

Environmental Science Processes & Impacts ◽

10.1039/c9em00606k ◽

2020 ◽

Vol 22 (5) ◽

pp. 1110-1124 ◽

Cited By ~ 2

Author(s):

Colin J. Cunningham ◽

Maria S. Kuyukina ◽

Irena B. Ivshina ◽

Alexandr I. Konev ◽

Tatyana A. Peshkur ◽

...

Keyword(s):

Antibiotic Resistance ◽

Contaminated Soil ◽

Contaminated Soils ◽

Petroleum Hydrocarbon ◽

Resistant Bacteria ◽

Careful Selection ◽

Bacterial Strains ◽

Antibiotic Resistant ◽

Potential Risks ◽

Selection Of

The problems associated with potential risks of antibiotic resistance spreading during bioremediation of oil-contaminated soil are discussed. Careful selection of bacterial strains and pretreatment of organic wastes used as fertilizers are suggested.

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Small-Colony Mutants of Staphylococcus aureus Allow Selection of Gyrase-Mediated Resistance to Dual-Target Fluoroquinolones

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.46.8.2498-2506.2002 ◽

2002 ◽

Vol 46 (8) ◽

pp. 2498-2506 ◽

Cited By ~ 38

Author(s):

Xiao-Su Pan ◽

Penelope J. Hamlyn ◽

Raquel Talens-Visconti ◽

Fabiana L. Alovero ◽

Ruben H. Manzo ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Drug Target ◽

Quinolone Resistance ◽

Second Step ◽

Resistant Bacteria ◽

Topoisomerase Iv ◽

Small Colony ◽

Dual Target ◽

Selection Of

ABSTRACT Fluoroquinolones acting equally through DNA gyrase and topoisomerase IV in vivo are considered desirable in requiring two target mutations for emergence of resistant bacteria. To investigate this idea, we have studied the response of Staphylococcus aureus RN4220 to stepwise challenge with sparfloxacin, a known dual-target agent, and with NSFQ-105, a more potent sulfanilyl fluoroquinolone that behaves similarly. First-step mutants were obtained with both drugs but only at the MIC. These mutants exhibited distinctive small-colony phenotypes and two- to fourfold increases in MICs of NSFQ-105, sparfloxacin, and ciprofloxacin. No changes were detected in the quinolone resistance-determining regions of the gyrA, gyrB, grlA, or grlB gene. Quinolone-induced small-colony mutants shared the delayed coagulase response but not the requirement for menadione, hemin, or thymidine characteristic of small-colony variants, a subpopulation of S. aureus that is often defective in electron transport. Second-step mutants selected with NSFQ-105 had gyrA(S84L) alterations; those obtained with sparfloxacin carried a gyrA(D83A) mutation or a novel gyrB deletion (ΔRKSAL, residues 405 to 409) affecting a trypsin-sensitive region linking functional domains of S. aureus GyrB. Each mutation was associated with four- to eightfold increases in MICs of NSFQ-105 and sparfloxacin, but not of ciprofloxacin, which we confirm targets topoisomerase IV. The presence of wild-type grlB-grlA gene sequences in second-step mutants excluded involvement of topoisomerase IV in the small-colony phenotype. Growth revertants retaining mutant gyrA or gyrB alleles were quinolone susceptible, indicating that resistance to NSFQ-105 and sparfloxacin was contingent on the small-colony mutation. We propose that small-colony mutations unbalance target sensitivities, perhaps through altered ATP or topoisomerase levels, such that gyrase becomes the primary drug target. Breaking of target parity by genetic or physiological means eliminates the need for two target mutations and provides a novel mechanism for stepwise selection of quinolone resistance.

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Relationship between Ceftolozane-Tazobactam Exposure and Drug Resistance Amplification in a Hollow-Fiber Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00461-13 ◽

2013 ◽

Vol 57 (9) ◽

pp. 4134-4138 ◽

Cited By ~ 32

Author(s):

Brian VanScoy ◽

Rodrigo E. Mendes ◽

Mariana Castanheira ◽

Jennifer McCauley ◽

Sujata M. Bhavnani ◽

...

Keyword(s):

Drug Resistance ◽

Hollow Fiber ◽

Drug Exposure ◽

Resistant Bacteria ◽

Infection Model ◽

Drug Resistant ◽

Dose Ratio ◽

Bacterial Drug Resistance ◽

Dosing Regimens ◽

Selection Of

ABSTRACTIn an era of rapidly emerging antimicrobial-resistant bacteria, it is critical to understand the importance of the relationships among drug exposure, duration of therapy, and selection of drug resistance. Herein we describe the results of studies designed to determine the ceftolozane-tazobactam exposure necessary to prevent the amplification of drug-resistant bacterial subpopulations in a hollow-fiber infection model. The challenge isolate was a CTX-M-15-producingEscherichia coliisolate genetically engineered to transcribe a moderate level ofblaCTX-M-15. This organism'sblaCTX-M-15transcription level was confirmed by relative quantitative reverse transcription-PCR (qRT-PCR), β-lactamase hydrolytic assays, and a ceftolozane MIC value of 16 mg/liter. In these studies, the experimental duration (10 days), ceftolozane-tazobactam dose ratio (2:1), and dosing interval (every 8 h) were selected to approximate those expected to be used clinically. The ceftolozane-tazobactam doses studied ranged from 125-62.5 to 1,500-750 mg. Negative- and positive-control arms included no treatment and piperacillin-tazobactam at 4.5 g every 6 h, respectively. An inverted-U-shaped function best described the relationship between bacterial drug resistance amplification and drug exposure. The least- and most-intensive ceftolozane-tazobactam dosing regimens, i.e., 125-62.5, 750-375, 1,000-500, and 1,500-750 mg, did not amplify drug resistance, while drug resistance amplification was observed with intermediate-intensity dosing regimens (250-125 and 500-250 mg). For the intermediate-intensity ceftolozane-tazobactam dosing regimens, the drug-resistant subpopulation became the dominant population by days 4 to 6. The more-intensive ceftolozane-tazobactam dosing regimens (750-375, 1,000-500, and 1,500-750 mg) not only prevented drug resistance amplification but also virtually sterilized the model system. These data support the selection of ceftolozane-tazobactam dosing regimens that minimize the potential for on-therapy drug resistance amplification.

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Co-selection of antibiotic and heavy metal resistance in freshwater bacteria

Journal of Limnology ◽

10.4081/jlimnol.2016.1198 ◽

2016 ◽

Vol 75 (s2) ◽

Cited By ~ 34

Author(s):

Andrea Di Cesare ◽

Ester Eckert ◽

Gianluca Corno

Keyword(s):

Heavy Metal ◽

Resistance Genes ◽

Heavy Metal Resistance ◽

Resistance Mechanisms ◽

Metal Resistance ◽

Resistant Bacteria ◽

Human Pathogens ◽

Antibiotic Resistant Bacteria ◽

Antibiotic Resistant ◽

Selection Of

Antibiotic resistant bacteria are found in most environments, especially in highly anthropized waters. A direct correlation between human activities (e.g., pollution) and spread and persistence of antibiotic resistant bacteria (ARB) and resistance genes (ARGs) within the resident bacterial communities appears more and more obvious. Furthermore, the threat posed for human health by the presence of ARB and ARGs in these environments is enhanced by the risk of horizontal gene transfer of resistance genes to human pathogens. Although the knowledge on the spread of antibiotic resistances in waters is increasing, the understanding of the driving factors determining the selection for antibiotic resistance in the environment is still scarce. Antibiotic pollution is generally coupled with contamination by heavy metals (HMs) and other chemicals, which can also promote the development of resistance mechanisms, often through co-selecting for multiple resistances. The co-selection of heavy metal resistance genes and ARGs in waters, sediments, and soils, increases the complexity of the ecological role of ARGs, and reduces the effectiveness of control actions. In this mini-review we present the state-of-the-art of the research on antibiotic- and HM-resistance and their connection in the environment, with a focus on HM pollution and aquatic environments. We review the spread and the persistence of HMs and/or ARB, and how it influences their respective gene co-selection. In the last chapter, we propose Lake Orta, a system characterized by an intensive HM pollution followed by a successful restoration of the chemistry of the water column, as a study-site to evaluate the spread and selection of HMs and antibiotic resistances in heavily disturbed environments.

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