Researchers Discover More Strains of Klebsiella Bacteria Cause HAIs Than Previously Thought

A big culprit behind many healthcare-associated infections (HAIs) are Klebsiella bacteria, which cause significant morbidity and mortality on a global scale. In fact, many strains of the bacteria are increasingly developing antimicrobial resistance, making these infections that much harder to treat. One of the best ways to fight back is to learn more about the nature of Klebsiella bacteria, and a team of researchers may have just uncovered a bombshell: three species of Klebsiella bacteria are able to cause HAIs. Arguably even more concerning is that all three species share drug-resistance genes.

In order for an individual to get infected with a Klebsiella-related HAI, he or she must first be exposed to the Klebsiella bacteria. If the bacteria enter the respiratory tract, they can cause pneumonia; if the bacteria get in the blood, they can cause bloodstream infections. Although much progress has been made in preventing these kinds of infections thanks to hospitals and healthcare facilities ramping up antimicrobial stewardship programs, there is still much work left to be done. Indeed, the Centers for Disease Control and Prevention reports that about 1 in 25 hospital patients will get an HAI on any given day.

“Since 2001, we’ve seen a global explosion of drug-resistant Klebsiella infections,” lead study author S. Wesley Long, associate medical director of the Diagnostic Microbiology Lab at Houston Methodist Hospital, Texas, explained in a press release. “They are drug-resistant bacteria that are increasingly difficult to treat because they are resistant to many of the available antibiotics.”

With the number of antibiotic-resistant Klebsiella infections on the rise, the research team conducted a large, comprehensive, population-based investigation to better understand the nature of the bacteria. “We need to understand the pathogen on a population level, then we can use the bacterial genomes to predict virulence or antibiotic resistance of the strain, or mortality,” Dr. Long explained.

Previous to this investigation, Klebsiella pneumoniae (K. pneumoniae) was thought to be the only Klebsiella species responsible for the most serious infections, such as pneumonia, bloodstream infections, wound or surgical site infections, and even meningitis; however, Dr. Long and his team of US researchers conducted a study through which they found that K. pneumoniae is not the only strain responsible for several serious, sometimes life-threatening HAIs; rather, two other species of Klebsiella bacteria are capable of causing deadly HAIs.

For their research, published in mBio, the researchers “sequenced the entire genome of 1777 Klebsiella clinical specimens across the greater Houston, Texas area.” They found that 28 of the samples seemed to be genetically different. Upon closer examination, they found that “depending on the collection, between 2% to 12% of the samples had been misidentified as K. pneumoniae,” when, in fact, those samples consisted of related species—Klebsiella variicola and Klebsiella quasipneumoniae—species that were thought to rarely cause infections in humans. The researchers found that these species that had been previously characterized as “commensal, nonpathogenic bacteria of the gastrointestinal tract or agricultural pests,” are able to cause invasive, severe infections in patients and that they have the same mortality rate as K. pneumoniae.

“Not only are these cousins of K. pneumoniae causing similar infections,” Dr. Long shared, “but they are also sharing these powerful drug-resistance genes.” In fact, genome sequencing found that all three of the species “were sharing drug-resistance genes amongst themselves—including at least 2 genes that code for powerful enzymes that disable a broad spectrum of penicillin-like antibiotics.”

Although these findings will most likely not have any bearing on how these infections are currently treated, Dr. Long stressed, these findings expand on what is known about Klebsiella and could help inform future therapies against the bacteria.