Foodborne Pathogenic Vibrios: Antimicrobial Resistance

Foodborne illness caused by pathogenic Vibrios is generally associated with the consumption of raw or undercooked seafood. Fish and other seafood can be contaminated with Vibrio species, natural inhabitants of the marine, estuarine, and freshwater environment. Pathogenic Vibrios of major public health concerns are Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus. Common symptoms of foodborne Vibrio infection include watery diarrhea, stomach cramping, nausea, vomiting, fever, and chills. Administration of oral or intravenous rehydration salts solution is the mainstay for the management of cholera, and antibiotics are also used to shorten the duration of diarrhea and to limit further transmission of the disease. Currently, doxycycline, azithromycin, or ciprofloxacin are commonly used for V. cholerae, and doxycycline or quinolone are administered for V. parahaemolyticus, whereas doxycycline and a third-generation cephalosporin are recommended for V. vulnificus as initial treatment regimen. The emergence of antimicrobial resistance (AMR) in Vibrios is increasingly common across the globe and a decrease in the effectiveness of commonly available antibiotics poses a global threat to public health. Recent progress in comparative genomic studies suggests that the genomes of the drug-resistant Vibrios harbor mobile genetic elements like plasmids, integrating conjugative elements, superintegron, transposable elements, and insertion sequences, which are the major carriers of genetic determinants encoding antimicrobial resistance. These mobile genetic elements are highly dynamic and could potentially propagate to other bacteria through horizontal gene transfer (HGT). To combat the serious threat of rising AMR, it is crucial to develop strategies for robust surveillance, use of new/novel pharmaceuticals, and prevention of antibiotic misuse.

Presence, seasonal distribution and biomolecular characterization of Vibrio parahaemolyticus and Vibrio vulnificus in shellfish harvested and marketed in Sardinia (Italy) between 2017 and 2018

In the present study, we aimed to investigate the presence, seasonal distribution and biomolecular characterization of Vibrio parahaemolyticus and Vibrio vulnificus in samples of bivalve molluscs ( Mytilus galloprovincialis, Crassostrea gigas, Ruditapes decussatus, Venus verrucosa and Solen vagina ) and gastropod molluscs (Murex brandaris) harvested and marketed in Sardinia (Italy) between 2017 and 2018. A total of 444 samples were submitted to qualitative determination of Vibrio spp., V. parahaemolyticus and V. vulnificus. Identification and virulence profile of the isolated strains were performed by biomolecular methods. The overall prevalence of Vibrio spp. was 7%. The highest prevalence was pointed out in R. decussatus (8.3%). The prevalence of V. parahaemolyticus and V. vulnificus were 2.7% and 4.7% respectively. Higher levels of V. parahaemolyticus and V. vulnificus prevalence were highlighted in R. decussatus (4.2%) and C. gigas (6.2%) respectively. Potentially pathogenic V. parahaemolyticus strains were a minority ( n. 2 isolates tdh-/trh+ and n. 1 isolate tdh+/trh- ) and were recovered from M. galloprovincialis . None of the isolates was tdh+/ trh+. Pathogenic Vibrios infections are often underestimated and the reports of human infections in Europe are constantly increasing. European data on the true distribution of Vibrionaceae are scarce: the results of the present study highlight the need of constant monitoring plans to update the distribution of potentially pathogenic Vibrios.

Thiophenesulfonamides are specific inhibitors of quorum sensing in pathogenic Vibrios

Vibrio bacteria are pathogens of fish, shellfish, coral, and humans due to contaminated seafood consumption. Vibrio virulence factors are controlled by the cell-to-cell communication called quorum sensing, thus this signaling system is a promising target for therapeutic design. We screened a compound library and identified nine compounds, including several 2-thiophenesulfonamides, that inhibit the master quorum sensing transcription factor LuxR in Vibrio campbellii but do not affect cell growth. We synthesized a panel of 50 thiophenesulfonamide compounds to examine the structure-activity relationship effects on quorum sensing in vivo. The most potent molecule identified, PTSP (3-phenyl-1-(thiophen-2-ylsulfonyl)-1H-pyrazole), specifically inhibits LuxR homologs in multiple strains of Vibrio vulnificus, Vibrio parahaemolyticus, and V. campbellii with sub-micromolar concentrations. PTSP efficacy is driven by amino acid conservation in the binding pocket, which is accurately predicted using in silico modeling of inhibitors. Our results underscore the potential for developing thiophenesulfonamides as specific quorum sensing-directed treatments for Vibrio infections.

An Integrative, Multi-parametric Approach for the Comprehensive Assessment of Microbial Quality and Pollution in Aquaculture Systems

As the aquaculture sector significantly expanded worldwide in the past decades, the concept of sustainable aquaculture has developed with the challenge of not only maximizing benefits but also minimizing the negative impacts on the environment assuring, at the same time, food security. In this framework monitoring and improving the microbiological water quality and animal health is a central topic. In the present study, we evaluated the seawater microbiological quality in a mariculture system located in a Mediterranean coastal area (Northern Ionian Sea, Italy). We furnished, for the first time, a microbial inventory based on conventional culture-based methods, integrated with the 16S rRNA gene metabarcoding approach for vibrios identification and diversity analyses, and further implemented with microbial metabolic profiling data obtained from the Biolog EcoPlate system. Microbiological pollution indicators, vibrios diversity, and microbial metabolism were determined in two different times of the year (July and December). All microbial parameters measured in July were markedly increased compared to those measured in December. The presence of potentially pathogenic vibrios is discussed concerning the risk of fish disease and human infections. Thus, the microbial inventory here proposed might represent a new multi-parametric approach for the suitable surveillance of the microbial quality in a mariculture system. Consequently, it could be useful for ensuring the safety of both the reared species and the consumers in the light of sustainable, eco-friendly aquaculture management.

The Roseobacter-group bacterium Phaeobacter as safe probiotic solution for aquaculture

Phaeobacter inhibens has been assessed as a probiotic bacterium for application in aquaculture. Studies addressing the efficacy and safety indicate that P. inhibens maintains it antagonistic activity against pathogenic vibrios in aquaculture live cultures (live feed and fish egg/larvae), while having no or a positive effect on the host organisms, and a minor impact on the host microbiomes. While producing antibacterial and algicidal compounds, no study has so far found a virulent phenotype of P. inhibens cells against higher organisms. Additionally, an in silico search for antibiotic resistance genes using published genomes of representative strains did not raise concern regarding the risk for antimicrobial resistance. P. inhibens occurs naturally in aquaculture systems supporting its safe usage in this environment. Concluding, at the current state of knowledge, P. inhibens is a “safe-to-use” organism.