Epidemiologic and clinical features of patients infected with Shigella who attended a diarrheal disease hospital in Bangladesh

Prevalence of Antibiotic-Resistant Shigella spp. in Bangladesh: A Systematic Review and Meta-Analysis of 44,519 Samples

Shigella is the leading global etiological agent of shigellosis, especially in poor and underdeveloped or developing nations with insufficient sanitation such as Bangladesh. Antibiotics are the only treatment option for the shigellosis caused by Shigella spp. as no effective vaccine exists. However, the emergence of antimicrobial resistance (AMR) poses a serious global public health concern. Therefore, a systematic review and meta-analysis were conducted to establish the overall drug resistance pattern against Shigella spp. in Bangladesh. The databases of PubMed, Web of Science, Scopus, and Google Scholar were searched for relevant studies. This investigation comprised 28 studies with 44,519 samples. Forest and funnel plots showed any-drug, mono-drug, and multi-drug resistance. Any fluoroquinolone had a resistance rate of 61.9% (95% CI: 45.7-83.8%), any trimethoprim-sulfamethoxazole-60.8% (95% CI: 52.4-70.5%), any azithromycin-38.8% (95% CI: 19.6-76.9%), any nalidixic acid-36.2% (95% CI: 14.2-92.4%), any ampicillin-34.5% (95% CI: 25.0-47.8%), and any ciprofloxacin-31.1% (95% CI: 11.9-81.3%). Multi-drug-resistant Shigella spp. exhibited a prevalence of 33.4% (95% CI: 17.3-64.5%), compared to 2.6% to 3.8% for mono-drug-resistant strains. Since resistance to commonly used antibiotics and multidrug resistance were higher, a judicious use of antibiotics, the promotion of infection control measures, and the implementation of antimicrobial surveillance and monitoring programs are required to tackle the therapeutic challenges of shigellosis.

Identification and management of Shigella infection in children with diarrhoea: a systematic review and meta-analysis

BACKGROUND

Shigella infections are a leading cause of diarrhoeal death among children in low-income and middle-income countries. WHO guidelines reserve antibiotics for treating children with dysentery. Reliance on dysentery for identification and management of Shigella infection might miss an opportunity to reduce Shigella-associated morbidity and mortality. We aimed to systematically review and evaluate Shigella-associated and dysentery-associated mortality, the diagnostic value of dysentery for the identification of Shigella infection, and the efficacy of antibiotics for children with Shigella or dysentery, or both.

METHODS

We did three systematic reviews (for mortality, diagnostic value, and antibiotic treatment of Shigella and dysentery), and meta-analyses where appropriate, of studies in resource-limited settings. We searched MEDLINE, Embase, and LILACS database for studies published before Jan 1, 2017, in English, French, and Spanish. We included studies of human beings with diarrhoea and accepted all study-specific definitions of dysentery. For the mortality and diagnostic value searches, we excluded studies that did not include an effect estimate or data necessary to calculate this estimate. The search for treatment included only randomised controlled trials that were done after Jan 1, 1980, and assessed antibiotics in children (aged <18 years) with dysentery or laboratory-confirmed Shigella. We extracted or calculated odds ratios (ORs) and 95% CIs for relative mortality and did random-effects meta-analysis to arrive at pooled ORs. We calculated 95% CIs assuming a binomial distribution and did random-effects meta-regression of log-transformed sensitivity and specificity estimates for diagnostic value. We assessed the heterogeneity of papers included in these meta-analyses using the I2 statistic and evaluated publication bias using funnel plots. This review is registered with PROSPERO (CRD42017063896).

FINDINGS

3649 papers were identified and 60 studies were included for analyses: 13 for mortality, 27 for diagnostic value, and 20 for treatment. Shigella infection was associated with mortality (pooled OR 2·8, 95% CI 1·6-4·8; p=0·000) whereas dysentery was not associated with mortality (1·3, 0·7-2·3; p=0·37). Between 1977 and 2016, dysentery identified 1·9-85·9% of confirmed Shigella infections, with sensitivity decreasing over time (p=0·04). Ten (50%) of 20 included antibiotic trials were among children with dysentery, none were placebo-controlled, and two (10%) evaluated antibiotics no longer recommended for acute infectious diarrhoea. Ciprofloxacin showed superior microbiological, but not clinical, effectiveness compared with pivmecillinam, and no superior microbiological and clinical effectiveness compared with gatifloxacin. Substantial heterogeneity was reported for meta-analyses of the Shigella-associated mortality studies (I2=78·3%) and dysentery-associated mortality studies (I2=73·2%). Too few mortality studies were identified to meaningfully test for publication bias. No evidence of publication bias was found in this analysis of studies of diagnostic value.

INTERPRETATION

Current WHO guidelines appear to manage dysentery effectively, but might miss opportunities to reduce mortality among children infected with Shigella who present without bloody stool. Further studies should quantify potential decreases in mortality and morbidity associated with antibiotic therapy for children with non-dysenteric Shigella infection.

FUNDING

Bill & Melinda Gates Foundation and the Center for AIDS Research International Core.

Housefly population density correlates with shigellosis among children in Mirzapur, Bangladesh: a time series analysis

Background

Shigella infections are a public health problem in developing and transitional countries because of high transmissibility, severity of clinical disease, widespread antibiotic resistance and lack of a licensed vaccine. Whereas Shigellae are known to be transmitted primarily by direct fecal-oral contact and less commonly by contaminated food and water, the role of the housefly Musca domestica as a mechanical vector of transmission is less appreciated. We sought to assess the contribution of houseflies to Shigella-associated moderate-to-severe diarrhea (MSD) among children less than five years old in Mirzapur, Bangladesh, a site where shigellosis is hyperendemic, and to model the potential impact of a housefly control intervention.

Methods

Stool samples from 843 children presenting to Kumudini Hospital during 2009–2010 with new episodes of MSD (diarrhea accompanied by dehydration, dysentery or hospitalization) were analyzed. Housefly density was measured twice weekly in six randomly selected sentinel households. Poisson time series regression was performed and autoregression-adjusted attributable fractions (AFs) were calculated using the Bruzzi method, with standard errors via jackknife procedure.

Findings

Dramatic springtime peaks in housefly density in 2009 and 2010 were followed one to two months later by peaks of Shigella-associated MSD among toddlers and pre-school children. Poisson time series regression showed that housefly density was associated with Shigella cases at three lags (six weeks) (Incidence Rate Ratio = 1.39 [95% CI: 1.23 to 1.58] for each log increase in fly count), an association that was not confounded by ambient air temperature. Autocorrelation-adjusted AF calculations showed that a housefly control intervention could have prevented approximately 37% of the Shigella cases over the study period.

Interpretation

Houseflies may play an important role in the seasonal transmission of Shigella in some developing country ecologies. Interventions to control houseflies should be evaluated as possible additions to the public health arsenal to diminish Shigella (and perhaps other causes of) diarrheal infection.

Whereas previous researchers have noted that seasonal peaks in the numbers of houseflies and patients suffering from Shigella diarrheal infection seemed to coincide, this is the first research to quantify the association using time-series statistical methods. The results show that houseflies could account for approximately 37% of all cases of shigellosis in an area in rural Bangladesh. This research adds to the existing published experimental and observational evidence from other parts of the world implicating houseflies as mechanical transmission vectors for Shigella. The results can be used to advocate for cluster-randomized intervention trials that can demonstrate how much control of housefly density can diminish Shigella disease incidence. This question should be answered because there are currently no licensed Shigella vaccines, and rising antibiotic resistance is limiting treatment options. Control of houseflies using methods such as baited fly traps could be an affordable, effective intervention to add to the public health arsenal for routine use and in the context of disaster response.

Calicivirus from novel Recovirus genogroup in human diarrhea, Bangladesh

To identify unknown human viruses in the enteric tract, we examined 105 stool specimens from patients with diarrhea in Bangladesh. A novel calicivirus was identified in a sample from 1 patient and subsequently found in samples from 5 other patients. Phylogenetic analyses classified this virus within the proposed genus Recovirus.

Clinical and Epidemiologic Features of Diarrheal Disease due to Aeromonas hydrophila and Plesiomonas shigelloides Infections Compared with Those due to Vibrio cholerae Non-O1 and Vibrio parahaemolyticus in Bangladesh

Using data from the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) from 1996 to 2001, we compared the clinical features of diarrhea in patients with stool specimens yielding only A. hydrophila (189 patients; 1.4% of 13,970 patients screened) or P. shigelloides (253 patients) compared to patients with sole V. cholerae non-O1 infection (99 patients) or V. parahaemolyticus infection (126 patients). Patients exhibited similar frequencies of fever (temperature >37.8°C), stools characterized as watery, and stools containing visible mucus. Dehydration was observed more often among patients with V. parahaemolyticus or V. cholerae non-O1 infection. Compared to patients infected with V. parahaemolyticus, those with A. hydrophila, P. shigelloides, or V. cholerae non-O1 infection were less likely to report visible blood in the stool and, on microscopic examination, less likely to exhibit stool red blood cell and white blood cell counts exceeding 20 cells per high power field. The proportion of patients reporting subjective cure at the time of discharge was significantly smaller for those infected with V. parahaemolyticus. These findings suggest that A. hydrophila and P. shigelloides produce diarrheal disease that is less severe than that resulting from infection with V. cholerae non-O1 or V. parahaemolyticus.

Presumptive shigellosis: Clinical and laboratory characteristics of Bangladeshi patients

The aim of the study was to examine some selected clinical and laboratory parameters in distinguishing non-Shigella invasive diarrhoeas from culture-confirmed Shigella cases. We conducted a clinic-based, cross-sectional study at the Dhaka Hospital of ICDDR,B located in Bangladesh. In total, 389 patients of all age groups and of both genders, with a history of diarrhoea of less than 96 h and presence of visible blood and/or mucus in the stool were presumed to have shigellosis and enrolled in the study. Shigella was isolated from faecal cultures in 227 (58.4%) patients. The remaining 162 (41.6%) patients did not have Shigella isolated from their faecal cultures and constituted the comparison group. Another 238 randomly selected patients with non-Shigella diarrhoea from the Diarrhoeal Disease Surveillance System database of the Dhaka Hospital constituted another comparison group. Cases of culture-proven Shigella were similar to non-Shigella invasive diarrhoeal patients with presumptive shigellosis with regard to several biosocial variables. The nutritional status of children with shigellosis was significantly inferior to those with non-Shigella diarrhoea. The presence of macrophages more than 5/HPF in stool microscopic examination was significantly more frequent among patients infected with Shigella. Empirical antimicrobial therapy for shigellosis might be considered for malnourished diarrhoeal children presenting with history of visible blood and/or mucus in stool, and children older than 1 y of age. Further studies are needed in different geographical settings to identify clinical and laboratory parameters that could help identify patients with shigellosis.

Characterization of Shigella strains in Iran by plasmid profile analysis and PCR amplification of ipa genes

To characterize Shigella clinical strains, we studied 82 Shigella strains recovered from 719 stool samples of patients with bloody diarrhea in Shiraz, Iran, over the period from April to October 2003. Serological assay classified the Shigella isolates as follows: 61 (74.39%) Shigella sonnei isolates, 16 (19.51%) Shigella flexneri isolates, 3 (3.65%) Shigella boydii isolates, and 2 (2.43%) Shigella dysenteriae isolates. In an antibiogram test, all Shigella strains were susceptible to ceftazidime, ciprofloxacin, and ceftriaxone. They showed high degrees of sensitivity to nalidixic acid, gentamicin, cephalothin, and amikacin. Approximately 90.24% of the Shigella isolates were resistant to co-trimoxazole. The plasmid profile patterns of all strains were determined by a modified alkaline lysis method. The average number of plasmid bands for each strain was 9.5. By plasmid profile analysis we identified 56 genotypes among all isolates and 42, 14, 3, and 2 genotypes among the S. sonnei, S. flexneri, S. boydii, and S. dysenteriae strains, respectively. PCR assays showed that all isolates were positive for two virulence genes, ipaBCD and ipaH. In conclusion, these data mandate local monitoring of drug resistance and its consideration in the empirical therapy of Shigella infections. These results also demonstrate that plasmid profile analysis is more reliable than antibiotic susceptibility pattern analysis for the identification of Shigella epidemic strains isolated in Iran.

The epidemiology of travel-associated shigellosis—regional risks, seasonality and serogroups

OBJECTIVES

To give a detailed risk estimate of contracting travel-associated shigellosis in various regions of the world.

METHODS

Data on notifications of travel-associated shigellosis in Sweden 1997-2003 were compared with information on recent travel abroad from a comprehensive database based on telephone interviews with more than 160,000 Swedish travellers.

RESULTS

From the national notification database 2678 patients with travel-associated shigellosis were retrieved. The highest risk of being notified with shigellosis was seen in returning travellers from India and neighbouring countries (318/100,000 travellers), East Africa (219/100,000), West Africa (120/100,000), and North Africa (76/100,000). Data on serogroup was available for 2529 isolates. Shigella sonnei was the most common serogroup (67%), followed by Shigella flexneri (26%), Shigella boydii (5%), and Shigella dysenteriae (3%). A higher risk was seen in children below the age of six, compared to older children and adults and in women compared to men. A distinct seasonal pattern was noted with the highest risk of shigellosis in July-October and the lowest in May.

CONCLUSIONS

Denominator based data on reported travel-associated infections are well suited to give risk estimates per region of infection, that could be used to target high-risk groups for pre-travel advice.

An evaluation of current shigellosis treatment

Shigellosis or bacillary dysentery, characterised by the passage of frequent loose stools mixed with blood and mucous, is caused by Shigella spp. which can be subdivided into four serotypes, namely, S. sonnei, S. boydii, S. flexneri and S. dysenteriae. S. dysenteriae type 1 produces severe dysentery and may be associated with many complications like leukaemoid reaction and haemolytic-ureamic syndrome. It is known to produce protracted epidemics and pandemics and is usually multi-drug resistant. Antibiotics are the mainstay of therapy of all cases of shigellosis. Antibiotics such as tetracycline, ampicillin and co-trimoxazole, were previously highly effective. Newer fluoroquinolones such as norfloxacin, ciprofloxacin, ofloxacin, azithromycin and ceftriaxone are effective. Although single dose of norfloxacin 800 mg and ciprofloxacin 1 g have been shown to be effective, they are currently less effective against S. dysenteriae type 1 infection. Oral rehydration salt should be given concurrently to prevent or correct dehydration. Antimotility agents are contraindicated. Feeding during and after shigellosis is emphasised. Hand-washing practices with plenty of water and soap help to prevent the transmission of infection from person to person. A search is on for an effective vaccine against shigella.

Diagnostic accuracy of stool assays for inflammatory bacterial gastroenteritis in developed and resource-poor countries

Because acute bacterial gastroenteritis is often inflammatory, rapid stool assays that detect intestinal inflammation might be used to distinguish between bacterial and nonbacterial gastroenteritis. We performed meta-analyses to determine the discriminatory power, in developed and in resource-poor countries, of rapid stool assays that test for lactoferrin, fecal leukocytes, fecal erythrocytes, and occult blood. In developed countries, the area under the summary receiver operating characteristic curve (AUC/SROC) was 0.89 for fecal leukocytes and 0.81 for occult blood. In resource-poor countries, the AUC/SROC was 0.79 for lactoferrin, 0.72 for fecal leukocytes, 0.63 for occult blood, and 0.61 for fecal erythrocytes. In developed countries, positive and negative likelihood ratios (LR+ and LR-, respectively) for fecal leukocytes were 4.56 and 0.32 when a threshold of >5 cells/high-power field was used, compared with 2.94 and 0.6 in resource-poor countries; for lactoferrin, LR+ was 1.34 and LR- was 0.17 in resource-poor countries when the threshold was an agglutination rating of "+" and a dilution of 1:50. In developing countries, rapid stool assays performed poorly, whereas in developed countries, tests for fecal leukocytes, lactoferrin, and occult blood were moderately useful and could identify patients who were more likely to benefit from empirical antibiotic therapy.

Lactoferrin protects rabbits from Shigella flexneri-induced inflammatory enteritis

Shigella species cause bacillary dysentery in humans by invasion, intracellular multiplication, spread to adjacent cells, and induction of brisk inflammatory responses in the intestinal epithelium. In vitro data suggest that lactoferrin, a glycoprotein present in human mucosal secretions, has a role in protection from bacterial enteric infections. We sought to determine the activity of lactoferrin in vivo, using the concentration present in human colostrum, to investigate its effect on the development of clinical and pathological evidence of inflammation in a rabbit model of enteritis. Lactoferrin protected rabbits infected with Shigella flexneri from developing inflammatory intestinal disease. Typical histological changes in ill animals included villous blunting with sloughing of epithelial cells, submucosal edema, infiltration of leukocytes, venous congestion, and hemorrhage. Lactoferrin at a concentration normally found in human colostrum blocks development of S. flexneri-induced inflammatory enteritis.

Enteropathogens associated with diarrheal disease in infants of poor urban areas of Porto Velho, Rondônia: a preliminary study

One hundred and thirty cases of diarrhea and 43 age-matched controls, 0 to 5 years old, were studied in a pediatric outpatient unit from a poor peri urban area of Porto Velho, Rondônia. Eighty percent of diarrheal cases were observed in the groups under 2 years of age. Rotavirus (19.2%) was the most frequent enteropathogen associated with diarrhea, followed by Shigella flexneri (6.15%) and S. sonnei (1.5%) and Salmonella sp. (6.9%). Four cases of E. coli enterotoxigenic infections (3.1%), E. coli enteropathogenic (EPEC)(2.3%) one case of E. coli enteroinvasive infection (0.8%) and one case of Yersinia enterocolitica (0.8%) were also identified. Mixed infections were frequent, associating rotavirus, EPEC and Salmonella sp. with Entamoeba histolytica and Giardia lamblia.

Safety and immunogenicity of a proteosome-Shigella flexneri 2a lipopolysaccharide vaccine administered intranasally to healthy adults

We studied the safety and immunogenicity of a Shigella flexneri 2a vaccine comprising native S. flexneri 2a lipopolysaccharide (LPS) complexed to meningococcal outer membrane proteins-proteosomes-in normal, healthy adults. A two-dose series of immunizations was given by intranasal spray, and doses of 0.1, 0.4, 1.0, and 1.5 mg (based on protein) were studied in a dose-escalating design. The vaccine was generally well tolerated. The most common reactions included rhinorrhea and nasal stuffiness, which were clearly dose related (P < or = 0.05). These reactions were self-limited and generally mild. The vaccine elicited S. flexneri 2a LPS-specific immunoglobulin A (IgA), IgG, and IgM antibody-secreting cells (ASCs) in a dose-responsive manner. At doses of 1.0 or 1.5 mg, highly significant (P < 0.001) increases in ASCs of all antibody isotypes occurred and 95% of subjects had an ASC response in at least one antibody isotype. Dose-related serum antibody responses were observed, with geometric mean two- to fivefold rises in specific serum IgA and IgG titers and two- to threefold rises in IgM in the 1.0- and 1.5-mg-dose groups (P < 0.0001 for each isotype). Elevated serum antibody levels persisted through day 70. Increases in fecal IgG and IgA and also in urinary IgA specific for S. flexneri 2a LPS were demonstrated. These were most consistent and approached statistical significance (P = 0.02 to 0.12 for various measures) on day 70 after the first dose. The magnitude of immune responses to intranasally administered proteosome-S. flexneri 2a LPS vaccine is similar to those reported for live vaccine candidates associated with protective efficacy in human challenge models, and further evaluation of this product is warranted.

Detection of multivalent interactions through two-tiered energy transfer

A method based on two-tiered fluorescence resonant energy transfer (FRET) has been developed for selective and sensitive detection of species involved in a multivalent interaction. Pentavalent binding between cholera toxin and ganglioside GM1 is used as a model system to demonstrate the advantage of the two-tiered FRET over one-stage FRET in both conventional fluorimeter and flow cytometer. In the system, three fluorescent probes (namely, fluorescence donor, acceptor, and intermediate) are covalently tagged to receptors, and the intermediate is used to bridge the energy transfer between the donor and acceptor even though the donor's fluorescence spectrum does not overlap with absorption spectrum of the acceptor. One of the most significant improvements of the scheme over one-stage FRET is a dramatic decrease in the background fluorescence of the acceptor fluorescence, which, theoretically and practically, increases the detection sensitivity.

Population-based study of the incidence of Shigella diarrhea and causative serotypes in Santiago, Chile

BACKGROUND

Shigella is an important cause of diarrheal disease in children in developing countries. The increasing prevalence of antibiotic-resistant strains has stimulated interest in the use of multivalent Shigella vaccines. Because Shigella vaccines under development are based on eliciting immunity to O antigens, monitoring the distribution of serotypes in defined target populations is critical. We initiated health center-based surveillance in a poor semirural community in Colina, Santiago (7489 children <60 months of age) to determine the age-specific incidence of Shigella disease and the responsible serotypes.

FINDINGS

Surveillance was maintained at the 2 health centers during warm seasons (November 1 through April 30) for 4 successive years (1994 to 1998). Shigella was recovered from 54 of 243 cases of dysentery (22%) and from 215 of 3966 cases of nondysenteric diarrhea (5.4%) (P < 0.001). The peak mean annual incidence of shigellosis occurred among children 12 to 47 months of age (9.0 to 12.6 cases/10(3) children), although the incidence in infants (5.2/10(3)) and children 48 to 59 months of age (6.2/10(3)) was also substantial. During the 1995 through 1996 season, an age-matched healthy control was cultured for every child <60 months of age with diarrhea. Shigella isolation from cases (34 of 576, 5.9%) was >8-fold higher than controls (4 of 576, 0.7%) (P < 0.01). Four serotypes, Shigella sonnei (45%), Shigella flexneri 2b (19%), S. flexneri 2a (14%) and S. flexneri 6 (11%), accounted for 89% of all cases.

INTERPRETATION

Shigella remains an important pediatric pathogen in Santiago. The serotype distribution from Colina, which closely resembles data from a population-based surveillance study in Santiago in the mid-1980s, demonstrates a remarkable degree of serotype stability in Santiago during a 15-year period.

Shigellosis in children: a clinico-epidemiological comparison between Shigella dysenteriae type I and Shigella flexneri

We reviewed the clinical and epidemiological features of 390 children under 5 years of age infected with either Shigella dysenteriae type I or Shigella flexneri attending a diarrhoea treatment centre from 1993 to 1995 in Dhaka, Bangladesh. Older age (24 months or more), underweight and wasting but not stunting were the host factors significantly more associated with Shigella dysenteriae type I infection than in Shigella flexneri-infected children. Moreover, use of antibiotics at home, use of water from tubewells or pipe-water for drinking and lack of sanitary facilities for defaecation were the behavioural and environmental factors strongly associated with S. dysenteriae type I infection. Children with diarrhoea due to S. flexneri presented with more watery/liquid stools and had a shorter duration of illness. Duration of diarrhoea for 4 or more days was typical of S. dysenteriae type I infection. Interventions to address malnutrition and to promote environmental hygiene would be predicted to offer greater protection against shigellosis due to S. dysenteriae than S. flexneri.

Cloning and analysis of the glucosyl transferase gene encoding type I antigen in Shigella flexneri

The O-antigen of most Shigella flexneri serotypes contains an identical tetrasaccharide repeating unit. Apart from serotype Y, the O-antigen is modified by addition of a glucosyl and/or O-acetyl residue to a specific position in the O-unit. In this study the glucosyl transferase gene from a serotype 1 a has been cloned and identified. The bacteriophage SfV integrase (int) gene was used to probe a S. flexneri Y53 (serotype 1 a) cosmid library and 18 unique clones were identified. Southern hybridisation of these clones indicated two unlinked regions of the chromosome contained the int homologue. When expressed in a live candidate vaccine strain of S. flexneri serotype Y (SFL124), clones with one region produced type I antigen, whereas clones containing the other region produced mainly type Y antigen. One of the cosmid clones positive for type I antigen by agglutination and Western blotting was selected for further study. Genes involved in O-antigen glucosyl modification were mapped on a 5.8 kb fragment and subclones were produced which fully or partially expressed the type I antigen, depending on the extent of the clone. Fully and partially expressing clones may be useful vaccine candidate strains for protection against disease caused by two serotypes of S. flexneri.

Long-term oral supplementation with iron is not harmful for young children in a poor community of Bangladesh

The effect of long-term oral iron supplementation on morbidity due to diarrhea, dysentery and respiratory infections in 349 children, aged 2-48 mo, living in a poor community of Bangladesh, was evaluated in this double-blind study. The treatment group received 125 mg of ferrous gluconate (15 mg elemental iron) plus multivitamins and the controls received only multivitamins, daily for 15 mo. House-to-house visits were made on alternate days by trained community health workers for recording symptoms and duration of illnesses and for monitoring medicine intake. Seventy-six percent of the children continued the syrup for over 1 y. No untoward effects were noticed in either treatment group. The attack rates for diarrhea, dysentery and acute respiratory tract infections (ARI) were 3, 3 and 5 episodes per child per year, respectively. Each episode of diarrhea lasted a mean of 3 d, and those of dysentery and ARI, 5 d. The two treatment groups did not differ in the number of episodes, mean duration of each episode, or total days of illnesses due to diarrhea, dysentery and ARI. However, a 49% greater number of episodes of dysentery was observed with iron supplementation in a subset of the study children who were less than 12 mo old (P = 0.03). The results of this study suggest that long-term oral iron supplementation is not harmful for older children in a poor community. Further studies are needed to demonstrate the safety and efficacy of iron administration in young infants.

Epidemiological and clinical profiles of acute invasive diarrhoea with special reference to mucoid episodes: a rural community-based longitudinal study

A study was carried out in 3 villages near Calcutta, India, having a population of 5464, between August 1992 and December 1994. A cohort of rural children below 4 years of age was prospectively observed to determine the clinico-epidemiological aspects of mucoid diarrhoea and examine propensity to invasiveness. Overall, the incidence of diarrhoea was 1.7 episodes/child/year, and that of mucoid and bloody dysentery was 0.8 and 0.2 episodes/child/year, respectively. Children aged 6-11 months had a higher incidence of mucoid diarrhoea (1.3 episodes/child/year) and the peak season occurred in June and July. Multivariate analysis using logistic regression showed that mucoid diarrhoea and bloody dysentery were closely similar in both clinical and laboratory findings, including raised faecal leucocyte count (> 10/high power microscope field [hpf]). However, abdominal pain occurred more frequently in bloody dysentery than in mucoid diarrhoea. Faecal leucocyte count (> 10/hpf) can therefore be used as an indicator for invasiveness of mucoid diarrhoea at the community level.

Fecal screening tests in the approach to acute infectious diarrhea: a scientific overview

OBJECTIVE

To evaluate the value of fecal leukocytes, fecal occult blood, fecal lactoferrin and combination of fecal leukocytes with clinical data in the workup of patients with inflammatory diarrhea.

DATA IDENTIFICATION

A systematic literature search in all languages using MEDLINE (1970 to 1994), reference lists of articles primarily retrieved and of review articles and correspondence with experts in the field.

STUDY SELECTION

The search identified 2603 references, 81 of which were deemed relevant on the basis of prespecified selection criteria. Of these 25 contained sufficient data for further analysis and thus were finally included.

DATA EXTRACTION

All data from the selected articles were extracted by one observer whereas the second reviewer checked these data for accuracy. True positive rates and false positive rates were calculated from each 2 x 2 table.

RESULTS OF DATA ANALYSIS

The study summarizes the diagnostic accuracy of the signaled tests as predictors of inflammatory diarrhea as defined by stool culture (the reference test). Plots of true positive rates against false positive rates demonstrated widely scattered points, indicating heterogeneity. A summary receiver operating characteristic curve was fitted to the data with the use of logistic transforms and weighted least squares linear regression. Of the 25 studies analyzed 38 data points were used to construct summary receiver operating characteristic curves for index tests.

CONCLUSIONS

Fecal lactoferrin was the most accurate index test. Fecal leukocytes showed the lowest performance as assessed by the area under the curve. Occult blood and combination of fecal leukocytes with clinical data yielded intermediate curves. A limited number of studies (fecal lactoferrin, and fecal leukocytes with clinical data) and methodologic flaws identified in the assessed studies must be solved in future primary studies to improve the usefulness of the metaanalytic approach used here.

Surface components of shigellae involved in adhesion and haemagglutination

Strains of Shigella species were studied for their ability to adhere and agglutinate mammalian erythrocytes. Shigella dysenteriae and Sh. flexneri exhibited haemagglutinating (HA) properties when cultured in Casamino Acids-Yeast Extract (CYE) broth in the presence of 1 mmol 1-1 calcium chloride, but other shigellae did not show this property under the same culture conditions. Repeated subcultivation of Sh. boydii, Sh. sonnei and HA negative strains of Sh. dysenteriae and Sh. flexneri in CYE broth medium induced adhesive and haemagglutinating properties that were inhibited by sodium periodate. HA activities of Shigella spp. were also inhibited by N-acetylneuraminic acid, alpha 1-glycoprotein and fetuin, but not by protease. Electron microscopy of Sh. dysenteriae 1, Sh. flexneri 2a, Sh. boydii 12 and Sh. sonnei 1 grown in CYE broth showed the presence of an extracellular slime layer that promoted agglutination of erythrocytes. The slime layer extracted from the cell surface of Shigella spp. showed HA properties, whereas lipopolysaccharide (LPS) obtained from the same strains, except Sh. dysenteriae 1, did not agglutinate erythrocytes. This evidence suggests that the cell surface haemagglutinin is a loosely bound slime layer which is expressed in CYE broth medium.

Shigella enterotoxin 1: an enterotoxin of Shigella flexneri 2a active in rabbit small intestine in vivo and in vitro

Culture filtrates of Shigella flexneri 2a strain M4243 grown in iron-depleted medium, caused significant fluid accumulation in rabbit ileal loops. Also, when tested in Ussing chambers, a greater rise in potential difference and short circuit current was seen with such filtrates compared with the medium control. Analogous filtrates from two M4243 derivatives lacking the 140-MD invasiveness plasmid (either M4243avir or BS103) retained 60-65% of the wild-type enterotoxic activity. Ultrafiltration and gel exclusion size fractionation of M4243 filtrate revealed that the activity was approximately 60 kD. SDS-PAGE performed on this fraction showed 18 bands, 5 of which reacted with human convalescent sera. Genes encoding this enterotoxin, named ShET1 for Shigella enterotoxin 1, were cloned from the S. flexneri 2a chromosome, and two separate open reading frames of 534 and 186 bp were sequenced. These observations suggest that S. flexneri 2a elaborates two distinct enterotoxins: ShET1, encoded by genes located on the chromosome, and ShET2, encoded by a gene on the 140-MD invasiveness plasmid. ShET1, which is composed of two distinct subunits and is elaborated in vivo, where it elicits an immune response, may be important in the pathogenesis of diarrheal illness due to S. flexneri 2a.

Intransal or intragastric immunization with proteosome-Shigella lipopolysaccharide vaccines protects against lethal pneumonia in a murine model of Shigella infection

Mice immunized intransally or intragastrically with proteosome vaccines containing either Shigella sonnei or S. flexneri 2a lipopolysaccharide were protected against lethal pneumonia caused by homologous organisms in an experimental murine intranasal challenge model of Shigella infection. Histopathological analysis demonstrated that immunization also protected against the progressive lesions resulting from invasion of the pulmonary mucosa by S. sonnei. These data show that mucosal proteosome-lipopolysaccharide vaccines can protect against lethal bacterial pneumonia and indicate that such vaccines are promising candidates for protection against intestinal shigellosis.

Detection of provisional serovars of Shigella dysenteriae and designation as S. dysenteriae serotypes 14 and 15

In initial studies of slide and tube agglutination tests of shigella-like isolates from diarrheal stools from Bangladesh, 10 and 8 strains of Shigella dysenteriae were identified as provisional serovars (serovars that have been defined but not given a number in the antigenic schema) E22383 and E23507, respectively. Further screening of diarrheal stool isolates in a slide agglutination test with antisera (made with the international reference strains) to the two provisional serovars of S. dysenteriae identified an additional 36 isolates as belonging to E22383 and 8 isolates as belonging to E23507. All strains had properties typical of invasive Shigella strains in that they were positive in the Sereny test and had the 120- to 140-MDa plasmid associated with invasiveness. On the basis of these markers of pathogenicity and isolation from various geographical locations, now we recommend that provisional serovars E22383 and E23507 be designated S. dysenteriae serotypes 14 and 15, respectively.

Epidemiological, clinical and microbiological features of shigellosis among hospitalized children in northern Israel

The epidemiological, clinical, and bacteriological aspects of shigellosis were studied in a population of hospitalized children in northern Israel. During the 6-year period 1987-92, 262 children were hospitalized due to shigella infection. Shigellosis represented 10% of pediatric admissions for diarrhea. Admissions for the disease peaked during the summer and autumn. The median age of the patients was 3 years. Shigella sonnei was isolated in 74% of patients and S. flexneri in 21%, compared with relative frequencies of 87% and 10%, respectively, in the non-hospitalized population of the area, detected during the same period (p < 0.001). Shigella sonnei represented 82% of isolates of hospitalized Jewish patients but only 60% of hospitalized Arab children, many of whom live in poverty and overcrowding (p < 0.001). Shigella flexneri was particularly frequent among hospitalized infants, and was associated with Arab origin, large families and residence in agricultural settlements. Duration of hospitalization was 4.7 +/- 2.3 days for S. sonnei infections and 5.8 +/- 3.6 days for S. flexneri (p < 0.005). No cases of shigella sepsis, hemolytic uremic syndrome, or fatalities were observed. Overall 37% of all shigella isolates from hospitalized children were resistant to ampicillin, 71% to cotrimoxazole, 28% to both and 13% were resistant to > or = 3 different drugs. It is concluded that shigellosis is an important cause of hospitalization in northern Israel. Resistance to antimicrobial drugs is widespread among all Shigella spp. Although S. sonnei is the most common species, S. flexneri is particularly frequent in infants.

Interaction of the Shiga-like toxin type 1 B-subunit with its carbohydrate receptor

A study of the binding of the Shiga-like toxin 1 (SLT-1) to the P(k) trisaccharide [methyl 4-O-(4-O-alpha-D-galactopyranosyl)-4-O-beta-D- glucopyranoside] and its constituent dissacharides was carried out. The trisaccharide represents the carbohydrate recognition domain of the neutral glycolipid receptor of the SLT-1, globotriosylceramide (GbOse3). The binding constant for soluble trisaccharide to the soluble pentameric B-subunit is weak, with a K(a) of (0.5-1) x 10(3) M-1 for B-subunit monomer. Scatchard analysis of the binding data indicates five identical non-interacting carbohydrate binding sites per B-subunit pentamer and no cooperativity in binding. Despite weak binding (delta G = -3.6 kcal mol-1), the enthalpy of binding (delta H = -12 kcal mol-1) and the change in molar heat capacity accompanying binding (delta C(p) = -40 eu) are comparable to other protein-carbohydrate interactions. Dynamic light scattering studies indicate that carbohydrate binding induces protein aggregation. At carbohydrate concentrations where > 90% of B-subunit monomers are bound, the far-UV CD spectra were unchanged, whereas a change in the near-UV CD, maximal near 270 nm, titrated to give an apparent binding constant in good agreement with that obtained by isothermal microcalorimetry. Steady-state fluorescence and fluorescence lifetime measurements indicated that the environments of the central tryptophans are perturbed during saccharide binding, and the changes correlate with the extent of protein aggregation. On the basis of the thermodynamics of binding, optical spectroscopy, and binding-induced aggregation, we propose a model of SLT-1-membrane interaction that relies on protein-carbohydrate interaction for specificity and protein-lipid interaction for tight binding.

Shigellosis in neonates and young infants

To determine the clinical features and outcome of shigellosis in young infants, we reviewed the hospital records of 159 infants < or = 3 months of age (including 30 neonates) and 159 children 1 to 10 years of age with shigellosis who were admitted to the Diarrhoea Treatment Centre in Dacca, Bangladesh. Infants more commonly had a history of nonbloody diarrhea (82.8% vs 42.7%; p < 0.001), moderate or severe dehydration (59.9% vs 32.1%; p < 0.001), or bacteremia (12.0% vs 5.0%; p = 0.027) and less commonly had fever (32.7% vs 58.6%; p < 0.001), abdominal tenderness (1.9% vs 12.6%; p < 0.001), or rectal prolapse (0% vs 8.3%; p = 0.001). Infections caused by Shigella boydii (20.8% vs 6.3%; p < 0.001) and Shigella sonnei (7.5% vs 1.3%; p = 0.006) were more common, and Shigella dysenteriae type 1 (9.4% vs 31.4%; p < 0.001) infections were less common in infants than in older children; the proportion of Shigella flexneri infections was equivalent in the two groups (59.1% vs 60.4%). Infants were twice as likely to die as older children (16.4% vs 8.2%; p = 0.026). Only 17 infants (14.3%) were being exclusively breast fed at the onset of their illness. In a multiple logistic regression analysis, independent predictors of death in infants were gram-negative bacteremia, ileus, decreased bowel sounds, hyponatremia, hypoproteinemia, and a lower number of erythrocytes detected on microscopic examination of stool specimens. Diarrhea management algorithms that rely only on clinical findings of dysentery to diagnose and treat shigellosis are likely to be unreliable in this high-risk age group.

Comparison of pivmecillinam and nalidixic acid in the treatment of acute shigellosis in children

The efficacy of oral pivmecillinam was compared with nalidixic acid in the treatment of acute shigellosis in children 1-8 years of age. In a double-blind trial we studied 80 comparable children with bloody diarrhoea of less than 3 days' duration. Shigella spp. was isolated in 71 children. Patients were randomly assigned to receive either pivmecillinam, 50 mg/kg.day, or nalidixic acid, 60 mg/kg.day, both given orally for 5 days. The stool frequency decreased progressively in both treatment groups. Nalidixic acid failed to eradicate Shigella species in 10 patients, compared with three in the pivmecillinam group (p = 0.04). Similarly, clinical failure was observed in 11 of 37 patients receiving nalidixic acid and in 2 of 26 patients infected with nalidixic acid-susceptible strains as against none in the group receiving pivmecillinam. The results suggest that pivmecillinam given orally was, in fact, more effective than nalidixic acid in the treatment of acute shigellosis in children, particularly when the resistant strains are taken into account.

Effect of dietary nucleotide supplementation on diarrhoeal disease in infants

The effects of a nucleotide-supplemented formula on diarrhoeal disease was studied in 141 infants (group 1) who belonged to the low socioeconomic stratum; 148 controls (group 2) received the same formula but unsupplemented. Group 1 experienced less episodes of diarrhoea (109 versus 140), including less first episodes (74 versus 102; chi-square = 8.19, p < 0.004; odds ratio 2.01) and for a lesser number of days (807 versus 996 days); 45.0% and 31.1% of infants in groups 1 and 2, respectively, never developed episodes of diarrhoea. There were no differences in the clinical characteristics of the episodes or in the enteropathogens isolated from symptomatic or asymptomatic infants. The mechanisms through which nucleotides decrease the incidence of diarrhoeal disease in infants remain unclear.

Local immune response and protection in the guinea pig keratoconjunctivitis model following immunization with Shigella vaccines

This study used the guinea pig keratoconjunctivitis model to examine the importance of route of administration (mucosal versus parenteral), frequency and timing of immunization (primary versus boosting immunization), and form of antigen given (live attenuated vaccine strain versus O-antigen-protein conjugate) on the production of protective immunity against Shigella infection. Since local immune response to the lipopolysaccharide (LPS) O-antigen of Shigella spp. is thought to be important for protection against disease, O-antigen-specific antibody-secreting cells (ASC) in the spleen and regional lymph nodes of immunized animals were measured by using an ELISPOT assay. Results indicated that protective efficacy was associated with a strong O-antigen-specific ASC response, particularly in the superficial ventral cervical lymph nodes draining the conjunctivae. In naive animals, a strong ASC response in the cervical lymph nodes and protection against challenge were detected only in animals that received a mucosal immunization. Protection in these animals was increased by a boosting mucosal immunization. While parenteral immunization alone with an O-antigen-protein conjugate vaccine did not protect naive animals against challenge, a combined parenteral-mucosal regimen elicited enhanced protection without the addition of a boosting immunization. Although O-antigen-specific serum immunoglobulin A titers were significantly higher in animals receiving a mucosal immunization, there was no apparent correlation between levels of serum antibody and protection against disease.

Rotaviruses: immunological determinants of protection against infection and disease

Although studies of rotavirus immunity in experimental animals and humans have often yielded conflicting data, a preponderance of evidence supports the following answers to the questions initially posed. 1. What is the importance of virus serotype in formulating an optimal vaccine? Both vp4 and vp7 induce virus-neutralizing antibodies after either natural infection or immunization; the capacity of vp4 to induce rotavirus-specific neutralizing antibodies is probably greater than that of vp7. However, protection against disease after immunization of infants and young children is induced by strains heterotypic to the challenge virus (e.g., immunization with WC3 induces protection against disease induced by serotypically distinct human G1 strains). In addition, oral inoculation of infants with primate or bovine reassortant rotaviruses containing genes that encode human vp7 has not consistently induced a higher level of protection against challenge than that induced by parent animal rotaviruses (see Table I). Therefore, although vp4 or vp7 or both are probably important in inducing protection against challenge, it has not been clearly demonstrated that inclusion of the epidemiologically important human (as distinct from animal) P or G type is important in protection against human disease. 2. Which immunological effector arm most likely protects against rotavirus disease? No immunological effector arm clearly explains protection against heterotypic challenge. Protection against disease is not predicted by rotavirus-specific neutralizing antibodies in serum. Rotavirus-specific, binding sIgA in feces [detected by enzyme-linked immunosorbent assay (ELISA)] induced after natural infection does correlate with protection against disease induced by subsequent infection. However, protection after immunization with WC3 may occur in the absence of a detectable fecal sIgA response. The relationship between rotavirus-binding sIgA and sIgA-mediated neutralizing activity directed against the challenge virus remains to be determined. Binding rotavirus-specific sIgA in feces detected by ELISA may only be a correlate of other events occurring at the intestinal mucosal surface. The presence of broadly cross-reactive, rotavirus-specific CTLs at the intestinal mucosal surface of mice acutely after infection is intriguing. It would be of interest to determine the degree to which the presence of cross-reactive, rotavirus-specific CTLs in the circulation is predictive of the presence of virus-specific CTLs among intestinal lymphocytes and protection against challenge. Unfortunately, studies of virus-specific CTLs are difficult to perform in children. 3. By what means is virus antigen best presented to the host to elicit a protective immune response? Oral inoculation may not be necessary to induce a protective, virus-specific immune response at the intestinal mucosal surface.(ABSTRACT TRUNCATED AT 400 WORDS)

Serum IgG antibody responses to Shigella invasion plasmid-coded antigens detected by immunoblot

Serum IgG antibody responses to Shigella invasion plasmid-coded antigens (Ipa) from 58 Shigella flexneri, S. sonnei, and S. dysenteriae infected Swedish patients were investigated by immunoblot technique. Intense responses to most components of Ipa (Ipas A, B, C, D, and VirG-virulence determinant on SalI fragment G of the plasmid) were evident in sera from S. flexneri infected patients. The strongest response was to Ipa B and the weakest, to Ipa D. In contrast, there were weaker responses to Ipas A, B, C, and VirG but none at all to Ipa D in sera from S. sonnei infected patients. After absorption of the Ipa-positive sera by Ipa expressing strains of S. flexneri and S. sonnei, most IgG antibodies to components of Ipa were removed in sera absorbed by S. flexneri, but IgG antibodies to Ipas--especially to Ipa D--were only slightly reduced in sera absorbed by S. sonnei, suggesting that Ipa D in S. sonnei may not be exposed on the S. sonnei cell surface.

Childhood diarrhoea and acute respiratory infections in developing countries

In 1990 childhood diarrhoea and acute respiratory infections together accounted for 7.5 million deaths of children younger than five years of age in developing countries. To decrease mortality and treatment costs associated with these illnesses, the World Health Organization has developed standard diagnostic and treatment procedures for health staff, and is working on strategies for disease prevention. Immunisation against measles, adequate nutrition, including exclusive breastfeeding for the first four to six months, and improved water supplies and sanitation are the most important preventive measures. The 1990 World Summit for Children has set goals of a 50% reduction in childhood mortality from diarrhoea and a 33% reduction in mortality from acute respiratory diseases by the year 2000. These goals can be achieved by political commitment and a major investment of resources, but sustained support for these efforts from the medical professions is crucial.

Health Effects of the 1991 Bangladesh Cyclone: Report of a UNICEF Evaluation Team

To assess the impact on health of the cyclone and tidal wave that struck the southern coast of Bangladesh on the evening of 29 April 1991, a team of health professionals visited cyclone affected areas from 4-27 June, 1991. Team members met with health workers and officials of the Government of Bangladesh and with staff pom nongovernmental organizations, and conducted field surveys in two severely affected areas. Mortality among the 135 households surveyed (pre-cyclone population 1,123) was 14 per cent. At highest risk of deaths were children of less than 10 years (26 per cent mortality) and women of more than 40 (31 per cent mortality). Almost all deaths occurred as a result of drowning from the tidal wave that accompanied the cyclone. Although 95 per cent of the population surveyed had received warning of the cyclone four or more hours before it struck, the 300 existing cyclone shelters had capacity for only 450,000 of the 5,000,000 people affected by the cyclone. Deaths following the cyclone were few. Diarrhea caused by Vibrio cholerae and Shigella dysenteria type 1, both of which are endemic in Bangladesh, occurred in the post-cyclone period. Reports by the national Diarrhea Surveillance System of large increases in diarrheal incidence following the cyclone were difficult to assess because of inconsistencies in pre-and post-cyclone reporting methods. No increase in other infectious diseases was identified. Although water availability had been a major concern following the cyclone, the tubewell system was functioning well in the area that was surveyed. Distribution of relief assistance by the Government of Bangladesh and by non-governmental organizations was good, with 95 per cent of families surveyed receiving food aid within five days of the cyclone. The major health effect of this cyclone was acute deaths due to drowning. Preventing deaths during future cyclones will require increasing accessible shelter.

Serum antibody responses against shigella lipopolysaccharides and invasion plasmid-coded antigens in shigella infected Swedish patients

Serum antibody responses to shigella lipopolysaccharide (LPS) and invasion plasmid-coded antigens (Ipa) were studied in 74 Swedish patients with culture verified bacillary dysentery using class-specific enzyme immunoassay (EIA). Anti-LPS responses were found in 80% and 79% serum samples, respectively, from S. flexneri and S. sonnei infected patients and anti-Ipa responses in 60% and 43%, respectively. The mean anti-Ipa IgG antibody titres in S. flexneri infected patients remained high for 4-6 months after onset while the anti-LPS IgG antibody titres had dropped to normal levels. The specificity of EIA for shigella Ipa was 90% and for S. dysenteriae, S. flexneri and S. sonnei LPSs it varied between 84% and 90%. No close correlations between the anti-LPS and anti-Ipa antibody responses were observed indicating that they may be differently regulated. The dynamics of the serum antibody responses indicates that an anti-LPS response is a good indicator of a recent shigella infection and an anti-Ipa IgG response a good indicator of a previous infection.

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.

Measurement of fecal lactoferrin as a marker of fecal leukocytes

While diarrheal illnesses are extremely common in communities and hospitals throughout the world, an etiologic diagnosis may be expensive and cost-ineffective. Although the presence of fecal leukocytes are helpful in the diagnosis and specific therapy of inflammatory diarrheas, this requires prompt microscopic examination of fecal specimens (preferably obtained in a cup rather than a swab or diaper) by a trained observer. We developed a simple, sensitive test for the detection of leukocytes in fecal specimens using antilactoferrin antibody. Whereas radial immunodiffusion detected 0.02 micrograms of lactoferrin (LF) per microliter or greater than or equal to 2,000 leukocytes per microliter, latex agglutination (LA) readily detected greater than or equal to 0.001 micrograms of LF per microliter or greater than or equal to 200 leukocytes per microliter added to stool specimens. Despite the destruction or loss of morphologic leukocytes on storage for 1 to 7 days at 4 degrees C or placement of specimens on swabs, measurable LF remained stable. Initial studies of stool specimens from six patients with Salmonella or Clostridium difficile enteritis were positive and those from three controls were negative for LF by LA. Of 17 children in Brazil with inflammatory diarrhea (greater than or equal to 1 leukocyte per high-power field), 16 (94%) had LF titers of greater than 1:50 by LA, whereas only 3 of 12 fecal specimens with less than 1 leukocyte per high-power field on methylene blue examination and none of 7 normal control specimens had an LF titer of greater than 1:50 by LA. Of 16 fecal specimens from patients with C. difficile diarrhea (cytotoxin titers, >/= 1:1,000), 95% (n = 15) had detectable LF by LA (in titers of 1:100 to 1: 800). Finally, of 48 fecal specimens from healthy adult U.S. volunteers before and after experimental shigellosis and of 29 fecal specimens from children with documented shigellosis and hospitalized controls in northeastern Brazil, fecal LF titers ranged from 1:200 to >/= 1:5,000 in 96% (25 of 26) samples from patients with shigellosis (and reported positive for fecal leukocytes), while 51 controls consistently had fecal LF titers of </= 1:200. We conclude that fecal LF is a useful marker for fecal leukocytes, even when they are morphologically lost swab specimens or when they are destroyed on transport or storage or by cytotoxic fecal specimens.

Fluorescent antibody staining test for rapid diagnosis of Shigella dysenteriae 1 infection

An indirect fluorescent antibody test for rapid detection of Shigella dysenteriae 1 in diarrheal stools was developed. A diagnosis could be made within 90 min of submission of specimens to the laboratory. On comparison with culture results, the test had a sensitivity of 92%, a specificity of 93%, and positive and negative predictive values of 94% and 92%, respectively.

The relative importance of Shigella in the aetiology of childhood gastroenteritis in Saudi Arabia

The role of shigella infection in childhood gastroenteritis was studied over a 2-year period. Shigella species were found in the faecal specimens of 70 (1%) of 7369 children with gastroenteritis, but in only 1 (0.1%) of 1130 controls. S. flexneri was the commonest isolate (51%), followed by S. sonnei (37%). Most shigella species were isolated during the winter. The prevalence of shigellosis was highest for children 1-5 years of age but equal for both sexes. Fever, abdominal cramps, vomiting, and bloody diarrhoea were the predominant clinical features. Of the shigella isolates, 73% were resistant to cotrimoxazole, 43% to ampicillin, and 41% to chloramphenicol. One-third of isolates were resistant to greater than or equal to 3 antibiotics. All isolates were susceptible to nalidixic acid. The illness was mild and self-limiting and most patients recovered without antimicrobial therapy.

Evidence for long-term memory of the mucosal immune system: milk secretory immunoglobulin A against Shigella lipopolysaccharides

Although the common mucosal immune system has generally been considered to have only short-term memory, recent data suggest that long-term memory exists for Shigella virulence plasmid antigens. Because such antigens might cross-react with environmental antigens, we investigated milk for the persistence of antibodies to the specific Shigella lipopolysaccharide (LPS) antigens. Enzyme-linked immunosorbent assays to detect secretory immunoglobulin A (sIgA) against Shigella flexneri and Shigella sonnei LPS in milk samples were developed; 15 random milk samples tested on different days correlated from one day to the next (P = 0.0001). Of 18 Mexican mothers, 18 (100%) had one or more milk samples positive for anti-S. flexneri LPS, 14 (78%) had one or more milk samples positive for anti-S. sonnei LPS, and 14 (78%) had one or more milk samples positive for both. Of 27 Houston mothers, 16 (59%) had one or more milk samples positive for anti-S. flexneri LPS, 7 (26%) had one or more milk samples positive for anti-S. sonnei LPS, and 5 (19%) had one or more milk samples positive for both. Mexican mothers were significantly more likely than Houston mothers to have at least one sample with a positive titer for anti-S. flexneri LPS (P less than 0.02) and at least one sample with a positive titer for anti-S. sonnei LPS (P less than 0.002). Although the Houston women had a lower rate of titer positivity for both Shigella species, the rate was too high to be consistent with short-lived mucosal immunity. It is unlikely that 18 of the 27 Houston women had shigellosis during or just prior to lactation. The data suggest that there exists a long-term hormonally driven memory in the secretory immune system for Shigella spp.

Effect of duration of diarrhoea and predictive values of stool leucocytes and red blood cells in the isolation of different serogroups or serotypes of Shigella

Diarrhoeal stools from 11,358 patients were microscopically examined for the presence of white and red blood cells (WBC and RBC) and cultured for enteric pathogens. Of the 3895 patients who had Shigella as sole pathogens, 2681 (72.3%) showed the presence of both WBC and RBC and the remainder had only WBC (P less than 0.001). The presence of both WBC and RBC was as good a predictor of shigellosis as the presence of greater than 25 WBC per high power field (hpf) of the microscope with or without RBC. However, the best predictor of shigellosis (positive predictive value 85%, negative predictive value 83%) was the presence of greater than 25 WBC/hpf and the presence of RBC regardless of their number. More patients infected with S. dysenteriae 1, S. flexneri and S. boydii shed both WBC and RBC than those infected with S. sonnei, most of whom shed WBC only (P less than 0.001). A greater number of patients infected with S. dysenteriae 1 shed more WBC and RBC than those infected with S. flexneri (P less than 0.001). The same trend was found when patients infected with S. flexneri were compared with those infected with S. boydii (though the difference was not statistically significant) and when patients infected with S. boydii were compared with patients infected with S. sonnei (P less than 0.001). There was a progressive decline in the isolation rate of Shigella as the duration of dysentery, before stool culture, increased.

Genetic basis of virulence in Shigella species

Shigella species and enteroinvasive strains of Escherichia coli cause disease by invasion of the colonic epithelium, and this invasive phenotype is mediated by genes carried on 180- to 240-kb plasmids. In addition, at least eight loci on the Shigella chromosome are necessary for full expression of virulence. The products of these genes can be classified as (i) virulence determinants that directly affect the ability of shigellae to survive in the intestinal tissues, e.g., the aerobactin siderophore (iucABCD and iutA), superoxide dismutase (sodB), and somatic antigen expression (rfa and rfb); (ii) cytotoxins that contribute to the severity of disease, e.g., the Shiga toxin (stx) and a putative analog of this toxin (flu); and (iii) regulatory loci that affect the expression of plasmid genes, e.g., ompR-envZ, which mediates response to changes in osmolarity, virR (osmZ), which mediates response to changes in temperature, and kcpA, which affects the translation of the plasmid virG (icsA) gene which is associated with intracellular bacterial mobility and intracellular bacterial spread. A single plasmid regulatory gene (virF) controls a virulence-associated plasmid regulon including virG (icsA) and two invasion-related loci, i.e., (i) ipaABCD, encoding invasion plasmid antigens that may be structural components of the Shigella invasion determinant; and (ii) invAKJH (mxi), which is necessary for insertion of invasion plasmid antigens into the outer membrane.

Waterborne transmission and the evolution of virulence among gastrointestinal bacteria

Diarrhoeal diseases are primary contributors to millions of deaths annually. Yet, little is known about the evolutionary reasons for the differences in virulence among gastrointestinal pathogens. Applying the comparative, cost/benefit approach of evolutionary biology this paper proposes that waterborne transmission should favour evolution towards high virulence. This hypothesis is supported by a cross-specific test, which shows that waterborne transmission is strongly correlated with the virulence of bacterial gastrointestinal pathogens of humans. Alternative explanations of this correlation are not supported by available data. These findings bear on public health policy because they draw attention to a previously unrecognized long-range benefit gained from purification of water supplies; diarrhoeal pathogens may evolve to lower levels of virulence.

Is acute watery diarrhoea an important cause of morbidity and mortality among rural Bangladeshi children?

To assess the relative importance of acute watery diarrhoea (AWD) and other types of acute diarrhoea as causes of morbidity and mortality among infants and 1-4 years old children, we examined 3 different data sources from the Matlab field project of the International Centre for Diarrhoeal Disease Research, Bangladesh. In infants, prevalence rates for AWD and non-watery diarrhoeas were similar. In children, prevalence of AWD was 1.8 times lower than prevalence of other acute diarrhoeas. In infants, admission rate to a diarrhoea hospital was 4.1 times higher for AWD than for other acute diarrhoeas (P less than 0.001). In children, admission rate was only 1.7 times higher for AWD than for acute diarrhoeas (P less than 0.001). Infant mortality was 1.7 times higher for AWD than for other acute diarrhoeas, but child mortality was 3 times lower for AWD. These data suggest that, while diarrhoeal disease control programmes should give more importance to oral rehydration therapy in infants, field management of the other types of acute diarrhoea should receive more emphasis in children.