Nasty 'superbug' causes serious, life-threatening infections in healthy people

Washington, Feb 18 (ANI): A new, under-recognized, much more potent variant of a common bacterium has begun causing community-acquired infection in young, healthy individuals in the U.S. for the past 10 to 15 years, say scientists.

University at Buffalo researchers are concerned that these hypervirulent strains of Klebsiella pneumoniae have the potential to become highly resistant to antibiotics, similar to Escherichia coli and classical Klebsiella pneumoniae.

"Historically, in Western countries, classical strains of Klebsiella pneumoniae have caused infections mostly in sick, hospitalized patients whose host defense systems are compromised," said Thomas Russo, MD, professor in the Department of Medicine at the UB School of Medicine and Biomedical Sciences and head of its Infectious Disease Division.

"But in the last 10 to 15 years, a new variant of it has begun causing community-acquired infection in young, healthy individuals. This variant causes serious, life-threatening, invasive infections and is able to spread to other organs from the initial site of infection.

"These hypervirulent strains are the next 'superbugs' A-in-waiting. If they become resistant to antibiotics, they will become difficult, if not impossible to treat," he added.

With recent funding from the National Institutes of Health under a program to fund high-risk, high-reward research, Russo and his UB colleagues are studying the microbiology of the new variant of Klebsiella pneumoniae in an effort to identify the genes that make it hypervirulent so they can figure out how to stop it in its tracks.

The researchers' concern stems from the fact that classical Klebsiella pneumoniae is one of the bacterial species that can easily acquire mobile genetic units, called plasmids, that contain multiple genes that confer high levels of antimicrobial resistance.

"That's in part why we're concerned. We know that this bacterium has the potential to acquire these plasmids and it almost certainly will," said Russo.

While the new hypervirulent variant was first seen exclusively in the Pacific Rim, it has now been found in several cities in North America, including Buffalo, and in Europe, Canada, Israel and South Africa as well. The UB researchers characterize it as "under-recognized" both by physicians and microbiology laboratories.

The disease most commonly presents as a liver abscess, which is not typical for otherwise healthy patients.

"This new variant presents with unique and scary features: first is its tendency to infect young, healthy people in the community and the second is its unique propensity for metastatic spread to other parts of the body," explained Russo.

"It spreads to sites beyond the initial source of the infection, such as the lungs, the central nervous system and the eye, potentially causing loss of vision. If infection spreads to the brain, there can be brain damage as well. Between 10 and 30 percent of cases are fatal," he added.

In Buffalo, this hypervirulent variant of Klebsiella pneumoniae was identified in an otherwise healthy, young person several years ago. The patient, who was in his 20s, was hospitalized for several months before making a full recovery. Similar cases are causing concern throughout the international infectious disease community.

At the moment, most cases of hypervirulent Klebsiella pneumoniae resolve if treated aggressively with antibiotics and drainage of abscesses; however, some infections, despite optimal treatment, result in a persistent morbidity or death, Russo said.

He notes that the potential for the bug to acquire drug resistance is adding a sense of urgency to the research.

Russo's team at UB is now beginning to develop a clearer picture of this formidable bacterial opponent.

In November, he and his colleagues published a PLoS ONE paper that showed that hypervirulent Klebsiella pneumoniae acquires iron more efficiently than the usual strains of K. pneumoniae.

"With the NIH grant, we hope to further elucidate the precise details of the bacterial factors that are responsible for hypervirulent Klebsiella pneumoniae acquiring iron so much more efficiently," he noted.

"The goal of this line of research is that these iron-acquisition factors possessed by hypervirulent Klebsiella pneumoniae will then lend themselves as therapeutic or vaccine targets so that we can better treat or prevent infection," he said. (ANI)

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