Scallop larvae hatcheries as source of bacteria carrying genes encoding for non-enzymatic phenicol resistance

The main aim of the study was to evaluate the role of scallop hatcheries as source of the floR and cmlA genes. A number of 133 and 121 florfenicol-resistant strains were isolated from scallop larval cultures prior to their transfer to seawater and from effluent samples from 2 commercial hatcheries and identified by 16S rRNA gene sequence analysis, observing a predominance of the Pseudomonas, Pseudoalteromonas and Halomonas genera and exhibiting an important incidence of co-resistance to streptomycin, oxytetracycline and co-trimoxazole. A high percentage of strains from both hatcheries carried the floR gene (68.4% and 89.3% of strains), whereas a lower carriage of the cmlA gene was detected (27.1% and 54.5% of strains). The high prevalence of floR-carrying bacteria in reared scallop larvae and hatchery effluents contributes to enrich the marine resistome in marine environments, prompting the need of a continuous surveillance of these genes in the mariculture environments.