Effect of oxygen limitation and starvation on the benzalkonium chloride susceptibility of Escherichia coli.
OBJECTIVE
To investigate the effect of oxygen limitation, glucose-starvation and temperature on the susceptibility of Escherichia coli towards the quaternary ammonium biocide benzalkonium chloride (BAC).


RESULTS
The effect of BAC on planktonic and sessile cells were investigated using the gfp-tagged E. coli K-12 strain MG1655[pOX38Km]. Increasing temperature from 10 degrees C to 30 degrees C increased the bactericidal effect of BAC for both starved and nonstarved E. coli under aerobic and anaerobic conditions. The lowest minimum bactericidal concentration was observed for cells in anaerobic media at 30 degrees C (30 mg l(-1) BAC). Decreasing cell densities increased the decay rate for BAC-exposed cells for both starved and nonstarved E. coli. Biofilms of E. coli exposed to BAC in anaerobic medium showed a greater percentage of membrane-compromised cells than biofilms grown in aerobic medium. Image analyses of BAC-exposed biofilms showed that membrane-compromised cells were occasionally located in the interior structure of the biofilm microcolonies.


CONCLUSIONS
Increasing temperatures and the absence of oxygen, and energy substrates increased the antimicrobial effect of BAC towards E. coli.


CONCLUSIONS
The results are relevant for understanding the disinfection efficacy of quaternary ammonium compounds towards planktonic and sessile bacteria.
Bjergbaek
L A
LA
Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Aalborg, Denmark.
Haagensen
J A J
JA
Molin
S
S
Roslev
P
P
D000693:Anaerobiosis; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002245:Carbon Dioxide / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D010100:Oxygen / Q000494:pharmacology*; D010933:Plankton / Q000187:drug effects / Q000254:growth & development; D013696:Temperature
D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D001548:Benzalkonium Compounds; D002245:Carbon Dioxide; D005947:Glucose; D010100:Oxygen