Escherichia coli associated with childhood diarrheas

Estimates of Rotavirus Disease Burden in Hong Kong: Hospital‐Based Surveillance

BACKGROUND

We conducted prospective, hospital-based surveillance for rotavirus disease for a 2-year period at 4 of 12 public government (Hospital Authority [HA]) hospitals in Hong Kong. It has been estimated that HA hospitals provide 90% of inpatient care in Hong Kong.

METHODS

Information was collected for children <5 years old who had a primary or secondary diagnosis of diarrhea or for whom a stool sample was tested for the presence of rotavirus (by enzyme immunoassay) or bacteria (by culture). Surveillance data were compared with routine discharge information from the HA's computerized Clinical Management System (CMS).

RESULTS

During a 2-year period (1 April 2001 through 31 March 2003), 7391 children were admitted to the hospital with diarrhea or developed diarrhea during their hospital stay. Of these children, 5881 (80%) had a stool sample tested for the presence of rotavirus, and 30% were positive for rotavirus (representing 24% of all diarrhea-associated admissions). CMS data underreported the total percentage of diarrhea-associated admissions (15% vs. 20%) and the percentage of diarrhea-associated admissions that were the result of rotavirus infection (13% vs. 24%). Estimated rates of hospitalization for rotavirus infection (8.8 admissions/1000 children <5 years old and 18.4 admissions/1000 children <1 year old) were 4-fold higher than our previous estimates, which were determined on the basis of CMS data alone. We estimate that the cumulative risk of hospitalization with rotavirus diarrhea by age 5 years is 1 in 24. Combined active and passive (CMS) surveillance data indicate that 4.6% of all general pediatric admissions to HA hospitals in Hong Kong were associated with rotavirus infection.

CONCLUSION

Our study combined passive surveillance data from all Hong Kong HA hospitals with active surveillance data from 4 sentinel hospitals. The estimates of rotavirus disease burden obtained will help emphasize the effect of this important disease and create awareness of the potential for rotavirus vaccines. The surveillance model developed could also be a powerful tool for monitoring the effect of a vaccine.

Molecular epidemiology of Escherichia coli diarrhea in children in Hong Kong

This pediatric hospital-based study of 388 diarrhea cases and 306 controls analyzed predominant E. coli colonies from primary culture (253 cases and 177 controls) with eight DNA probes for enteropathogenic, enterotoxigenic, enteroaggregative, and diffusely adherent E. coli. Only enteropathogenic E. coli adherence factor was identified significantly more frequently in cases (10) than in controls (0).

The emergency department approach to diarrhea

Enteric disease represents a significant medical problem on a worldwide basis. The evaluation of patients with diarrhea in the emergency department should follow a stepwise methodology to identify potentially serious disorders. The evaluation of the stool for fecal leukocytes is an important differentiation point in the evaluation of the moderately to seriously ill diarrhea patient. Oral rehydration alone can treat the vast majority of diarrhea patients. Oral rehydration solution takes advantage of the sodium glucose coupled active absorption mechanism, which is largely unaffected by enteric toxins. Antimicrobial or antidiarrheal agents are rarely indicated in the treatment of diarrhea.

Aetiology of acute diarrhoea in hospitalized children in Hong Kong

To determine the role of enteric pathogens in acute childhood diarrhoea in Hong Kong, 388 children with diarrhoea and 306 children of similar age without diarrhoea were evaluated in a hospital-based study during a one-year period from August 1994 to July 1995. Of the diarrhoeal cases, 55% were under 1 year and 95% were below 5 years of age. On admission, 22% had some dehydration but none was severely dehydrated. All children were well nourished. Oyer 60% of children with diarrhoea had one or more pathogens in their stool. Rotavirus was the most commonly isolated pathogen (34.6%), followed by Salmonella (23.3%), Campylobacter (4.7%) and Shigella (2.1%). Rotavirus was not assessed in the controls and was detected mainly during the winter months December to February. Bacterial pathogens were identified more commonly in diarrhoea patients (30%) than in controls (5.6%) (P < 0.001). Despite rapid recent socioeconomic development in Hong Kong, non-typhoidal Salmonella diarrhoea remains a significant local problem in infants under 1 year. Further detailed assessment of the transmission and prevention of this infection is required.

Two-year study of endemic enteric pathogens associated with acute diarrhea in New Caledonia

A longitudinal study of diarrheal disease among patients of all ages with acute diarrhea was carried out in New Caledonia from January 1990 to December 1991. Stool samples from 2,088 diarrheal patients were examined for parasites, rotavirus, and bacterial pathogens. Potential sources of contamination (drinking water, seawater and bovine and porcine feces) were investigated. One or more enteric pathogens were identified in 41.8 and 40.6% of the persons with diarrhea, in 1990 and 1991, respectively. Salmonella spp., Shigella spp., HEp-2 cell adherent Escherichia coli (diffuse adherent and enteroaggregative), enteropathogenic E. coli (EPEC) (EPEC adherence factor-positive strains belonging to classical serotypes), localized adherent E. coli (non-EPEC), and enterotoxigenic E. coli were the frequently identified enteropathogenic bacteria. Other major enteropathogens were Entamoeba histolytica and Giardia lamblia. Campylobacter jejuni, Clostridium difficile, Clostridium perfringens, Yersinia enterocolitica, and rotavirus were isolated from only a few patients. No Vibrio spp., Aeromonas spp., Plesiomonas spp., Shiga-like-toxin-producing E. coli, enterohemorrhagic E. coli, or enteroinvasive E. coli were identified. Shiga-like toxin I-producing E. coli were present in adult bovines and calves, and heat-stable enterotoxin II-producing enterotoxigenic E. coli were found in pigs.

Molecular characterization of enterotoxigenic Escherichia coli (ETEC) isolated in New Caledonia (value of potential protective antigens in oral vaccine candidates)

The role of enterotoxigenic Escherichia coli (ETEC) in childhood diarrhoea in New Caledonia was demonstrated in previous epidemiological works. This study was undertaken in order to characterize these strains and to determine whether bacterial components of current vaccine candidates (toxin, colonization factor antigens, O:H antigens) would be useful in our region. A total of 24 ETEC strains were studied: 5 strains produced heat-labile enterotoxin, 17 strains produced heat-stable enterotoxin (9 STp and 8 STh), and 2 strains produced both toxins (1 LT/STp/STh and 1 LT/STh). E. coli strains were screened for the presence of genes encoding for enterotoxins (DNA dot blot and Southern hybridization assays); results obtained with probes were closely correlated and were in agreement with biological assays. No two ETEC strains possessed similar plasmid profiles, and DNA sequences encoding for enterotoxins were located on plasmids ranging from 58 to 75 MDa. The O:H (O1:H-,O2:H7, O6:H16, O25:H-, O27:H7, O28ab:H9, O52:H10, O64:H5, O70:H-, O78:H12, O88:H25, O99:H6, O101:H-, O126:H12, O166:H30) serotypes are presented (all the strains were typable, but some ETEC serotypes were unusual). By using antisera against colonization factor antigens (CFA) I and II, results showed that 9 of the 24 ETEC strains expressed CFA (2 CFA/II and 7 CFA/I). These strains possessed high bacterial surface hydrophobicity. Fifteen ETEC did not possess CFA; among these, 11 did not exhibit high hydrophobicity or show haemagglutination activity. Four of the 15 CFA-negative strains exhibited high hydrophobicity (two O64:H45, one O70:H- and one O88:H25) but no haemagglutination in the presence or absence of mannose.(ABSTRACT TRUNCATED AT 250 WORDS)

Early child health in Lahore, Pakistan: VIII. Microbiology

The causative agents of acute diarrhoea were investigated in children under the age of five years from 1985-1991 in three socio-economically different areas in Lahore, Pakistan. The aim was to determine the frequencies of the most common enteropathogens in faeces. The total isolation rate was 73.4%; two thirds (53.5%) were of bacterial and one third (19.9%) of viral origin. ETEC-LT (23.4%), Rota virus (19.9%), EPEC (15%) and Campylobacter (12%) were the single most frequent pathogens in all age groups and areas of living. The positivity of Campylobacter increased from 1.6% to 12% after the change of isolation technique. Shigella was isolated significantly (p > 0.001) more in children over than under one year of age. The incidence of bacterial infections was high during all seasons, while in certain years Rota virus was relatively low in the summer compared to the cooler months. The prevalence of ETEC-LT diarrhoea was higher in the periurban slum as compared to the village and the urban slum. The study is the first of its kind in Pakistan, and the results are similar to other comparable studies. It is thus possible to establish a well functioning and reliable microbiological laboratory in developing countries in a setting with restricted trained personnel and material resources.

Evaluation and optimization of a latex agglutination assay for detection of cholera toxin and Escherichia coli heat-labile toxin

The effectiveness of a latex agglutination assay kit for the detection of Escherichia coli heat-labile toxin and cholera toxin was determined for the identification of natural isolates of the corresponding enteric pathogens in Southeast Asia. By selection of the appropriate culture media, the sensitivity of the assay was improved from 90.6% (for the detection of heat-labile toxin) and 75% (for the detection of cholera toxin) to 100%, and the results were confirmed with bioassays and DNA hybridization assays for both clinical and environmental isolates.

Comparison of cloth, paper, and warm air drying in eliminating viruses and bacteria from washed hands

We compared the efficiency of paper, cloth, and electric warm air drying in eliminating rotaviruses and Escherichia coli remaining on finger pads washed with 70% isopropanol, a medicated liquid soap, an unmedicated liquid soap, or tap water alone. The contaminated area on the finger pads of a volunteer was exposed to the hand-washing agent for 10 seconds and then rinsed in 40 degrees C tap water. The washed areas were dried for 10 seconds by one of the three methods. Irrespective of the hand-washing agent used, electric air drying produced the highest and cloth drying the lowest reduction in the numbers of both test organisms. These findings indicate the importance of selecting the right means for drying washed hands, particularly when less effective hand-washing agents are used.

Rotavirus infection of the oropharynx and respiratory tract in young children

Oropharyngeal aspirates were obtained from 89 infants hospitalized with respiratory illnesses accompanied or not by diarrhea and 33 control patients without the diseases. Rotavirus was detected from 25 of these patients by immunocytology, isolation of the virus in cultures of MA104 cells, or both. None of the control patients gave a positive result. The infection involves squamous cells and globlet cells probably originating from the oropharynx, and ciliated columnar epithelial cells from the respiratory tract. The virus from 2 specimens was propagated by repeatedly passaging in the cultures and found to have characteristic morphology of rotavirus. The electrophoretic patterns of the viral RNA extracted from them are closely similar to those obtained with the rotavirus genome extracted from the stool of the same patients. Repeated stool specimens were also obtained, and sera were paired from some of these subjects. All but one of the patients who gave a positive virology for their aspirates also showed a significant rise in the titres of common group A rotavirus antibody, neutralizing antibody against one or more of serotypes of rotavirus, or both. Patients who excreted rotavirus in their stools were younger and had significantly lower titres of rotavirus antibodies in their acute sera, than those who shedded the virus in the oropharynx but did not excrete the virus in repeated stool specimens. The prevalence of rotavirus in the oropharyngeal aspirates from these patients surpassed that of adenovirus, respiratory syncytial virus, influenza virus, and herpes simplex virus combined.

Distinct populations of rotaviruses circulating among neonates and older infants

We obtained three stool specimens from each of 371 neonates. Two specimens were obtained between days 1 and 3 after birth, while they were in the hospital, and one specimen was obtained between days 6 and 14 after birth, after they had been discharged from the hospital. Seventy neonates excreted human rotavirus (HRV) while they were in the hospital, and the incidence rate for the cohort was 0.094 episodes per infant day. The incidence rate of community-acquired neonatal infections was markedly reduced to 0.022 episodes per infant day, with eight additional episodes of infection being detected after the infants were discharged from the hospital. Nevertheless, this was higher than the incidence of community-acquired HRV infection of 0.0037 episodes per infant day previously estimated by serology for the same cohort during the subsequent 2 years of infancy. None of the 78 episodes of neonatal HRV infection was accompanied by diarrhea. There were at least 44 distinct electropherotypes of HRV circulating among older infants in the community during the study period, and they comprised at least four different serotypes. Despite the genetic and antigenic diversity of the prevalent HRV isolates, only five electropherotypes with either serotype 2 or 4 specificity were isolated from the neonates, while serotype 1 and 3 viruses were not detected. Two of these electropherotypes, including one which was isolated from 57 of the 78 infants with episodes of infection, were isolated exclusively from the neonates. The other three electropherotypes were also isolated from the older infants; one was a major electropherotype and two were minor electropherotypes which were prevalent among the older infants. These results suggest that distinct populations of HRV cocirculate among neonates and older infants.

Clonal origin, restricted natural distribution, and conservation of virulence factors in isolates of enterotoxigenic Escherichia coli serogroup O126

Enterotoxigenic Escherichia coli serogroup O126 isolates have been isolated in Hong Kong since 1982 from sporadic cases of infantile diarrhea and from one outbreak in a neonatal ward. A 64-megadalton plasmid encoding colonization factor antigen I and heat-stable enterotoxin was identified in all 23 isolates. Enterotoxigenic E. coli strains producing heat-stable enterotoxin from different regions of Southeast Asia were collected and compared by biotyping, antibiotic resistance patterns, and plasmid profiles. Restriction endonuclease digestion of plasmids and subsequent Southern blot analysis with the heat-stable enterotoxin gene probe of representative strains showed a unique plasmid was harbored by all heat-stable enterotoxin-producing O126 strains tested. These results are consistent with conservative inheritance of enterotoxin plasmids within enterotoxigenic E. coli strains over a 2-year period in Hong Kong.