Factors associated with typical enteropathogenic Escherichia coli infection among children <5 years old with moderate-to-severe diarrhoea in rural western Kenya, 2008-2012.

Typical enteropathogenic Escherichia coli (tEPEC) infection is a major cause of diarrhoea and contributor to mortality in children <5 years old in developing countries. Data were analysed from the Global Enteric Multicenter Study examining children <5 years old seeking care for moderate-to-severe diarrhoea (MSD) in Kenya. Stool specimens were tested for enteric pathogens, including by multiplex polymerase chain reaction for gene targets of tEPEC. Demographic, clinical and anthropometric data were collected at enrolment and ~60-days later; multivariable logistic regressions were constructed. Of 1778 MSD cases enrolled from 2008 to 2012, 135 (7.6%) children tested positive for tEPEC. In a case-to-case comparison among MSD cases, tEPEC was independently associated with presentation at enrolment with a loss of skin turgor (adjusted odds ratio (aOR) 2.08, 95% confidence interval (CI) 1.37-3.17), and convulsions (aOR 2.83, 95% CI 1.12-7.14). At follow-up, infants with tEPEC compared to those without were associated with being underweight (OR 2.2, 95% CI 1.3-3.6) and wasted (OR 2.5, 95% CI 1.3-4.6). Among MSD cases, tEPEC was associated with mortality (aOR 2.85, 95% CI 1.47-5.55). This study suggests that tEPEC contributes to morbidity and mortality in children. Interventions aimed at defining and reducing the burden of tEPEC and its sequelae should be urgently investigated, prioritised and implemented.

Diarrhoea, enteric pathogen detection and nutritional indicators among controls in the Global Enteric Multicenter Study, Kenya site: an opportunity to understand reference populations in case-control studies of diarrhoea.

Given the challenges in accurately identifying unexposed controls in case-control studies of diarrhoea, we examined diarrhoea incidence, subclinical enteric infections and growth stunting within a reference population in the Global Enteric Multicenter Study, Kenya site. Within 'control' children (0-59 months old without diarrhoea in the 7 days before enrolment, n = 2384), we examined surveys at enrolment and 60-day follow-up, stool at enrolment and a 14-day post-enrolment memory aid for diarrhoea incidence. At enrolment, 19% of controls had ⩾1 enteric pathogen associated with moderate-to-severe diarrhoea ('MSD pathogens') in stool; following enrolment, many reported diarrhoea (27% in 7 days, 39% in 14 days). Controls with and without reported diarrhoea had similar carriage of MSD pathogens at enrolment; however, controls reporting diarrhoea were more likely to report visiting a health facility for diarrhoea (27% vs. 7%) or fever (23% vs. 16%) at follow-up than controls without diarrhoea. Odds of stunting differed by both MSD and 'any' (including non-MSD pathogens) enteric pathogen carriage, but not diarrhoea, suggesting control classification may warrant modification when assessing long-term outcomes. High diarrhoea incidence following enrolment and prevalent carriage of enteric pathogens have implications for sequelae associated with subclinical enteric infections and for design and interpretation of case-control studies examining diarrhoea.

Antigen-specific IgA B memory cell responses to Shigella antigens elicited in volunteers immunized with live attenuated Shigella flexneri 2a oral vaccine candidates.

We studied the induction of antigen-specific IgA memory B cells (B(M)) in volunteers who received live attenuated Shigella flexneri 2a vaccines. Subjects ingested a single oral dose of 10(7), 10(8) or 10(9) CFU of S. flexneri 2a with deletions in guaBA (CVD 1204) or in guaBA, set and sen (CVD 1208). Antigen-specific serum and stool antibody responses to LPS and Ipa B were measured on days 0, 7, 14, 28 and 42. IgA B(M) cells specific to LPS, Ipa B and total IgA were assessed on days 0 and 28. We show the induction of significant LPS-specific IgA B(M) cells in anti-LPS IgA seroresponders. Positive correlations were found between anti-LPS IgA B(M) cells and anti-LPS IgA in serum and stool; IgA B(M) cell responses to IpaB were also observed. These B(M) cell responses are likely play an important role in modulating the magnitude and longevity of the humoral response.

Enteric adenovirus infection and childhood diarrhea: an epidemiologic study in three clinical settings.

During a 2-year prospective study of gastroenteritis in children less than 2 years of age, the role of enteric adenovirus as a cause of infantile diarrhea was examined in three clinical settings in a case-control fashion. Using a monoclonal antibody-based enzyme-linked immunosorbent assay with specificity for adenovirus serotypes 40 and 41, enteric adenovirus was identified in 10 of 246 episodes of diarrhea in outpatients (4.1%), 13 of 211 children admitted to the hospital with diarrhea (6.2%), and 5 of 81 children in whom nosocomial diarrhea developed (6.2%), making this agent the third most commonly identified etiologic agent of diarrheal disease. Asymptomatic infections were uncommon (5 of 372 control subjects, or 1.3%) and were seen most frequently in the nosocomial setting. Cases occurred in every calendar month except March and April of each year. A syndrome of watery diarrhea of longer duration compared with other patients with diarrhea (mean 5.4 vs 3.8 days, P = .01), associated with vomiting and dehydration, was present in most cases. Compared with patients with rotavirus, patients were as likely to experience fever and dehydration and more likely to vomit. Household contact with gastroenteritis, often with a child 2 to 5 years of age, was a predisposing factor. It was concluded that enteric adenovirus is an important cause of infantile diarrhea in Baltimore children. Although far less common than rotavirus, this agent was associated with diarrheal illnesses that were at least as severe as those seen with rotavirus.

Acute diarrhea in Baltimore children attending an outpatient clinic.

Acute diarrheal illnesses in Baltimore children younger than 2 years of age attending an outpatient clinic were studied during a 12-month period. One in five acute care visits made to the clinic by children younger than 2 years was for diarrhea, and 5% of diarrhea cases required hospitalization. With the use of comprehensive methodology, a potential etiologic agent was identified in the stool of 105 (43%) of the 246 episodes of diarrhea in cases and in 43 (28%) of the 155 controls. Viral pathogens were found in 26% of episodes, and bacterial pathogens were found in 14%. Only rotavirus, enteric adenovirus and Salmonella were significantly associated with diarrhea. Cases were more likely to have measures of socioeconomic deprivation, such as household crowding, low maternal educational level and low birth weight, when compared to controls. Racial differences in morbidity from diarrheal illnesses were observed but could be attributed to these specific sociodemographic factors. Despite the low mortality caused by infantile gastroenteritis in the United States, it remains an important public health problem. However, even with intensive investigation the etiologies remain largely unknown.

Volunteer studies investigating the safety and efficacy of live oral El Tor Vibrio cholerae O1 vaccine strain CVD 111.

A live oral cholera vaccine should ideally protect against both classical and El Tor biotypes of Vibrio cholerae O1. An El Tor biotype vaccine strain, therefore, would complement classical cholera vaccine strain CVD 103-HgR, a strain already in use in some countries. In this study, 25 healthy adult volunteers received a single dose of 10s colony-forming units of El Tor vaccine strain CVD 111, a derivative of El Tor Ogawa strain N16117 deleted in the virulence cassette. Three (12%) volunteers developed mild diarrhea (mean stool volume = 813 ml) but no systemic symptoms; 23 (92%) of the 25 volunteers developed serum vibriocidal antibodies (geometric mean titer = 1:2,291). Five weeks after vaccination, 18 vaccines and eight uninimunized control volunteers underwent wild-type challenge with El Tor Ogawa strain 3008. Three (16.7%) of 18 vaccinees and seven (87.5%) of eight controls developed diarrhea (P = 0.001) (vaccine efficacy = 80.9%). Further studies are underway to determine a dosage of CVD 111 that will be more clinically acceptable but equally immunogenic and protective.

Antigen-specific B memory cell responses to lipopolysaccharide (LPS) and invasion plasmid antigen (Ipa) B elicited in volunteers vaccinated with live-attenuated Shigella flexneri 2a vaccine candidates.

We evaluated B memory responses in healthy adult volunteers who received one oral dose of live-attenuated Shigella flexneri 2a vaccine. LPS-specific B(M) cells increased from a median of 0 at baseline to 20 spot forming cells (SFC)/10(6) expanded cells following vaccination (p=0.008). A strong correlation was found between post-vaccination anti-LPS B(M) cell counts and peak serum anti-LPS IgG titers (rs=0.95, p=0.0003). Increases in B(M) specific for IpaB approaching significance were also observed. In sum, oral vaccination with live-attenuated S. flexneri 2a elicits B(M) cells to LPS and IpaB, suggesting that B(M) responses to Shigella antigens should be further studied as a suitable surrogate of protection in shigellosis.

Genotypic analysis of invasive Streptococcus pneumoniae from Mali, Africa, by semiautomated repetitive-element PCR and pulsed-field gel electrophoresis.

As part of a large, ongoing study of invasive infections in pediatric patients in Bamako, Mali, 106 cases of invasive pneumococcal disease were identified from June 2002 to July 2003 (J. D. Campbell et al., Pediatr. Infect. Dis. J. 23:642-649, 2004). Of the 12 serotypes present, the majority of isolates were not contained in PCV7 (the 7-valent pneumococcal conjugate vaccine), including 1 isolate that was serotype 1, 12 isolates that were serotype 2, 58 isolates that were serotype 5, 7 isolates that were serotype 7F, and 1 isolate that was serotype 12F. To determine whether clonal dissemination of the predominant serotypes had taken place, genotyping was performed on 100 S. pneumoniae isolates by using two methods: pulsed-field gel electrophoresis (PFGE) of SmaI-digested genomic DNA, and the Bacterial Barcodes repetitive-element PCR (rep-PCR) method. Criteria for delineating rep-PCR genotypes were established such that isolates of different serotypes were generally not grouped together. The two methods were equally discriminatory within a given pneumococcal serotype. PFGE separated the isolates into 15 genotypes and 7 subtypes; rep-PCR separated isolates into 15 genotypes and 6 subtypes. Using either method, isolates within serotypes 2, 5, and 7 formed three large, separate clusters containing 1 genotype each. Both methods further distinguished related subtypes within serotypes 2 and 5. Interestingly, one of the PFGE subtypes of serotype 5 is indistinguishable from the Columbia(5)-19 clone circulating in Latin America since 1994. The data support that serotypes 2 and 5 were likely to be the result of dissemination of particular clones, some of which are responsible for invasive disease over a broad population range.

Helicobacter pylori and gastroduodenal disorders: new approaches for prevention, diagnosis and treatment.

Prevention and treatment of H. pylori infection through immunization would be an important achievement considering the high cost of drug therapy, the appearance of antibiotic resistant strains, and the failure of drug therapy to prevent reinfection. Success hinges on determining the extent to which immunologic memory can be evoked in the stomach, and the ability to identify antigens and delivery systems which stimulate protective immunity rather than disease-promoting responses. Recent experiments by several groups have demonstrated that mice immunized orally or intragastrically (along with mucosal adjuvant) with whole H. pylori lysate, purified or recombinant urease, or purified VacA were significantly protected against challenge with virulent Helicobacter. Several vaccine candidates will enter clinical trials in humans in the near future.

Molecular epidemiology of rotavirus infection in a room for convalescing newborns.

In a prospective study, all patients admitted to a unit for convalescing newborns on an infant-toddler ward between January and April 1985 were tested every other day for rotavirus (RV) excretion by using an enzyme-linked immunosorbent assay. RNA electrophoresis of the RV strains identified in this population were analyzed to determine whether specific strains of virus were associated with infections in newborns. RV strains infecting older, symptomatic children from the infant-toddler ward were used for comparison. Among the 39 patients enrolled in the study, RV was detected in the stools of 13 (33%), 11 (86%) of whom were asymptomatic. Three different electropherotypes were seen among the newborns who were RV positive; these electropherotypes were identical to those identified in older children with community-acquired diarrhea and nosocomial-acquired diarrhea who were hospitalized on the infant-toddler ward during the same study period. Each of the three strains was first identified in the general ward and subsequently detected in the room with newborns within three to six days. We failed to identify a particular strain that exclusively infected newborns.

Cryptosporidium infection in acquired immunodeficiency syndrome: not always a poor prognosis.

Chronic diarrhea and malabsorption accompanied by simultaneous infection with the protozoa Giardia lamblia and Cryptosporidium occurred in a 22-year-old homosexual man with antibody to human immunodeficiency virus (HIV). Small bowel biopsy demonstrated total villous atrophy and marked mononuclear infiltration in the lamina propria simulating celiac disease. Treatment with metronidazole resulted in resolution of diarrhea, clearance of parasites, and marked improvement in small bowel histology. Although diarrhea and malabsorption in immunocompromised patients with cryptosporidiosis are regarded as ominous, our patient remained disease free for the next 3 years. Thus, infection with Cryptosporidium in patients with HIV does not always lead to intractable diarrhea or death.

Immunologic response to oral cholera vaccination in a crossover study: a novel placebo effect.

The authors conducted a two-period crossover study of the reactogenicity and immunogenicity of live oral cholera vaccine CVD 103-HgR among US university students. Subjects ingested 5 x 10(8) colony forming units of either killed Escherichia coli K12 placebo or vaccine, followed by the opposite treatment one week later. Surprisingly, the dynamics of the immunologic response were influenced by prior ingestion of placebo. Subjects who received placebo first showed stronger vibriocidal antibody responses 2 weeks after vaccination compared with subjects who received vaccine first; this same pattern was seen for antitoxin titers. The authors suggest that ingestion of E. coli K12 one week prior to immunization boosts the immunologic response to vaccine by an unknown mechanism. Future crossover studies that examine immunologic outcomes might be designed to explore the ubiquity of such an effect.

Safety and immunogenicity of a tetravalent group B streptococcal polysaccharide vaccine in healthy adults.

Proposed strategies for prevention of neonatal group B streptococcal (GBS) infection have included active immunization of pregnant women and passive immunization of high-risk infants with hyperimmune GBS globulin derived from vaccinated plasma donors. To explore the feasibility of a program for generating hyperimmune GBS globulin, we evaluated the safety and immunogenicity of a candidate multivalent GBS vaccine containing purified polysaccharide from types Ia, Ib, II, and III among subjects most likely to develop an immune response following vaccination, i.e. those with pre-existing antibody to GBS. Thirty volunteers prescreened for serum antibody to type III GBS were immunized with a single subcutaneous injection of vaccine containing either 10, 25, or 50 micrograms of each polysaccharide type (Group 1). An additional ten volunteers prescreened for antibody to type Ia were vaccinated with the 50 micrograms dose (Group 2). Vaccination was generally well tolerated with minor reactions occurring in 27% of subjects. Using a quantitative enzyme-linked immunosorbent assay (ELISA), the seroconversion rates (> or = fourfold rise) and geometric mean antibody concentration (GMC in microgram IgG ml-1) 6 weeks after vaccination in Group 1 to type Ia, II, and III were 33% (GMC 5.2), 17% (GMC 3.6), and 70% (GMC 43.4), respectively. Quantitative titers were not available for type Ib, but a fourfold rise in ELISA units was seen in 13% of subjects. In Group 2, seroconversion rates to type Ia and III were 90% (GMC 73.4) and 40% (GMC 22.2), respectively. No significant dose-response effect was detected. Combined analysis of Groups 1 and 2 demonstrated that subjects with prevaccination antibody concentrations > 2 micrograms IgG ml-1 had significantly higher type-specific antibody concentrations following vaccination compared with subjects possessing lower levels of antibody before immunization. We conclude that our tetravalent GBS polysaccharide vaccine is safe but only modestly immunogenic in healthy seropositive adults. More potent vaccines will be required for public health use.

Safety and immunogenicity in North Americans of a single dose of live oral cholera vaccine CVD 103-HgR: results of a randomized, placebo-controlled, double-blind crossover trial.

We conducted a double-blind, placebo-controlled, randomized crossover study to evaluate the safety and immunogenicity of a single 5 x 10(8)-CFU dose of live oral recombinant cholera vaccine CVD 103-HgR in 94 North American adults. The vaccine was well tolerated without associated adverse reactions. Despite minimal fecal excretion of vaccine, 97% of subjects exhibited serum vibriocidal antibody and 72% had antitoxin responses.

Development and evaluation of an enzyme-linked immunosorbent assay for serum Vi antibodies for detection of chronic Salmonella typhi carriers.

An enzyme-linked immunosorbent assay (ELISA) measuring, in serum, immunoglobulin G (IgG), IgM, and IgA to Vi capsular polysaccharide antigen that was tyraminated (Vi-Tyr) to increase its binding efficiency to microtiter plates was compared with the standard passive hemagglutination assay (PHA) as a screening test for chronic Salmonella typhi carriers. Initially, three populations were evaluated: 22 healthy U.S. adults, 17 young Chilean adults with acute typhoid fever, and 51 Chileans who had bacteriologically confirmed S. typhi chronic carriage. IgG-specific Vi-Tyr antibodies were preferentially present in the S. typhi chronic carrier state. A total of 44 of 51 (81%) chronic carriers, 0 of 22 (0%) healthy U.S. adults, and 2 of 17 (12%) Chileans with acute typhoid fever had reciprocal IgG Vi-Tyr ELISA antibody titers in serum of greater than or equal to 200. The IgG Vi-Tyr ELISA was then compared with the PHA as a screening test for chronic carriers in 141 Chilean female food handlers. One woman was serologically incriminated as a carrier by both the IgG ELISA and PHA; her coprocultures were positive for S. typhi. One other woman, identified as a carrier by PHA, was negative by culture and IgG ELISA. The IgG Vi-Tyr ELISA is as sensitive as the PHA (86 versus 76%) and as specific (95 versus 95%) in screening for chronic carriers.