Antimicrobial susceptibility changes and T-OMP shifts in pyrithione-passaged planktonic cultures of Pseudomonas aeruginosa PAO1.
OBJECTIVE
The aim of this study was to determine whether passaging Pseudomonas aeruginosa PAO1 with sub-MICs of the pyrithione biocides results in both the induction of decreased susceptibility towards these antimicrobials and associated outer membrane profile changes.


RESULTS
Previous work by this group has shown that it is possible to induce susceptibility changes towards the isothiazolone biocides in Ps. aeruginosa PAO1 by successive passages in the presence of increasing sub-MICs of biocide. This procedure was accompanied by the loss of a 35 kDa outer membrane protein, T-OMP. In this experiment, this process was repeated with the biocides sodium pyrithione (NaPT), zinc pyrithione (ZnPT) and cetrimide. The pattern of susceptibility was similar to that observed with the isothiazolone biocides. Upon removal of biocide, the observed MIC did not return to the original pre-exposure value. The onset and development of resistance was accompanied by the loss of T-OMP from outer membrane profiles, which suggests that this is a non-specific membrane channel whose production within the cell is sensitive to biocide presence. The T-OMP reappeared when the cells were passaged in the absence of pyrithione. Cross-resistance studies indicated that induced resistance to one biocide yields partial resistance towards other members of the group and the positive control.


CONCLUSIONS
These results indicate that the pyrithione biocides have similar susceptibility profiles in Ps. aeruginosa to those exhibited by the isothiazolones, but that the acquired changes in susceptibility to the pyrithiones is largely irreversible.


CONCLUSIONS
This study indicates that acquired susceptibility changes towards sub-MICs of selected biocides are multifactorial in nature.
Abdel-Malek
S M A
SM
School of Pharmacy & Medical Technology, University of Petra, Amman, Jordan.
Al-Adham
I S I
IS
Winder
C L
CL
Buultjens
T E J
TE
Gartland
K M A
KM
Collier
P J
PJ
D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000494:pharmacology; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D008826:Microbial Sensitivity Tests; D009942:Organometallic Compounds / Q000494:pharmacology; D010933:Plankton / Q000187:drug effects* / Q000254:growth & development*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development*; D011725:Pyridines / Q000494:pharmacology*; D013871:Thiones
D001425:Bacterial Outer Membrane Proteins; D002593:Cetrimonium Compounds; D003470:Culture Media; D009942:Organometallic Compounds; D011725:Pyridines; D013871:Thiones; C008704:pyrithione; C010423:pyrithione zinc; D000077286:Cetrimonium