Title : Development of Antimicrobial Resistance to Quaternary Ammonium Compounds in the Human Skin Microbiota
Abstract:
The use of disinfectants and sanitizers are a common practice in homes, workplaces, industries and hospitals. Quaternary ammonium compounds (QACs) are positively charged polyatomic ions with broad-spectrum antimicrobial activity that are frequently used as the active ingredient in many antimicrobial products. Considering the abundant use of these products, QACs are perpetually in contact with the skin. While the human skin functions as a physical barrier between the external environment and the body proper, it is also colonized by a diverse microbiota that actively influence health and disease. To investigate the impact of QACs on the human skin microbiome, common skin bacterial species were exposed to purified benzalkonium chloride (BAC) and cetyltrimethylammonium bromide (CTAB) QACs with various alkyl chain lengths in short-term and long-term cultures. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined. While alkyl chain length directly affected the antimicrobial activity of the QAC, sensitivity to QAC inhibition was observed to be species specific. We found that the standard test organism used for antimicrobial effectiveness testing, Staphylococcus aureus, was 10-100 times more sensitive to QAC inhibition than other opportunistic and commensal skin bacterial species. Repeated exposure to sublethal QAC concentrations significantly reduced bacterial susceptibility to QAC inhibition. These results suggest that prolonged exposure to sublethal doses of QACs can lead to the development of QAC tolerance that may render these QAC disinfectants and biocides ineffective at the directed use concentrations.
These results:
- Provide insights into the potential impact of widespread use of QACs on human health.
- Guide the selection and use of QAC-containing products.
- Identify potential concerns in the evaluation of QAC effectiveness.
- Establish a foundation to assess antibiotic co-resistance in QAC-tolerant bacteria.
