Bactericidal activity of four disinfectant products against Legionella pneumophila serogroup 1

Abstract

lntroduction: Chlorine is a well known disinfectant in the treatment of cooling towers, frequently identified as origin of legionnaires' disease, and there is a few experience in the use of other products. Objectives: This study describes the bactericida[ activity, in vitro, of tour disinfectants used in cooling-towers against Legionella pneumophila serogroup 1 isolates. Methods: We tested the susceptibility of 28 clinical or environmental isolates of L. pneumophila serogroup 1 against tour disinfectants, chlorine and three disinfectant registered in the Plaguicides Register: Adiclene 1352, Adicida 182 and PAB 17. We determined the Minimal lnhibitory Concentration (MIC) by macrodilution method in BYE broth , the Minimal Bactericidal Concentration (MBC) and the bactericidal effect. Results: The MIC50 and MIC90 values were similar (512 ppm far chlorine, 256 ppm far PAB 17, 8 ppm far Adicida 182 and 4 ppm far Adiclene 1352). The CMB values increased no more than 3 twofold dilutions. All disinf ectants were a ble to produce at least a 104 reduction in viable count of bacteria against all isolates to concentrations ?.2 ppm far chlorine, 8 ppm far PAB-17 and 16 ppm far Adiclene 1352 and Adicida 182. This reduction in all isolates was showed within 60min (rapidly bactericida[ effect) to concentrations ?.4 ppm far chlorine, 128 ppm far PAB 17 and Adiclene 1352 and 256 ppm for Adicida 182. Conclusions: All disinfectants showed rapid bactericidal activity to concentrations recommended by the man uf acturer in cooling-tower disinfections and slow bactericidal effect to lower concentrations. Chlorine was the most effective with regard to bactericidal effect. Chlorine and PAB-17 showed a decrease in activity when BYE broth medium was used.