News-Medical.Net interviewed Professor Robert Bragg of the University of the Free State on the topic of pathogens, particularly bacteria, developing resistance to common disinfectants.
Professor Robert Bragg said that the control of diseases rests on three pillars: 1) vaccinations and vaccines, 2) treatment options (such as antibiotics for bacterial diseases), and 3) biosecurity.
Proff Brage explained that 10 to 15 years ago, there was an assumption that bacteria would not evolve resistance against disinfectants, but the COVID pandemic prompted a rethink. Now, disinfectant resistance is being looked at in the same light as antibiotic resistance. Biosecurity, he said, is ensuring that individuals do not come into contact with the pathogens in the first place. This is easily seen in the COVID pandemic, where face masks are worn (with a protection against contracting the disease of up to 70%), social distancing is enforced and hands and surfaces are sanitised. Though Prof Bragg’s main area of research is not antibiotic resistance, he notes that, “There are resistance mechanisms that are shared between antibiotics and disinfectants and we are looking at how these mechanisms increase resistance to disinfectants.”
The protection of antibiotics is something taken for granted, but although mostly easily treatable (for now), bacteria can spread much faster than viruses, which require cells to reproduce in and whose re[plication rate is measured in days. “A common well-known bacterium such as Escherichia coli has a doubling time of around 20 min under ideal conditions. In other words, it only takes just 20 minutes for a population of E. coli to go from 1 million to 2 million and another 20 mins to reach 4 million, and so on,” Prof Bragg said. In the post-antibiotic era, there would be some treatment options such as bacteriophages, but for livestock the best protection would be biosecurity. However, disinfectant resistance would reduce the effectiveness of that option.
His research team has conducted a number of studies into the mechanisms of bacterial disinfectant resistance. “My research team has been working on various aspects of efficacy and resistance to disinfectants for quite some time and we have various projects that are currently underway,” he said. “Recently we identified a highly resistant strain of a Serratia species of bacteria. This strain was substantially more resistant to many different disinfectants than the reference strain. This great difference in the levels of susceptibility has allowed us to investigate various possible research mechanisms and also to look for possible novel resistance mechanisms.”
One of his team’s discoveries was that this highly resistant bacteria strain could grow on disinfectant if it was the sole source of carbon. Other areas of research around the resistant strain include sequencing and analysis of its genome, the role of bacterial efflux pumps removing disinfectant, and the role of plasmids (vehicles of genetic transfer between bacteria) in resistance and whether they are transferrable.
With regard to viruses, there are two kinds of viruses, enveloped and naked, and disinfectant has different effects on them. Enveloped viruses such as SARS-CoV-2, have a lipid layer picked up from their host cell, and are easy to kill with simple disinfectants because they break up the lipid layer, killing the cell. Naked cells are much harder to kill, and the few disinfectants that work against them are thought to do so by somehow disrupting the virus’ receptors.
One sanitiser of concern is alcohol, where 70% is considered optimal. However, people believe that ‘more is better’, yet increasing the alcohol percentage actually makes it evaporate faster, reducing contact time and thus leaving more of the virus behind. Similarly, some sanitisers include low levels of other disinfectant substances which are below the minimum threshold to kill the pathogens. This can leave surviving bacteria to develop resistance against these other sanitisers.
Prof Bragg advised that the public should purchase and use sanitisers prudently, following their instructions for use appropriately, and preferably checking to see if they are registered. He also cautioned
Source: News-Medical.Net
