Acquiring Multi-Drug Resistance in Aquatic Environments: The Role of Chitin in Conjugation Frequencies of the IncA/C Plasmid between Aeromonas salmonicida subs. salmonicida AS03 and Vibrio cholerae MQ1795 (Bangladeshi isolate)

Bacterial species have the unique ability to exchange genetic information necessary for environmental fitness; of great concern is the exchange of genes encoding resistance to antimicrobials and antibiotics. Incompatibility group A/C (IncA/C) of transferable multi-drug resistance (MDR) plasmids confer high-level resistance to numerous antibiotics and have been isolated in pathogenic and commensal bacterial in terrestrial and aquatic habitats (Welch et al. 2007). The plasmid’s wide host range enables it to transfer to other potentially efficient donor strains. Vibrio species found in many of the same aquatic environments as AS03 could provide a plasmid shuttling service to more deadly pathogens imposing a risk to ecological resistrome profiles and public health. Evidence suggests surface attachment of Vibrio cholerae to chitinous surfaces increases the conjugation frequency with strains containing conjugative MDR IncA/C plasmids (Thomas et al. manuscript in preparation). Conjugation experiments were carried out between AS03 and Vibrio cholerae MQ1795 (Bangladeshi isolate), C6707, O395, and O395-N1 in the presence and absence of chitin beads. Transfer frequencies of the plasmid to the Vibrio strains were significantly higher given the added protection of chitin in simulated microenvironments. This study provides alarming evidence that enteric strains such as MQ1795 have the ability to provide reservoirs for resistance genes and possibly transfer said genes to potentially more dangerous human pathogens