JUN 10, 2018 1:39 PM PDT

Killer Antibiotic-resistant Pathogen Isolated in the US

WRITTEN BY: Carmen Leitch

For decades, people have relied on antibiotics and similar drugs to treat microbial infections, and those drugs have been very effective until recently. Their widespread and sometimes irresponsible use has made them less effective, and antibiotic-resistant microbes are seen as a rising public health threat. Of the two million people that are infected with these pathogens every year, around 23,000 patients die; that number is projected to rise to ten million by 2050. Now researchers at the Emory Antibiotic Resistance Center have investigated a new strain of highly resistant bacteria to learn more about it, and how to combat it.

A human neutrophil interacting with Klebsiella pneumoniae (pink), a multidrug-resistant bacterium that causes severe hospital infections. / Credit: NIAID

"The problem of antibiotic resistance is becoming increasingly alarming. The combination of increased virulence and multidrug resistance makes the situation worse," said Dr. David Weiss, director of the Emory Antibiotic Resistance Center, which is featured in the video below.

The researchers sequenced the entire genome of the bacterium, which is the first known strain of carbapenem-resistant hypermucoviscous Klebsiella pneumoniae, with enhanced virulence (indicating its likelihood to cause infection) and heteroresistance to colistin. Colistin is a last-resort antibiotic that is used only in dire cases. The bacterium is a member of the carbapenem-resistant Enterobacteriaceae (CRE) superbug family, which the CDC considers an urgent threat.

Heteroresistance characterizes a mixed population in which some cells are resistant to a drug and others are not. That can render an antibiotic treatment ineffective.

In 2016, a hospital in China experienced an outbreak from hypervirulent, carbapenem-resistant, K. pneumoniae. An analysis was recently reported in Lancet Infectious Diseases.

"The isolate we are studying is not nearly as virulent in a mouse model as the bacteria from China," said Dr. Weiss, "However, finding the combination of antibiotic resistance and enhanced virulence from a clinical isolate in the United States (New York) is still alarming."

The scientists suggested that doctors and clinics should be watching out for this kind of bacteria; it has the potential to be very dangerous in healthcare settings.

The research team, which included Jessie Wozniak, a Microbiology and Molecular Genetics graduate student at Emory University School of Medicine, used a simple “string test’ on 265 isolates of carbapenem-resistant K. pneumoniae bacteria.

"The string test is very low-tech. You take a loop, touch it to the bacterial colony, and pull back. The hypermucoviscous one looks like a string of cheese being pulled from a pizza,” Wozniak explained. The stretchiness comes from a compound the microbes make, capsule polysaccharide. Previous work has linked the chemical to virulence. 

The researchers also used whole-genome sequencing to find several antibiotic resistance genes the bacterium carried, which were in a new arrangement. Similar isolates of K. pneumoniae from Asia have a different set.

The team stressed that these findings could indicate that colistin may not be useful much longer as a treatment of last resort, and that heterogeneous populations of bacteria could help explain why the treatment fails in some patients. Tests that are meant to indicate how effective colistin will be may also not be reliable when confronted with these heteroresistant bacteria.

 

 

Sources: AAAS/Eurekalert! via ASM, CDCmBio

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
DEC 04, 2019
Clinical & Molecular DX
DEC 04, 2019
Genetic platform takes the guesswork out of catching infections
A physician is faced with 3 patients: an elderly person with a chronic cough, a child being wheeled out of surgery and a young mother with a high fever. Ho...
DEC 02, 2019
Microbiology
DEC 02, 2019
Understanding How a Superbug Spreads in the Home
Superbugs, which are pathogens that are resistant to the effects of antibiotics, are a rising threat to human health....
DEC 12, 2019
Microbiology
DEC 12, 2019
Gaining New Insight Into Sleeping Sickness
Sleeping sickness is a threat to public health in some parts of Sub-Saharan Africa....
DEC 23, 2019
Cell & Molecular Biology
DEC 23, 2019
An Antioxidant Found in Green Tea Can Fight Tuberculosis
In 2018, around ten million people around the globe were sickened by tuberculosis (TB) and about 1.5 million people were killed by tuberculosis....
JAN 11, 2020
Microbiology
JAN 11, 2020
Twins Still Have Microbial Strains in Common After Living Apart for Years
Twins can offer researchers an opportunity to study health and biology in people with the same genes, raised in the same environment....
JAN 27, 2020
Microbiology
JAN 27, 2020
Microbes in Household Dust May Be Spreading Antibiotic Resistance
Bacteria live in household dust, and sometimes a few of those microbes are pathogenic or carry genes that confer resistance to antibiotics....
Loading Comments...