Effectiveness of disinfectants used in cooling towers against Legionella pneumophila.
BACKGROUND
Legionella persists in man-made aquatic installations despite preventive treatments. More information about disinfectants could improve the effectiveness of treatments. This study tests the susceptibility of Legionella pneumophila serogroup (sg) 1 against 8 disinfectants used in cooling tower treatments.


METHODS
We determined the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and bactericidal effect of sodium hypochlorite (A), hydrogen peroxide with silver nitrate (B), didecyldimethylammonium chloride (C), benzalkonium chloride (D), tributyltetradecylphosphonium chloride (E), tetrahydroxymethylphosphonium sulfide (F), 2,2-dibromonitropropionamide (G) and chloromethylisothiazolone (H) against 28 L. pneumophila sg 1 isolates.


RESULTS
MIC and MBC values were equivalent. Bacteria are less susceptible to disinfectants F, B, D and A than to H, E, C and G. All disinfectants induced a bactericidal effect. The effect rate is dose dependent for G, H, F and B; the effect is fast for the rest of disinfectants at any concentration. The bactericidal activity of disinfectants A, G and F depends on the susceptibility test used.


CONCLUSIONS
All disinfectants have bactericidal activity against L. pneumophila sg 1 at concentrations used in cooling tower treatments. Results depend on the assay for some products.
García
M T
MT
Laboratorio de Legionella, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
Pelaz
C
C
D004202:Disinfectants / Q000494:pharmacology*; D006801:Humans; D016952:Legionella pneumophila / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology; D008826:Microbial Sensitivity Tests / Q000295:instrumentation; D014871:Water Microbiology; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*; D014881:Water Supply / Q000032:analysis
D004202:Disinfectants