A long-term observation for ecology of pathogenic Yersinia in wild rodents living in Fukushima Prefecture, Japan.

From 2012 to 2021, prevalence of pathogenic Yersinia in wild rodents captured in Fukushima Prefecture, Japan was investigated twice a year to clarify the ecology of this pathogen in wild rodent populations. Pathogenic Yersinia enterocolitica O8 was isolated from 13 (1.7%) of 755 wild rodents. The Y. enterocolitica O8 isolates harbored three virulent genes (ail, fyuA, and virF). This pathogen was isolated repeatedly from wild rodents in April 2015, 2016, and 2017, in June and November 2020, and in April 2021, which was 6 of 19 times of observations. All Y. enterocolitica O8 isolates showed the same PFGE patterns. These results indicated that the same clone of pathogenic Y. enterocolitica O8 has been maintained in wild rodent populations in Fukushima Prefecture. Therefore, wild rodent populations contribute substantially to the continuous transmission of Y. enterocolitica O8 and its persistence in the ecosystem. This is the first report on the isolation of pathogenic Y. enterocolitica O8 in wild rodents in Fukushima Prefecture, Japan.

Prevalence of Vibrio parahaemolyticus Causing Acute Hepatopancreatic Necrosis Disease of Shrimp in Shrimp, Molluscan Shellfish and Water Samples in the Mekong Delta, Vietnam.

A total of 481 samples, including 417 shrimp and molluscan shellfish samples from retail shops and farms and 64 water samples from shrimp and molluscan shellfish farms in the Mekong Delta located the southern part of Vietnam, were examined for the presence of Vibrio parahaemolyticus (VpAHPND) caused acute haepatopancreatic necrosic disease (AHPND) in shrimp. VpAHPND strains were isolated in two of 298 (0.7%) molluscan shellfish samples from retail shops, seven of 71 (9.9%) shrimp samples from shrimp ponds, and two of 42 (4.8%) water samples from shrimp ponds. VpAHPND strains were classified into two types of O antigen, including O1 and O3, in which O1 was the predominant. VpAHPND strains isolated showed high resistance rates to colistin (100%), ampicillin (93.8%), and streptomycin (87.5%). These results indicate that VpAHPND is widely prevalent in environment in the Mekong Delta, Vietnam.

Prevalence of Vibrio parahaemolyticus in seafood and water environment in the Mekong Delta, Vietnam.

A total of 449 samples including 385 seafood and 64 water samples in the Mekong Delta of Vietnam collected in 2015 and 2016 were examined. Of 385 seafood samples, 332 (86.2%) samples were contaminated with Vibrio parahaemolyticus and 25 (6.5%) samples were pathogenic V. parahaemolyticus carrying tdh and/or trh genes. The tdh gene positive V. parahaemolyticus strains were detected in 22 (5.7%) samples and trh gene positive V. parahaemolyticus strains were found in 5 (1.3%) samples. Of 25 pathogenic V. parahaemolyticus strains, two strains harbored both tdh and trh genes and the other 23 strains carried either tdh or trh gene. Of 64 water samples at aquaculture farms, 50 (78.1%) samples were contaminated with V. parahaemolyticus. No tdh gene positive V. parahaemolyticus strains were detected; meanwhile, trh gene positive V. parahaemolyticus strain was detected in 1 (1.6%) sample. Twenty-six pathogenic V. parahaemolyticus strains isolated were classified into 6 types of O antigen, in which the serotype O3:K6 was detected in 4 strains. All pathogenic strains were group-specific PCR negative except for 4 O3:K6 strains. The result of antimicrobial susceptibility test indicated that pathogenic strains showed high resistance rates to streptomycin (84.6%), ampicillin (57.7%) and sulfisoxazole (57.7%). These findings can be used for understanding microbiological risk of seafood in the Mekong Delta, Vietnam.