In 2021, we quantitatively examined commercial chicken meat (56 samples) and liver (17 samples) for contamination with the hygiene indicator bacteria, Campylobacter and Salmonella. Campylobacter spp. was isolated from 14.3% (8/56) of meat and 17.6% (3/17) of liver samples; the predominant isolates were C. jejuni, and the Penner serotype was gB. One liver sample had a high value of ≥11,000 MPN/100 g, while the other samples were <999 MPN/100 g. Salmonella spp. were isolated from 17.9% (10/56) of meat and 35.3% (6/17) of liver samples; the predominant serovar was S. Schwarzenground (12 samples), followed by S. Infantis (3 samples) and S. Manhattan (1 sample). One liver sample showed a high value of ≥11,000 MPN/100 g, while the others were <999 MPN/100 g. Campylobacter isolates were susceptible to macrolides (Erythromycin), whereas Salmonella isolates were susceptible to fluoroquinolone (Ofloxacin) and cephem antibiotics (Cefmetazole), which appear to be effective treatments, but it is necessary to monitor trends in antimicrobial-resistant bacteria. The aerobic count (mean±standard deviation), Enterobacteriaceae count, coliform group count, and Escherichia coli count were respectively 4.59±1.01, 3.26±0.69, 3.14±0.64, and 1.62±0.70 log cfu/g in meat and 3.86±0.94, 2.74±0.89, 2.56±1.10, and 1.70±0.56 log cfu/g in liver. The risk ratio of Salmonella positive samples for aerobic count (≥ 4.0 log cfu/g),Enterobacteriaceae count and coliform count (≥ 3.0 log cfu/g) in chicken liver are 7.14, 9.17 and 9.17, respectively. The results suggest that aerobic bacteria count, Enterobacteriaceae count, and coliform group count might be useful for determining whether Salmonella is present in Li­ver, whereas the hygiene indicator bacteria could not be used to determine whether Campylobacter and Salmonella were present in chicken meat.

Campylobacter jejuni (C. jejuni) is a causative food poisoning bacterium, it mainly ingesting undercooked chicken meat. Additionally, cooking utensils treated with raw chicken meat contaminated with C. jejuni and can induce the cross-contamination of food. Therefore, disinfection of kitchen equipment is a critical for prevention of C. jejuni infection. Ultraviolet (UV) irradiation is useful method for sterilization and UVC wavelength is mainly utilized. Recently, we developed UVA-light emitting diode (LED) irradiation system as new disinfection methods. However, the effect of UVA-LED irradiation against the cooking utensils contaminated with C. jejuni is poorly understood. In this study, we investigated the effect of UVA irradiation for C. jejuni contaminated kitchen equipment, stainless tray and kitchen knife. We treated the cooking utensils with raw chicken meat and/or C. jejuni suspension and irradiated UVA-LED for 30 min. After UVA-LED irradiation, the log survival ration of general bacteria and C. jejuni were reduced at −1.63 and −3.13, respectively in stainless tray experiments. In kitchen knife experiments, general bacteria and C. jejuni was not detected in UVA-LED irradiated kitchen knife. Our results indicate that UVA-LED irradiation may be useful for cooking utensils contaminated with bacteria, especially C. jejuni.

Diarrheagenic Escherichia coli strains are mainly classified into the following five pathotypes; enteropathogenic E. coli, enterotoxigenic E. coli, enteroinvasive E. coli, enterohemorrhagic E. coli and enteroaggregative E. coli. E. coli strains of various pathotypes can be further classified by their serotypes combined by O-serogroup and H-type. Generally in Japan, the commercial O-antisera and H-antisera are used to serotype strains. These serotypes provide useful information in investigations of outbreaks and epidemiological studies. In May 2021, a large-scale food poisoning outbreak thought to be caused by E. coli occurred in Saitama City. Serotyping of 21 E. coli strains carrying virulence genes isolated from patients and an asymptomatic cooking worker was carried out using a commercially available kit, but most of the strains (57%) could not be serotyped. Therefore, in this study, we tried the multiplex PCR methods including E. coli O-genotyping PCR and E. coli H-genotyping PCR. As a result, only 5% of strains could not be determined their Og-types, and the main genotype in this case was found to be Og104:Hg4 (12/21 strains) carrying astA+aggR or estA2+elt+astA+aggR. In conclusion, we believe that Og-typing PCR and Hg-typing PCR are effective methods in investigating cases caused by pathogenic E. coli belonging to rare pathotypes.