Biological properties of Mycobacterium tuberculosis (Mtb) resistant to biocides

Abstract

The problem of resistance of Mtb to antibiotics is a global threat to humanity. Along with drug resistance, Mtb can also develop resistance to other biocides (e.g. disinfectants), but this phenomenon is currently not well understood and became the goal of this study.

Materials and methods: We studied 21 isolates of Mtb that are resistant to biocides and isolated from the surfaces of the TB hospital. Growth properties, virulence, genotype, spectrum of drug resistance and resistance to 4 classes of chemical disinfectants (chlorine, hydrogen peroxide, aldehyde containing and quaternary ammonium compounds (QACs)) were determined. Since surfactants account for up to 70% of all biocides in the disinfectant market, we present data only for this class of chemical compounds.

Resistance mutations and genetic family were determined by TB-Biochip system. Mtb resistance to biocides were estimated following the UNE-EN 14348 standard and tissue test-object method. To study the virulence of Mtb, guinea pigs were infected with a dose of 1000 сfu in 0,1 ml.

Results: All Mtb isolates were characterized by increased growth ability on the grow media and virulence in vivo experiments. 17 isolates belonged to the Beijing genotype; four isolates were mixed cultures of Beijing and Ural genotypes. 15 isolates (71.4%) were XDR Mtb, 6 (28.6%) were pre-XDR Mtb.

When determining the minimum inhibitory concentration of QACs, the ability to grow was found in all Mtb isolates after exposure to a concentration 6-10 times higher than recommended for use.

Conclusions: Thus, on the surfaces of the TB hospital, we found highly virulent Mtb of Beijing genotype, resistant to a wide class of the biocides and a high degree of TB drug resistance.