Efficacy of disinfectants against Legionella pneumophila by an inverse biofilm assay

Abstract number: P1869

Portillo M.E., Aguinaga A., Alonso C.A., Leiva J.

Objectives:Legionella pneumophila persists in man-made aquatic installations despite treatments. More information about disinfectants could improve the effectiveness of treatments. This study tests the susceptibility of both the planktonic and biofilm bacteria against 3 disinfectants used in cooling tower treatments.

Methods: We determined the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), biofilm's minimal inhibitory concentration (BMIC) and biofilm's minimal bactericidal concentration (BMBC) of sodium hypochlorite (SH), chloramite T trihydrate (CT) and benzalkonium chloride (BC) against 6 L. pneumophila serogoup 1 isolates (5 native isolates and 1 type culture collection ATCC 33152). The MIC and BMIC were determined by the conventional microdilution method in a buffered yeast extract broth. The MBC and BMBC were determined by a variant of the Calgary's method. We determined these values after 3 h and after 48 h of disinfectant exposure. Replicated assays produced identical results for all strains.

Results: The distribution of MIC and MBC values was similar for each disinfectant against all strains after 3 h and 48 h treatment. The MIC and BMIC values were similar too. (Table 1).

Conclusions: The method described for biofilm formation and determination of biofilm susceptibility for L. pneumophila is reproducible. Efficacy of disinfectants is similar against planktonic and biofilm bacteria. The more effective disinfectant tests is benzalkonioum chloride. Disinfectants can be applied in shock and continuous treatments of water systems. Our results demonstrate that 3 h treatments are as effective as 48 h treatments for these disinfectants.

StrainsDisinfectantsTreatment time 48 hTreatment time 3 h
  MIC (ppm)BMIC (ppm)CBI/BMICMIC (ppm)CIB (ppm)CBI/MIC
ATCC 33152CT5121024264102416

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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