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Importance: The travelers' gut microbiome is potentially assaulted by acute and chronic perturbations (e.g., diarrhea, antibiotic use, and different environments). Prior studies of the impact of travel and travelers' diarrhea (TD) on the microbiome have not directly compared antibiotic regimens, and studies of different antibiotic regimens have not considered travelers' microbiomes. This gap is important to be addressed as the use of antibiotics to treat or prevent TD-even in moderate to severe cases or in regions with high infectious disease burden-is controversial based on the concerns for unintended consequences to the gut microbiome and antimicrobial resistance (AMR) emergence. Our study addresses this by evaluating the impact of defined antibiotic regimens (single-dose treatment or daily prophylaxis) on the gut microbiome and resistomes of deployed servicemembers, using samples collected during clinical trials. Our findings indicate that the antibiotic treatment regimens that were studied generally do not lead to adverse effects on the gut microbiome and resistome and identify the relative risks associated with prophylaxis. These results can be used to inform therapeutic guidelines for the prevention and treatment of TD and make progress toward using microbiome information in personalized medical care., Competing Interests: The authors declare no conflict of interest.

Meta-analyses have not examined the prophylactic use of orally ingested probiotics, prebiotics, and synbiotics for preventing gastrointestinal tract infections (GTIs) of various etiologies in adult populations, despite evidence that these gut microbiota-targeted interventions can be effective in treating certain GTIs. This systematic review and meta-analysis aimed to estimate the effects of prophylactic use of orally ingested probiotics, prebiotics, and synbiotics on GTI incidence, duration, and severity in nonelderly, nonhospitalized adults. CENTRAL, PubMed, Scopus, and Web of Science were searched through January 2022. English-language, peer-reviewed publications of randomized, placebo-controlled studies testing an orally ingested probiotic, prebiotic, or synbiotic intervention of any dose for ≥1 wk in adults who were not hospitalized, immunosuppressed, or taking antibiotics were included. Results were analyzed using random-effects meta-analyses of intention-to-treat (ITT) and complete case (CC) cohorts. Heterogeneity was explored by subgroup meta-analysis and meta-regression. The risk of bias was assessed using the Cochrane risk-of-bias 2 tool. Seventeen publications reporting 20 studies of probiotics (n = 16), prebiotics (n = 3), and synbiotics (n = 1) were identified (n > 6994 subjects). In CC and ITT analyses, risk of experiencing ≥1 GTI was reduced with probiotics (CC analysis-risk ratio: 0.86; 95% CI: 0.73, 1.01) and prebiotics (risk ratio: 0.80; 95% CI: 0.66, 0.98). No effects on GTI duration or severity were observed. Sources of heterogeneity included the study population and number of probiotic strains administered but were often unexplained, and a high risk of bias was observed for most studies. The specific effects of individual probiotic strains and prebiotic types could not be assessed owing to a lack of confirmatory studies. Findings indicated that both orally ingested probiotics and prebiotics, relative to placebo, demonstrated modest benefit for reducing GTI risk in nonelderly adults. However, results should be interpreted cautiously owing to the low number of studies, high risk of bias, and unexplained heterogeneity that may include probiotic strain-specific or prebiotic-specific effects. This review was registered at PROSPERO as CRD42020200670., (Published by Elsevier Inc.)

International travel contributes to the global spread of antimicrobial resistance. Travelers' diarrhea exacerbates the risk of acquiring multidrug-resistant organisms and can lead to persistent gastrointestinal disturbance post-travel. However, little is known about the impact of diarrhea on travelers' gut microbiomes, and the dynamics of these changes throughout travel. Here, we assembled a cohort of 159 international students visiting the Andean city of Cusco, Peru and applied next-generation sequencing techniques to 718 longitudinally-collected stool samples. We find that gut microbiome composition changed significantly throughout travel, but taxonomic diversity remained stable. However, diarrhea disrupted this stability and resulted in an increased abundance of antimicrobial resistance genes that can remain high for weeks. We also identified taxa differentially abundant between diarrheal and non-diarrheal samples, which were used to develop a classification model that distinguishes between these disease states. Additionally, we sequenced the genomes of 212 diarrheagenic Escherichia coli isolates and found those from travelers who experienced diarrhea encoded more antimicrobial resistance genes than those who did not. In this work, we find the gut microbiomes of international travelers' are resilient to dysbiosis; however, they are also susceptible to colonization by multidrug-resistant bacteria, a risk that is more pronounced in travelers with diarrhea., (© 2022. The Author(s).)

Background: Acute diarrhea is the most frequent diagnosis among ill travelers. Sleep loss may weaken the body's defense against pathogens and increase susceptibility to infection. The relationship between sleep and infectious diarrhea has not been studied and was assessed utilizing data from a controlled human infection model (CHIM) for enterotoxigenic Escherichia coli (ETEC)., Methods: During a CHIM assessing the efficacy of an immunoprophylactic targeting ETEC against moderate-to-severe diarrhea (MSD) following challenge, we measured sleep via actigraphy over an 8-day inpatient period. We hypothesized better sleep pre-challenge would predict illness symptomatology following challenge., Results: Among 57 participants (aged 34.4 ± 8.1 years, 64% male), there was no relationship between sleep metrics and incidence of MSD. However, longer total sleep time the night preceding ETEC challenge was associated with lower maximum 24 h diarrhea volume (B = -1.80, p = 0.01) and total diarrhea volume (B = -2.45, p = 0.01)., Conclusions: This novel study showed that shorter sleep duration predicted diarrhea severity over the course of an ETEC infection. Future work should experimentally manipulate sleep to further clarify its impact on diarrhea-related outcomes for ETEC and other important enteric pathogens., (Copyright © 2022. Published by Elsevier B.V.)

Background: Among women whose cervical specimens tested positive for high-risk human papillomaviruses (hrHPV) via the Hybrid Capture 2 assay in the Canadian Cervical Cancer Screening Trial (CCCaST), we assessed hrHPV genotype concordance between BD Onclarity HPV Assay and Roche's Linear Array, overall and stratified by hrHPV viral load. We also evaluated the performance of cytology, cytology combined with hrHPV genotyping (Onclarity assay) for HPV16/18 and non-HPV16/18 types, and hrHPV genotyping triage strategies for the detection of cervical intraepithelial neoplasia grade 2 or 3 and worse (CIN2+/CIN3+)., Methods: Standard measures (expected agreement, agreement, and κ values) were used to compare Onclarity to the reference test, Linear Array. Twenty-four triage strategies were evaluated by calculating their sensitivities, specificities, and positive and negative predictive values for CIN2+ and CIN3+ detection., Results: Among 734 hrHPV+ samples tested, there was near perfect concordance irrespective of viral load between the Onclarity and Linear Array assays for the individual genotypes [human papillomaviruses (HPV) 16, 18, 31, 45, 51, 52] by Onclarity (κ values ranged from 0.92-0.98). Strategies with adequate specificity (>75%) and the highest sensitivities to detect CIN3+ among 617 women positive for hrHPV, were positivity to HPV16 and/or 31 (Sensitivity: 65.2%, Specificity: 76.9%) and HPV16 and/or 18 (Sensitivity: 58.7%, Specificity: 81.6%)., Conclusions: While confirming the importance of HPV16, we found that HPV31 was comparable with HPV18 for the detection of CIN2/3+ in the triage of women positive for hrHPV., Impact: HPV31 may be an important genotype in the triage of women positive for hrHPV., (©2022 American Association for Cancer Research.)

The use of the controlled human infection model to facilitate product development and to advance understanding of host-pathogen interactions is of increasing interest. While administering a virulent (or infective) organism to a susceptible host necessitates an ongoing evaluation of safety and ethical considerations, a central theme in conducting these studies in a safe and ethical manner that yields actionable data is their conduct in facilities well-suited to address their unique attributes. To that end, we have developed a framework for evaluating potential sites in which to conduct inpatient enteric controlled human infection model to ensure consistency and increase the likelihood of success.

The controlled human infection model (CHIM) for enterotoxigenic Escherichia coli (ETEC) has been instrumental in defining ETEC as a causative agent of acute watery diarrhea, providing insights into disease pathogenesis and resistance to illness, and enabling preliminary efficacy evaluations for numerous products including vaccines, immunoprophylactics, and drugs. Over a dozen strains have been evaluated to date, with a spectrum of clinical signs and symptoms that appear to replicate the clinical illness seen with naturally occurring ETEC. Recent advancements in the ETEC CHIM have enhanced the characterization of clinical, immunological, and microbiological outcomes. It is anticipated that omics-based technologies applied to ETEC CHIMs will continue to broaden our understanding of host-pathogen interactions and facilitate the development of primary and secondary prevention strategies., (© 2021. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Campylobacter jejuni infection is a leading cause of foodborne disease, common to children, adult travelers, and military populations in low- to middle-income countries. In the absence of a licensed vaccine, efforts to evaluate prophylactic agents are underway. The prophylactic efficacy of a twice-daily, 550 mg dose of the antibiotic rifaximin demonstrated no efficacy against campylobacteriosis in a controlled human infection model (CHIM); however, samples from the CHIM study were utilized to assess how the human gut microbiome responds to C. jejuni infection, and if a 'protective' microbiota exists in study participants not developing campylobacteriosis. Statistically significant, but minor, differences in study participant beta diversity were identified during the challenge period (p = 0.002, R 2 = 0.042), but no significant differences were otherwise observed. Pre-challenge alpha diversity was elevated in study participants who did not develop campylobacteriosis compared to those who did (p < 0.001), but alpha diversity declined in all study participants from the pre-challenge period to post-discharge. Our work provides insight into gut microbiome shifts observed during a C. jejuni CHIM and following antibiotic treatment. This study utilized a high dose of 1.7 x 10 5 colony-forming units of C. jejuni ; future work could include CHIM studies performed with inocula more closely mimicking natural exposure as well as field studies involving naturally-occurring enteric infections., Competing Interests: BS is an employee of UES, Inc. JK, SI, AM, and RL are (or were at the time of the study) employees of the Henry M. Jackson Foundation for the Advancement of Military Medicine. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Stamps, Kuroiwa, Isidean, Schilling, Harro, Talaat, Sack, Tribble, Maue, Rimmer, Laird, Porter, Goodson and Poly.)

Introduction: While Campylobacter jejuni is a leading foodborne bacterial pathogen worldwide, it poses a particular risk to susceptible populations in low- and middle-income countries (LMICs). A capsule-conjugate vaccine approach has been proposed as a potential solution, but little information exists on circulating C. jejuni capsule types in LMICs. The capsule is the major serodeterminant of the Penner typing scheme, which is based on serum recognition of Campylobacter heat-stable antigens. We conducted a systematic review and meta-analysis to estimate the distribution of Penner serotypes associated with C. jejuni enteritis in LMICs. Vaccine coverage assessments for hypothetical regional and global C. jejuni vaccines were also estimated., Methods: A systematic review of the literature published from 1980 to 2019 was performed using PubMed, Scopus, and Web of Science databases. Articles were assessed for eligibility and data were abstracted. Pooled C. jejuni serotype prevalence in LMICs was estimated by region and globally using random-effects models., Results: A total of 36 studies were included, capturing 4,434 isolates from LMICs. Fifteen serotypes were present in a sufficient number of studies to be included in analyses. Among these, HS4c was the most common serotype globally (12.6%), though leading capsule types varied among regions. HS2, HS3c, HS4c, HS5/31, HS8/17, and HS10 were all among the 10 most common region-specific serotypes., Conclusions: The results of this review suggest that an octavalent vaccine could provide up to 66.9% coverage of typable strains worldwide, and 56.8-69.0% regionally. This review also highlights the paucity of available data on capsules in LMICs; more testing is needed to inform vaccine development efforts., Competing Interests: The authors have declared that no competing interests exist.

The performance of cervical cancer screening will decline as a function of lower disease prevalence-a consequence of successful human papillomavirus (HPV) vaccination. Replacement of cytology with molecular HPV testing as the primary screening test and adoption of risk-based screening, with less intense screening of vaccinated individuals and initiated at older ages is expected to improve efficiency. However, policy officials may decide to further reduce or eliminate screening as the ratio of benefits to harms continues to decline. To evaluate the level of risk currently tolerated for different cancers in the United States (ie, for which clinical guidelines do not recommend secondary prevention though effective screening methods exist), we used US cancer registry data to compare incidence (2008-2012) and survival (1988-2011) associated with different cancers for which organized screening is recommended and not recommended. The most common cancer at ages 70 to 74 years (ie, age group with highest cancer incidence and reasonable life expectancy to consider screening in the US) satisfying Wilson and Jungner's classic screening criteria was vulvar cancer (incidence = 9/100 000 females). In comparison, the incidence of cervical cancer among females 65 years of age (the upper recommended age limit for screening) was 13 cases per 100 000 females (low as a reflection of effective screening), whereas 10-year survival was 66% (similar to vulvar cancer at 67%). Our approach of defining tolerable risk in cancer screening could help guide future decisions to modify cervical screening programs., (© 2020 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of Union for International Cancer Control.)

Given that high-risk human papillomavirus (HPV) is the necessary cause of virtually all cervical cancer, the clinical meaning of HPV-negative cervical precancer is unknown. We, therefore, conducted a literature search in Ovid MEDLINE, PubMed Central, and Google Scholar to identify English-language studies in which (i) HPV-negative and -positive, histologically confirmed cervical intraepithelial neoplasia grade 2 or more severe diagnoses (CIN2+) were detected and (ii) summarized statistics or deidentified individual data were available to summarize proportions of biomarkers indicating risk of cancer. Nineteen studies including 3,089 (91.0%) HPV-positive and 307 (9.0%) HPV-negative CIN2+ were analyzed. HPV-positive CIN2+ (vs. HPV-negative CIN2+) was more likely to test positive for biomarkers linked to cancer risk: a study diagnosis of CIN3+ (vs. CIN2; 18 studies; 0.56 vs. 0.24; P < 0.001) preceding high-grade squamous intraepithelial lesion cytology (15 studies; 0.54 vs. 0.10; P < 0.001); and high-grade colposcopic impression (13 studies; 0.30 vs. 0.18; P = 0.03). HPV-negative CIN2+ was more likely to test positive for low-risk HPV genotypes than HPV-positive CIN2+ ( P < 0.001). HPV-negative CIN2+ appears to have lower cancer risk than HPV-positive CIN2+. Clinical studies of human high-risk HPV testing for screening to prevent cervical cancer may refer samples of HPV test-negative women for disease ascertainment to correct verification bias in the estimates of clinical performance. However, verification bias adjustment of the clinical performance of HPV testing may overcorrect/underestimate its clinical performance to detect truly precancerous abnormalities., (©2020 American Association for Cancer Research.)

Accurate assessment of risks for developing cervical intraepithelial neoplasia of grade 2 or worse (CIN2+) after a given set of screening test results is instrumental to reaching valid conclusions and informing cervical cancer screening recommendations. Using data from the Canadian Cervical Cancer Screening Trial (CCCaST), we assessed prognostic values of enrollment screening test results to predict CIN2+ among women attending routine cervical screening using multivariable Cox proportional hazards (PH) regression and its flexible extension during each of two follow-up periods (protocol-defined and extended). Nonproportional (time-dependent (TD)) and/or nonlinear effects were modeled, as appropriate. Women with abnormal cytology had hazard ratios (HRs) for CIN2+ detection of 17.61 (95% CI: 11.25-27.57) and 10.46 (95% CI: 5.41-20.24) relative to women with normal cytology during the protocol-defined and extended follow-up periods, respectively. High-risk human papillomavirus (HR-HPV) positivity was an even stronger predictor of CIN2+ risk, with significant TD effects during both follow-up periods (p <0.001 for both TD effects). Risks among women co-testing HR-HPV+ with and without abnormal cytology (relative to women co-testing negative) were highest immediately after baseline, and decreased significantly thereafter (p <0.001 for both TD effects). HRs for HPV16+ and HPV18+ women (relative to those testing HR-HPV-) did not vary significantly over time (HR = 182.96; 95% CI: 95.16-351.77 and HR = 111.81; 95% CI: 44.60-280.31, respectively). Due to TD effects, conventional Cox model estimates considerably underestimated adjusted HRs associated with positive HR-HPV testing results early on in the follow-up periods., (© 2018 UICC.)

Background: High-risk human papillomavirus (HR-HPV) testing has become a preferred cervical cancer screening strategy in some countries due to its superior sensitivity over cytology-based methods for identifying cervical intraepithelial neoplasia of grade 2 or worse (CIN2 + ). Improved sensitivity has been accompanied by reductions in specificity and concerns regarding overscreening and overtreatment of women with transient or nonprogressing HR-HPV infections. Triage of HR-HPV + women to colposcopy is, thus, warranted for appropriate management and treatment. Methods: Using data from the Canadian Cervical Cancer Screening Trial (CCCaST), we compared the performance of cytology and HR-HPV strategies to detect CIN2 + among HR-HPV + women (age, 30-69 years). Colposcopy referral rates and performance gains from adding other HR-HPV genotypes to HPV16/18 + triage were also evaluated. Results: A strategy referring all women HPV16/18 + and HPV16/18 - , but with atypical squamous cells of undetermined significance or worse cytology (ASC-US + ) had the highest sensitivity [82.5%; 95% confidence interval (CI), 70.9%-91.0%] but yielded the highest colposcopy referral rate. HPV16/18 + triage was the next most sensitive strategy (64.1%; 95% CI, 51.1%-75.7%). Low-grade squamous intraepithelial lesion or worse cytology (LSIL + ) triage yielded a low sensitivity (32.8%; 95% CI, 21.9%-45.4%) but had the most favorable specificity (93.6%; 95% CI, 91.0%-95.6%), positive predictive value (41.5%; 95% CI, 28.1%-55.9%), and colposcopy referral rate of strategies examined. HPV viral load triage strategies did not perform optimally overall. Inclusion of HR-HPV genotypes 31 and 52 to HPV16/18 + triage provided the highest sensitivities. Conclusion: Concerns surrounding HPV-based screening can be effectively mitigated via triage. Impact: Balancing the benefits of HPV-based primary cervical screening with informed management recommendations for HR-HPV + women may decide the success of its widening utilization. Cancer Epidemiol Biomarkers Prev; 26(6); 923-9. ©2017 AACR ., (©2017 American Association for Cancer Research.)

The Canadian Cervical Cancer Screening Trial was a randomized controlled trial comparing the performance of human papillomavirus (HPV) testing and Papanicolaou cytology to detect cervical intraepithelial neoplasia of grades 2 or worse (CIN2+) among women aged 30-69 years attending routine cervical cancer screening in Montreal and St. John's, Canada (n = 10,154). We examined screening and prognostic values of enrollment cytologic and HPV testing results. Extended follow-up data were available for St. John's participants (n = 5,754; 501,682.6 person-months). HPV testing detected more CIN2+ than cytology during protocol-defined (82.9 vs. 44.4%) and extended (54.2 vs. 19.3%) follow-up periods, respectively. Three-year risks ranged from 0.87% (95% CI: 0.37-2.05) for HPV-/Pap- women to 35.77% (95% CI: 25.88-48.04) for HPV+/Pap+ women. Genotype-specific risks ranged from 0.90% (95% CI: 0.40-2.01) to 43.84% (95% CI: 32.42-57.24) among HPV- and HPV16+ women, respectively, exceeding those associated with Pap+ or HPV+ results taken individually or jointly. Ten-year risks ranged from 1.15% (95% CI: 0.60-2.19) for HPV-/Pap- women to 26.05% (95% CI: 15.34-42.13) for HPV+/Pap+ women and genotype-specific risks ranged from 1.13% (95% CI: 0.59-2.14) to 32.78% (95% CI: 21.15-48.51) among women testing HPV- and HPV16+, respectively. Abnormal cytology stratified risks most meaningfully for HPV+ women. Primary HPV testing every 3 years provided a similar or greater level of reassurance against disease risks as currently recommended screening strategies. HPV-based cervical screening may allow for greater disease detection than cytology-based screening and permit safe extensions of screening intervals; genotype-specific testing could provide further improvement in the positive predictive value of such screening., (© 2016 UICC.)

Prophylactic HPV vaccines hold tremendous potential for reducing cervical and non-cervical HPV-related disease burden worldwide. To maximize on this potential, policy officials will need to carefully consider available evidence, existing uncertainties and the cost-effectiveness of mass HPV vaccination programs in the context of their respective nations and/or regions. Proper harmonization of primary prevention strategies with secondary prevention efforts will also be important. Decisions following such considerations may ultimately depend on programmatic objectives, infrastructure and available resources. Continued research and surveillance surrounding HPV vaccination will be essential for filling current knowledge gaps, and forcing ongoing reconsiderations of selected immunization strategies.

Cervical cancer screening incorporating high-risk human papillomavirus (HPV) detection has become the preferred screening strategy in some countries and is increasingly more widespread in other countries with organized or opportunistic screening programs. Given knowledge that high-risk HPV genotypes differ in their oncogenic potential, commercial HPV assays with genotyping capabilities have been developed and have garnered attention in the recent literature. The cobas 4800 HPV Test is a qualitative multiplex assay that provides specific genotyping information for HPV types 16 and 18, while concurrently detecting 12 other high-risk HPV genotypes as a pooled result. It is currently the only clinically validated, US FDA-approved assay with this capability. Since HPV types 16 and 18 have been designated as conferring the greatest risk for cervical disease, their detection may prove useful in guiding patient management.

Changes in screening guidelines that imply suppression of procedures once recommended are always controversial because of the perception that benefits are being curtailed. Prior to 2012, cervical cancer screening guidelines issued by US-based expert bodies differed in several decision areas, making clinicians essentially cherry-pick among recommendations. To some extent, this approach to screening practices also served to shield clinicians from litigation. It implied starting screening earlier, doing it more frequently, and stopping later in life than necessary. This state of affairs changed in 2012, when the most influential professional groups updated their cervical screening guidelines, and recommendations became essentially unified. All groups recommended that women older than 65 years of age discontinue cervical cancer screening on the basis of evidence that screening benefits in this age group were minor and far outweighed by harms. The guidelines are very specific about the exceptions, which ensure acceptable safety. It is expected that the new guidelines will permit less wasteful cervical screening, while fostering the opportunity to direct resources towards ensuring adequate coverage of high-risk women.

The recognition that human papillomavirus (HPV) infection is the central, necessary cause of cervical cancer paved the way to new fronts of prevention via improved screening methods and HPV vaccination. Much has been learned in all fronts, from the molecular basis of our understanding of how HPV causes disease to the health economics of preventive strategies at the individual and population levels. Progress in other areas of cancer control has yet to show the same multi- and trans-disciplinary gains seen in research on HPV-associated malignancies, which is one of the unequivocal success stories in disease prevention. Yet, as an embarrassment of riches, much more research is needed to fill the gaps in knowledge that remain before we are able to reap the benefits from the knowledge translation from all fronts. Public health research on setting-specific implementation of HPV-based preventive strategies and more concerted advocacy to counter barriers facing the adoption of these strategies are likely to yield major dividends in reducing the burden of HPV-associated diseases. This article forms part of a special supplement entitled "Comprehensive Control of HPV Infections and Related Diseases" Vaccine Volume 30, Supplement 5, 2012., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Introduction: Vaccine development for enterotoxigenic Escherichia coli (ETEC) is dependent on in-depth understanding of toxin and colonization factor (CF) distribution. We sought to describe ETEC epidemiology across regions and populations, focusing on CF and toxin prevalence., Methods: We conducted a systematic review of the published literature, including studies reporting data on ETEC CF and toxin distributions among those with ETEC infection. Point estimates and confidence intervals were calculated using random effects models., Results: Data on 17,205 ETEC isolates were abstracted from 136 included studies. Approximately half of the studies (49%) involved endemic populations, and an additional 17% involved only travel populations. Globally, 60% of isolates expressed LT either alone (27%) or in combination with ST (33%). CFA/I-expressing strains were common in all regions (17%), as were ETEC expressing CFA/II (9%) and IV (18%). Marked variation in toxins and CFs across regions and populations was observed., Discussion/conclusions: These results demonstrate the relative importance of specific CFs in achieving target product profiles for a future ETEC vaccine. However, heterogeneity across time, population, and region, confounded by variability in CF and toxin detection methodologies, obfuscates rational estimates for valency requirements., (Published by Elsevier Ltd.)

Volunteer challenge with enterotoxigenic Escherichia coli (ETEC) has been used for four decades to elucidate the pathogenesis and immune responses and assess efficacy of various interventions. We performed a systematic review of these studies and a meta-analysis of individual patient-level data (IPD) from a subset of studies using standard methodology. We identified 27 studies of 11 ETEC strains administered to 443 naive subjects at doses from 1×10(6) to 1×10(10) colony forming units (cfu). Diarrhea attack rates varied by strain, dose and enterotoxin. Similar rates were seen at doses of 5×10(8) to 1×10(10)cfu with the three most commonly used strains B7A, E24377A, H10407. In IPD analysis, the highest diarrhea attack rates were seen with strains B7A, H10407 and E24377A. The H10407 induced significantly higher stool output than the other strains. Additionally, the rate of output was different across strains. The risk of diarrhea, abdominal cramps, nausea and headaches differed significantly by ETEC strain. An increased risk of nausea, abdominal cramps and headaches was seen for females. Baseline anti-LT IgG titers appeared to be associated with a decrease risk of diarrhea outcomes, a trend not seen with anti-LT IgA or seen consistently with anti-colonization factor antibodies. Neither early antibiotic treatment nor diarrhea duration significantly affected the frequency or magnitude of serologic responses. These studies have served as an invaluable tool in understanding disease course, pathogenicity, innate immune responses and an early assessment of product efficacy. When designing and planning experimental ETEC infection studies in this age of increased ethical scrutiny and growing appreciation of post-infectious sequelae, better understanding of available data is essential., (Published by Elsevier Ltd.)