Volume 4, Number 1—March 1998
Escherichia coli O157:H7 Infection in Colombia
To the Editor: The prevalence of Escherichia coli O157:H7 in Colombia is not known; we conducted a study to determine its prevalence in children with infectious diarrhea, in adult cattle, and in ground beef.
Between March 1996 and March 1997, we examined 538 children under 5 years of age with infectious diarrhea who had been admitted to either of the two children's hospitals in Bogotá. Diarrhea was defined as three or more loose stools within the previous 24 hours. One hundred and sixty-one children under 10 years of age admitted to the hospital for a medical reason other than infectious diarrhea served as controls.
Stool samples from children with and without diarrhea were placed in Stuart transport medium and sent to the laboratory within 24 hours; the samples were injected into sorbitol MacConkey agar (Oxoid Basingstoke, United Kingdom). After 24 hours of incubation at 37°C, sorbitol nonfermenting colonies were tested with 4-methylumbelliferyl-ß-glucuronide (MUG); all typical colonies of E. coli O157:H7 that were sorbitol-negative were confirmed as E. coli by biochemical tests (1,2) and were tested for agglutination with a latex test kit (Oxoid Basingstoke, United Kingdom) for detecting E. coli O157 and E. coli H antiserum H7 (Difco, Detroit, MI, USA). All human isolates were confirmed as Shiga-toxin producers by latex agglutination (Oxoid Basingstoke, United Kingdom). We used as a control strain E. coli O157:H7 provided by M. Karmali.
Rectal swabs from 307 healthy adult cattle from farms in Cundinamarca and Meta Departments were placed in Stuart transport medium, stored at 4°C, and transported to the laboratory within 6 hours. Swabs were injected into sorbitol MacConkey agar, and colonies that did not ferment sorbitol were characterized by standard techniques (3).
One hundred and fifty beef patties (31 cooked, 119 raw), collected in Bogotá, were examined by direct plating and enrichment culturing. Samples (1.0 g each) were serially diluted (1:10) in 0.85% NaCl solution, and 0.1 ml portions were plated in duplicate onto sorbitol MacConkey agar. Serologic and biochemical confirmation was done as mentioned above.
E. coli O157:H7 prevalence among children was 7.2%, with an age range of 0–60 months (average 21 months); diarrheal illness lasted an average of 2.5 days. Of 39 patients, eight were 6 months old or younger, five were 6 to 12 months old, 17 were 12 to 24 months old, and nine were older than 24 months. Renal failure associated with hemolytic uremic syndrome (HUS) developed in three (7.7%). Epidemiologic data were not collected regarding contaminated foods as a possible source of E. coli O157:H7 infection in the patients. E. coli O157:H7 was isolated from five (3.1%) of the 161 controls; the prevalence of E. coli O157:H7 was substantially higher in patients with infantile diarrhea than in controls.
All 39 strains from human cases were sorbitol-negative; five did not display MUG activity. Overall, 39 strains agglutinated strongly with antiserum O157:H7. Antimicrobial susceptibility tests were performed by the Bauer method (4). All E. coli O157:H7 isolated were susceptible to ciprofloxacin; 92% were resistant to ampicillin; 76% were resistant to furazolidone; and 76% were resistant to trimethoprim-sulfamethoxazole (TMP-SMZ).
E. coli O157:H7 was isolated from 20 (6.5%) of 307 rectal swabs from cattle. The strains isolated were sorbitol-negative and agglutinated strongly with antisera; five did not present activity. All strains were susceptible to ciprofloxacin; 90% were resistant to ampicillin; and 26% were resistant to TMP-SMZ. E. coli O157:H7 was isolated from 13 (87%) of 150 beef patties, six from raw beef, and seven from cooked beef.
Stool cultures of all patients with acute bloody diarrhea should be tested for E. coli O157:H7 to identify those at risk for HUS (5); however, serotyping, cytotoxicity assays, or DNA probing for E. coli O157:H7 are not routinely performed in Colombia.
This preliminary report suggests that E. coli O157:H7 is emerging as an important cause of endemic childhood diarrhea in Colombia and that the chain of contamination is present. The incidence is greatly underestimated because of limited surveillance and reporting. Further studies are needed to identify the pathogenic mechanisms of these E. coli O157:H7 strains and to determine the fecal carriage rate in healthy children. Data obtained will help elucidate the role of E. coli O157:H7 in childhood diarrhea. In addition, molecular analysis should be performed to establish the connection between the strains isolated from different sources in Colombia.
Our findings suggest that the risk for E. coli O157:H7 infection in Colombia is high; therefore, more active screening and surveillance would enhance case detection, epidemiologic understanding of E. coli O157:H7 infection and HUS, and could lead to more specific therapeutic interventions.
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