Molecular identification and antibiotic resistance patterns of diverse bacteria associated with shrimp PL nurseries of Bangladesh: suspecting Acinetobacter venetianus as future threat

Shrimp aquaculture has been accomplished with breeding and nursing of shrimp in an artificial environment to fulfill the increasing demand of shrimp consumption worldwide. However, the microbial diseases appear as a serious problem in this industry. The study was designed to identify the diverse bacteria from shrimp PL (post-larvae) nurseries and to profile antibiotic resistance patterns. The rearing water (raw seawater, treated and outlet water) and shrimp PL were collected from eight nurseries of south-west Bangladesh. Using selective agar plates, thirty representative isolates were selected for 16S rRNA gene sequencing, antibiotic susceptibility test and MAR index calculation. Representative isolates were identified as Aeromonas caviae, Pseudomonas monteilii, Shewanella algae, Vibrio alginolyticus, V. brasiliensis, V. natriegens, V. parahaemolyticus, V. shilonii, V. xuii, Zobellella denitrificans which are Gram-negative, and Bacillus licheniformis and B. pumilus which are Gram-positive. Notably, six strains identified as Acinetobacter venetianus might be a concern of risk for shrimp industry. The antibiotic resistance pattern reveals that the strain YWO8-97 (identified as P. monteilii) was resistant to all twelve antibiotics. Ceftazidime was the most powerful antibiotic since most of the studied strains were sensitive against it. The six strains of A. venetianus showed multiple antibiotic resistance patterns. MAR index were ranged from 0.08 to 1.0, and values of 26 isolates were more than 0.2 which means prior high exposure to the antibiotics. From the present study, it can be concluded that shrimp PL nurseries in southern part of Bangladesh are getting contaminated with antibiotic resistant pathogenic bacteria.