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CMAJ
CMAJ - November 3, 1998JAMC - le 3 novembre 1998

Careful with the antibiotics

CMAJ 1998;159:1083

See also:
The public health report "Just when you thought it was safe to eat a burger . . ." (CMAJ 1998;158[12]:1637 [full text]), by Dr. John Hoey, highlights concerns about food-borne infections, such as those due to verocytotoxin-producing strains of Escherichia coli, E. coli O157:H7. The report is a good summary of the epidemiologic features associated with this organism and emphasizes the importance of proper food handling and preparation.

However, there is little evidence to support the statement that antimicrobial therapy for this infection is "helpful." Few randomized controlled trials to determine the efficacy of antimicrobial therapy for E. coli O157:H7 infection have been reported. Although most isolates are susceptible in vitro to many antimicrobial agents, studies have not found any clinical advantage of treatment with antibiotics over no treatment.1­3 In fact, one study reported a significantly longer duration of illness in those who were treated with antibiotics than in untreated individuals,1 and an association between the use of antibiotics and increased mortality rate has also been reported.4 Admittedly, nonrandomized studies may be biased if patients with more severe disease are more likely to receive antibiotics, but it has been suggested that antimicrobial therapy for E. coli O157:H7 infection may be harmful because the antibiotics are able to lyse or damage the infective organisms, leading to release of greater amounts of toxin.5 Consequently, antibiotic therapy for patients with intestinal infection due to E. coli O157:H7 is not currently recommended.3

Andrew E. Simor, MD
Department of Microbiology
SD Laboratory Services
Sunnybrook Health Science Centre
Toronto, Ont.

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References

  1. Ostroff SM, Kobayashi JM, Lewis JH. Infections with Escherichia coli O157:H7 in Washington State. The first year of statewide disease surveillance. JAMA 1989;262:355-9.
  2. Proulx F, Turgeon JP, Delage G, Lafleur L, Chicione L. Randomized, controlled trial of antibiotic therapy for Escherichia coli O157:H7 enteritis. J Pediatr 1992;121:299-303.
  3. Su C, Brandt LJ. Escherichia coli O157:H7 infection in humans. Ann Intern Med 1995;123:698-714.
  4. Carter AO, Borczyk AA, Carlson JA, Harvey B, Hockin JC, Karmali MA, et al. A severe outbreak of Escherichia coli O157:H7-associated hemorrhagic colitis in a nursing home. N Engl J Med 1987;317:1496-500.
  5. Walterspiel JN, Ashkenazi S, Morrow AL, Cleary TG. Effect of subinhibitory concentrations of antibiotics on extracellular Shiga-like toxin I. Infection 1992;20:25-9.