Campylobacter species is slow-growing and extremely susceptible to atmospheric conditions. Therefore, the administrative disposition of this species is difficult and time-consuming in food poisoning incidences. We aimed to develop a two-step screening method for determining Campylobacter food poisoning. The method selected for suspected Campylobacter incidence using information from epidemiological investigation and subsequently detected the presence of Campylobacter jejuni and C. coli by polymerase chain reaction (PCR). We studied the epidemiological characteristics and performed PCR screening of 17 incidences of suspected food poisoning by C. jejuni and C. coli in the Gifu Prefecture. The epidemiological characteristics of incidences caused by C. jejuni and C. coli included a meal provided at the suspected causative facility, duration since the onset of symptoms after the intake of pathogen (incubation period), and the clinical symptoms exhibited by patients. The meals consumed included either raw/undercooked chicken meat at a restaurant or cooked meat prepared at dormitory/school by students. Incubation period of the pathogens was observed to be over 24 hr. There was a high prevalence of diarrhea and a low prevalence of vomiting. We aimed to target C. jejuni and C. coli for PCR screening. The results of PCR screening against the cultures revealed a sensitivity of 88% and specificity of 90% for C. jejuni and a sensitivity of 100% and specificity of 98% for C. coli. The proposed PCR screening was found to be similarly apt for the identification of both C. jejuni and C. coli. These PCR results can be quickly obtained, thus offering a rapid system of diagnosis by food sanitation inspector and bacteriological examiner. Moreover, the two-step screening would be more economical and convenient to perform than comprehensive PCR screening.
Vibrio vulnificus is widely present in brackish water area and can cause fatal infections in patients with chronic liver diseases and other symptoms through raw seafood consumption and/or seawater exposure. A number of serious cases of Vibrio vulnificus infection have been reported along coastal area of the Ariake Sea in Japan. In the present study, we report on a sensitive typing method to V. vulnificus on the bases of restriction fragment length polymorphism (RFLP) of the intergenic spacer (ITS) region between 16S and 23S ribosomal RNA operons of the bacterial genomes. A total of 158 strains of V. vulnificus derived from coastal area of Nagasaki prefecture including the Ariake Sea and patients in northern Kyushu were examined. Among the resultant 7 clusters (I to VII), 57% (16/28) of the clinically derived strain was fallen into the cluster III and 96% (47/49) of the strains contained in the cluster III had clinical-type of virulence-correlated genes (vcg). Strains derived from the Ariake Sea were distributed across all the 7 clusters, and 64% of the strains had clinical type vcg genes, and 53% of them were fallen into the cluster III. This was in contrast to the characteristics of strains derived in coastal areas other than the Ariake Sea in Nagasaki Prefecture. These results indicate that (1) the rITS-RFLP method presented here is sensitive enough to detect V. vulnificus strains with high risk of infection, and (2) coastal area of the Ariake Sea holds greater diversity of V. vulnificus compared with other coastal areas of Nagasaki prefecture.
Heat-resistant microorganisms can cause food deterioration even after heat sterilization. Generally, heat-resistant microorganisms are screened by cultivating heat-treated samples. However, biased cultivation conditions can inhibit comprehensive isolation of these microorganisms. EMA-PCR-DGGE is considered a comprehensive detection method to selectively analyze viable microbial flora that eliminates bias in the cultivation conditions.
In this study, we screened heat-resistant bacteria by analyzing heated samples using EMA-PCR-DGGE. Specifically, the screening was performed on wipe test fluid samples from a fruit canning factory, and the bacteria were isolated by the addition of cultivation conditions on the screened strains.
We successfully isolated Micromonospora sp. and Propionibacterium sp. The evaluation of heat resistance in these bacteria revealed that Micromonospora sp. was indeed heat resistant; thus, the validity of this method for screening heat-resistant bacteria was confirmed.