Interference of modern antibacterials with bacillus Calmette-Guerin viability

Purpose: We determine the effects of modern antibacterial chemotherapeutics on bacillus Calmette-Guerin (BCG) viability, particularly those of cyclose rine, which has been recommended for treating BCG induced sepsis. Materials and Methods: The minimal inhibitory concentrations of 31 antibact erial drugs against Connaught BCG strain were determined in vitro by the ra diometric BACTEC 460TB method.* Minimal inhibitory concentrations were comp ared with the drug concentrations achievable in blood and urine to estimate systemic or intravesical susceptibility. Susceptibility testing of cyclose rine was performed with Connaught, Tice and RIVM BCG strains, using the mod ified proportion method on Lowenstein-Jensen agar. Results: Connaught BCG was susceptible to quinolones in systemic infections but resistant to beta-lactams, macrolides and some aminoglycosides. It was resistant to pyrazinamide but showed good susceptibility toward the other antituberculosis drugs tested. All 3 BCG strains analyzed were resistant to cycloserine. Most antibacterials may interfere with BCG in the bladder bec ause of high urinary recovery. Conclusions: Antibacterial drug interference with BCG viability should be a voided during intravesical instillation therapy. In cases of severe complic ations quinolones rather than cycloserine may be given in addition to stand ard triple antituberculosis drug therapy or if one of these drugs is not to lerated. Our data may contribute toward enhancing the therapeutic safety an d efficacy of intravesical BCG immunotherapy by the appropriate use of anti bacterial drugs.