In this study, 77 clinical and 67 oyster Vibrio parahaemolyticus isolates from North America were examined for biochemical profiles, serotype, and the presence of potential virulence factors (tdh, trh, and type III secretion system [T3SS] genes). All isolates were positive for oxidase, indole, and glucose fermentation, consistent with previous reports. The isolates represented 35 different serotypes, 9 of which were shared by clinical and oyster isolates. Serotypes associated with pandemic strains (O1:KUT, O1:K25, O3:K6, and O4:K68) were observed for clinical isolates, and 7 (9%) oyster isolates belonged to serotype O1:KUT. Of the clinical isolates, 27% were negative for tdh and trh, while 45% contained both genes. Oyster isolates were preferentially selected for the presence of tdh and/or trh; 34% contained both genes, 42% had trh but not tdh, and 3% had tdh but not trh. All but 1 isolate (143/144) had at least three of the four T3SS1 genes examined. The isolates lacking both tdh and trh contained no T3SS2␣ or T3SS2␤ genes. All clinical isolates positive for tdh and negative for trh possessed all T3SS2␣ genes, and all isolates negative for tdh and positive for trh possessed all T3SS2␤ genes. The two oyster isolates containing tdh but not trh possessed all but the vopB2 gene of T3SS2␣, as reported previously. In contrast to the findings of previous studies, all strains examined that were positive for both tdh and trh also carried T3SS2␤ genes. This report identifies the serotype as the most distinguishing feature between clinical and oyster isolates. Our findings raise concerns about the reliability of the tdh, trh, and T3SS genes as virulence markers and highlight the need for more-detailed pathogenicity investigations of V. parahaemolyticus. Vibrio parahaemolyticus is the leading cause of seafood-associated illness in the United States and is generally associated with the consumption of raw molluscan shellfish (17). Even so, V. parahaemolyticus illnesses are believed to be highly underdiagnosed (143-fold), possibly due to the relatively low hospitalization (22.5%) and fatality (0.9%) rates (36). Another factor that may influence the underdiagnosis is the fact that traditional biochemical identification of V. parahaemolyticus has proven less reliable than molecular identification for clinical and food isolates (8,21). When an isolate is confirmed as V. parahaemolyticus, virulence characterization is typically performed. The virulence of V. parahaemolyticus was initially attributed to the production of a thermostable direct hemolysin (TDH) (15, 26). The TDH is encoded by the tdh gene, and subsequently a related gene, termed the tdhrelated hemolysin (trh), was identified (26). Together, tdh and trh are widely considered the predominant indicators of strain virulence in V. parahaemolyticus (26,37,38). This is substantiated by the prevalence of tdh and/or trh in clinical V. parahaemolyticus isolates and the infrequent detection of these virulence markers in food and environmental samples (9,27,28,35,40).Investigati...

Typhoid fever is more common than paratyphoid fever in the urban Bangladeshi slum; children<5 years old have the highest incidence. Multidrug resistance is common in S. Typhi isolates and is associated with prolonged illness. Strategies for typhoid fever prevention in children aged<5 years in Bangladesh, including immunization, are needed.

Cryptosporidium is an important zoonotic parasite globally. Few studies have examined the ecology and epidemiology of this pathogen in rural tropical systems characterized by high rates of overlap among humans, domesticated animals, and wildlife. We investigated risk factors for Cryptosporidium infection and assessed cross-species transmission potential among people, non-human primates, and domestic animals in the Gombe Ecosystem, Kigoma District, Tanzania. A cross-sectional survey was designed to determine the occurrence and risk factors for Cryptosporidium infection in humans, domestic animals and wildlife living in and around Gombe National Park. Diagnostic PCR revealed Cryptosporidium infection rates of 4.3% in humans, 16.0% in non-human primates, and 9.6% in livestock. Local streams sampled were negative. DNA sequencing uncovered a complex epidemiology for Cryptosporidium in this system, with humans, baboons and a subset of chimpanzees infected with C. hominis subtype IfA12G2; another subset of chimpanzees infected with C. suis; and all positive goats and sheep infected with C. xiaoi. For humans, residence location was associated with increased risk of infection in Mwamgongo village compared to one camp (Kasekela), and there was an increased odds for infection when living in a household with another positive person. Fecal consistency and other gastrointestinal signs did not predict Cryptosporidium infection. Despite a high degree of habitat overlap between village people and livestock, our results suggest that there are distinct Cryptosporidium transmission dynamics for humans and livestock in this system. The dominance of C. hominis subtype IfA12G2 among humans and non-human primates suggest cross-species transmission. Interestingly, a subset of chimpanzees was infected with C. suis. We hypothesize that there is cross-species transmission from bush pigs (Potaochoerus larvatus) to chimpanzees in Gombe forest, since domesticated pigs are regionally absent. Our findings demonstrate a complex nature of Cryptosporidium in sympatric primates, including humans, and stress the need for further studies.