GUT BACTERIAL COMMUNITIES AND ANTIBIOTIC SUSCEPTIBILITY OF THE LONGTAIL BUTTERFLY RAY (GYMNURA POECILURA) FROM BAY OF BENGAL, BANGLADESH

Abstract

Marine elasmobranchs' gut microbiota remains poorly characterized, despite its vital role in host health and ecosystem function, particularly for the longtail butterfly ray, Gymnura poecilura, a benthic predator in the Bay of Bengal. This study aimed to identify gut bacteria from a specimen collected at Cox's Bazar, Bangladesh and to profile their antibiotic susceptibilityGut contents were cultured using serial dilution, and isolates were identified via biochemical assays (VITEK® 2 System). Antibiotic susceptibility was evaluated using the Kirby-Bauer disc diffusion method, interpreted through Clinical and Laboratory Standards Institute (CLSI) guidelines as a reference framework. Two dominant Gram-negative bacteria were isolated: Vibrio fluvialis (an opportunistic pathogen) and Sphingomonas paucimobilis (a commensal). V. fluvialis showed intermediate resistance to ciprofloxacin (23 mm) and susceptibility to ceftriaxone (26 mm) and chloramphenicol (28 mm), while S. paucimobilis was susceptibile to all five antibiotics tested. Fungal contamination in the 10⁻¹ dilution highlighted the need for stricter aseptic protocols. As these findings are based on a single specimen, they represent preliminary, baseline data rather than a generalizable resistance profile for the species; nonetheless, the intermediate ciprofloxacin resistance observed in V. fluvialis signals a potential antimicrobial resistance (AMR) in coastal ecosystems may reflect the species' benthic feeding behavior and interaction with coastal sediments influenced by anthropogenic activities.This study provides the first baseline data on the gut microbiota of G. poecilura, underscores the potential of benthic elasmobranchs as indicators of coastal environmental quality and underscores the need for expanded molecular monitoring to understand antimicrobial resistance dynamics in marine food webs.