Occurrence, virulence factors, and antimicrobial susceptibility patterns ofVibriospp. isolated from live oyster (Crassostrea gigas) in Korea

Seasonal variation, virulence gene and antibiotic resistance of Vibrio in a semi-enclosed bay with mariculture (Dongshan Bay, Southern China)

In this study, the virulence genes, antibiotic resistance of culturable Vibrio and the environmental factors affecting Vibrio abundance were analyzed in four seasons in DongShan Bay with different intensity of aquaculture practice. A total of 253 bacteria isolates were obtained, of which 177 Vibrio strains belonged to 26 species. Annual Vibrio abundance in this region ranged from 20 to 11,600 CFU mL^-1 and the most significant positive correlation occurred with temperature. Detection of 9 different Vibrio virulence genes revealed that most isolates contained atypical virulence genes in addition to the typical ones. In particular, virulence genes of hemolysin such as tdh, trh, and hlyA (6.32 %, 15.52 %, and 11.30 %) showed different degrees of horizontal gene transfer (HGT). In our antibiotic resistance test, the multiple antibiotic resistance (MAR) index of the isolates ranged from 0.01 to 0.03 in different seasons, and three MAR Vibrio strains were detected. Overall, our study sheds new light on the spatial distribution patterns and the occurrence of virulence genes and antibiotics resistance Vibrio isolated from a subtropical bay with intensive aquaculture. Our study provides a suitable microbial quality surveillance in a mariculture impacted coastal environment. It will help to establish effective disease prevention measures in this area and provide useful guidance and support for formulating local antibiotics use policies.

Comparison of different cultures and culturing conditions for the biological deterioration of organic load from real saline bilge wastewater: microbial diversity insights and ecotoxicity assessment

Bilge wastewater is a high strength, typically saline wastewater, originating from operation of ships. In this study, the treatment of real bilge wastewater was tested using pure isolated aerobic strains and mixed cultures (aerobic and anaerobic). The Chemical Oxygen Demand (COD) and ecotoxicity decrease were monitored over time, while the microbial dynamics alterations in mixed cultures were also recorded. The isolated strains Pseudodonghicola xiamenensis, Halomonas alkaliphila and Vibrio antiquaries were shown to significantly biodegrade bilge wastewater. Reasonable COD removal rates were achieved by aerobic mixed cultures (59%, 9 days), while anaerobic mixed cultures showed lower performance (34%, 51 days). The genus Pseudodonghicola was identified as dominant under aerobic conditions both in the mixed cultures and in the control sample (raw wastewater), after exposure to bilge wastewater, demonstrating natural proliferation of the genus and potential contribution to COD reduction. Biodegradation rates were higher when initial organic load was high, while the toxicity of raw wastewater partially decreased after treatment.

Vibrios from the Norwegian marine environment: Characterization of associated antibiotic resistance and virulence genes

A total of 116 Vibrio isolates comprising V. alginolyticus (n = 53), V. metschnikovii (n = 38), V. anguillarum (n = 21), V. antiquarius (n = 2), and V. fujianensis (n = 2) were obtained from seawater, fish, or bivalve molluscs from temperate Oceanic and Polar Oceanic area around Norway. Antibiotic sensitivity testing revealed resistance or reduced susceptibility to ampicillin (74%), oxolinic acid (33%), imipenem (21%), aztreonam (19%), and tobramycin (17%). Whole-genome sequence analysis of eighteen drug-resistant isolates revealed the presence of genes like β-lactamases, chloramphenicol-acetyltransferases, and genes conferring tetracycline and quinolone resistance. The strains also carried virulence genes like hlyA, tlh, rtxA to D and aceA, E and F. The genes for cholerae toxin (ctx), thermostable direct hemolysin (tdh), or zonula occludens toxin (zot) were not detected in any of the isolates. The present study shows low prevalence of multidrug resistance and absence of virulence genes of high global concern among environmental vibrios in Norway. However, in the light of climate change, and projected rising sea surface temperatures, even in the cold temperate areas, there is a need for frequent monitoring of resistance and virulence in vibrios to be prepared for future public health challenges.

Manila clam (Ruditapes philippinarum) marketed in Korea as a source of vibrios harbouring virulence and β-lactam resistance genes

The present study assessed the occurrence, virulence determinants and antimicrobial susceptibility patterns of Vibrio spp. isolated from live Manila clam (Ruditapes philippinarum). A total of 31 Vibrio spp. including 27 V. diabolicus, two V. fluvialis, one V. alginolyticus and one V. antiquarius were isolated and identified. Phenotypic detection of DNase, lipase, phospholipase, amylase and caseinase activities was 100%; and 87% gelatinase, 45% slime production and 6% haemolysin activities were also observed. The prevalence of toxin-related virulence genes for collagenase (94%), toxR (100%), tlh (68%), and VPI (71%) was detected by PCR. Additionally, two V. fluvialis isolates carried F-toxR and hupo genes. Moreover, 61% of the isolates showed multiple antimicrobial resistance indices >0·2. The resistance rates of ampicillin, piperacillin, colistin sulfate, rifampicin, and cephalothin were 100, 81, 71, 77 and 68% respectively. The prevalence of blaCTX-M (87%), blaTEM (55%) and Int1 (90%) genes was observed, whereas blaSHV, strA-strB, tetA, tetB, and aadA2 gene cassette were reported in varying combinations. However, armA, aac(3)-IIa and quinolone resistance genes (qnrA, qnrB, qnrS) were not amplified. Thus, the virulence along with extended-spectrum β-lactamases (ESBLs) and other antimicrobial resistance genes in multidrug-resistant Manila clam-borne vibrios may pose a public health threat for consumers. SIGNIFICANCE AND IMPACT OF THE STUDY: In Korea, eating raw seafood is considered a great delicacy. This has negatively affected the public by increasing health issues over the years due to the ingestion of vibrios. For the first time, we could identify Vibrio diabolicus and Vibrio antiquarius in marketed Manila clams in Korea. The prevalent Vibrio diabolicus isolates demonstrated the Vibrio parahaemolyticus and Vibrio cholerae homologous virulence genes (toxR, tlh, and VPI). Additionally, the abundance of extended-spectrum β-lactamases (ESBLs) and integron (IntI1) harboured by Manila clam-borne vibrios elucidate the potential health risk for consumers and may complicate health treatments in the case of infection.

Prevalence of virulence and extended-spectrum β-lactamase (ESBL) genes harbouring Vibrio spp. isolated from cockles (Tegillarca granosa) marketed in Korea

The present study aimed to investigate the incidence, virulence and antibiotic properties in Vibrio spp. isolated from cockles (Tegillarca granosa) marketed in Korea. A total of 32 Vibrio spp. isolates including V. parahaemolyticus (n = 4), V. alginolyticus (n = 11), V. diabolicus (n = 14) and V. harveyi (n = 3) were detected using gyrB sequencing. The phenotypic pathogenicity revealed that the DNase, amylase and phospholipase activities were 100%, while lipase, slime production, gelatinase and caseinase were detected in 72, 88, 88 and 81% of the isolates respectively. The PCR amplification for the detection of V. parahaemolyticus species-specific tdh, tlh, trh and toxR genes were positive in 4 (13%), 16 (50%), 0 (0%) and 4 (13%) isolates respectively. The V. alginolytuicus species-specific tdh, tlh, trh, toxR and vac genes were carried by 15 (47%), 29 (91%), 0 (0%), 15 (47%) and 25 (78%) of the isolates respectively. In addition, multidrug resistance was observed by 27 (84%) isolates, whereas higher resistant rates were observed against ampicillin, piperacillin, streptomycin and cephalothin. The occurrence of bla_CTX (78%), bla_TEM (40%), bla_SHV (22%) and aac(6')-Ib (94%) were prevalent, while strAB, tetB, aphAI-IAB, intl1 and aadA1 gene cassettes were also detected. The results signify the potential health risks resulting from the consumption of raw cockles in Korea. SIGNIFICANCE AND IMPACT OF THE STUDY: Vibrios are well known to cause human infections following consumption of raw or undercooked seafood. This phenomenon has undoubtedly increased the number of health issues over the past few years in Korea. Among the identified Vibrio spp., we could detect V. diabolicus and V. harveyi for the first time in marketed cockles in Korea. The presence of species-specific genes (tdh-VA, tlh-VP, tlh-VA and toxR-VA) in V. diabolicus exhibits the close genetic affinity among V. parahaemolyticus and V. alginolyticus. Furthermore, the prevalence of extended-spectrum β-lactamases (ESBLs) and other antibiotic resistance genes along with multidrug resistance signifies the potential threat for consumers.