pseudomonad biofilm resistance NOT due to known efflux pumps

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This free text is cool if you want to know whats up with biofilm

drug resistance:

http://www.pubmedcentral.gov/articlerender.fcgi?

tool=pubmed & pubmedid=11353623

Planktonic cells (free swimming cells) of P. aeruginosa get their

natural resistance via efflux (potentiated by their having a slow

rate of drug uptake). This may NOT be true of the same beast when it

grows in biofilms (which according to some, like Kim , is

probably how many bugs usually grow in vivo).

" As illustrated by the antibiotic sensitivity profiles in Tables 2

to 5, there is clearly an enhanced resistance associated with the

biofilm mode of growth, yet the mechanisms underlying this

phenomenon remain an enigma. Limited diffusion of antibiotics would

not likely be a contributing factor, since the biofilms formed on

the MBEC device (5) were grown for a short period of time and

reached only intermediate thickness. Furthermore, nutrient

deprivation leading to a decline in metabolic activity would not

play a role because the biofilms were only formed for a 6-h period.

Thus, it appears that the innate antibiotic resistance we observed

can be attributed to physiological changes in cells associated with

the biofilm mode of growth unrelated to MDR efflux [by the four

pumps P. aeruginosa usually depends on for resistance, that is]. "

" Nonetheless, there are at least six additional uncharacterized loci

with homology to RND [efflux] pumps that may still play a role in

resistance (47). "

Kim studied the same problem and expressed a comparable

perspective:

http://www.pubmedcentral.gov/articlerender.fcgi?

tool=pubmed & pubmedid=10681331

Looking at this 2005 paper it looks like no progress has been made

on these problems:

" There are many possible resistance mechanisms that have been

introduced in the literature. " PMID: 15893555