Occurrence and characterization of ciprofloxacin‐resistant Escherichia coli from bovine and ovine bulk tank milk samples in Turkey

Abstract

AbstractThe objective of this study was to examine the occurrence and characteristics of ciprofloxacin‐resistant (CipR) Escherichia coli isolates on bulk tank milk (BTM) samples (bovine and ovine origins) in Turkey. A total of 91 BTM samples (41.7%, 95% confidence intervals 35.2–48.6%) out of 218 were found to be positive for CipR E. coli isolates (MIC values of ≥4 μg/ml). Analysis of PFGE fingerprint profile for E. coli isolates resulted in the 55 different pulsotypes based on >85% homology. All isolates were resistant to enrofloxacin and nalidixic acid and the resistance rates in bovine and ovine origin isolates were 94.9 and 78.1% for norfloxacin (p < .05) and 27.1 and 34.4% for levofloxacin, respectively. Additionally, resistance to non‐quinolone antibiotics was commonly observed against tetracycline (resistance rates in bovine and ovine = 91.5 and 87.5%, respectively), trimethoprim‐sulfamethoxazole (83.1 and 93.8%, respectively), gentamycin (15.3 and 40.6%, respectively, p < .05) and chloramphenicol (23.7 and 65.6%, respectively, p < .05). The qnrS1 gene (3.1 and 6.8%, respectively) was the most prevalent PMQR genes in isolates from ovine and bovine origins, followed by aac (6′)‐Ib‐cr (0 and 5.1%, respectively) and qnrB19 (0 and 1.7%, respectively). The other resistance genes including tetA, tetB, strA/B, aPozhA1, aadA, aadB, blaCTX‐M, and blaTEM were also identified in various frequencies. The most frequently observed virulence trait was fimH. The low‐level presence of PMQR genes and as well as some virulence traits is an important finding, yet the results of this study are worrisome because quinolone antibiotics are still the drugs of choice for severe infections in humans.