Tag: Klebsiella pneumoniae

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Klebsiella Thrives in Nutrient-deprived Hospital Environments

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Photo by Hush Naidoo Jade Photography on Unsplash

Scientists at ADA Forsyth Institute (AFI) have identified a critical factor that may contribute to the spread of hospital-acquired infections (HAIs), shedding light on why these infections are so difficult to combat. Their study reveals that the dangerous multidrug resistant (MDR) pathogen, Klebsiella, thrives under nutrient-deprived polymicrobial community conditions found in hospital environments.

According to the World Health Organization, HAIs pose significant risks to patients, often resulting in prolonged hospital stays, severe health complications, and a 10% mortality rate. One of the well-known challenging aspects of treating HAIs is the pathogens’ MDR. In a recent study published in Microbiome, AFI scientists discovered that Klebsiella colonising a healthy person not only have natural MDR capability, but also dominate the bacterial community when starved of nutrients.

“Our research demonstrated that Klebsiella can outcompete other microorganisms in its community when deprived of nutrients,” said Batbileg Bor, PhD, associate professor at AFI and principal investigator of the study. “We analysed samples of saliva and nasal fluids to observe Klebsiella‘s response to starvation conditions. Remarkably, in such conditions, Klebsiella rapidly proliferates, dominating the entire microbial community as all other bacteria die off.”

Starvation environments

Klebsiella is one of the top three pathogens responsible for HAIs, including pneumonia and irritable bowel disease. As colonising opportunistic pathogens, they naturally inhabit the oral and nasal cavities of healthy individuals but can become pathogenic under certain conditions. “Hospital environments provide ideal conditions for Klebsiella to spread,” explained Dr Bor. “Nasal or saliva droplets on hospital surfaces, sink drains, and the mouths and throats of patients on ventilators, are all starvation environments.”

Dr Bor further elaborated, “When a patient is placed on a ventilator, they stop receiving food by mouth, causing the bacteria in their mouth to be deprived of nutrients and Klebsiella possibly outcompete other oral bacteria. The oral and nasal cavities may serve as reservoirs for multiple opportunistic pathogens this way.”

Additionally, Klebsiella can derive nutrients from dead bacteria, allowing it to survive for extended periods under starvation conditions. The researchers found that whenever Klebsiella was present in the oral or nasal samples, they persisted for over 120 days after being deprived of nutrition.

Other notable findings from the study include the observation that Klebsiella from the oral cavity, which harbours a diverse microbial community, was less prevalent and abundant than those from the nasal cavity, a less diverse environment. These findings suggest that microbial diversity and specific commensal (non-pathogenic) saliva bacteria may play a crucial role in limiting the overgrowth of Klebsiella species. 

The groundbreaking research conducted by AFI scientists offers new insights into the transmission and spread of hospital-acquired infections, paving the way for more effective prevention and treatment strategies.

Source: Forsyth Institute

Categories : Antibiotics Diseases, Syndromes and ConditionsTags : Leave a comment

Multidrug-resistant Hypervirulent K. Pneumoniae Still Vulnerable to Immune Defences

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A human neutrophil interacting with Klebsiella pneumoniae (pink), a multidrug–resistant bacterium that causes severe hospital infections. Credit: National Institute of Allergy and Infectious Diseases, National Institutes of Health

New “hypervirulent” strains of the bacterium Klebsiella pneumoniae have emerged in healthy people in community settings, prompting researchers to investigate how the human immune system defends against infection by it. After exposing the strains to components of the human immune system in vitro, they found that some strains were more likely to survive in blood and serum than others, and that neutrophils are more likely to ingest and kill some strains than others. The study, published in mBio, was led by researchers at NIH’s National Institute of Allergy and Infectious Diseases (NIAID).

“This important study is among the first to investigate interaction of these emergent Klebsiella pneumoniae strains with components of human host defence,” Acting NIAID Director Hugh Auchincloss, MD, said. “The work reflects the strength of NIAID’s Intramural Research Program. Having stable research teams with established collaborations allows investigators to draw on prior work and quickly inform peers about new, highly relevant public health topics.”

K. pneumoniae was identified over a hundred years ago as a cause of serious, often fatal, human infections, mostly in already ill or immunocompromised patients and especially if hospitalised. Over decades, some strains developed resistance to multiple antibiotics. Often called classical Klebsiella pneumoniae (cKp), this bacterium ranks as the third most common pathogen isolated from hospital bloodstream infections. Certain other Klebsiella pneumoniae strains cause severe infections in healthy people in community settings (outside of hospitals) even though they are not multidrug-resistant. They are known as hypervirulent Klebsiella pneumoniae, or hvKp. More recently, strains with both multidrug resistance and hypervirulence characteristics, so-called MDR hvKp, have emerged in both settings.

NIAID scientists have studied this general phenomenon before. In the early 2000s they observed and investigated virulent strains of methicillin-resistant Staphylococcus aureus (MRSA) bacteria that had emerged in US community settings and caused widespread infections in otherwise healthy people.

Now, the same NIAID research group at Rocky Mountain Laboratories in Hamilton, Montana, is investigating similar questions about the new Klebsiella strains, such as whether the microbes can evade human immune system defenses. Their findings were unexpected: the hvKp strains were more likely to survive in blood and serum than MDR hvKp strains. And neutrophils had ingested less than 5% of the hvKp strains, but more than 67% of the MDR hvKp strains – most of which were killed.

The researchers also developed an antibody serum specifically designed to help neutrophils ingest and kill two selected hvKp and two selected MDR hvKp strains. The antiserum worked, though not uniformly in the hvKp strains. These findings suggest that a vaccine approach for prevention/treatment of infections is feasible.

Based on the findings, the researchers suggest that the potential severity of infection caused by MDR hvKp likely falls in between the classical and hypervirulent forms. The work also suggests that the widely used classification of K. pneumoniae into cKp or hvKp should be reconsidered.

The researchers also are exploring why MDR hvKp are more susceptible to human immune defences than hvKp: Is this due to a change in surface structure caused by genetic mutation? Or perhaps because combining components of hypervirulence and antibiotic resistance reduces the bacterium’s ability to replicate and survive in a competitive environment.

As a next step, the research team will use mouse models to determine the factors involved in MDR hvKp susceptibility to immune defences. Ultimately, this knowledge could inform treatment strategies to prevent or decrease disease severity.

Source: NIH/National Institute of Allergy and Infectious Diseases