Differentiation of PathogenicEscherichia coliStrains in Brazilian Children by PCR

A PCR technique to differentiate pathogenic entericEscherichia colistrains in afield setting was evaluated. Among76childrenwithacutediarrhea,thistechniqueidentified12children(16%)withenterotoxigenicE.coli, 6 (8%) with enteropathogenic E. coli, and 1 (1%) with enteroinvasive E. coli infection. Compared with the conventionalassays,thePCRmethodprovedtobesimpler,morerapid,andinexpensiveandthereforesuitable for application in a developing-countryfield setting. Diarrheal disease remains a major public health problem in developing countries (25). Escherichia coli strains are among the most important bacterial causes of childhood diarrhea. At leastfive categories of diarrheagenicE. colistrains are recog- nized on the basis of distinct epidemiological and clinical fea- tures,specificvirulencedeterminants,andassociationwithcer- tain serotypes (12, 15). Because of the costly and labor- intensive diagnostic procedures, the epidemiology of E. coli infections remains obscure in many parts of the world. This study was undertaken to evaluate the application of a PCR- based test to differentiate E. coli isolates and determine their distribution among children with and without diarrhea. The study was conducted at Hospital Infantil of the Federal University of Bahia in Salvador de Bahia, Brazil. From 1 June to 31 August 1993, all children under 5 years of age with acute diarrhea who were brought to the hospital ambulatory clinic in the afternoon, Monday through Friday, were enrolled in the study. Two rectal swabs were collected from each child, placed in Cary-Blair transport medium, and processed within 4 h. One swab was processed by routine microbiological and biochemi- cal tests to identify E. coli, Salmonella spp., Shigella spp., and Campylobacter jejuni, while the second swab was stored in 2 ml of phosphate-buffered saline (pH 7.4) at 48C until tested for rotavirus by enzyme immunoassay (EIA) (LMD Laboratories, Inc., Carlsbad, Calif.). Fecal samples and/or rectal swab spec- imens were obtained for detection ofCryptosporidium parvum byenzyme-linkedimmunosorbentassay(ELISA)(AlexonInc., Sunnyvale, Calif., and LMD Laboratories, Inc.). Three to six lactose-fermenting colonies and up to three lactose-negative colonies from each child were selected from MacConkey plates to be tested by conventional and PCR pro- cedures. A total of 239 isolates were obtained from the 76 children and stored on tryptic soy agar (Difco Laboratories, Detroit, Mich.) gridplates for later testing by reference viru- lence assays. In addition, 43 isolates from 16 children without diarrhea were tested as controls. All conventional virulence assays were performed in the research laboratory at Cornell