Atorvastatin does not display an antimicrobial activity on its own nor potentiates the activity of other antibiotics against ATCC17978 or AB030.

With the current arsenal of antibiotics increasingly becoming ineffective against bacteria, there is an increasing interest in the possibility of using previously approved non-antibiotic drugs as antimicrobials. Statins have recently been investigated for their antimicrobial activity and their ability to potentially synergize with current treatment options. Atorvastatin had been shown previously to be the most promising candidate for effectivity against ATCC17978. In this study, we tested atorvastatin for its activity against an extensively drug-resistant (XDR) strain AB030. However, our data show that atorvastatin has no effect AB030. Intriguingly, atorvastatin was also ineffective against our laboratory's ATCC17978. This lack of atorvastatin activity against ATCC17978 cannot be attributed to RND efflux pumps as a strain deficient in the three most clinically relevant RND efflux systems in showed no change in susceptibility compared to its parent strain ATCC17978. Further, atorvastatin failed to potentiate the activity of tobramycin and ciprofloxacin. While it is not clear to us why atorvastatin is not active against ATCC17978 used in our study, our study shows that evaluation of compounds for their antibacterial activity should involve multiple strains to account for strain-to-strain variation.