The growing threat of antimicrobial resistance has taken a serious turn in Africa with a steady rise in resistance to colistin, one of the last resort antibiotics used when all other treatments fail, according to a new study.
The study focused on two high-priority pathogens, Acinetobacter baumannii and Pseudomonas aeruginosa, both of which are known to cause severe hospital-acquired infections and are already resistant to multiple antibiotics. These bacteria are already resistant to multiple antibiotics and are classified as critical threats by the World Health Organization. Due to limited treatment options, colistin has been increasingly reused despite its known toxicity.
Colistin, also known as polymyxin E, is a last-resort antibiotic used to treat infections caused by multidrug-resistant (MDR) bacteria, particularly A. baumannii and P. aeruginosa.
Colistin exerts its bactericidal effect by targeting and disrupting the bacterial membrane, making it particularly effective against resistant strains of A. baumannii and P. aeruginosa.
The antibiotic was initially restricted to veterinary medicine due to its potential toxicity, particularly to the kidneys and nervous system in humans, which is why it is reserved as a last-resort option.
The study, based on 35 research papers, found that colistin resistance is rising significantly in Africa. The overall resistance rate was about 13.75 per cent for A. baumannii and 14.42 per cent for P. aeruginosa, with variations across countries. For instance, resistance in A. baumannii reached as high as 18.26 per cent in Egypt, while South Africa reported lower rates at around 10.89 per cent. East Africa showed particularly high levels, exceeding 20 per cent in some cases. A similar pattern was observed for P. aeruginosa, with the highest resistance rates also recorded in East Africa.
Even more concerning is the sharp increase in resistance over time. Between 2010 and 2017, colistin resistance in A. baumannii stood at 5.64 per cent, but this figure rose dramatically to 16.45 per cent between 2018 and 2023. The trend was even more pronounced in P. aeruginosa, where resistance surged from just 2.26 per cent to over 30 per cent in the same period. These figures suggest that resistance is accelerating rapidly rather than stabilising.
However, these findings should be interpreted with caution due to the limited number of studies available per location.
Only subgroup and sensitivity analyses were performed as part of the study; more advanced approaches, such as meta-regression and narrative exploration, which could offer deeper insights into sources of heterogeneity, were not conducted.
The study underscores the urgent need for strict colistin regulation, strengthened antimicrobial stewardship programmes, the implementation of rapid diagnostic tools for resistance detection and further molecular epidemiological research.
The study was published in open access journal JAC-Antimicrobial Resistance on March 17, 2026.