Hypervirulent Bacteria Strain May Be Next Superbug, Scientists Say

Thomas Russo, MD

Published March 1, 2012

UB researchers are studying a hypervirulent strain of a common bacterium with the potential to become a superbug that is difficult, if not impossible, to treat.

“If [this hypervirulent bacterium] also becomes highly resistant to antimicrobials, we will have a significant problem to manage.”
Thomas Russo, MD
professor of medicine, chief, Division of Infectious Disease

Klebsiella Pneumoniae Strain Affects Young and Healthy

Most antibiotic-resistant bacteria do not infect healthy people. The strain of Klebsiella pneumoniae that UB researchers are investigating could prove an exception.

”In the last 10 to 15 years, this new variant of the bacterium has begun causing community-acquired infection in young, healthy individuals,” says Thomas Russo, MD, professor in the Department of Medicine and head of its Division of Infectious Disease.

“It causes serious, life-threatening, invasive infections and is able to spread to other organs from the initial site of infection.

“If it also becomes highly resistant to antimicrobials, we will have a significant problem to manage.”

Identifying Genes Implicated in Antimicrobial Resistance

Under a program to fund high-risk, high-reward research, the National Institutes of Health has awarded Russo and his UB colleagues a $238,000 grant so they can try to identify the genes that make the new variant of Klebsiella pneumoniae hypervirulent.

It is important to better understand this bacterial species because it can easily acquire mobile genetic units, called plasmids, that contain multiple genes conferring high levels of antimicrobial resistance.

Discovered Strain Acquires Iron More Efficiently

The UB team has already begun to develop a clearer picture of the formidable bacterium.

In October, Russo and his colleagues published a PLoS ONE paper that showed that hypervirulent Klebsiella pneumoniae acquires iron more efficiently than the usual strains. With the NIH grant, they hope to further elucidate the bacterial factors responsible for this process.

“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.”

Variant Identified in Buffalo Man Several Years Ago

While the hypervirulent variant of Klebsiella pneumoniae was first seen exclusively in the Pacific Rim, it has since been found in several cities in North America, including Buffalo, and in Europe, Canada, Israel and South Africa.

In Buffalo, the variant was identified in an otherwise healthy young man several years ago. The patient, in his 20s, was hospitalized for several months before fully recovering.

Similar cases are causing concern throughout the international infectious disease community.

Strain Underrecognized by Physicians, Laboratories

UB researchers say that the new strain is underrecognized by physicians and microbiology laboratories.

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

It has a propensity for metastatic spread to other parts of the body, including the lungs, the central nervous system and the eye, potentially causing vision loss.

“If infection spreads to the brain, there can be brain damage as well,” Russo says. “Between 10 and 30 percent of cases are fatal.”

In the laboratory, an important characteristic of these hypervirulent strains, also known as hypermucoviscous strains, is the viscous “string” that forms: When bacterial colonies grown on a solid surface are stretched by an inoculation loop, they form a string longer than five millimeters.

Currently, Russo notes, most cases of hypervirulent Klebsiella pneumoniae resolve if treated aggressively with antibiotics and drainage of abscesses. Despite optimal treatment, some infections result in a persistent morbidity or death.