Helicobacter pylori is the leading bacterial cause of food-borne illness worldwide and plays a major role in the development of chronic gastritis, peptic ulcer, and gastric cancer. Strains isolated from patients contain the cagA gene (cytotoxin-associated gene A) and produce the vacuolating cytotoxin, VacA. Recent molecular and cellular studies of VacA action have begun to unravel its structure and the details of the mechanism of gastric injury caused by H. pylori infection.

In recent years, advances in the diagnosis and treatment of herpes simplex encephalitis (HSE) have been achieved due to the prevalence of antiviral drugs and the introduction of the polymerase chain reaction (PCR) to test the cerebrospinal fluid. The several clinical forms of herpes simplex virus type 1 (HSY-1) infections of the central nervous system (CNS), including acute disseminated encephalomyelitis and brainstem encephalitis, have been clarified. However, fatal, prolonged, or relapsed cases are still observed, and early detection and appropriate treatment is necessary to lead to a good prognosis for these intractable HSE cases. In adult HSV-2 infections, meningitis and myelitis associated with genital herpes are common. In the past, HSV-2 myelitis has been reported as a form of fatal necrotizing myelopathy; however, using PCR and magnetic resonance imaging studies, mild surviving cases are increasingly likely to be identified. Meanwhile, various CNS syndromes resulting from the herpes group viruses, including varicella-zoster virus and Epstein-Barr virus have also been reported. These herpesviruses have several characteristics in common, e.g., they exist in the latent state and they occur in both mucocutaneous and CNS infections. Adult HSV-1 and -2 infections of the CNS are discussed together with other herpes group virus infections of the CNS.

To elucidate the importance of enteropathogenic Escherichia coli (EPEC) and enteroaggregative E. coli (EAggEC) as etiological agents in traveler's diarrhea, the detection of the eaeA and aggR gene in E. coli strains isolated from overseas travelers with diarrhea in Tama, Tokyo was carried out using a PCR method. Of 192 travelers who were mostly adults and had visited Asian countries from April 1998 to March 1999, aggR-positive E. coli strains were detected in 26 (13.5%). These strains represent the second predominant enteropathogen following enterotoxigenic E. coli (ETEC), whereas eaeA-positive E. coli strains were confirmed in seven subjects (3.6%). In 13 cases with aggR and four cases with eaeA, the organisms were detected in stool samples of patients as the only potential enteric pathogen. The clinical symptoms of these patients were similar to those in patients with ETEC; however, the severity of illness was milder than that associated with ETEC alone. Three strains with eaeA and five strains with aggR were typed as six different kinds of O serogroups, of which four strains belonged to the classical EPEC serogroups (O55, O114, O119, and O127a). These findings suggest that aggR-positivc E. coli (EAggEC) is a significant causative agent in traveler's diarrhea. In addition, it was demonstrated that eaeA-positive E. coli (EPEC) is markedly correlated with diarrhea in adults.

Genotyping of 1,102 enterohemorrhagic Escherichia coli isolates by the use of pulsed-field gel electrophoresis (PFGE) carried out from January to November 2000 has revealed the high genomic diversity of these isolates in Japan. By combining the results of genotyping of the isolates with the information from other epidemiological investigations of the cases, we identified a diffuse outbreak in Japan in the year 2000 that seemed to be sporadic but was actually linked. Isolates with only the Shiga toxin 2 gene derived from patient specimens and the contaminated food involved in this diffuse outbreak showed an indistinguishable PFGE profile and the same phage type. Based on the diversity of genotypes among the isolates of enterohemorrhagic E. coli O157:H7/- in Japan, we suggest the presence of a few other possible diffuse outbreaks due to the organisms, showing indistinguishable genotypes.

We compared a municipal sentinel surveillance system for influenza with the Microbial Isolation Surveillance System (MISS) in Kyoto City, Japan. Sensitivity, specificity, and predictive value positive (PVP) of the Influenza Sentinel Surveillance System (ISSS) compared to the MISS were calculated by influenza season and by month. Sensitivity ranged from 80 to 97%, specificity ranged from 55 to 77%, and PVP ranged from 29 to 52% by season (P < 0.001). On the other hand, sensitivity ranged from 86 to 100%, specificity ranged from 38 to 66%, and PVP ranged from 31 to 50% by month (P < 0.001). Specificity was calculated as 93% in November. The sensitivity of ISSS was found to be sufficient regardless of the magnitude of influenza activity. Specificity varied by season, indicating the difficulty of clinically diagnosing other respiratory illnesses. The PVP remained at less than 50% before and after the influenza seasons and it varied year by year. In general, the ISSS is a good surveillance system for monitoring influenza activity.