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Articles by B.C.J. De Silva
Total Records ( 2 ) for B.C.J. De Silva
  B.C.J. De Silva , S.H.M.P. Wimalasena , Sabrina Hossain , H.N.K.S. Pathirana and Gang-Joon Heo
  Background and Objective: Infections of antibiotic-resistant bacteria in both human and animals own a great significance. The current study aimed to determine the quinolone susceptibility and the genetic characteristics of quinolone resistance of 20 strains of Pseudomonas aeruginosa isolated from pet Chinese stripe-necked turtles (Ocadia sinensis ). Methodology: Susceptibility of four antimicrobials including nalidixic acid, ciprofloxacin, ofloxacin and levofloxacin was examined. The PCR was carried out to amplify Quinolone Resistance Determining Region (QRDR) and to screen Plasmid Mediated Quinolone Resistance (PMQR) genes. Results: All tested isolates were resistant to nalidixic acid (100%), but none of the isolates show complete resistance to other tested antimicrobials. Two isolates showed intermediate resistance to ciprofloxacin (5%) and ofloxacin (5%), one each in Minimum Inhibitory Concentration (MIC) test. The qnrB gene was identified in one isolate (5%) and qnrS in three isolates (15%). The PCR assay could amplify aac(6’)-Ib gene from 8 isolates (40%) and none of them harbored aac(6’)-Ib-cr variant. Sequences obtained by amplifying gyrA and parC regions did not show any point mutation in QRDR. Neighbor-joining phylogenetic tree for gyrA indicated three distinct clads comprising first, current study isolates, second, clinical isolates of human and dogs and third, isolates from soil and water. Conclusion: All results suggest that studied strains of P. aeruginosa are less resistant to quinolones and are genetically more conserved with regards to gyrA gene region.
  Sabrina Hossain , B.C.J. De Silva , S.H.M.P. Wimalasena , H.N.K.S. Pathirana and Gang-Joon Heo
  Background and Objective: Citrobacter freundii is a normal bacterial flora in pet turtles, which could opportunistically become pathogenic. Their possession of quinolone resistance genes owns significance both in humans and animals. Therefore, the aim of the study was to determine the quinolone resistance genes in C. freundii isolated from seven species of pet turtles. Methodology: Antimicrobial susceptibility was determined by disk diffusion test and minimum inhibitory concentration (MIC) values against quinolones. Transferrable quinolone resistance determinants such as plasmid-mediated quinolone resistance (PMQR) genes were identified by PCR. Nucleotide sequencing was performed to detect aac(6')-Ib-cr variant and point mutations in quinolone resistance determining region (QRDR) of gyrA gene. Results: Twenty-nine C. freundii isolates were obtained from 41 fecal samples of pet turtles. All the isolates were resistant against nalidixic acid in disk diffusion test. Each isolate from river cooter turtles showed a high quinolone resistance compared to others in disk diffusion test and MIC values. Four isolates from Chinese stripe-necked turtles showed reduced susceptibility to ciprofloxacin in MIC. With regards to PMQR determinants, the qnrB was the most prevalent gene (51.17%) among all isolates. The qnrS gene was present in seven C. freundii isolates (24.14%). The aac(6')-Ib-cr gene was detected only in four isolates (13.79%). A single amino acid substitution (Thr83-Ile) was observed in the gyrA gene of 8 (27.59%) isolates. Conclusion: The current study revealed that most of the C. freundii strains isolated from pet turtles are resistant to quinolones and harbored PMQR genes and QRDR mutations.
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