Distribution, Antibiotic Resistance, and Virulence Factors of Vibrio parahaemolyticus in the Southern Coastal Waters of Republic of Korea

<b>Background/Objectives:</b><i>Vibrio parahaemolyticus</i> is a marine bacterium and a major cause of food poisoning worldwide, primarily associated with gastric illnesses such as gastroenteritis. This study aimed to investigate the distribution, antibiotic resistance, and virulence genes of <i>V. parahaemolyticus</i> present in shellfish and seawater of the southern coast of Korea, a major shellfish harvesting area. <b>Methods:</b> Shellfish and seawater samples were collected monthly in 2023 from 24 coastal sites in Korea. <i>V. parahaemolyticus</i> was isolated and identified using the MPN method, biochemical tests, MALDI-TOF mass spectrometry, and 16S rRNA sequencing. Antimicrobial susceptibility was tested for 673 isolates using the Sensititre MIC system, and virulence genes (<i>tdh</i> and <i>trh</i>) were detected by PCR. <b>Results:</b><i>V. parahaemolyticus</i> had a detection rate of 18.2-58.3% in shellfish and 8.3-50% in seawater samples. Among the isolates, 97.9% and 97.3% were resistant to ampicillin and colistin, respectively, while 8.3% showed resistance to four or more antibiotics. The virulence genes <i>tdh</i> and <i>trh</i> were detected in 0.45% and 3.34% of shellfish samples and 1.23% and 4.46% of seawater samples, respectively. <b>Conclusions:</b> These findings will help implement appropriate precautionary measures to prevent potential human health risks arising from exposure to multidrug-resistant or pathogenic <i>V. parahaemolyticus</i>.