Genetic characterization ofVibrio vulnificusstrains isolated from oyster samples in Mexico

Abstract

Vibrio vulnificus strains were isolated from oysters that were collected at the main seafood market in Mexico City. Strains were characterized with regard to vvhA, vcg genotype, PFGE, multilocus sequence typing (MLST), and rtxA1. Analyses included a comparison with rtxA1 reference sequences. Environmental (vcgE) and clinical (vcgC) genotypes were isolated at nearly equal percentages. PFGE had high heterogeneity, but the strains clustered by vcgE or vcgC genotype. Select housekeeping genes for MLST and primers that were designed for rtxA1 domains divided the strains into two clusters according to the E or C genotype. Reference rtxA1 sequences and those from this study were also clustered according to genotype. These results confirm that this genetic dimorphism is not limited to vcg genotyping, as other studies have reported. Some environmental C genotype strains had high similarity to reference strains, which have been reported to be virulent, indicating a potential risk for oyster consumers in Mexico City.

Occurrence of Virulence Genes Associated with Human Pathogenic Vibrios Isolated from Two Commercial Dusky Kob (Argyrosmus japonicus) Farms and Kareiga Estuary in the Eastern Cape Province, South Africa

“…This result is similar to that of a study recording a significantly higher percent of the E-genotype of V. vulnificus isolates recovered from oysters [ 56 ]. Although such a result is expected from environmental samples, it is, however, contrary to a report where nearly an equal percent of vcgE (47%) and vcgC (53%) were detected from oyster isolates [ 57 ] and water areas surrounding oyster harvest [ 56 ]. Continuous monitoring of seafood and fish products remains a necessity as infection with V. vulnificus , although rare, is usually fatal, particularly in immunocompromised persons.…”

Whole-genome comparison between reference sequences and oyster Vibrio vulnificus C-genotype strains

“…vulnificus strains does not necessarily correspond to their clinical or environmental isolation. Guerrero et al [8], have reported close homology between environmental isolates of C-genotype strains by PFGE, MLST, and rtxA1 analysis, in which V . vulnificus C-genotype strains from oysters clustered with C-type rtxA1 V .…”

“…We have compared the whole-genome sequences of 2 V . vulnificus strains from oyster samples that have been studied by Guerrero et al [8]—CICESE-316 and CICESE-325 (MLST lineage I, C-genotype, rtxA1 -C type)—with 2 reference genomes of the V . vulnificus strains CMCP6 and YJ016 (MLST lineage I, C-genotype, rtxA1 -C type), which have been reported to be acute human pathogens (Genbank Accession Numbers AE016795.3, AE016796.2, and BA000037.2, BA000038.2, respectively) and examined by several groups [22, 23, 26–28].…”

“…vulnificus have focused on C-genotype strains from clinical samples, resulting in a lack of studies on C-genotype strains from environmental sources. Using the MLST and rtxA1 approaches, Guerrero et al [8], noted high genetic similarity between C-genotype strains from clinical cases and environmental samples and sharp differences with E-genotype strains.…”

“…vulnificus strains have not been established, whole-genome analysis could increase our understanding of the differences between clinical and environmental isolates within the same genotype. This study compared high-virulence C-genotype reference sequences with C-genotype strains isolated from oysters studied by Guerrero et al [8], to confirm the absence or presence of specific pathogenic genes, in C-genotype strains from environmental sources.…”