Multilocus Sequence Typing and Virulence Potential of Vibrio parahaemolyticus Strains Isolated from Aquatic Bird Feces

Migratory Shorebird Gut Microbes are not Associated with Bivalve Prey in Monsoon Tropical Australia

Migratory animals can carry symbionts over long distances. While well-studied for parasite and pathogen transmission, less is known about use of this route by other symbiotic taxa, particularly those non-pathogenic. Here we ask the question of whether gut bacteria can be spread between continents by long-distance bird migration, although gut microbiomes in birds may not be as stable or persistent as those of non-volant animals. We used amplicon sequencing of both bacterial 16S rRNA gene and Vibrio-centric hsp60 gene to determine whether the faecal bacteria of migratory great knots (Calidris tenuirostris) also occur in their main food source in Northern Australia or in nearby sand, comparing samples before and after the birds' long-distance migration. Our data suggest that there is little connectivity among the bacterial microbiomes, except in the bivalve prey. Our results are consistent with previous studies finding that bird faecal microbiomes were not host-specific and contrast with those showing an influence of diet on bird faecal bacteria. We also found little connectivity among Vibrio spp. However, although faecal sample sizes were small, the dominance of different individual Vibrio spp. suggests that they may have been well-established in knot guts and thus capable of moving with them on migration. We suggest that the physiological impacts of a long-distance migration may have caused shifts in the phyla comprising great knot faecal communities.

Advance typing of Vibrio parahaemolyticus through the mtlA and aer gene: A high-resolution, cost-effective approach

Vibrio parahaemolyticus is a significant cause of foodborne illness, and its incidence worldwide is on the rise. It is thus imperative to develop a straightforward and efficient method for typing strains of this pathogen. In this study, we conducted a pangenome analysis of 75 complete genomes of V. parahaemolyticus and identified the core gene mtlA with the highest degree of variation, which distinguished 44 strains and outperformed traditional seven-gene-based MLST when combined with aer, another core gene with high degree of variation. The mtlA gene had higher resolution to type strains with a close relationship compared to the traditional MLST genes in the phylogenetic tree built by core genomes. Strong positive selection was also detected in the gene mtlA (ω > 1), representing adaptive and evolution in response to the environment. Therefore, the panel of gene mtlA and aer may serve as a tool for the typing of V. parahaemolyticus, potentially contributing to the prevention and control of this foodborne disease.

Vibrio parahaemolyticus from Migratory Birds in China Carries an Extra Copy of tRNA-Gly and Plasmid-Mediated Quinolone Resistance Gene qnrD

Vibrio parahaemolyticus is a marine bacterium coming from estuarine environments, where the migratory birds can easily be colonized by V. parahaemolyticus. Migratory birds may be important reservoirs of V. parahaemolyticus by growth and re-entry into the environment. To further explore the spreading mechanism of V. parahaemolyticus among marine life, human beings, and migratory birds, we aimed to investigate the characteristics of the genetic diversity, antimicrobial resistance, virulence genes, and a potentially informative gene marker of V. parahaemolyticus isolated from migratory birds in China. This study recovered 124 (14.55%) V. parahaemolyticus isolates from 852 fecal and environmental (water) samples. All of the 124 strains were classified into 85 known sequence types (STs), of which ST-2738 was most frequently identified. Analysis of the population structure using whole-genome variation of the 124 isolates illustrated that they grouped into 27 different clonal groups (CGs) belonging to the previously defined geographical populations VppX and VppAsia. Even though these genomes have high diversity, an extra copy of tRNA-Gly was presented in all migratory bird-carried V. parahaemolyticus isolates, which could be used as a potentially informative marker of the V. parahaemolyticus strains derived from birds. Antibiotic sensitivity experiments revealed that 47 (37.10%) isolates were resistant to ampicillin. Five isolates harbored the plasmid-mediated quinolone resistance (PMQR) gene qnrD, which has not previously been identified in this species. The investigation of antibiotic resistance provides the basic knowledge to further evaluate the risk of enrichment and reintroduction of pathogenic V. parahaemolyticus strains in migratory birds. IMPORTANCE The presence of V. parahaemolyticus in migratory birds' fecal samples implies that the human pathogenic V. parahaemolyticus strains may also potentially infect birds and thus pose a risk for zoonotic infection and food safety associated with re-entry into the environment. Our study firstly highlights the extra copy of tRNA as a potentially informative marker for identifying the bird-carried V. parahaemolyticus strains. Also, we firstly identify the plasmid-mediated quinolone resistance (PMQR) gene qnrD in V. parahaemolyticus. To further evaluate the risk of enrichment and reintroduction of pathogenic strains carried by migratory birds, we suggest conducting estuarine environmental surveillance to monitor the antibiotic resistance and virulence factors of bird-carried V. parahaemolyticus isolates.