Oral human papillomavirus (HPV) infection is a cause of oropharyngeal cancer. We investigated whether sexual behaviors that elevated the odds of oropharyngeal cancer developing in a case-control study similarly elevated the odds of oral HPV infection developing among control patients. HPV infection was detected in 4.8% of 332 control patients from an outpatient clinic and in 2.9% of 210 college-aged men (age range, 18–23 years). Among control patients, the odds of infection developing independently increased with increases in the lifetime number of oral (P = .007, for trend) or vaginal sex partners (P = .003, for trend). Among college-aged men, the odds of oral HPV infection developing increased with increases in the number of recent oral sex partners (P = .046, for trend) or open-mouthed kissing partners (P = .023, for trend) but not vaginal sex partners. Oral sex and open-mouthed kissing are associated with the development of oral HPV infection.

Rifaximin was compared with placebo and ciprofloxacin for treatment of travelers' diarrhea in a randomized, double-blind clinical trial. Adult travelers (N = 399) consulting travel clinics in Mexico, Guatemala, and India were randomized to receive rifaximin 200 mg three times a day, ciprofloxacin (500 mg two times a day and placebo once a day), or placebo three times a day for 3 days. Patients recorded in daily diaries the time and consistency of each stool and documented symptoms for 5 days after treatment. Stool samples were collected for microbiologic evaluations before and after treatment. The median time to last unformed stool (TLUS) in the rifaximin group (32.0 hours) was less than one half that in the placebo group (65.5 hours; P = 0.001; risk ratio 1.6; 95% confidence interval 1.2, 2.2; primary efficacy endpoint). The median TLUS in the ciprofloxacin group was 28.8 hours (P = 0.0003 versus placebo; P = 0.35 versus rifaximin). Rifaximin was less effective than ciprofloxacin for invasive intestinal bacterial pathogens. Oral rifaximin is a safe and effective treatment of travelers' diarrhea caused by noninvasive pathogens.

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Clostridial neurotoxins are zinc endopeptidases that block neurotransmission and have been shown to cleave, in vitro, specific proteins involved in synaptic vesicle docking and/or fusion. We have used immunohistochemistry and immunoblotting to demonstrate alterations in toxin substrates in intact neurons under conditions of toxin-induced blockade of neurotransmitter release. Vesicle-associated membrane protein, which colocalizes with synaptophysin, is not detectable in tetanus toxin-blocked cultures. Syntaxin, also concentrated in synaptic sites, is cleaved by botulinum neurotoxin C. Similarly, the carboxyl terminus of the synaptosomal-associated protein of 25 kDa (SNAP-25) is not detectable in botulinum neurotoxin A-treated cultures. Unexpectedly, tetanus toxin exposure causes an increase in SNAP-25 immunofluorescence, reflecting increased accessibility of antibodies to antigenic sites rather than increased expression of the protein. Furthermore, botulinum neurotoxin C causes a marked loss of the carboxyl terminus of SNAP-25 when the toxin is added to living cultures, whereas it has no action on SNAP-25 in vitro preparations. This study is the first to demonstrate in functioning neurons that the physiologic response to these toxins is correlated with the proteolysis of their respective substrates. Furthermore, the data demonstrate that botulinum neurotoxin C, in addition to cleaving syntaxin, exerts a secondary effect on SNAP-25.

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To increase understanding of the antigenic structure of Pneumocystis carinii, we developed monoclonal antibodies to rat and human P. carinii. The specificity of the antibodies was demonstrated by immunofluorescence and immunoblot studies. Only one of five monoclonal antibodies to rat P. carinii reacted with human P. carinii, and none of four monoclonal antibodies to human P. carinii reacted with rat P. carinii. Two antibodies to human P. carinii reacted by immunofluorescence with only one human P. carinii isolate. Immunoblot studies identified major antigens of rat P. carinii with molecular masses of 40,000-100,000 daltons and of human P. carinii with molecular masses of 22,000-95,000 daltons. These studies document the existence of antigenic differences between rat and human P. carinii and are consistent with the suggestion that individual isolates of human P. carinii are also antigenically different. Further studies with these antibodies should increase understanding of the antigenic nature of P. carinii and of the interaction of P. carinii with its host.

Traveler's diarrhea (TD) is the most common infectious illness acquired by visitors to developing nations. The purpose of this study was to utilize molecular diagnostic techniques to determine the prevalence of norovirus (NoV) in TD occurring among visitors from the United States to Guatemala and Mexico. Stool samples (n ‫؍‬ 54) were collected from 34 TD cases and analyzed for NoV by reverse transcription-PCR and oligoprobe confirmation. The overall prevalence of NoV was 65%. Interestingly, all NoV-positive stool samples were identified as genogroup I NoVs, and time spent at travel destinations was found to be an important factor in determining the frequency of infection (P ‫؍‬ 0.003). Eleven NoV-positive stool samples also tested positive for enterotoxigenic Escherichia coli, indicating that dual infections with this leading bacterial cause of TD were very common. Results of this study suggest that NoV infection is a frequent occurrence among travelers to Mexico and Guatemala who experience episodes of TD. In addition, the simple molecular detection method utilized here will serve to facilitate more in-depth epidemiological studies of this emergent viral pathogen in travelers and other at-risk populations.