Bacterial and Parasitic Profile of Acute Infectious Pediatric Diarrhoea and the Role of Faecal Screening Tests in Prediction of The Invasive Type of Diarrhoea

Diarrhoea is one of the leading causes of morbidity and mortality in children worldwide. Faecal screening methods as detection of faecal leucocytes, faecal lactoferrin and faecal occult blood, have diagnostic and therapeutic implications in the provisional diagnosis of invasive diarrhea before culture results made available. Aim of the work was to outline the bacterial and parasitic profile of acute pediatric diarrhoea and to evaluate faecal screening tests in preliminary diagnosis of invasive diarrhoea. Three hundred children under five years of age, suffering from acute diarrhoea (<4 days) and attending the out-patient clinic of El Shatby Children's University Hospital in Alexandria, over a period of 1 year, were recruited in the study. Stool samples were collected from the children and were subjected to bacteriological examination, parasitological examination and 3 faecal screening tests to distinguish invasive (inflammatory) from non invasive (non inflammatory) diarrhoea. Forty eight percent of samples were positive for enteric pathogens. Enteric bacterial pathogens were isolated from 25% of samples. Parasites 29% and mixed bacterial and parasitic infections were detected in 6% of samples. Enterotoxigenic E.coli (ETEC) was the most common bacterial isolate detected in10% of samples, followed by Salmonella (8%), Shigella (6.67%) Campylobacter (5%) and Vibrio parahaemolyticus (1.33%). Cryptosporidium was the most commonly identified parasite (13%) followed by Giardi lamblia (11%), Entamoeba histolytica (8%) and Cyclospora cayetanensis (3%). Ascaris lumbricoides and Haeminolipus nana were only identified in 1% of samples, each. The gold standard for evaluation of faecal screening tests was positive culture for invasive bacterial pathogens and/or positive E. histolytica on microscopic examination of stool samples. Leuko test had the highest sensitivity (85.54%), specificity (73.73%), positive predictive value (55.47%), negative predictive value (93.02%) and accuracy (77%). False positive results of the Leuko-test were significantly higher in the breast-fed children than non breast-fed ones (26.7%, 11.7% respectively, p < 0.01). Better sensitivity, specificity, positive and negative predictive values of the Leuko-test was recorded in the non breast-fed children than in the breast-fed ones. The recorded values in the first group were: 91.11%. 83.64%, 69.5% and 95.83%, respectively compared to 78.95%, 63.55%, 43.48% and 89.47%, respectively in the second group. The study concluded that, Leuko test is the best applicable faecal screening test in differentiation of invasive and non invasive diarrhoea but is better avoided in breast-fed infants as many false positive results might be interpreted. 42 Bull High Inst Public Health Vol.40 No.1 [2010] INTRODUCTION: Diarrhoea is defined as the passage of three or more loose or watery stools per day or a single loose stool containing blood, pus or mucus (invasive diarrhoea). (1,2) Diarrhoea is still one of the leading causes of morbidity and mortality in children worldwide, causing one billion episodes of illness and 3-5 million deaths annually. (3). The incidence of diarrhoeal episodes in developing countries ranges from 2-5 illnesses per year. (4). In Egypt it was estimated that 10 million Egyptian children, under five, suffer 30 million episodes of diarrhoea annually and that diarrhoea is responsible for about 14.64 % of deaths in this age group and is the leading cause of malnutrition ;impairing the quality of life of Egyptian children. (5,6) The main bacterial causative agents of pediatric diarrhoea include: Shigella, Salmonella, Campylobacter, E. coli and vibrios. (7,8) Notable parasitic infections include those of Giardia lamblia, Entamoeba histolytica and Cryptosporidium. (9) Unlike most diarrhoeal illnesses which are self-limited, invasive diarrhoea necessitates extensive diagnostic studies and specific antimicrobial therapy to shorten the clinical course, decrease excretion of multiresistant organisms or to prevent complications. (3,10,11) . Stool culture is the standard method for diagnosis, however it is tedious, laborious and time consuming. Faecal screening methods (as detection of faecal leuocytes, faecal lactoferrin and faecal occult blood), have diagnostic and therapeutic implications in the provisional diagnosis of invasive diarrhea, as they are rapid and simple to perform. (2,12) Examination of methylene blue-stained smears is the traditional method for detection of leucocytes in stool samples. (13) To be interpreted as positive; ≥5 leucocytes HPF must be identified in the majority of fields or >10 leucocytes in a