The Escherichia coli flora of infants in developed countries is dominated by one or a few strains which persist for prolonged periods of time, but no longitudinal studies have been performed in developing countries. To this end, we studied the rectal enterobacterial flora in 22 home-delivered Pakistani infants during their first 6 months of life. Three colonies were isolated and species typed on each of 11 sampling occasions. E. coli isolates were strain typed using electromorphic typing of cytoplasmic enzymes, and their O serogroups were determined. There was a very rapid turnover of enterobacterial strains in the rectal flora of individual infants. On average, 8.5 different E. coli strains were found per infant, and several biotypes of other enterobacteria. Less than 50% of the infants were colonized with E. coli from their mothers, but strains of maternal origin were four times more likely to persists in the infants' flora than other E. coli strains. Enterobacteria other than E. coli were always of non-maternal origin, and Enterobacter cloacae and Klebsiella pneumoniae biotypes recovered from contaminated feeds were later identified in the infants' rectal flora. An early colonization with klebsiella or enterobacter was significantly associated with diarrhoea during the neonatal period, although these bacteria were not likely to be the cause of the disease. The results suggest that poor hygienic conditions result in an unstable and diverse enterobacterial flora, which may influence infant health.

The study was conducted to isolate and characterize campylobacter, enterotoxigenic Escherichia coli-labile toxin (ETEC-LT), shigella and salmonella in flies and water. The material for the study, flies (n = 300) and water samples (n = 148), was collected from different localities in and around Lahore, Pakistan. Cultivation of the samples was performed on conventional standard media. Membrane filtration technique was used for water prior to culture. Determination of ETEC-LT was done by GM1 ELISA. Results of our study showed that flies and water were reservoirs for all the four pathogens, campylobacter, ETEC-LT, shigella and salmonella. Flies from the village were carrying fewer enteropathogens, while water from the village was found to be more contaminated as compared to the city. Campylobacter and ETEC-LT were the most frequently isolated pathogens in both flies and water. Thus the incidence of diarrhoeal disease in children of developing countries may be decreased by providing plenty of safe drinking water, improving excreta disposal, toilet facilities and giving education in personal hygiene.

Resident and transient Escherichia coli strains were identified in the rectal flora of 22 Pakistani infants followed from birth to 6 months of age. All strains were tested for O-antigen expression, adhesin specificity (P fimbriae, other mannose-resistant adhesins or type 1 fimbriae) and adherence to the colonic cell line HT-29. Resident strains displayed higher mannose-resistant adherence to HT-29 cells, and expressed P fimbriae (P = 0.0036) as well as other mannose-resistant adhesins (P = 0.012) more often than transient strains. In strains acquired during the first month of life, P fimbriae were 12 times more frequent in resident than in transient strains (P = 0.0006). The O-antigen distribution did not differ between resident and transient strains, and none of the resident P-fimbriated strains belonged to previously recognized uropathogenic clones. The results suggest that adhesins mediating adherence to intestinal epithelial cells, especially P fimbriae, enhance the persistence of E. coli in the large intestine of infants.

The aim of the present investigation was to study the frequency of Shigella spp. in patients with bloody diarrhea in Pakistan and the susceptibility of isolated Shigella to three antibiotics: ampicillin, cotrimoxazole and nalidixic acid. In addition, the frequency of Campylobacter and Salmonella was also determined. Stool samples (n ϭ 152) were collected from 152 diarrheic children less than six years of age passing blood and mucus in their stools who were admitted to Paediatric Department of Mayo Hospital in Lahore, Pakistan from June to September 1990. The samples were cultivated on standard media for Shigella, Campylobacter, and Salmonella. Susceptibility of Shigella isolates was tested by disk diffusion method. The frequency of isolation was 19.1% for Shigella spp., 7.9% for Campylobacter, and 4.6% for Salmonella. Shigella flexneri (7.9%) was the most frequently isolated species, followed by S. dysenteriae (6.6%), S. boydii, (3.3%) and S. sonnei (1.3%). All Shigella isolates were susceptible to nalidixic acid (100%), while only a few were susceptible to cotrimoxazole (7.0%) and ampicillin (3.5%). In Pakistan, selfmedication and purchases of drugs without a prescription are commonly practiced. Thus, there is a greater possibility of development of resistant strains due to over use of antibiotics. Acute diarrhea with dehydration is an important health problem in children less than five years of age in developing countries. 1-3 The Paediatric Department of Mayo Hospital in Lahore, Pakistan is the center for the Control of the Diarrheal Disease Program for the World Health Organization, where enteropathogens causing diarrhea in children have been previously investigated. 4 Shigella is well known for its clinical severity in bacterial dysentery. Dysentery is characterized by blood, pus, and mucus in stools, which indicates colorectal inflammation. These types of symptoms are common to infections by Shigella, Campylobacter, Salmonella, amoeba, and Clostridium difficile. 5 Shigella spp. are a major cause of acute dysentery in children. 6, 7 Most severe infections require treatment with antibiotics, which leads to over use and misuse of many of the drugs. Moreover, knowledge is insufficient in Pakistan regarding the development of resistant strains to antibiotics most frequently used for the treatment of shigellosis. The aim of the present study was to determine the frequency of Shigella in stools of hospitalized children with enterocolitis and the susceptibility of Shigella spp. to three antibiotics, ampicillin, cotrimoxazole and nalidixic acid, which are generally used for the treatment of bacillary dysentery. In addition, the frequency of Campylobacter and Salmonella was also determined. PATIENTS, MATERIALS, AND METHODS Study population. All children (n ϭ 152) with acute dysentery who were admitted to the diarrhea ward of the Paediatric Department of Mayo Hospital, Lahore from June to September 1990 were selected. Their ages ranged from 1 to 72 months. There were 52 females and 100 males. The mean duration of bloo...

Modelado de la biodegradación en biorreactores de lodos de hidrocarburos totales del petróleo intemperizados en suelos y sedimentos (Biodegradation modeling of sludge bioreactors of total petroleum hydrocarbons weathering in soil and sediments)