Polymerase chain reaction based method for the detection of BCG retention after intravesical instillation in guinea pig bladders

Objective In intravesical Bacille bilie de Calmette-Guerin (BCG) immunother apy of superficial bladder cancer, a T cell mediated immunological reaction is associated with the antitumor activity. To gain insight into the approx imate number of BCG bacteria retained in the normal, noninjured, urinary bl adder after intravesical application responsible for induction of the immun e reaction, the utility of a sensitive polymerase chain reaction (PCR) base d assay was investigated in a guinea pig model. Methods: After one single or six subsequent weekly instillations with 1x10( 7) CFU Of BCG, the bladders were resected and processed for BCG determinati on with PCR. The bladders were resected 24 h after instillation, aiming at (semi)quantifying the number of BCG organisms able to resist the natural vo iding washout of the bladder. The PCR was based on amplification of a 249 b ase pair fragment of the insertion element IS6110 and is specific for bacte ria belonging to the Mycobacterium tuberculosis complex which includes Myco bacterium bovis BCG. Results: After one single instillation no detectable BCG retention was foun d. However, after six weekly instillations, BCG bacteria could be demonstra ted in 2 out of 5 guinea pig bladders, indicating that the number of adheri ng BCG organisms was around the detection limit of the assay (600-1,000 BCG bacteria per bladder). Conclusions: The data suggest that after six instillations, the retention o f BCG in the guinea pig bladder is enhanced as compared with one single ins tillation. This finding is suggestive of a role of the inflammatory process that is, besides immune system mediated reactions, associated with intrave sical BCG instillations. The nature of the molecules involved in enhanced B CG retention after repeated instillations remains to be investigated. Copyr ight (C) 2000 S. Karger AG, Basel.