RESUMEN
In supermarkets and chemists worldwide, consumers are faced with an array of antimicrobial domestic cleaning and personal hygiene products purporting to kill germs and keep people safe. Many of these proven active ingredients (biocides) encourage the development of antimicrobial resistance (AMR) in microbes and microbial populations, in turn increasing the likelihood of AMR infections. In order to understand and address the selective pressure towards AMR posed by the unrestricted use of biocides, it is necessary to understand which biocides are most frequently found in consumer products and the current regulatory framework that governs their use. In this research we survey the biocidal active ingredients in the major categories of cleaning and personal care products available from supermarkets and pharmacies in Australia, and comment on the regulations that dictate how these products are tested and marketed. Benzalkonium chloride and ethanol were the two most prevalent antimicrobial biocides in this study, while triclosan, which is banned in several jurisdictions, was found in a small number of products. In Australia, many antimicrobial consumer products are regulated for efficacy and safety under the Therapeutic Goods Act, but the potential to drive microbial adaptation and AMR is not considered. Overall this survey underscores the broad use and light regulation of antimicrobial biocides in products available to the general public in Australia, and provides an information resource to inform further research and stewardship efforts.
RESUMEN
Biofilm formation and capsule production are known microbial strategies used by bacterial pathogens to survive adverse conditions in the hospital environment. The relative importance of these strategies individually is unexplored. This project aims to compare the contributory roles of biofilm formation and capsule production in bacterial survival on hospital surfaces. Representative strains of bacterial species often causing hospital-acquired infections were selected, including Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa. The importance of biofilm formation and capsule production on bacterial survival was evaluated by comparing capsule-positive wild-type and capsule-deficient mutant strains, and biofilm and planktonic growth modes respectively, against three adverse hospital conditions, including desiccation, benzalkonium chloride disinfection and ultraviolet (UV) radiation. Bacterial survival was quantitatively assessed using colony-forming unit (CFU) enumeration and the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay and qualitatively by scanning electron microscopy (SEM). Correlations between capsule production and biofilm formation were further investigated. Biofilm formation contributed significantly to bacterial survival on hospital surface simulators, mediating high resistance to desiccation, benzalkonium chloride disinfection and UV radiation. The role of capsule production was minor and species-specific; encapsulated A. baumannii but not K. pneumoniae cells demonstrated slightly increased resistance to desiccation, and neither showed enhanced resistance to benzalkonium chloride. Interestingly, capsule production sensitized K. pneumoniae and A. baumannii to UV radiation. The loss of capsule in K. pneumoniae and A. baumannii enhanced biofilm formation, possibly by increasing cell surface hydrophobicity. In summary, this study confirms the crucial role of biofilm formation in bacterial survival on hospital surfaces. Conversely, encapsulation plays a relatively minor role and may even negatively impact bacterial biofilm formation and hospital survival.