Intrinsic and acquired resistance to quaternary ammonium compounds in food-related Pseudomonas spp.
OBJECTIVE
To determine the sensitivity of a strain used for disinfectants testing (Pseudomonas aeruginosa ATCC 15442) and food-associated isolates to benzalkonium chloride and didecyl dimethylammonium chloride (DDAC). To determine whether the increase in bacterial resistance after adaptation to DDAC can be associated with phenotypic changes. To test the activity of alternative disinfectants to eliminate resistant Pseudomonas spp.


RESULTS
Pseudomonas aeruginosa ATCC 15442 was among the most resistant strains tested using a bactericidal suspension test. Growth of a sensitive Ps. fluorescens in gradually higher concentrations of DDAC resulted in stable higher resistance and to some cross-resistance to several antibacterial agents, with the exception of disinfectants containing chloramine T, glutaraldehyde or peracetic acid. It was shown by microscopy that adaptation was followed by loss of flagella, and slime formation. Removal of the slime by sodium dodecyl sulphate resulted in partial loss of the acquired resistance.


CONCLUSIONS
Pseudomonas spp. may adapt to survive against higher concentrations of quaternary ammonium compounds (QACs), but resistant strains can be eliminated with chemically unrelated disinfectants.


CONCLUSIONS
The work supports the rotation of disinfectants in food processing environments for avoiding the development of bacterial resistance to QACs. The alternating disinfectants should be chosen carefully, because of possible cross-resistance.
Langsrud
S
S
MATFORSK, Norwegian Food Research Institute, Oslo, Norway. solveig.langsrud@matforsk.no
Sundheim
G
G
Borgmann-Strahsen
R
R
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D002700:Chloramines / Q000494:pharmacology; D004202:Disinfectants / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D005516:Food Microbiology; D005976:Glutaral / Q000494:pharmacology; D008826:Microbial Sensitivity Tests / Q000379:methods; D008855:Microscopy, Electron, Scanning; D010463:Peracetic Acid / Q000494:pharmacology; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000648:ultrastructure; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013501:Surface-Active Agents / Q000494:pharmacology; D014105:Tosyl Compounds / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001548:Benzalkonium Compounds; D002700:Chloramines; D004202:Disinfectants; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D014105:Tosyl Compounds; C016300:chloramine-T; D012967:Sodium Dodecyl Sulfate; D010463:Peracetic Acid; D005976:Glutaral; C027118:didecyldimethylammonium