Effect of antimicrobial (nalidixic acid) therapy in shigellosis and predictive values of outcome variables in patients susceptible or resistant to it

Abstract

We observed the clinical features and results of simple laboratory tests on stools of 33 children with bacteriologically proven shigellosis to identify features that could be used to assess the effectiveness of antimicrobial therapy. Persistence of fever (rectal temperature > 37.8 degrees C), abdominal pain/tenderness and anorexia on days 3 and 5 were significantly more common (P < 0.001) among children who received an antimicrobial to which the infecting Shigella was resistant. Similarly, a significantly higher number of children treated with an ineffective antimicrobial had faecal leucocytes of > 50/high power microscopic field (HPF), erythrocytes of > 50/HPF and macrophages of > 5/HPF on study day 5. The best predictors of ineffective antimicrobial therapy on days 3 and 5 of treatment were fever, presence of blood by naked eye examination of stool, and minimum change in stool frequencies. These observations suggest that by careful follow-up of clinical features and simple laboratory tests, such as stool microscopic examinations, it is possible to identify patients unlikely to respond to initial therapy by 72 hours permitting the start of alternative antimicrobial treatment. This may be of great help where stool culture and sensitivity facilities for Shigella spp. are not available.