In this study, we compared 142 Yersinia ruckeri isolates collected between 2013 and 2016 from 6 different regions in Turkey. A total of 18 different genogroups were found, though most of the isolates clustered into the same genogroup as serotype O1. As immunization of fish with inactivated Y. ruckeri by injection, immersion, or feeding provide minimal protection against Y. ruckeri infection in Turkey, many fish producers use antimicrobials unrestrictedly, resulting in antimicrobial resistance in aquatic pathogens. Accordingly, we investigated resistance to the antimicrobials most commonly used to treat yersiniosis. More than 80% of the Y. ruckeri isolates were susceptible to sulfamethoxazole-trimethoprim (SXT), florfenicol (FFC), and tetracycline, whereas none were susceptible to sulfamethoxazole. The most commonly used antimicrobials (SXT and FFC) can be effectively administered because the resistance levels to these drugs are the lowest among those reported for agents used to control enteric red mouth disease (12.6 and 14.7%, respectively). In conclusion, to the best of our knowledge, this study is the first characterization of the antimicrobial resistance genes floR, sulI, tetC, tetD, and tetE in Y. ruckeri isolates from aquaculture. Additionally, we detected the sulII gene but not the tetA, tetB, tetM, tetS, or sulIII genes.
Three lichen species of Ramalina (R. farinacea, R. fastigiata and R. fraxinea) were examined. Evernic, fumarprotocetraric, lecanoric, stictic and usnic acid levels were determined by high performance liquid chromatography‐diode array detection. Acetone, methanol and ethanol were used to examine the efficiencies of different solvent systems for the extraction of lichen acids. The total phenol contents in the extracts were determined by the Folin–Ciocalteu method. The antioxidant capacities were determined by the ABTS (2,2′‐azino‐bis[3‐ethylbenzothiazoline‐6‐sulphonic acid]) method. The methanol extracts of the Ramalina species showed the highest antioxidant capacities. Broth microdilution testing was performed to determine the minimum inhibitory concentration (MIC) of the methanol extracts of the three Ramalina species. The MIC values of all extracts ranged from 64 to 512 μg/mL for all bacterial strains tested in this study.
Practical Applications
Lichens and their natural products are used worldwide for decorations, brewing and distilling, food, fodder, spice and natural remedies, and in the perfume and dying industries. Lichens produce a large number of phenolic compounds, such as depsides, depsidones and dibenzofurans. Lichens with antioxidant activity have increased abilities to scavenge toxic‐free radicals due to their phenolic groups. In recent years, many lichen substances have been found to have several biological activities. This article evaluates the antimicrobial and antioxidant activities and lichen acids of three Ramalina species. This is the first study to determine the stictic acid level in a R. farinacea extract and fumarprotocetraric acid and lecanoric acid levels in an R. fastigiata extract. The results of this study will contribute significantly to current knowledge regarding the utility of antimicrobial and antioxidant materials.
2. Materials and methods 2.1. Strains and susceptibility testing Random amplified polymorphic DNA (RAPD) analysis was used to determine the genetic relatedness of 58 E. coli isolates from cattle, goats, sheep, cats, and dogs. Twenty different RAPD patterns were observed among these isolates and one representative isolate was chosen from each pattern based on resistance genotype.
The aim of this study were to detect the gyrA, parC and marR mutations and qnr genes (qnrA, qnrB and qnrS) in 120 strains of Escherichia coli isolated from animals. European Committee on Antimicrobial Susceptibility Testing and Clinical Laboratory Standards Institute disc diffusion and minimum inhibitory concentration (MIC) tests, respectively, were used to determine fluoroquinolone (FQ) resistance, and molecular methods were used to detect the mutations and the genes. E coli isolates with an MIC of ≥8 mg/l had mutation at Ser-80 in parC in addition to mutations at Ser-83, Asp-87 or both in gyrA. The nucleotide change was detected in marR (Ser-3 → Asn, Ala-53 → Glu, Gly-103 → Ser, Tyr-137 → His). Only four E coli isolates (3.3 per cent) contained qnrA and qnrS, and qnrB was not detected. Two E coli isolates from healthy calves also contained qnrA and qnrS. The MICs of enrofloxacin and danofloxacin for qnr-containing E coli isolates ranged from 32 mg/l to 256 mg/l. The results of this study indicated that the FQ-resistant E coli isolates presented an alteration in gyrA (Ser-83 → Leu, Asp-87 → Asn) and parC (Ser-80 → Ile) with high MICs (8-256 mg/l), and there was a low prevalence of qnr genes among E coli isolated from animals.
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