Continued widespread dissemination and increased poultry host fitness of Campylobacter jejuni ST-4526 and ST-4253 in Japan.

AIMS: Campylobacter jejuni is a major cause of foodborne gastroenteritis. We previously reported the widespread Camp. jejuni sequence type (ST)-4526 in Japan from 2005 to 2006. This study assesses the potential for this genotype to thrive thereafter. METHODS AND RESULTS: Fifty human Camp. jejuni isolates collected in 2010-2011 in Osaka, Japan, were genotyped by multilocus sequence typing (MLST). This approach identified 22 STs and 11 clonal complexes (CCs), including four novel STs. A comparative analysis to the previous data set showed the predominance of CC-21, in which ST-4526 and ST-4253 represented 39 and 63% in each of the two time frames, indicating their continued widespread presence. These two STs belong to close evolutionary lineages and are also isolated from chicken meat. The superior abilities of ST-4526/ST-4253 representatives to colonize chicken gut were demonstrated by co-infections with ST-21, ST-50 and ST-8 representatives. CONCLUSIONS: Data provide evidence for the continued widespread of ST-4526/ST-4253 among human clinical isolates in Japan. These STs showed adaptive fitness to chicken. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first evidence of the continued thriving of ST-4526/ST-4253 in Japan with their increased in vivo fitness. Our findings suggest that poultry mediates the microevolution of this pathogen, thereby enabling these STs to become widespread.

Prevalence and growth kinetics of Shiga toxin-producing Escherichia coli (STEC) in bovine offal products in Japan.

Recent epidemiological data suggest a link between the consumption of bovine offal products and Shiga toxin-producing Escherichia coli (STEC) infection in Japan. This study thus examined the prevalence of STEC in various types of these foods. PCR screened 229 bovine offal products for the presence of Shiga toxin (stx) gene. Thirty-eight (16·6%) samples were stx positive, of which eight were positive for rfbE(O157) and three were positive for wzy(O26). Four O157 and one O26 STEC isolates were finally obtained from small-intestine and omasum products. Notably, homogenates of bovine intestinal products significantly reduced the extent of growth of O157 in the enrichment process compared to homogenates of beef carcass. As co-incubation of O157 with background microbiota complex from bovine intestinal products in buffered peptone water, in the absence of meat samples, tended to reduce the extent of growth of O157, we reasoned that certain microbiota present in offal products played a role. In support of this, inoculation of generic E. coli from bovine intestinal products into the homogenates significantly reduced the extent of growth of O157 in the homogenates of bovine intestinal and loin-beef products, and this effect was markedly increased when these homogenates were heat-treated prior to inoculation. Together, this report provides first evidence of the prevalence of STEC in a variety of bovine offal products in Japan. The prevalence data herein may be useful for risk assessment of those products as a potential source of human STEC infection beyond the epidemiological background. The growth characteristic of STEC O157 in offal products also indicates the importance of being aware when to test these food products.

Survey of Japanese layer farms for Salmonella enteritidis with vaccination- and infection-specific antigens for egg yolk antibodies.

Japanese layer farms were surveyed for Salmonella Enteritidis vaccination and infection with specific antigens for egg yolk antibodies with the use of vaccination-specific antigen Salmonella Enteritidis FliC-specific 9-kDa polypeptide (SEP9) and infection-specific antigen deflagellated Salmonella Enteritidis whole cell (DEWC). The specific antibodies in eggs from 201 commercial layer farms throughout Japan were surveyed. The percentages of farm flocks with a mean enzyme-linked immunosorbent assay (ELISA) titer of over 0.1 were 56.2% (113 of 201) in DEWC-ELISA and 22.3% (45 of 201) in SEP9-ELISA. Flocks indicating high titers in SEP9-ELISA always showed high titers in DEWC-ELISA. Because both specific antibody titers of the vaccinated flocks monitored long term remained high throughout life, flocks with high titers of both ELISAs in this survey must be vaccinated. On the other hand, 34.3% (69 of 201) of flocks had high titers of DEWC-specific antibody alone. Because Salmonella Enteritidis infection induces the DEWC-specific antibody but not the SEP9-specific antibody, detecting only high ELISA titers of DEWC-specific antibody can be an effective monitoring tool for Salmonella Enteritidis exposure rather than vaccination. These results suggest that vaccination programs in Japanese layer farms would be insufficient to control Salmonella Enteritidis infection, and egg screening to detect specific antibodies would be valuable in obtaining the necessary information to control Salmonella Enteritidis infection.