Development of novel aptamer-based enzyme-linked apta-sorbent assay (ELASA) for rapid detection of mariculture pathogen Vibrio alginolyticus

Deletion of ArmPT, a LamB-like protein, increases cell membrane permeability and antibiotic sensitivity in Vibrio alginolyticus

Vibrio bacterial species are dominant pathogens in mariculture animals. However, the extensive use of antibiotics and other chemicals has increased drug resistance in Vibrio bacteria. Despite rigorous investigative studies, the mechanism of drug resistance in Vibrio remains a mystery. In this study, we found that a gene encoding LamB-like outer membrane protein, named ArmPT, was upregulated in Va under antibiotic stress by RT-qPCR. We speculated that ArmPT might play a role in Va's drug resistance. Subsequently, using ArmPT gene knockout and gene complementation experiments, we confirmed its role in resistance against a variety of antibiotics, particularly kanamycin (KA). Transcriptomic and proteomic analyses identified 188 and 83 differentially expressed genes in the mutant strain compared with the wild-type (WT) before and after KA stress, respectively. Bioinformatic analysis predicted that ArmPT might control cell membrane permeability by changing cadaverine biosynthesis, thereby influencing the cell entry of antibiotics in Va. The higher levels of intracellular reactive oxygen species and the infused content of KA showed that antibiotics are more likely to enter the Va mutant strain. These results uncover the drug resistance mechanism of Va that can also exist in other similar pathogenic bacteria.

Antibiotic resistance, virulence and genetic characteristics of Vibrio alginolyticus isolates from aquatic environment in costal mariculture areas in China

Vibrio alginolyticus has been the second most common Vibrio species in the world and mainly grows in the ocean or estuary environment, which can induce epidemics outbreaks under marine organisms, and causing serious economic losses in aquaculture industry. In this study, the genetic populations and evolutionary relationship analysis of V. alginolyticus isolated from different geographical locations in China with typical interannual differences were exhibited originally genetic diversity. Then the virulence genes prevalence, antibiotic resistance phenotype, and antimicrobial resistance genes risk diversity of V. alginolyticus were analyzed by phenotypic and molecular typing methods. And they were complex correlations among antibiotic phenotypes, resistance and virulence genes under different genotype of V. alginolyticus. The results provide a theoretical foundation for further understanding the genetic and metabolic diversity among V. alginolyticus in China, and lay a theoretical foundation for the transmission risk assessment and regional diagnosis of Vibrio in aquatic animals.

Effect of Food Matrix Type on Growth Characteristics of and Hemolysin Production by Vibrio alginolyticus

ABSTRACT

The growth of and hemolysin production by two V. alginolyticus strains (HY9901 and ATCC 17749T) at 30°C were investigated in briny tilapia, shrimp, scallop, oyster, pork, chicken, freshwater fish, and egg fried rice. Bacteria were enumerated by plate counting. Hemolysin production was evaluated with blood agar and hemolytic titer tests. The two V. alginolyticus strains had similar growth and hemolysin production patterns in all tested foods. Based on the goodness-of-fit primary model statistics (coefficient of determination, mean square error, bias factor, and accuracy factor), the modified Gompertz model was a better fit than the logistic model to V. alginolyticus growth in foods. Growth kinetic parameters of V. alginolyticus had a higher μmax and shorter λ in the following order: briny tilapia > shrimp > freshwater fish > egg fried rice > scallop > oyster > chicken > pork. V. alginolyticus levels were similar at the stationary phase, with no significant growth difference between raw and cooked foods. Significantly higher thermostable direct hemolysin activity (P < 0.05) was found for V. alginolyticus in the following order: briny tilapia > freshwater fish > shrimp > chicken > egg fried rice > scallop > oyster > pork. However, the hemolytic titer was not consistent with the thermostable direct hemolysin activity and was significantly higher (P < 0.05) in the following order: briny tilapia > egg fried rice > shrimp > freshwater fish > chicken > scallop > oyster > pork. Contrary to current belief, V. alginolyticus produced more hemolysin in some nonseafoods (freshwater fish, egg fried rice, and chicken) than in scallops or oysters. This report is the first on the growth and toxicity of V. alginolyticus in different food matrices and confirms that some nonseafoods can be contaminated with pathogenic V. alginolyticus. These results should increase awareness of nonseafood safety issues and improve the accuracy of V. alginolyticus risk assessments.

HIGHLIGHTS

Application of MALDI-TOF MS Profiling Coupled With Functionalized Magnetic Enrichment for Rapid Identification of Pathogens in a Patient With Open Fracture

Posttraumatic infections can occur in orthopedic trauma patients, especially in open fractures. Rapid and accurate identification of pathogens in orthopedic trauma is important for clinical diagnosis and antimicrobial treatment. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been successfully used for first-line identification of pathogens grown on culture plates. However, for direct analysis of liquid clinical specimens, pre-purification of the sample is necessary. Herein, we investigated the feasibility of coupling Fc-MBL@Fe₃O₄ enrichment with MALDI-TOF MS profiling in the identification of pathogens in liquid-cultured samples. This method is successfully used for the identification of pathogens in a patient with an open-leg fracture obtained at sea. Pathogens were enriched by Fc-MBL@Fe₃O₄ from briefly pre-cultured liquid media and identified by MALDI-TOF MS. We identified an opportunistic pathogen, Vibrio alginolyticus, which is uncommon in clinical orthopedic trauma infection but exists widely in the sea. Therefore, combining Fc-MBL@Fe₃O₄ enrichment and MALDI-TOF MS profiling has great potential for direct identification of microbes in clinical samples.