Are aquatic snails reservoirs and vectors of microbes bearing antibiotic resistant genes?

Abstract

The role of Stagnicola elodes, a freshwater snail, as a reservoir and vector for transporting antibiotic resistant genes (ARGs) was explored under laboratory conditions. We hypothesized that ARG-bearing microorganisms would become part of the snail gut microbiome allowing ARGs to be spread from their initial point of origin should snails be transported or the input of pharmaceuticals cease. We exposed snails in jars for 14 days wherein they grazed on biofilms that contained microbes resistant to the antibiotic sulfamethoxazole (SMX). Snails were then transferred to fresh media with no SMX for either a 7-day hibernation or depuration period. SMX-related ARGs were quantified in the 14-day treatment and 7-day depuration and hibernation systems. On day 14, treated jars had 6.6% of SMX resistant genes in the water phase, and the 7-day hibernation and depuration vessels had an average of 3.9% and 1.4%, respectively, relative to the total water-borne microbial community. Methods of extracting snail samples for SMX-related ARGs were unsuccessful. This was attributed to the snails’ having extensive mucus sugars that interfere with extraction. Our findings suggest that ARGs could be transferred to new environments from snails excreting gut flora in their feces, warranting further investigation.