Wanda Swart (left), Robert Bragg, and Samantha Mc Carlie are investigating how disinfectant resistance is transferred between bacterial species, and whether disinfectant resistance and antibiotic resistance are linked.Credit: Robert R Bragg
Researchers puzzled by a tenacious and omnipresent bacterium in their laboratory, despite their best cleaning efforts, eventually discovered its survival strategy. The culprit, known as Serratia sp. Strain HRI, had made itself at home inside the bottles of disinfectant.
“The more we cleaned everything, the more we were just spreading the bacterium,” explains Samantha Mc Carlie, a doctoral student at the University of Free State, in South Africa, conducting research on the resistance that pathogens are building up to both antibiotics and disinfectants.Mc Carlie and researchers at UFS’s department of microbiology and biochemistry are conducting genetic studies to understand, on the molecular level, how Serratia sp. HRI and other organisms are able to develop this resistance. Studies have found that some bacteria are not just able to survive in what should be hostile environments, like a bottle of disinfectant, but are also adapting the means to metabolise and feed on certain compounds in disinfectants.
Expanding the field of understanding
Mc Carlie is looking at the under-researched role that genomic islands play in reduced susceptibility to antimicrobials and disinfectants. Genomic islands are essentially clusters of genes within a bacterial genome that it’s thought were acquired through a process known as horizontal gene transfer. This is when genetic information is passed between organisms, allowing one organism to, for example, share the genomic tools to develop antibiotic resistance with another.
Mc Carlie is exploring the expression of some 90 genes possibly linked to increased resistance. In particular, she wants to know how active or non-active they are. “Just because the gene is present doesn’t mean it’s actually playing a role,” she explains. “And it may even be that none of these genes are involved.”
The work has value in combatting the rise of ‘superbugs’, strains of bacteria resistant to several types of antibiotics. Nosocomial infections – or hospital-acquired infections (HAI) – are becoming more common and dangerous.
Consequences of inaction
The 2022 global report by the World Health Organization (WHO) suggests that the risks of HAIs in Africa are double that in developed nations, especially in intensive care units and neonatal/paediatric wards.
In September 2022, for instance, the latest in a series of outbreaks of Klebsiella pneumoniae, a multi-drug-resistant bacterium, killed at least six of 13 newborns infected at one Nairobi hospital.
The risk for such outbreaks was elevated during COVID-19 when a slew of often unregistered disinfectants and sanitisers were brought onto the market. Usually, improper use, such as the incorrect concentrations, that renders these products ineffective, says Mc Carlie’s supervisor, Robert Bragg.
“If you’re not using the products correctly, or if it’s not a good product, you’re not killing the organisms,” Bragg says. “Instead, you’re allowing them to develop resistance.”
