Detection of antimicrobial activity in urine for epidemiologic studies of antibiotic use

Antibiotic resistance is the inevitable consequence of the selective pressu re of antimicrobial drug use and the adaptive plasticity of the microorgani sms. Excessive and irrational use of antimicrobial drugs is a problem in al l countries. It is particularly troublesome in developing countries where t here is a heavy burden of infectious diseases. This study was designed to d etermine whether detection of antimicrobial activity in the urine might be a useful tool for epidemiologic studies of the interaction between antibiot ic use and resistance in developing countries. A laboratory marker is neces sary because the history of antimicrobial drug use may be unreliable. Seria l specimens or spontaneously voided urine were obtained from healthy volunt eers given a single oral dose of commonly used antimicrobial drugs. Urine w as also obtained from hospitalized patients the morning after the last dose of an antimicrobial drug and from untreated controls. Assays were performe d with standard American Type Culture Collection (Rockville, MD) stains of Bacillus stearothermophilus, Escherichia coli, and Streptococcus pyogenes. Antimicrobial activity could not be detected in pretreatment urine. After a single oral dose, the beta lactam antibiotics and erythromycin could be de tected for about 12 to 24 hours, whereas clindamycin, tetracycline, trimeth oprim/sulfamethoxazole, and ciprofloxacin could be detected for 48 or more hours. In hospitalized patients, receiving multiple drugs, the following we re the sensitivity and specificity for detection of antimicrobial activity: for B. stearothermophilus, 100.0% and 85.9%, respectively; for S. pyogenes , 94.9% and 94.9%, respectively; and for E. coli, 71.8% and 98.7%, respecti vely. The combination of E. coli and Streptococcus pyogenes exhibited a sen sitivity of 97.4% and specificity of 94.9%. Detection of antimicrobial acti vity in urine is a promising method to determine antimicrobial drug use in epidemiologic studies, particularly in populations in which drug use histor y is unreliable. (C) 1999 Elsevier Science Inc.