It is estimated that one million people are dually infected with Human Immunodeficiency Virus type-I (HIV-1) and type-II (HIV-2) in West Africa and parts of India. HIV-1 and HIV-2 use the same receptor and coreceptors for entry into cells, and thus target the same cell populations in the host. Additionally, we first examined whether RNAs from HIV-1 and HIV-2 can be copackaged into the same virion. Therefore these properties suggest that in the dually infected population, it is likely that some cells can be infected by both HIV-1 and HIV-2, thereby providing opportunities for these two viruses to interact with each other. We constructed recombination assay system for measurement recombination frequencies and analyzed recombination rate between HIV-1 and HIV-2. We used modified near-full-length viruses that each contained a green fluorescent protein gene (gfp) with a different inactivating mutation. Thus, a functional gfp could be reconstituted via recombination, which was used to detect copackaging of HIV-1 and HIV-2 RNAs. In this study, approximately 0.2％ of infection events generated the GFP^＋ phenotype. Therefore, the appearance of the GFP^＋ phenotype in the current system is approximately 35-fold lower than that between two homologous HIV-1 or HIV-2 viruses. We then mapped the general structures of the recombinant viruses and characterized the recombination junctions by DNA sequencing. We observed several different recombination patterns including those only had crossovers in gfp. The most common hybrid genomes had heterologous LTRs. Although infrequent, crossovers were also identified in the viral sequences. Such chimeric HIV-1 and HIV-2 viruses have yet to be observed in the infected population. It is unclear whether the lack of observed chimeras is due to the divergence between HIV-1 and HIV-2 being too great for such an event to occur, or whether such events could occur but have not yet been observed. Given the number of coinfected people, the potential for interactions between HIV-1 and HIV-2 should not be ignored.

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Bacterial pathogens possesses certain secretion systems to maintain their homeostasis and to exert full virulence. Currently, two translocons including Sec and Tat, and 7 secretion systems are found in Gram positive and -negative bacteria. Some virulence factors, which are referred to as effectors, are directly translocated into the host cell via an injection apparatus, i.e., the type III secretion system. Thus, characterization of secretion systems and their delivered proteins into extracellular milieus is required for understanding of strategies of bacterial pathogens.

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In a study of the effect of the widely used, commercially available Enterococcus faecium BIO probiotic on enteropathogen growth, we determined the effect using a new, growth inhibition test on layered agar medium. E. faecium BIO and test organisms did not come into direct mutual contact and effects were judged by test organism growth on the agar surface. E. faecium BIO showed antibiotic effects on all pathogens tested. We also confirmed that E. faecium BIO suppressed organism growth mainly by producing lactic acid, but due to lactate alone.

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The National Epidemiological Surveillance of Infectious Diseases (NESID) estimates the number of influenza patients using sentinel medical institutions reports (NESID estimate) rather than the actual number of patients visiting medical institutions. We estimated Hyogo Prefecture influenza patient numbers using Oseltamivir consumption (Oseltamivir estimate) to determine NESID estimate validity for the Nov-May,2003-2007 influenza seasons. We divided the seasonal Oseltamivir estimate by the NESID estimate to derive an estimated prescription rate assuming that the NESID estimate was accurate. Estimated prescription rates ranged from 50％ to 100％, but the NESID estimate assumption is appropriate from the relationship between the estimated prescription rate and prescription status. In 2004-2005 and 2005-2006 years 94％ and 100％ for the estimated prescription rate were close to the results (90％) from nationwide Oseltamivir prescription investigation. Nationwide analysis and investigations needed in other seasons on prescription rate of influenza medicine (Oseltamivir, Zanamivir, etc.) are thus needed for generalization on the validity of “NESID estimate”.

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We evaluated the usefulness of WHONET, free software from the World Health Organization (WHO), in a laboratory-based survey analyzing infectious disease, i.e., Streptococcus pneumoniae, and its antimicrobial susceptibility, i.e., to levofloxacin (LVFX), between 2003 and 2006 at 5 hospitals. The percentage of resistant strains (MIC/8µg/mL) isolated by the Maebashi Red Cross Hospital Laboratory between 2003 and 2005 was 3.8％ (26/684＝number of resistant isolates/number of all isolates), significantly higher (p＜0.001, Fisherʼs exact test) than the 0.5％ (8/1717) recorded at 4 other hospital laboratories. In 2006 the Maebashi Red Cross Hospital Laboratory percentage of resistant strains was 0.9％ (2/221) in the absence of intervention to reduce the percentage of resistant isolates, while that at 4 other hospital laboratories was 1.3％ (9/717)- a difference not statistically significant (p＝0.574). Of resistant strains, 86％(24/28) came from patients older than 67 years and 71％ (20/28) from outpatients or those newly hospitalized 1 or 2 days. Where and when pathogens are isolated are the two priority factors in epidemiological analysis. Superimposing plot of patient residences and isolated times of LVFX-resistant S. pneumoniae strains for each incidences showed no unusual trends in pathogen distribution. Analysis of possible multiple drug resistance for all LVFX-resistant S. pneumoniae isolates, i.e., resistance profile determination, indicated that no strain isolated in any one-month period shared an identical resistance profile, suggesting that the probability of a community outbreak of one specific S. pneumoniae strain is minimal. We did not find possible causes for the high resistance percentage of isolates recorded by the Maebashi Red Cross Hospital Laboratory during 2003-2005, or for the low resistance percentage for strains isolated during 2006. Analysis of our survey indicated that LVFX-resistant S. pneumoniae isolates are still rare in the communities tested, but ongoing surveys have keenly aroused public interest in potential risk and the consequences of the increase in antibiotic-resistant pathogens. This study showed WHONET to be indispensable as an epidemiological investigation tool.

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The TaqMan-based real-time quantitative reverse transcription-polymerase chain reaction（RT-PCR）assay we developed is sensitive and detects seven (1-7) human astrovirus (HAstV) serotypes. We chose conserved regions at the 5ʼend of the open reading frame 2 (ORF2) was chosen at the assay targets for designing new primers and the TaqMan MGB probe that detects all HAstV serotypes. Real-time RT-PCR reactivity was confirmed with HAstV serotype 1 through 7 control plasmids and efficiency ranged from 30 to 3.0×10⁷ copies/tube. The assay developed detected HAstV sequences from clinical HAstV-positive samples. The assay was 10 to 10³ times more sensitive than Conventional RT-PCR assay and free of cross reactivity against other enteric viruses, including norovirus, sapovirus, rotavirus, and adenovirus. These results indicate that our real-time RT-PCR assay rapidly detects and quantitatively analyzes HAstV serotype 1 through 7.

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Infection with Helicobacter pylori carrying a cagA virulence gene is a potential risk factor for gastric cancer. Since obtaining clinical isolates from healthy subjects is difficult, epidemiological analysis of cagA-positive H. pylori in healthy populations is not well studied. To assess H. pylori infection in a healthy population, we applied coprodiagnostic analysis to determine H. pylori infection prevalence. H. pylori antigen in stool specimens was detected by immunochrmoatograpy in 54.1％ of participants. The average age in the H. pylori-positive group was higher than in the negative group. The alcohol intake group showed a significantly higher H. pylori prevalence. The genotype of cagA was assessed by polymerase chain reaction after bacterial DNA extraction from H. pylori-positive stool specimens. Only 20.0％ of participants in sample in which H. pylori DNA was detected were infected with cagA-positive H. pylori, but all cagA-positive H. pylori was of the East-Asian genotype. These results indicate that a significant number of healthy adults in Panama are infected with H. pylori, but the majority of bacteria are less virulent. Alcohol intake may be a risk factor for H. pylori infection.

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