In vitro evaluation of Povidone-Iodine and Chlorhexidine against Outbreak and Non-outbreak strains of Mycobacterium abscessus using Standard Quantitative Suspension and Carrier Testing [PublishAheadOfPrint]

Background

Povidone-iodine (PI) and chlorhexidine (CHX) are widely used antiseptics active against conventional Staphylococcus aureus, Enterobacteriaceae, Candida species and viruses but their efficacy against Mycobacterium abscessus remain unproven.

Methods

We determined the in vitro potency of alcoholic PI and CHX against M. abscessus subspecies abscessus (ATCC 19977), M. abscessus subspecies bolletii (BCRC 16915), our outbreak strain of M. abscessus subspecies massiliense (TPE 101) in reference to Staphylococcus aureus (ATCC 29213) by standard quantitative suspension and carrier methods (EN 14563).

Results

By suspension, all mycobacterial strains compared to S. aureus were significantly more resistant to CHX but not PI. By carrier, the mean logarithmic reductions (LR) achieved by PI under clean (dirty) conditions were 6.575 (2.482), 5.540 (2.298), 4.595 (1.967), 1.173 (0.889) while that achieved by CHX under clean (dirty) conditions were 3.164 (5.445), 5.307 (2.564), 3.844 (2.232), 0.863 (0.389) for S. aureus, M. abscessus subspecies bolletii, M. abscessus subspecies abscessus, and M. abscessus subspecies massiliense, respectively. M. abscessus subspecies massiliense (outbreak strain) was significantly more resistant than the other tested strains to PI and CHX. By both methods, the mean LR achieved by PI was higher than for CHX for all mycobacterial strains, but under dirty conditions neither antiseptic was effectively mycobactericidal (LR<5).

Conclusions

These preliminary findings caution against the universal replacement of PI with CHX as the first-line skin antiseptic since all M. abscessus isolates were resistant to CHX. More studies are needed to establish the best practice for skin antisepsis if mycobacterial infections are also to be prevented.

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