Abstract
BackgroundFluoroquinolone resistance and ESBL-production are concurrently found in a limited number of Salmonella serotypes. The present study was aimed to characterize fluoroquinolone-resistant and ESBL-producing Salmonella enteric serotype Derby (S. Derby) isolates in terms of antimicrobial susceptibility, relevant genetic mechanisms, and PFGE.ResultsFrom 2013 to 2017 in Ningbo China, 52 S. Derby isolates were identified out of 826 non-typhoidal Salmonella isolates from patient feces, food, and environmental water samples. Three S. derby isolates were identified to be fluoroquinolone-resistant and ESBL-producing with cefotaxime MIC of 64 μg/mL and ciprofloxacin MIC of 4 μg/mL. The three isolates contained the same genetic structure of quinolone resistance, including a silent gyrA mutation S (TCC) 83S (TCT) and three PMQR genes qnrB, qnrS and aac(6′)-Ib-cr. As withβ-lactams resistance mechanisms, two isolates contained blaTEM, blaOXA, and blaCTX-M genes and one isolate contained blaOXA and blaCTX-M genes. Additionally, two isolates displayed more identical PFGE pattern than the third isolate, whereas three isolates showed the same plasmid profile of I1, W and P by PCR-based replicon typing. The conjugation experiment showed no dissemination of β-lactam resistance by direct contact among isolates; the transformation experiment failed to transfer plasmid conferring ampicillin resistance to E. coli DH5a.ConclusionThe present study demonstrates the emerging fluoroquinolone-resistant and ESBL-producing S. Derby in both humans and the environment. Seeing that S. Derby has become one of the most common Salmonella serotypes, this situation gives rise to a new major risk of food-borne diseases.
Highlights
Fluoroquinolone resistance and extended-spectrum βlactamase (ESBL)-production are concurrently found in a limited number of Salmonella serotypes
Most cases of salmonellosis are gastroenteritis that is not complicated and does not require antimicrobials for treatment, but severely invasive salmonellosis can sometimes be found in infants, the elderly and patients with weakened immunity, which needs appropriate treatment with antimicrobials such as fluoroquinolones and β-lactams
Colonies with typical Salmonella appearance were tested for biochemical reactions by API20E identification system
Summary
Fluoroquinolone resistance and ESBL-production are concurrently found in a limited number of Salmonella serotypes. The present study was aimed to characterize fluoroquinolone-resistant and ESBL-producing Salmonella enteric serotype Derby Derby) isolates in terms of antimicrobial susceptibility, relevant genetic mechanisms, and PFGE. Non-typhoidal Salmonella species that contaminate food products of animal origin are among the leading causes of human foodborne diseases globally [1, 2]. As fluoroquinolones and Salmonella enteric serotype Derby Derby) is one of the numerous non-typhoidal Salmonella serotypes and has been recognized as a food-borne pathogen. Derby is mainly associated with pig origin in many parts of the world [5]. Derby, which was frequently resistant to tetracycline
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