Abstract
High consumer demand for shellfish has led to the need for large-scale, reliable shellfish supply through aquaculture or shellfish farming. However, bacterial infections which can spread rapidly among shellfish poses a major threat to this industry. Shellfish farmers therefore often resort to extensive use of antibiotics, both prophylactically and therapeutically, in order to protect their stocks. The extensive use of antibiotics in aquaculture has been postulated to represent a major contributing factor in the rising incidence of antimicrobial resistant pathogenic bacteria in shellfish. This study aimed to investigate the incidence of pathogenic Vibrio parahaemolyticus and determine the antibiotic resistance profile as well as to perform plasmid curing in order to determine the antibiotic resistance mediation. Based on colony morphology, all 450 samples tested were positive for Vibrio sp; however, tox-R assay showed that only 44.4% (200/450) of these were V. parahaemolyticus. Out of these 200 samples, 6.5% (13/200) were trh-positive while none were tdh-positive. Antibiotic resistance was determined for all V. parahaemolyticus identified against 14 commonly used antibiotics and the multiple antibiotic resistance index (MAR) was calculated. The isolates demonstrated high resistance to several antibiotics tested- including second and third-line antibiotics- with 88% resistant to ampicillin, 81% to amikacin,70.5% to kanamycin, 73% to cefotaxime, and 51.5% to ceftazidime. The MAR index ranged from 0.00 to 0.79 with the majority of samples having an index of 0.36 (resistant to five antibiotics). Among the 13 trh-positive strains, almost 70% (9/13) demonstrated resistance to 4 or more antibiotics. Plasmid profiling for all V. parahaemolyticus isolates revealed that 86.5% (173/200) contained plasmids - ranging from 1 to 7 plasmids with DNA band sizes ranging from 1.2 kb to greater than 10 kb. 6/13 of the pathogenic V. pathogenic strains contained plasmid. After plasmid curing, the plasmid containing pathogenic strains isolated in our study have chromosomally mediated ampicillin resistance while the remaining resistance phenotypes are plasmid mediated. Overall, our results indicate that while the incidence of pathogenic V. parahaemolyticus in shellfish in Selangor still appears to be at relatively reassuring levels, antibiotic resistance is a real concern and warrants ongoing surveillance.
Highlights
Vibrio parahaemolyticus is a Gram-negative bacterium that is widely disseminated in marine and estuarine environments worldwide (Su and Liu, 2007; Ceccarelli et al, 2013; Zhang and Orth, 2013; Letchumanan et al, 2014; Velazquez-Roman et al, 2014; Wu et al, 2014)
To further confirm their identity, PCR was performed on all the presumptive V. parahaemolyticus isolates in order to confirm their identity by targeting species level toxin operon gene, 368bp
The presence of pathogenic strains of V. parahaemolyticus in the shellfish we studied does raise concern as these organisms are known to be a frequent cause of food-borne gastroenteritis in humans
Summary
Vibrio parahaemolyticus is a Gram-negative bacterium that is widely disseminated in marine and estuarine environments worldwide (Su and Liu, 2007; Ceccarelli et al, 2013; Zhang and Orth, 2013; Letchumanan et al, 2014; Velazquez-Roman et al, 2014; Wu et al, 2014). Around 0–6% of the environmental V. parahaemolyticus strains carry tdh and/or trh genes (DePaola et al, 2000; Vuddhakul et al, 2000; Wong et al, 2000; Alam et al, 2002; Hervio-Heath et al, 2002; Haley et al, 2014). These two genes are considered major virulence factors of V. parahaemolyticus (Kaysner and DePaola, 2001; Zhang and Austin, 2005; Xu et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
