Molecular characterization of multidrug-resistant ESBL-producing and carbapenem-resistant Klebsiella spp. clinical isolates from urine and wound infections in Togo

In the microscopic world of human infection, a group of bacteria known as Klebsiella has long been a formidable adversary. These organisms are opportunistic invaders, meaning they often lie dormant until a person's defenses are lowered, at which point they can cause severe infections in the urinary tract, wounds, and lungs. For decades, doctors have relied on antibiotics to defeat them. However, bacteria are relentless adapters. They possess a unique ability to swap genetic instructions with one another, allowing them to rapidly learn how to ignore the drugs designed to kill them. When a bacterium becomes resistant to multiple classes of antibiotics, it transforms from a treatable nuisance into a life-threatening crisis. This is the growing global crisis of antimicrobial resistance, a situation where common infections could once again become fatal because the medicines that usually cure them no longer work.

In the West African nation of Togo, scientists recently set out to map the current state of this battle. They focused on clinical samples taken from patients suffering from urinary tract infections and wound infections across sixteen different healthcare facilities. Their goal was not just to see which bacteria were present, but to understand exactly how they had learned to resist treatment. By examining the genetic makeup of these bacteria, the researchers could identify the specific molecular tools the microbes were using to survive, providing a clear picture of the resistance landscape in the country.

The study, conducted between October 2024 and June 2025, analyzed 161 distinct samples of Klebsiella bacteria. The team found that nearly all of these isolates, specifically 99.4%, were multidrug-resistant. This means they were immune to at least three different types of antibiotic classes, leaving doctors with very few options for treatment. Only a single isolate showed an even more severe level of resistance, known as extensively drug-resistant, where the bacteria survived almost every drug tested. Remarkably, none of the bacteria were completely untreatable by every known drug, a state called pan-drug resistance, which suggests that a narrow window of effective treatment still exists.

The researchers identified the specific species of bacteria responsible for the infections. The vast majority, nearly 79%, were a subspecies known as Klebsiella pneumoniae. Other types, including K. oxytoca and a less common subspecies called K. pneumoniae ozaenae, made up the rest. The infections were found mostly in urine samples, which aligns with the fact that these bacteria are a leading cause of urinary tract infections. The patients ranged from young children to the elderly, with the oldest group being the most affected, likely due to higher exposure in hospital settings and weaker immune systems.

To understand how these bacteria were resisting drugs, the scientists looked for specific resistance genes, which act like blueprints for building defense mechanisms. They found that the most common defense was a gene called blaSHV, present in over 60% of the bacteria. This gene helps the bacteria break down a major class of antibiotics called beta-lactams. Other important genes were also found, including those that produce enzymes capable of destroying even the strongest antibiotics, such as carbapenems. While the bacteria did not show high levels of resistance to carbapenems in standard lab tests, the researchers discovered that a significant number of them carried the genetic instructions to become resistant to these drugs in the future. Specifically, genes for New Delhi metallo-beta-lactamase (blaNDM) and Klebsiella pneumoniae carbapenemase (blaKPC) were found in about 14% and 8% of the samples, respectively.

Perhaps the most concerning discovery was the link between different types of resistance. The study found that bacteria carrying the blaKPC gene, which confers resistance to carbapenems, were highly likely to also carry a gene called mcr-1. This second gene provides resistance to colistin, an antibiotic often used as a last resort when all other drugs fail. This combination means that some bacteria in Togo are already equipped to resist both the strongest standard antibiotics and the final line of defense. The researchers also noted that the bacteria were highly resistant to common drugs like trimethoprim-sulfamethoxazole and ceftriaxone, making them ineffective for empirical treatment.

Despite the high levels of resistance, the study identified several antibiotics that still work well against these bacteria. Drugs like amikacin, nitrofurantoin, and fosfomycin remained effective in the vast majority of cases. Nitrofurantoin, in particular, showed excellent results against urinary infections, offering a viable treatment option for patients. The researchers also found that the bacteria's resistance to colistin was not always linked to the mcr-1 gene, suggesting that other, more complex mechanisms were at play, likely involving changes within the bacteria's own cellular structure rather than just acquired genes.

The findings highlight a critical gap between what the bacteria look like under a microscope and what they are capable of genetically. Many bacteria that appeared susceptible to carbapenems in standard tests actually carried the genes to become resistant. This "silent" reservoir of resistance genes poses a hidden danger, as these bacteria could easily pass their defenses to other strains or activate them under the pressure of antibiotic use. The study concludes that while the situation is alarming, it is not yet hopeless. By understanding exactly which genes are circulating and which drugs still work, health officials in Togo can update their treatment guidelines to avoid ineffective medications and preserve the few remaining options. The research serves as a vital baseline, urging for continued monitoring to ensure that the bacteria do not cross the final line into total untreatability.