Hideki Hayashidani

2020年10月～2021年2月に東京都ならびに神奈川県のスーパーマーケットや小売店，計39軒で購入した国産鶏肉を原材料とした鶏肉加工品95検体を供試検体とした．Salmonella分離・同定はSalmonella属菌標準試験法に則って行った．定性試験においてSalmonella陽性となった供試検体について，最確数法（most probable number method: MPN法）を用いて定量を行った．分離されたSalmonella菌株は，市販抗血清を用いて血清型を同定するとともに，薬剤感受性試験を実施した．供試検体95検体中30検体（31.6％）からSalmonellaが分離され，高度に汚染されていた．Salmonellaの汚染菌量は，Salmonella陽性検体30検体中19検体（63.3％）が，＜0.3 MPN/gで低いものが多かったが，中には高い菌量（2.3および4.3 MPN/g）のものもみられた．分離されたSalmonella 33株は，4血清型に型別され，S. Schwarzengrund （60.6％）が最も多く，次いでS. Infantis （24.2％），S. Agona （12.1％）ならびにS. Manhattan （3.0％）の順であった．分離されたSalmonella 33株中26株（78.8％）は，2薬剤以上に耐性を示す多剤耐性菌株であった．日本における鶏肉加工品のSalmonella汚染は，市販鶏肉を汚染しているSalmonellaの血清型とその割合が近似していることから，原材料の鶏肉が汚染源と思われ，鶏肉加工品はヒトへのサルモネラ感染源として重要であることが示唆された．

This study aimed to investigate the prevalence of antibodies against pathogenic Yersinia such as Y. enterocolitica and Y. pseudotuberculosis in domestic pigs. A total of 650 serum samples from pigs in nine regions of the Chiba Prefecture in Japan, were tested using plasmid-encoded Yersinia outer membrane protein (Yops) antigen ELISA. The cutoff value was calculated using 20 pathogenic Yersinia-free pig serum samples. According to the cutoff value, 246 (37.8 %) pigs from seven regions were considered seropositive for pathogenic Yersinia during the study period. These results indicate that pathogenic Yersinia is widespread in pigs in Chiba, which may become the source of human yersiniosis in this region.

Background and Aim: Salmonella is one of the leading causes of zoonotic and foodborne infectious outbreaks in humans and poultry and its associated environment is a potential reservoir of Salmonella. In recent years, the antibiotic resistance of bacteria, including Salmonella, has been increasing. This study aimed to investigate the prevalence and antibiotic resistance of Salmonella isolated from poultry, its environment, and the pest animals found at poultry farms and households of the Mekong Delta, Vietnam. Materials and Methods: A total of 3,055 samples were collected from the broiler farms and households of the Mekong Delta from 2017 to 2020. Salmonella was isolated using conventional methods (culturing on selective agar – BPLS and biochemical test) and the isolates were examined for antibiotic resistance against 14 antibiotics using the disk diffusion method. Results: Salmonella was isolated from 181 samples (5.92%), which included chicken feces (7.67%), pest animals (5.98%), and environmental samples (4.33%). The environmental samples comprised bedding (5.88%), feed (5.48%), and drinking water (0.70%). The prevalence of Salmonella was the highest in rats (15.63%) and geckos (12.25%) followed by ants (2.83%) and cockroaches (2.44%); however, Salmonella was not isolated from any fly species. Most of the isolates exhibited resistance to 1-9 antibiotics. The isolates were relatively resistant to chloramphenicol (62.98%), tetracycline (55.80%), ampicillin (54.14%), and sulfamethoxazole/trimethoprim (53.04%). Sixty-two multiple resistance patterns were found in the isolates, with ampicillin-cefuroxime-chloramphenicol-tetracycline- sulfamethoxazole/trimethoprim being the most frequent (7.18%). Conclusion: The chickens, husbandry environment, and pest animals at poultry farms and households were found to be important Salmonella sources in the Mekong Delta. Salmonella isolates from these sources also exhibited a wide-ranging resistance to antibiotics as well as several resistance patterns. Hence, biosecurity should be addressed in poultry farms and households to prevent cross-contamination and reduce the spread of Salmonella infections.

Avian pathogenic Escherichia coli (APEC) is the main causative agent of avian colibacillosis, which is an important systemic disease of profound economic and clinical consequences for the poultry industry worldwide. In this study, 975 E. coli strains were isolated from 2,169 samples collected from cloacal swabs of chickens, in-farm wild animals (ants, geckos, flies, and rats), and environment. The highest proportion of E. coli isolation was obtained from chicken cloacal swabs with 71.05 (95 confidence interval (CI) 66.6975.05) followed by the proportions of 38.15 (95 CI 35.4140.97) and 38.11 (95 CI 34.1542.24) from wild animals or environment, respectively. Distribution of O-antigen serotypes of the E. coli isolates, including O1, O2, O18, and O78, was determined by PCR. The most predominant serotype was O18 (10.56) followed by O2 (9.44), O1 (7.79), and O78 (6.56). Of note, serotype O18 was more likely distributed in the examined wild animals, especially in geckos. Polymorphic DNA fingerprints, generated by ERIC-PCR, of representative E. coli strains of each serotype revealed genetic heterogeneity of the examined E. coli, and O18 was more divergent with 63 clusters formed from 66 isolates. Furthermore, several E. coli strains from different sample sources shared high DNA fingerprint relatedness, suggesting that there exists complex transmission of E. coli from chickens to wild animals and environment and vice versa in poultry husbandry settings. Although pathotypes of the examined E. coli were not determined in this study, our results provided important findings of epidemiological and genetic characteristics of E. coli in the Mekong Delta and highlighted the prerequisite of stricter biocontainment to reduce the prevalence and consequences of APEC in poultry production.

2017年7月から2019年1月に，ベトナム・メコンデルタの市場やスーパーマーケット19か所から購入した計645検体の市販新鮮野菜における腸管出血性大腸菌 (EHEC) ならびに毒素原性大腸菌 (ETEC) の汚染状況を調べた．供試検体645検体中，EHECおよびETECがそれぞれ1検体の計2検体 (0.3%) から分離された．病原性大腸菌が分離された野菜はいずれもヘッドレタスであった．分離されたEHECの血清型は市販抗血清では型別されなかったが，ETECはO20であった．EHECとETECの2菌株は，用いた9種の抗生物質に対し，いずれも4と7薬剤に耐性を示す多剤耐性株であった．これらの結果から，ベトナム・メコンデルタにおいては，市販生鮮野菜はEHECとETECの感染源としては重要でない可能性が示された．

A total of 1,318 wild geckos were collected in Cambodia, Thailand and Vietnam (Hue and the Mekong Delta) from 2012 to 2015 to determine the prevalence of Salmonella Weltevreden. Those geckos belong to three species: common house gecko (Hemidactylus frenatus), flat‐tailed house gecko (Hemidactylus platyurus) and four‐clawed gecko (Gehyra mutilata). Of 1,318 gecko samples, 293 (22.2%) samples were positive for Salmonella in this study. The prevalence of Salmonella in geckos was 46.0% in Thailand, 17.3% in Cambodia and 16.3% in Vietnam. Among the Salmonella isolates, S. Weltevreden was the most predominant serovar (32.1%) isolated from wild geckos in these countries. There was no significant difference in the prevalence of Salmonella among gecko species. All S. Weltevreden isolates (100%) were susceptible to the nine antibiotics examined in this study. The PFGE assay by XbaI enzyme identified 19 different patterns from 75 S. Weltevreden isolates. These isolates showed high genetic heterogenicity, and there were specific types prevalent in each region. Furthermore, S. Weltevreden has been prevalent since the ancient times in this region. The results indicate that wild gecko seems to be an important natural reservoir for S. Weltevreden as well as a source of Salmonella infections in humans in Southeast Asian countries.