Effectiveness of SDST disinfectant against repetitive loadings of bacteria

Abstract

Ever since the latest global health threat, a novel virus named Severe Acute Respiratory Syndrome-Coronavirus-2, emerged from China in late 2019 and hit Singapore's shores, multiple measures have been in place to protect the public. These measures range from a mandatory 1 metre safe distancing to an increase in the public area's hygiene. One such high-risk public area is the thousands of lifts in the public housing estate in Singapore. Enclosed with poor ventilation and covered in non-porous stainless steel surfaces, air and surface transmission risk necessitates the need for a proper disinfection process to safeguard public health. Here in Singapore, SDST disinfectant, a benzalkonium chloride disinfectant treated with silane chemistry, has been the chosen disinfectant for its “self-disinfecting” property. The decrease in cleaning frequency when using the disinfectant and benzalkonium chloride's proven effectiveness against the virus has made SDST disinfectant extremely popular. However, benzalkonium chloride is known to be susceptible to biofilm formation, which reduces its efficacy. Researches for the increased effectiveness and “self-disinfecting” nature of the SDST disinfectant via the addition of silane chemistry to benzalkonium chloride is also severely lacking. In this study, the SDST disinfectant's efficacy against biofilm formed during repeated bacteria loading is investigated. Due to safety reasons and lack of access to the COVID-19 virus, E. coli bacteria has been chosen as the bacterium model to create the biofilm. The SDST disinfectant was applied on a stainless steel plate and tested in five different conditions: a control where no disinfectant was used, disinfectant applied but no wiping and wiping every 1, 2 and 5 days. After exposure to the disinfectant, a plate count of the E. coli was recorded each day to calculate the reduction percentage. The overall result shows a minimal increase of 60% in the efficiency of bacteria reduction when SDST disinfectant is applied. Wiping every 2 days to remove biofilm is recommended for cost reduction without compromising efficiency.