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.

Evaluation of an intervention program in the control of an urban outbreak of shigellosis.

Community-wide outbreaks of shigellosis are a persistent public health problem. We evaluated the effect of a household-based intervention program on the control of an urban outbreak of S. sonnei gastroenteritis. During the intervention we attempted to contact all households with culture-confirmed S. sonnei and provide education in methods to prevent spread of Shigella. Subsequently we conducted a survey of intervention (n = 43) and nonintervention (n = 33) households. We also conducted a serosurvey of children three to five years of age. The number of new cases of S. sonnei infection declined steadily over several months after the intervention began. Members of the intervention households were more knowledgeable about handwashing (rate ratio [RR] 4.7, 95% confidence interval [CI] = 2.1-10.8) and others methods of S. sonnei transmission and control than members of nonintervention households. However, intervention households had higher attack rates of Shigella-associated diarrhea in susceptible household members (RR 1.4, 95% CI = 1.0-2.0). During the intervention we were able to contact only 25% of households by the eighth day after onset of diarrhea in the index case, when 90% of intrahousehold transmission of Shigella had already occurred. Two months after the outbreak ended, 42% of children in the outbreak community had elevated antibody titers against S. sonnei; an additional 19% had borderline elevated titers. The intervention program improved knowledge but may have occurred too late to prevent intrahousehold transmission of Shigella. Exhaustion of susceptible hosts, rather than the education program, likely accounted for the decline in shigellosis cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between infectivity and cytopathology for L-929 cells, membrane proteins, and antigenicity of avian isolates of Chlamydia psittaci.

Seventeen isolates of Chlamydia psittaci from various avian species were examined. Based on their infectivity and cytopathology for L-929 cells, these isolates were separable into a high-infectivity group (HIG) and a low-infectivity group (LIG). Differences in the molecular weight of the major outer membrane proteins (MOMPs) of the isolates correlated with differences in infectivity. The HIG MOMPs had a molecular weight of 43,500, and the LIG MOMPs had a molecular weight of 45,500. The MOMP of one mammalian isolate of C. psittaci examined had a molecular weight of 43,500. Antisera raised against some of the isolates reacted with only the MOMP from isolates of their respective groups. The MOMPs of a mammalian C. psittaci isolate and of the C. trachomatis LGV 440 isolate did not react with HIG or LIG antisera. The MOMPs of some avian C. psittaci did react weakly with antiserum against the LGV 440 isolate of C. trachomatis.

Milk secretory IgA related to Shigella virulence antigens.

PIP: 20 Mexico City and 23 Houston, Texas colostrum samples, and 21 Mexican and 25 Houston mature milk samples were analyzed by ELISA and Western blot, respectively, for antibodies against the virulence plasmid of Shigella flexneri serotype 5 strain M9OT. The method involved comparing water extracts of milk in ELISA and Western blot determinations of antigens against shigella flexneri strain M9OT which is fully virulent, to those against M9OT A2 which lacks the virulence plasmid. While there are at least 37 know distinct lipopolysaccharide antigens on different strains of the 4 species of Shigella, all contain the same plasmid conferring virulence, the ability of the bacteria to invade mammalian cells. This provided a universal test for antigens to Shigella. Western blots showed antibodies in all 21 Mexican women and in 40% of 25 Houston women. Plasmid antibodies were detected by ELISA in all 20 Mexican colostrum samples and in 52% of 23 Houston colostrum samples. After 8 days of lactation, 93% of the Mexican and 46% of the Houston milk samples were positive. The actual protective factor in human milk against Shigella bacteria is unknown: these findings suggest a mechanism for protection against all serotypes of shigella. The high prevalence of antibodies against Shigella found in Houston women was attributed to infection in the distant past.^ieng

Western blot analysis of intestinal secretory immunoglobulin A response to Campylobacter jejuni antigens in patients with naturally acquired Campylobacter enteritis.

Secretory immunoglobulin A (sIgA) response at the intestinal mucosa is a primary defense against enteric infections. We sought to determine which antigens of Campylobacter jejuni outer membranes elicited sIgA responses in 8 patients with naturally acquired Campylobacter enteritis using Western blot analysis of fecal extracts. Naturally acquired Campylobacter infection elicited an sIgA response in 7 of 8 patients. Of these 7 patients, 5 had Campylobacter-specific sIgA titers of 1:16 and two had titers of 1:64. The C. jejuni antigens eliciting sIgA production varied, but 5 of 8 patients exhibited reactions to a 63-kilodalton flagellar antigen, and 7 of 8 patients had a reaction with a 58- and a 44-kilodalton antigen of C. jejuni and Campylobacter coli. Reaction with a 14.5- and a 97-kilodalton antigen was observed with the only stool that contained gross blood and mucus. Reactions with Campylobacter antigens were not detected in the fecal extracts of 5 healthy individuals. Identification of the antigens of C. jejuni that elicit an sIgA response may help us to better understand the immunology of Campylobacter enteritis and to identify antigens that are important in vaccine development.

Gram-negative, aerobic, enteric pathogens among intestinal microflora of wild turkey vultures (Cathartes aura) in west central Texas.

The prevalence of gram-negative bacterial species in the intestines of 20 apparently healthy turkey vultures (Cathartes aura) was determined. Edwardsiella tarda, Plesiomonas shigelloides, Salmonella, and Arizona hinshawii (Salmonella arizonae) were each recovered from 15% of these birds. Turkey vultures may be important reservoirs of these bacterial pathogens.

Human milk immunoglobulin A antibodies to Shigella virulence determinants.

Because human milk is thought to protect infants from shigellosis, we evaluated milk for immunoglobulin A to Shigella virulence determinants. Milk was preincubated to remove antibodies unrelated to each locus of interest, using defined Shigella and E. coli hybrids containing known Shigella genetic segments prior to immunoblotting. The milk could not be shown to contain antibodies to chromosomally encoded virulence loci except for the expected antibodies to the products of the histidine locus. However, all the milk samples contained antibodies to antigens encoded by the large virulence plasmid. The finding of these antibodies suggests a possible mechanism by which human milk might protect infants.

Adherence of enterohemorrhagic Escherichia coli strains to a human colonic epithelial cell line (T84).

Enterohemorrhagic Escherichia coli (EHEC) produce Shiga-like toxins and attach to certain tissue culture cells. T84 cells are human colonic carcinoma cells. Unlike previously studied cell lines, T84 cells grown on collagen-coated surfaces polarize and produce tight junctions and desmosomes, forming a colonic epithelial cell layer in vitro. The purpose of this study was to examine the attachment of EHEC strains to the T84 cell line as a possibly more relevant in vitro model of EHEC adherence. Twelve EHEC strains were grown overnight in Penassay broth, suspended in minimal essential medium with and without 0.5% mannose, and incubated for 1 to 3 h with 5- to 7-day-old T84 cell monolayers grown on collagen-coated coverslips. The bacteria were removed, and attachment was quantitated microscopically. For both E. coli O157:H7 and other EHEC serotypes, there were marked differences in adherence between strains (range of 152 to 3 bacteria per oil immersion field). Mannose partially inhibited the adherence of some EHEC strains. Adherence to the T84 cells appeared to be related to the amount of pili present and not to the serotype. Electron micrographs showed that a highly adherent strain (strain 43-12) tended to form microcolonies in the area of tight junctions on the T84 cell monolayers. In addition, the attachment of these EHEC strains to T84 cells correlated with their ability to adhere to isolated rabbit colonocytes (r = 0.91, P = 0.00004; without mannose) (r = 0.60, P = 0.04; with mannose). These data show that there are EHEC strain-related differences in adherence which can be demonstrated in a human-derived colonic epithelial cell line (T84) and that these cells can be used to study EHEC adherence.

Human milk secretory immunoglobulin A to Shigella virulence plasmid-coded antigens.

Although antibodies to the lipopolysaccharide antigens of Shigella have been demonstrated in human milk, such antibodies do not explain the putative protective effect of breast-feeding against symptomatic Shigella infection. Shigella species do not share related lipopolysaccharides, but they do possess closely related virulence plasmids that code for the proteins essential for cell invasion. We therefore sought to determine the frequency, amount, and duration of excretion of human milk antibodies to these shared virulence plasmid-associated antigens in populations of different rates of Shigella infection frequency (Mexico City, high; Houston, low). Such antibodies were present in the milk of virtually all the Mexican women but also were present in a large proportion of milk samples from the women living in Houston. The amounts of these antibodies were highest in colostrum but after 2 weeks of lactation fell to stable levels. The frequency and persistence of these antibodies in the milk of the women from Houston suggest that the memory and drive for secretion of these antibodies is extremely long lived.

Concentration of milk secretory immunoglobulin A against Shigella virulence plasmid-associated antigens as a predictor of symptom status in Shigella-infected breast-fed infants.

We conducted a prospective, community-based study of healthy breast-fed Mexican infants to determine the protective effects of anti-Shigella secretory IgA antibodies in milk. Milk samples were collected monthly, and stool culture specimens were obtained weekly and at the time of episodes of diarrhea. Nineteen breast-fed infants were found to have Shigella flexneri, Shigella boydii, or Shigella sonnei in stool samples. Ages of the 10 infants with symptomatic infection and the nine with asymptomatic infection did not differ significantly. Milk samples collected up to 12 weeks before infection were evaluated by enzyme-linked immunosorbent assay for secretory IgA antibodies against lipopolysaccharides of S. flexneri, S. boydii serotype 2, S. sonnei, and virulence plasmid-associated antigens. The geometric mean titers of anti-Shigella antibodies to virulence plasmid-associated antigens in milk received before infection were eightfold higher in infants who remained well than in those in whom diarrhea developed. The significance of milk secretory IgA directed against lipopolysaccharide was less clear. We conclude that human milk protects infants against symptomatic shigella infection when it contains high concentrations of secretory IgA against virulence plasmid-associated antigens.

An international foodborne outbreak of shigellosis associated with a commercial airline.

OBJECTIVE: To determine the source of an international outbreak of shigellosis associated with consumption of food served by a Minnesota-based airline. DESIGN: Cohort studies of players and staff of a Minnesota-based professional football team and passengers on flights with a confirmed case of outbreak-associated Shigella sonnei infection. SETTING: Community- and industry-based studies conducted from October through November 1988. PARTICIPANTS: Sixty-five football team players and staff, and 725 airline passengers in the cohort studies. RESULTS: Twenty-one (32%) of 65 football players and staff developed shigellosis that was associated with consumption of cold sandwiches prepared at the airline flight kitchen (relative risk [RR], 17.1; 95% confidence interval [Cl], 2.4 to 120; P < .001). Confirmed or probable shigellosis was identified among 240 passengers on 219 flights to 24 states, the District of Columbia, and four countries between September 14 and October 13. An outbreak-associated strain of S sonnei was isolated from football players and staff, airline passengers, and flight attendants. Thirty (4.1%) of 725 passengers on 13 flights with confirmed cases had confirmed or probable shigellosis. Illness was associated with consumption of cold food items served on the flights and prepared by hand at the airline flight kitchen (RR, 5.7; 95% Cl, 1.4 to 23.5; P < .01). CONCLUSIONS: This international outbreak of shigellosis was identified only because of the occurrence of an index outbreak involving a professional football team. Prevention of Shigella transmission in mass catering establishments may require reduction of hand contact in the preparation of cold food items or elimination of these items from menus.