Toxins and virulence factors of enterotoxigenic Escherichia coli associated with strains isolated from indigenous children and international visitors to a rural community in Guatemala.

Diarrhoea remains a common cause of illness in Guatemala, with children suffering most frequently from the disease. This study directly compared the frequency, enterotoxin, and colonization factor (CF) profiles of enterotoxigenic Escherichia coli (ETEC) strains isolated from children living in a rural community in Guatemala and from Western visitors to the same location during the same seasons, using similar detection methodologies. We found that ETEC accounted for 26% of severe cases of diarrhoea in children requiring hospitalization, 15% of diarrhoea in the community, and 29% of travellers' diarrhoea in visitors staying ⩾2 weeks. The toxin and CF patterns of the ETEC strains isolated from both groups differed significantly (P < 0·0005) as determined by χ 2 = 60·39 for CFs and χ 2 = 35 for toxins, while ETEC phenotypes found in Guatemalan children were comparable to those found in children from other areas of the world.

Peruvian Vibrio cholerae O1 El Tor strains possess a distinct region in the Vibrio seventh pandemic island-II that differentiates them from the prototype seventh pandemic El Tor strains.

A collection of environmental and clinical strains of Vibrio cholerae O1 isolated from the beginning of the Latin American epidemic of cholera in 1991 to 2003 from multiple locations in Peru were characterized and compared with V. cholerae O1 El Tor strains of the seventh pandemic from the rest of the world (Asia, Africa, Australia and Europe) using a multilocus virulence gene profiling strategy and DNA sequencing. Peruvian strains differed from El Tor strains from the rest of the world by the failure of PCR to amplify genes VC0512, VC0513, VC0514 and VC0515 in the Vibrio seventh pandemic island-II (VSP-II) gene cluster. Sequencing of the VSP-II gene cluster and its flanking regions in one Peruvian strain (PERU-130) confirmed the PCR results, indicating that the Peruvian strain had low DNA homology (46.6 %) compared to the reference strain N16961 within the VSP-II region encompassing genes VC0511 to VC0515. Based on these differences in VSP-II, and based on the overall similarity between the pulsotypes of the Peruvian strains and the El Tor reference strain N16961, we concluded that the Peruvian, Eurasian and African strains belonged to the same clonal complex, and that the Peruvian strains represented variants that had independently evolved for a relatively short time. Since these ORFs in VSP-II of Peruvian strains are unique and conserved, they could form the basis for tracking the origin of the Peruvian strains and therefore of the Latin American pandemic.

Evaluation of Peru-15, a new live oral vaccine for cholera, in volunteers.

A new live oral cholera vaccine, Peru-15, was studied for safety, immunogenicity, and excretion in 2 groups of healthy volunteers. Twelve inpatient volunteers received freshly harvested vaccine in doses of either 10(7) or 10(9) cfu. Subsequently 50 outpatient volunteers received freeze-dried vaccine in doses of 10(8) or 10(9) cfu or placebo in a three-cell, double-masked, placebo-controlled trial. The strain was well tolerated at all dose levels, and it stimulated high levels of vibriocidal antibodies in most inpatient volunteers and in all outpatient volunteers. Although antitoxin responses were less frequent and of lower magnitude than the vibriocidal responses, antitoxin responses were seen in >60% of the outpatient volunteers. About 60% of the volunteers excreted the vaccine in their feces; however, fecal excretion did not correlate with serologic responses. It is concluded that Peru-15 is a safe and immunogenic oral vaccine for cholera.

Comparison of alternative buffers for use with a new live oral cholera vaccine, Peru-15, in outpatient volunteers.

During development of Peru-15, a new live oral vaccine for cholera, the role of buffer needed to be evaluated. Generally, oral bacterial vaccines are acid labile and need to be administered by using a formulation which protects them from gastric acid. We compared three different buffers for use with Peru-15, including a standard bicarbonate-ascorbic acid buffer, Alka-Seltzer, and a new electrolyte-rice buffer, CeraVacx. Saline served as the control. Thirty-nine healthy adult volunteers received Peru-15 (10(8) CFU) with one of the three buffers or saline in a double-masked study. The volunteers were monitored for symptoms for 7 days after the dose, serum was tested for antibody responses by vibriocidal antibody and immunoglobulin G antitoxin enzyme-linked immunosorbent assays, and stool samples were tested for excretion of the vaccine strain. Side effects were minimal in all groups. All 30 volunteers who took Peru-15 with a buffer showed significant rises in vibriocidal antibody titer. The magnitude of the rises was higher in the CeraVacx group than in the other two buffer groups. Four of nine volunteers who took the vaccine with saline also showed increased titers, but they were lower than those in any of the three buffer groups. Excretion of the vaccine strain was similar in the buffer groups, but excretion was not associated with the magnitude of the vibriocidal responses. Excretion of Peru-15 was not detected in the saline group. We conclude that buffer does amplify the serological response to Peru-15 and that CeraVacx may provide benefits not provided by other buffers.

Safety and immunogenicity of oral killed whole cell recombinant B subunit cholera vaccine in Barranquilla, Colombia.

In January and February 1992, an assessment was conducted of the safety and immunogenicity of two doses of a new oral cholera vaccine prepared from the recombinant B subunit of the toxin and from killed whole cells (rBS/WC) in 1,165 individuals between the ages of 12 months and 64 years in Barranquilla, Colombia. This was a randomized, double-blind placebo-controlled study. Participants received two doses of either the vaccine or a placebo (killed Escherichia coli K12) over a two-week interval. Few symptoms were detected during the three days following administration of the initial dose and even fewer following the second. Sera obtained upon administration of the first dose and two weeks after administration of the second were tested for Vibrio cholerae 01 Inaba vibriocidal antibodies and antitoxins. Geometric mean titers (GMT) of vibriocidal antibodies were found to increase two-fold in subjects receiving the vaccine. In the paired samples taken from vaccinated subjects, two-fold or greater increases were observed in 44% and four-fold or greater increases were observed in 34%, as compared to similar increases in 9.2% and 2.2% of the sera taken from those receiving the placebo (P < 0.05). The GMTs of IgG and IgA antitoxins, as determined by ELISA, increased by factors of 4 and 3.2, respectively, in those receiving the vaccine, as compared to factors of 1.1 and 1.1 in those given the placebo (P < 0.001 for IgG, P < 0.01 for IgA). Approximately 80% of the paired samples from the vaccinated group showed an increase of both IgG and IgA antitoxins > or = 1.5, as compared to only about 20% of those in the placebo group (P < 0.000001). Belonging to the O blood group did not significantly affect the immune response. Children under age four tended to show a weaker vibriocidal antibody response and a stronger antitoxin response than older subjects. The two doses of oral vaccine were found to be safe and without attributable side-effects. The vibriocidal antibody and antitoxin responses were similar to those obtained previously with the conventional oral killed whole cell B subunit cholera vaccine.

PIP: In a randomized, double-blind, placebo-controlled study in January and February 1992, the safety and immunogenicity of two doses of a new oral cholera vaccine was assessed. The vaccine was prepared from the recombinant B subunit of the toxin and from killed whole cells (rBS/WC) in 1165 individuals between the ages of 12 months and 64 years in Barranquilla, Colombia. Participants received two doses of either the vaccine or a placebo (killed Escherichia coli K12) over a 2-week interval. Few symptoms were detected during the 3 days following administration of the initial dose and even fewer following the second one. Sera obtained upon administration of the first dose and 2 weeks after administration of the second dose were tested for Vibrio cholera 01 Inaba vibriocidal antibodies and antitoxins. Geometric mean titers (GMTs) of vibriocidal antibodies were found to increase two-fold in subjects receiving the vaccine. In the paired samples taken from vaccinated subjects, two-fold or greater increases were observed in 44% and four-fold or greater increases were observed in 34%. In comparison, similar increases were found only in 9.2% and 2.2% of the sera taken from those receiving placebo (p .05). The GMTs of IgG and IgA antitoxins, as determined by ELISA, increased by factors of 4 and 3.2, respectively, in those receiving the vaccine as compared with factors of 1.1 and 1.1, respectively, in those given the placebo (p .001 for IgG and p .01 for IgA). Approximately 80% of the paired samples from the vaccinated group showed an increase of both IgG and IgA antitoxins or= 1.5 as compared with only about 20% of those in the placebo group (p .000001). Belonging to the O blood group did not significantly affect the immune response. Children under the age of 4 years tended to show a weaker vibriocidal antibody response and stronger antitoxin response than did older subjects. The two doses of oral vaccine were found to be safe and without attributable side effects.

Comparison of dilevalol and enalapril administered once daily for mild hypertension.

This was a multicenter, randomized, double-blind, parallel-group study of the efficacy and safety of dilevalol, 200 mg (n = 86), compared with enalapril, 20 mg (n = 92), administered once daily to patients with mild hypertension. Three weeks of placebo washout were followed by 4 weeks of comparative treatment. Beginning with the first week of treatment, both drugs substantially decreased blood pressure from baselines of approximately 160/100 mm Hg. Decreases in systolic pressure were comparable throughout treatment, but dilevalol tended to have a greater effect on diastolic pressure. At the end of double-blind treatment, average decreases in blood pressure with dilevalol and enalapril were 16/13 and 16/11 mm Hg supine and 15/13 and 15/10 mm Hg standing (p = 0.03 for between-group comparisons of standing diastolic pressure). More dilevalol- than enalapril-treated patients achieved a diastolic pressure less than 90 mm Hg; 73 vs 55% (p = 0.02) supine, and 69 vs 43% (p less than 0.01) standing. The safety profiles of the 2 drugs were comparable. The incidence of adverse effects was low, and few patients discontinued treatment. Headache and gastrointestinal discomfort were reported in both groups. Average postural changes in blood pressure were similar to baseline. Electrocardiographic changes were rare and not treatment related. Changes in laboratory test results were minor. Heart rate decreased modestly with dilevalol relative to enalapril (6 vs 2 to 3 beats/min; p less than 0.01), but no bradycardia was observed.

Stool electrolyte content and purging rates in diarrhea caused by rotavirus, enterotoxigenic E. coli, and V. cholerae in children.

One hundred twenty children below 5 years of age with diarrhea caused by Vibrio cholerae, enterotoxigenic Escherichia coli, or rotavirus were studied for stool electrolyte composition and purging rates. The mean purging rate in cholera was 60.1 ml, in ETEC 39.2 ml, and in rotavirus infection 31.4 ml/kg/8 hour. The mean stool sodium concentration in cholera was 88.9 mMol/L, in ETEC 53.7 mMol/L, and in rotavirus infection 37.2 mMol/L. Stool potassium concentration did not show much variation, Mean CO2 concentration in rotavirus infection was 6 mMol/L, significantly lower than in cholera and in ETEC diarrhea. In cholera, stool sodium concentration increased significantly with increase in purging rates; the same was not true in rotavirus and ETEC diarrhea. These differences are considered important factors in formulating replacement therapy in diarrhea.

Oral therapy in children with cholera: a comparison of sucrose and glucose electrolyte solutions.

We performed a double-blind trial comparing sucrose electrolyte oral solution with glucose electrolyte oral solution in children less than 5 years of age with severe cholera-like diarrhea. Of 111 patients studied (102 with bacteriologically confirmed cholera), 55 received sucrose solution and 56 received glucose solution. The success rates, as defined by the absence of the need to give unscheduled intravenous therapy, were similar in the two groups (73% and 77% in the sucrose and glucose groups, respectively). There was no difference in purging rates between the two groups. The primary determinant of success for oral fluid regardless of the sugar was the purging rate. Sucrose malabsorption was responsible for oral therapy failure in one child. This study demonstrates that sucrose is an effective alternative to glucose in the oral therapy solution, but either must be used in conjunction with intravenous solution when treating severe dehydrating diarrhea.

PIP: This study compared, in children with cholera-like severe diarrhea, an oral glucose-electrolyte solution with an oral sucrose-electrolyte solution in equimolar amounts (WHO formula) in a double-blind manner. Of 111 patients, 55 were given sucrose and 56 glucose solutions. An absence of the need to use unscheduled intravenous therapy defined the success rate, which was similar in both groups: 73 and 77%, respectively, in the sucrose and glucose groups. Purgation rates also showed no difference between groups. The main determinant of success for oral fluid regardless of the sugar used was the purging rate. 1 failure of therapy in the sucrose group was attributed to sucrose malabsorption. It is concluded that sucrose is an effective alternative to glucose for oral rehydration therapy, but if the diarrhea has caused severe dehydration before the start of treatment, intravenous supplementation must also be used.

Prevalence of antibody to the Norwalk virus in various countries.

Serum samples from children and adults from several countries were tested by radioimmunoassay for antibody to the Norwalk virus. Antibody was commonly found in adults from all the countries tested. Antibody appears to be acquired more rapidly in children from underdeveloped countries than in children from the United States.

Travelers' diarrhea in Mexico. A prospective study of physicians and family members attending a congress.

We conducted a prospective study of travelers' diarrhea on 73 physicians and 48 family members attending a medical congress in Mexico City, in October, 1974. Fecal and blood specimens were collected before, during and after their visit and examined for enteric bacterial pathogens, viruses and parasites. In 59 (49 per cent) participants travelers' diarrhea developed. Median duration of illness was five days. Onset occurred a median of six days after arrival. An etiologic agent was found in 63 per cent of ill participants. Enterotoxigenic Escherichia coli of different, non-"enteropathogenic" serotypes was the most common cause; other responsible pathogens included salmonellae, invasive Esch. coli., shigellae, Vibrio parahaemolyticus, Giardia lamblia and the human reovirus-like agent. Consumption of salads containing raw vegetables was associated with enterotoxigenic Esch. coli infection (P = 0.014). Travelers' diarrhea in Mexico is a syndrome caused by a variety of pathogens, the most common of which is enterotoxigenic Esch. col.

Laboratory investigation of diarrhea in travelers to Mexico: evaluation of methods for detecting enterotoxigenic Echerichia coli.

A laboratory investigation was conducted on cultures collected from travelers before, during, and after a trip to Mexico to characterize the etiology of traveler's diarrhea. Four laboratory methods for detecting enterotoxigenicity of Escherichia coli were evaluated: the infant mouse assay, the Chinese hamster ovary (CHO) cell assay, the Y1 adrenal cell assay, and the rabbit ileal loop. Although a number of common enteric pathogens were identified as a cause of traveler's diarrhea, including six serotypes of Salmonella, two serotypes of Shigella, Vibrio parahaemolyticus, Giardia lamblia, and Entamoeba histolytica, enterotoxigenic Escherichia coli was most commonly isolated. Strains were identified that produced only heat-labile enterotoxin (LT), only heat-stable enterotoxin (ST), or both LT and ST. The infant mouse assay yielded results falling into two distinct groups, providing a clear separation of positive and negative cultures. The CHO assay also formed two groups, with positive cultures producing 11% or more of the elongated cells. There was good agreement between the CHO and the Y1 adrenal cell assays for detection of LT. The adrenal cell system for detection of LT was more suitable than the CHO assay for processing large numbers of specimens because of the miniculture modification of this method utilized in this study. The infant mouse method was a simple and reliable method for detecting ST.

Diarrhoea associated with heat-stable enterotoxin-producing strains of Escherichia coli.

Five patients who developed acute watery diarrhoea while travelling in Mexico in October, 1974, were found to have enterotoxigenic Escherichia coli in their stool which produced heat-stable enterotoxin (S.T.) without producing heat-labile enterotoxin (L.T.). These S.T.-only E. coli, which have previously been described as causing diseases in animals, must now be regarded as pathogenic for humans as well.