High turnover rate of Escherichia coli strains in the intestinal flora of infants in Pakistan

The Escherichia coli flora of infants in developed countries is dominated b y one or a few strains which persist for prolonged periods of time, but no longitudinal studies have been performed in developing countries. To this e nd, we studied the rectal enterobacterial flora in 22 home-delivered Pakist ani infants during their first 6 months of life. Three colonies were isolat ed and species typed on each of 11 sampling occasions. E. coil isolates wer e strain typed using electromorphic typing of cytoplasmic enzymes, and thei r O serogroups were determined. There was a very rapid turnover of enteroba cterial strains in the rectal flora of individual infants. On average, 8.5 different E, coil strains were found per infant, and several biotypes of ot her enterobacteria. Less than 50 % of the infants were colonized with E. co il from their mothers, but strains of maternal origin were four times more likely to persists in the infants' flora than other E. coil strains. Entero bacteria other than E. coli were always of non-maternal origin, and Enterob acter cloacae and Klebsiella pneumoniae biotypes recovered from contaminate d feeds were later identified in the infants' rectal flora. An early coloni zation with klebsiella or enterobacter was significantly associated with di arrhoea during the neonatal period, although these bacteria were not likely to be the cause of the disease. The results suggest that poor hygienic con ditions result in an unstable and diverse enterobacterial flora, which may influence infant health.