New insights into the resistome-mobilome-biofilm relationship in Vibrio parahaemolyticus.

Vibrio parahaemolyticus is a major foodborne pathogen frequently isolated from seafood, notable for its biofilm-forming capacity, which enhances its persistence in environments and increases resistance to disinfection. This study investigated the virulome, the associations between the resistome and mobilome of V. parahaemolyticus and its biofilm forming ability to better understand the genomic determinants of persistence. Among 845 isolates from imported seafood (mainly shrimp), 20.6% showed acquired resistance to at least one clinically important antibiotic class, most commonly tetracycline, sulfamethoxazole-trimethoprim, and streptomycin. Thirty-nine representative strains (resistant and susceptible) were selected for confocal laser scanning microscopy (CLSM) observation of biofilms and whole-genome sequencing (WGS). CLSM combined with image analysis revealed significant variability in biofilm formation, with no relation with specific phylogenetic lineage. Hybrid WGS (short and long reads) identified 49 distinct antimicrobial resistance genes (ARGs) and 44 highly conserved virulence genes. ARGs were found on both chromosomes and plasmids and were strongly associated with mobile genetic elements (MGEs). dfrA8 and blaCARB-3 and several novel ARG-MGE associations were detected by genomic analysis in V. parahaemolyticus genome, including blaCARB-3-IS6 or dfrA8-IS6. Interestingly, several resistome-mobilome associations, notably dfrA23, blaCTX-M-15-IS6, and floR-IS91, were significantly correlated with variations in biofilm height, roughness, substrate coverage, and volume. Moreover, a particularly strong association was observed for tet(A), whose presence was closely linked to reduced biofilm roughness. However, no association was found between phenotypic antibiotic resistance and biofilm formation metrics, except for a significant link between quinolone resistance and increased biofilm height. These findings provide new insights into the genomic factors underlying biofilm-associated persistence in V. parahaemolyticus.