Purpose: We determine the effects of modern antibacterial chemotherapeutics on bacillus Calmette-Guerin (BCG) viability, particularly those of cycloserine, which has been recommended for treating BCG induced sepsis.
Materials and methods: The minimal inhibitory concentrations of 31 antibacterial drugs against Connaught BCG strain were determined in vitro by the radiometric BACTEC 460TB method. Minimal inhibitory concentrations were compared with the drug concentrations achievable in blood and urine to estimate systemic or intravesical susceptibility. Susceptibility testing of cycloserine was performed with Connaught, Tice and RIVM BCG strains, using the modified 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 because of high urinary recovery.
Conclusions: Antibacterial drug interference with BCG viability should be avoided during intravesical instillation therapy. In cases of severe complications quinolones rather than cycloserine may be given in addition to standard triple antituberculosis drug therapy or if one of these drugs is not tolerated. Our data may contribute toward enhancing the therapeutic safety and efficacy of intravesical BCG immunotherapy by the appropriate use of antibacterial drugs.