Five versus three days of ofloxacin therapy for traveler's diarrhea: a placebo-controlled study

In this double-blind study with 232 patients, 300 mg of ofloxacin given orally twice daily for 5 or 3 days was compared with placebo for the treatment of acute diarrhea in U.S. students visiting Guadalajara, Mexico. The 3-day regimen of ofloxacin was found to be as effective as the 5-day regimen in producing a clinical and microbiologic cure. Clinical cures for patients who received ofloxacin for 5 days occurred in 59 of 66 (89%) subjects, whereas clinical cure occurred in 77 of 81 (95%) of those who received ofloxacin for 3 days and in 56 of 79 (71%) of those who took placebo (P = 0.0001). When the duration of diarrhea after therapy was begun was compared in subgroups, a significant (P less than 0.05) shortening of posttreatment illness occurred in comparison with that in the placebo group for the following groups: for 5 days of ofloxacin, cases of shigellosis (32 versus 98 h); for 3 days of ofloxacin, all cases (28 versus 56 h), cases of enterotoxigenic Escherichia coli diarrhea (26 versus 66 h), cases of shigellosis (24 versus 98 h), all cases of illnesses associated with a bacterial enteropathogen (28 versus 69 h), and cases of illnesses in which numerous leukocytes were found in stool by microscopy (22 versus 49 h). Microbiologic eradication rates were 75 of 78 (96%) for patients who received ofloxacin and 37 of 46 (80%) for patients who received placebo (P = 0.009). There was no significant difference in the number of adverse events reported by patients in either of the treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal secretory immune response to infection with Aeromonas species and Plesiomonas shigelloides among students from the United States in Mexico

Intestinal secretory IgA (sIgA) response or lack of response among adults in Mexico with diarrhea was used as an indicator of enteropathogenicity of Aeromonas species and Plesiomonas shigelloides. sIgA was extracted from stool specimens obtained at day of presentation and 5 days later. Total sIgA was standardized, and specific sIgA titer against the organism being shed by each patient was determined. Western blotting was used to determine which microbial antigens elicited an intestinal sIgA response. Of 12 subjects shedding Aeromonas sobria or Aeromonas hydrophila, 11 had a fourfold or greater sIgA titer rise against the infecting strain. Western blotting showed that somatic lipopolysaccharides were the immunodominant antigens. No sIgA titer rises were detected among two patients shedding Aeromonas caviae or in 14 shedding P. shigelloides. This study provides further evidence of the significance of A. sobria and A. hydrophila as pathogens in acute diarrhea but raises additional questions about the role of P. shigelloides, at least in US adults with travelers' diarrhea.

The role of home environment in infant diarrhea in rural Egypt

In 1982 and 1983, a descriptive environmental survey was conducted in 317 households with newborn infants in rural Bilbeis, Egypt. The incidence of infant diarrhea in these households was ascertained by twice-weekly home visits for a 1-year period (1981-1982). Using univariate and multivariate analyses, the authors identified household factors that were statistically associated with infant diarrhea incidence, including number of children in the house under 4 years of age; number of persons per household; incidence of diarrhea in other family members; having a dirt (vs. concrete) dining room floor; having multiple living areas in the house; having a house or roof in need of repair; using well water rather than tap water for cooking or bathin; the absence of a sewer for waste bathwater; food being left out at room temperature between meals; and having many rodents in the house. Two practices involving interaction with the environment appeared to be protective: butchering of cattle by the family for home consumption, and protection of the infant from flies by a veil during napping. The combined household variables explained 25% of the variance in the total incidence of diarrhea. Categories of variables that accounted for most of the total variance explained by environmental factors are, in decreasing order: house structure (28%); water usage (24%); toilet and bathing area (12%); animal management (11%); food preparation area (10%); hygiene (8%); and wastewater management (6%). This approach may be useful in identifying environmental characteristics whose change would reduce diarrheal illness among infants.

Importance of collaborative research to improve world health

The real health crisis is occurring silently in the developing world where infectious and nutritional diseases are preventing full expression of genetic potential and shortening life by one-third. The advances made in biotechnology over the last 10 years can now lead to breakthroughs as the biology of infectious agents and the host immune system are explored. Funding agencies and governments in developing countries should increase their support of collaborative research designed to improve world health, and health care professionals should work together to support their colleagues in developing areas who have potential interest in research careers. Scientists in the United States and Canada, regardless of the specific nature of their investigative activities, should initiate a scientific relationship with colleagues in developing countries. Given the scarce resources available, research teams using new techniques and identifying cost-effective interventions will point the way to improved world health.

The isolation and characterization of a Norwalk virus-specific cDNA

Norwalk virus, an important cause of epidemic, acute, nonbacterial gastroenteritis in adults and children, has eluded adaptation to tissue culture, the development of an animal model, and molecular cloning. In this study, a portion of the Norwalk viral genome encoding an immunoreactive region was cloned from very small quantities of infected stool using sequence-independent single primer amplification. Six overlapping complementary DNA (cDNA) clones were isolated by immunologic screening. The expressed recombinant protein from a representative clone reacted with six of seven high titer. Norwalk-specific, postinfection sera but not with corresponding preinfection sera. Nucleic acid sequence for all clones defined a single open reading frame contiguous with the lambda gt11-expressed beta-galactosidase protein. Only oligonucleotide probes specific for the positive strand (defined by the open reading frame) hybridized to an RNaseA-sensitive, DNaseI-resistant nucleic acid sequence extracted from Norwalk-infected stool. Furthermore, RNA extracted from serial postinfection, but not preinfection, stools from three of five volunteers hybridized to a Norwalk virus cDNA probe. Clone-specific oligonucleotide probes hybridized with cesium chloride gradient fractions containing purified Norwalk virion. In conclusion, an antigenic, protein-coding region of the Norwalk virus genome has been identified. This epitope has potential utility in future sero- and molecular epidemiologic studies of Norwalk viral gastroenteritis.

Use of quinolones in the treatment of gastrointestinal infections

Bacterial enteropathogens are responsible for between 40% and 80% of diarrheal illness depending upon the age of the persons affected and geographic areas where illness occurs. Antibacterial agents will shorten the illness associated with enteric infection caused by enterotoxigenic Escherichia coli, Shigella spp. and Campylobacter jejuni. These drugs also are effective in the therapy of certain clinical conditions (presumably because they are due to the same agents) which are characterized by moderate to severe diarrhea with one or more of the following: high fever, dysentery (passage of bloody mucoid stools), or high leukocyte counts in stools. Antimicrobial agents are also effective in the therapy of travelers' diarrhea. The quinolone drugs have several advantages in the management of bacterial diarrhea where strains causing illness from nearly all regions of the world will show general susceptibility: high concentrations are achieved in the intestinal lumen following oral administration and resistance development is unusual. A quinolone probably represents the optimal agent for therapy of bacterial diarrhea in adults in areas where trimethoprim-resistant enteric pathogens are common.

Occurrence of Norwalk virus infections among adults in Mexico

Norwalk virus infection was sought in 48 US, 49 Puerto Rican, and 27 Mexican adults attending medical school in Guadalajara (Mexico) who were enrolled in a 2-year longitudinal study. Serum specimens were collected quarterly and as acute- and convalescent-phase samples around episodes of gastroenteritis. The reciprocal Norwalk virus geometric mean titer (GMT) for Puerto Rican students (567) was significantly higher than that of the US students overall (294; P less than .001) and for four of nine quarterly periods. The reciprocal Norwalk GMT for Mexican students (748) was also significantly higher than that of the US students overall (P less than .001) and for seven of nine quarterly periods. The average percentage of students per year with seroconversions was 30%. The rate of Norwalk virus infection averaged 0.36 episodes per student-year. Symptoms of gastroenteritis associated with seroconversion occurred in 45% of students. Preexisting serum antibody did not protect against subsequent Norwalk virus infection in these subjects. All student groups had similar rates of infection and symptomatic gastroenteritis.

Comparative efficacy of loperamide hydrochloride and bismuth subsalicylate in the management of acute diarrhea

An open-label, parallel comparison of loperamide hydrochloride (Imodium A-D) and bismuth subsalicylate (Pepto-Bismol) was conducted using nonprescription dosages in adult students with acute diarrhea (three or more unformed stools in the preceding 24 hours plus at least one additional symptom of enteric infection). For the two-day study period, the daily dosage was limited to 8 mg (40 ml) for loperamide-treated subjects and to 4.9 g for bismuth subsalicylate-treated subjects. At these dosages, loperamide significantly reduced the average number of unformed bowel movements relative to bismuth subsalicylate. Following the initial dose of treatment, control of diarrhea was maintained significantly longer with loperamide than with bismuth subsalicylate. Time to last unformed stool was significantly shorter with loperamide than with bismuth subsalicylate. In providing overall subjective relief, subjects rated loperamide significantly better than bismuth subsalicylate at the end of the 24 hours. Both treatments were well tolerated, and none of the minor adverse effects reported resulted in discontinuation of therapy. It was concluded that loperamide is effective at a daily dosage limit of 8 mg (40 ml) for the treatment of acute nonspecific diarrhea and provides faster, more effective relief than bismuth subsalicylate.

A randomized, open-label comparison of nonprescription loperamide and attapulgite in the symptomatic treatment of acute diarrhea

The efficacy of nonprescription doses of loperamide hydrochloride (Imodium A-D) was compared with nonfibrous activated attapulgite (Diasorb) in a randomized, parallel, open-label study of adult patients with acute diarrhea. The results of the study showed loperamide to be more effective than attapulgite in the control of diarrhea. Loperamide significantly reduced stool frequency compared with attapulgite, particularly within the first 12-hour period following the start of therapy, and significantly shortened the mean time to last unformed stool (loperamide, 14.2 hours, versus attapulgite, 19.5 hours). Subjective evaluations of severity of enteric symptoms, overall relief following treatment, and overall relief after 48 hours of treatment were equivalent for both drugs. Both treatments were well tolerated, and there was no difference between treatments with respect to the proportion of patients reporting adverse experiences.

Comparison of two assay methods for patterns of adherence to HEp-2 cells of Escherichia coli from patients with diarrhea

To determine whether methodological differences in the HEp-2 adherence assay could explain conflicting results of field studies, 244 strains of Escherichia coli from Mexican children with diarrhea were tested for patterns of adherence by the method used at the Center for Vaccine Development, University of Maryland (CVD), and at the Center for Infectious Diseases, University of Texas Medical School and School of Public Health (UTH). The CVD assay differentiated three phenotypes of adherent E. coli, including localized, diffuse, or aggregative adherence (LA, DA, or AA, respectively). There was agreement on pattern of adherence in 241 of the 244 strains (98.8%) tested by the CVD method in both Baltimore and Houston, and AA+ was the most common phenotype (28.5% of isolates). Among these isolates, the UTH assay detected only two adherent phenotypes (LA and DA), since it did not distinguish the AA pattern. The LA+ strains detected by each assay were compared for positivity with the enteropathogenic E. coli adherence factor (EAF) gene probe. Of the 16 strains LA+ by the CVD method, 100% were EAF+; in contrast, only 11 of 22 strains LA+ by the UTH method were EAF+ (P = 0.00074). These results help explain why in pediatric field studies in Mexico where isolates were tested by the UTH method (J. J. Mathewson, R. A. Oberhelman, H. L. Dupont, F. J. de la Cabada, and E. V. Garibay, J. Clin. Microbiol. 25:1917-1919, 1987) LA+ strains often did not belong to enteropathogenic E. coli O serogroups and why the AA pattern was not observed; the opposite was found in studies of pediatric diarrhea in Chile in which the CVD assay was used (M. M. Levine, V. Prado, R. M. Robins-Browne, H. Lior, J. B. Kaper, S. Moseley, K. Gicquelais, J. P. Nataro, P. Vial, and B. Tall, J. Infect. Dis. 158:224-228, 1988). Since it appears that both assays identify E. coli strains associated with diarrheal illness, the genetic relationships among these strains should be examined in future studies.

Emergence of resistant fecal Escherichia coli in travelers not taking prophylactic antimicrobial agents

Fecal specimens from individuals traveling to Mexico were examined before, during, and after travel for the presence of Escherichia coli resistant to ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfonamides, trimethoprim (TMP), and TMP-sulfamethoxazole (TMP-SMX). None of these individuals took prophylactic antibiotics, although 4 of 13 took short courses of an antimicrobial agent for therapy of traveler's diarrhea. With an average of 9.3 E. coli per sample, resistance to all agents tested except gentamicin was shown to increase during the time in Mexico (P less than 0.001 to P less than 0.05). For example, no TMP-resistant (Tmpr) E. coli isolates were found by this method before travel, whereas 57% of the individuals had Tmpr and Tmpr-Smxr E. coli by the final week in Mexico. This increase in resistance occurred regardless of whether an individual took a short course of antimicrobial therapy. This study shows that travel itself, even without the use of prophylactic or therapeutic antimicrobial agents, is associated with the acquisition of resistant E. coli. Travel to developing nations may rival other sources of resistant organisms.

Treatment of traveler's diarrhea with sulfamethoxazole and trimethoprim and loperamide

In a randomized, double-blind, placebo-controlled trial, 227 US adults with acute diarrhea in Mexico received a single dose of sulfamethoxazole and trimethoprim (1600/320 mg) or 3 days of therapy with loperamide hydrochloride (4-mg loading dose, then 2 mg orally after each loose stool), sulfamethoxazole-trimethoprim (800/160 mg orally twice daily), or the combination of both. Subjects treated with the combination had the shortest average duration of diarrhea compared with the placebo group (1 hour vs 59 hours), took the least amount of loperamide after the loading dose (3.8 mg), and had the shortest duration of diarrhea associated with fecal leukocytes or blood-tinged stools (4.5 hours). A single dose of sulfamethoxazole-trimethoprim was also efficacious (28 vs 59 hours), but loperamide alone was significantly effective only when treatment failures were treated with antibiotics (33 vs 58 hours). The combination of sulfamethoxazole-trimethoprim plus loperamide can be highly recommended for the treatment of most patients with traveler's diarrhea.

Multiple-challenge study of host susceptibility to Norwalk gastroenteritis in US adults

In a multiple-challenge study of US adult volunteers with low or high levels of serum antibody to Norwalk virus, Norwalk inoculum 8FIIa was administered to 42 subjects, 22 were challenged 6 months later, and 19 received a third challenge after 6 more months. All 12 with high (greater than or equal to 1:200) but only 19 of 30 with low (less than 1:100) prechallenge titers experienced illness or a fourfold increase in titer after the first challenge (P less than .025). Only 4 of those challenged twice became ill; all had low initial titers but 3 had high titers before the second challenge. None became ill after a third challenge. Nine (47%) had high titers immediately before the third challenge; 3 had low titers before and after each challenge and remained asymptomatic. Thus, preexisting serum antibody to Norwalk virus does not seem to be associated with protective immunity, but antibody levels become associated with protection after repetitive exposure. Short-term resistance lasts greater than or equal to 6 months after challenge, and a small percentage of resistant individuals maintain low antibody titers even after multiple challenges.

Use of bismuth subsalicylate for the prevention of travelers' diarrhea

During the months of July 1977 and July 1985, students from the United States participated in a double-blind, placebo-controlled trial examining the effectiveness of liquid bismuth subsalicylate (BSS) (1977) and two dosages of the tablet formulation of BSS (1985) in preventing diarrhea while in Guadalajara, Mexico. In the first study, 62 subjects received BSS for 3 weeks at a dosage of 60 mL four times daily (4.2 g of BSS/d) compared with 66 students receiving an oral placebo at a similar dosage schedule. In the second study, 51 students took two tablets four times daily (2.1 g of BSS/d), 63 took one tablet four times daily (1.05 g of BSS/d), and 58 took a placebo (two tablets taken four times daily), each for 3 weeks. In the initial study, 14 (23%) BSS-treated subjects developed diarrhea compared with 40 (61%) placebo-tested persons (P less than .0001). In the second trial, seven (14%) subjects taking two tablets of BSS four times daily, 15 (24%) taking one tablet of BSS four times daily, and 23 (40%) receiving placebo tablets experienced diarrhea (P less than .001 for the higher dose). The percent protection provided by BSS was 62% for the group that received 4.2 g/d, 65% for 2.1 g/d, and 40% for 1.05 g/d, when compared with the corresponding placebo group. In cases in which stools were analyzed, seven (24%) of 29 BSS-treated subjects who had diarrhea had a detectable enteric pathogen, compared with 35 (59%) of 59 of those randomized to receive a placebo. BSS was well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

An observational study of naturally acquired immunity to rotaviral diarrhea in a cohort of 363 Egyptian children. Calculation of risk for second episodes using age-specific person-years of observation

A cohort of 363 rural children in Bilbeis, Egypt, were followed from birth from 1981 to 1983, with twice-weekly home visits made to detect diarrheal illness. Enzyme-linked immunosorbent assay was used for detection of rotavirus in stools collected during episodes of diarrhea. Rotavirus-associated diarrhea was detected once in 74 children and twice in 12 children. Using a technique not previously described, the authors calculated the age-specific incidence rates for initial episodes and second episodes of rotavirus-associated diarrhea to estimate the effectiveness of naturally acquired immunity. Assuming that the risk of exposure was the same before and after the first episode, the observed and expected numbers of second episodes of rotaviral diarrhea were equal (age-adjusted rate ratio = 1.01; 95 percent confidence interval 0.55-1.86), given the age-specific person-years at risk. The assumption of equal risk for reexposure to rotavirus appears to be invalid, however, since the children with one and two rotavirus-positive episodes appeared to be at greater risk for diarrheal illness of all causes (rate ratios of 1.42 and 1.78, respectively). The clinical illness may have been less severe in second episodes; emesis was reported more often with first rotavirus episodes than with second rotavirus episodes, and the only fatal case was in an initial episode. These data are compatible with the existence of partial immunity, since it appears that the risk of reexposure may be greater in children who experienced rotaviral gastroenteritis earlier in life. In four of seven children, rotavirus isolates from first and second episodes were of identical serotypes, indicating that even serotype-specific immunity for rotaviral diarrhea was incomplete.

Evaluation of assay systems for the detection of rotavirus in stool specimens

We tested 41 rotavirus positive and 42 negative specimens as determined by electron microscopy. The assays systems used were an indirect NIH-ELISA, Meritec-Rotavirus, Virogen Rotatest, and Rotazyme II. Meritec and Virogen (latex agglutination assays) were the most sensitive tests, detecting 95% of the positive specimens. The NIH-ELISA detected 81% and Rotazyme detected 63%. Rotazyme was the most specific (100%), followed by the NIH-ELISA (95%) and the two latex agglutination systems (91%). To determine the level of rotavirus detection, we tested three systems against serial two-fold dilutions of ten positive stools. The NIH-ELISA detected rotavirus in an average dilution of 1:723. Rotazyme detected rotavirus in an average stool dilution of 1:366, and Meritec showed an average of 1:164. Rotavirus strains representing serotypes 1-4 were also tested. Meritec was able to detect all four serotypes. Virogen did not react with serotype 2 strains. The NIH-ELISA and rotazyme were unable to detect serotype 3. These data suggest that some latex agglutination assays may be a useful alternative to ELISAs in the clinical laboratory.

A comparative study of furazolidone and placebo in addition to oral rehydration in the treatment of acute infantile diarrhea

Between July and October 1987 an outpatient study of 191 children with acute diarrhea was undertaken in two rural communities in Mexico. Through a double-blind randomization we compared the efficacy of a combination therapy of furazolidone, 7.5 mg/kg/day, plus standard oral rehydration therapy (ORT) (96 patients) versus a placebo plus ORT (95 patients), each given for 5 days. Diarrheal stool samples were collected from all patients before therapy. By means of a two-vial transport media system the samples were sent to a university laboratory and examined for viral, bacterial, and parasitic organisms. The most commonly isolated organisms were enterotoxigenic Escherichia coli (13%) and Giardia lamblia (13%). Patients who received furazolidone plus ORT showed a greater reduction in duration of diarrhea when compared with those receiving placebo plus ORT (63.4 h versus 71.44 h). There was also a trend toward shorter duration of diarrhea in patients with Giardia who were treated with furazolidone/ORT compared with Giardia patients in the placebo/ORT group. When fecal leukocytes were present in the stool, the furazolidone/ORT-treated patients had a significantly higher percentage of clinical cures (79% versus 54%, p = 0.03) and an overall shorter duration of diarrhea (62.0 h versus 80.6 h, p = 0.055) at the end of 5 days of therapy than did the placebo/ORT-treated group.

A cost-effectiveness comparison of the use of antimicrobial agents for treatment or prophylaxis of travelers' diarrhea

We conducted a decision analysis to compare the cost-effectiveness of antimicrobial agents used for treatment with their use for prophylaxis of travelers' diarrhea. Estimates of the likelihood and the cost of various outcomes were obtained from a panel of experts using the Delphi group opinion technique. Treatment with sulfamethoxazole-trimethoprim for three days was compared with daily prophylaxis with sulfamethoxazole-trimethoprim or doxycycline. The cost-effectiveness of prophylaxis with either agent (75% to 83%) was greater than that of treatment (38%). Treatment would become more cost-effective than prophylaxis when the cumulative risk of acquiring travelers' diarrhea was less than 0.05 episodes per person per week or if the effectiveness of prophylaxis fell below 35% for doxycycline and 46% for sulfamethoxazole-trimethoprim. The most important contributor to the mean cost of travelers' diarrhea in this analysis was the cost associated with a day of incapacitation due to illness. On the basis of the results of this decision analysis, we conclude that prophylaxis of travelers' diarrhea is an option that should be considered for individual situations and recommend further studies of its cost-effectiveness.