Tag: antifungal

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Ignore Antifungal Resistance at Your Peril, Scientists Warn

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Candida Auris

Without immediate action, humanity will potentially face further escalation in resistance in fungal disease, a renowned group of scientists from the across the world has warned. The commentary – published in ‘The Lancet’ this week – was coordinated by scientists at The University of Manchester, the Westerdijk Institute and the University of Amsterdam. According to the scientists most fungal pathogens identified by the World Health Organization – accounting for around 3.8 million deaths a year – are either already resistant or rapidly acquiring resistance to antifungal drugs.

The authors argue that the currently narrow focus on bacteria will not fully combat antimicrobial resistance (AMR). September’s United Nations meeting on antimicrobial resistance (AMR) must, they demand, include resistance developed in many fungal pathogens.

Devastating health impacts

Resistance is nowadays the rule rather than the exception for the four currently available antifungal classes, making it difficult – if not impossible – to treat many invasive fungal infections. Fungicide resistant infections include Aspergillus, Candida, Nakaseomyces glabratus, and Trichophyton indotineae, all of which can have devastating health impacts on older or immunocompromised people.

Dr Norman van Rhijn from The University of Manchester coordinated the comment with Professor Ferry Hagen from the University of Amsterdam and the Westerdijk Institute in the Netherlands.

Dr van Rhijn said: “Most people agree that resistant bacterial infections constitute a significant part of the AMR problem. However many drug resistance problems over the past decades have also been the result of invasive fungal diseases largely underrecognized by scientists, governments, clinicians and pharmaceutical companies. The threat of fungal pathogens and antifungal resistance, even though it is a growing global issue, is being left out of the debate.”

Unlike bacteria, the close similarities between fungal and human cells which, say the experts, means it is hard to find treatments that selectively inhibit fungi with minimal toxicity to patients.

Back to square one

Professor Ferry Hagen added: “Despite the huge difficulties in developing them, several promising new agents including entirely new classes of molecules, have entered clinical trials in recent years. But even before they reach the market after years of development, fungicides with similar modes of action are developed by the agrochemical industry resulting in cross-resistance. That sets us back to square one again. It is true many essential crops are affected by fungi, so antifungal protection is required for food security. But the question is, at what price?”

The scientists recommend:

  • Worldwide agreement on restricting the use of certain classes of antifungal molecules for specific applications.
  • Collaboration on solutions and regulations that ensure food security and universal health for animals, plants, and humans.
  • Adding priority to AMR to fungal infections at the UN’s meeting in September.

Source: Universiteit van Amsterdam

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Rise in Global Fungal Drug-resistant Infections

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Candida Auris

In a recent study published in Pathogens and Immunity, researchers issue a call to action over how rising antifungal resistance is worsening the problem of invasive fungal infections.

Fungal infections have become more than just Epidemiological data published in Microbial Cell indicates that a rise in severe fungal infections has resulted in over 150 million cases annually and almost 1.7 million fatalities globally.

Skin contact with microorganisms found in soil or on hard surfaces, such as common shower facilities, or exposure to infected pets, can result in fungal infections known as dermatomycoses. Rashes, itching, burning and skin irritation are among the symptoms of fungal infection.

Thomas McCormick and Mahmoud Ghannoum, professors of dermatology at the Case Western Reserve University School of Medicine and affiliated with University Hospitals Cleveland Medical Center, explained extent of the problem. “This is not just an issue that affects individual patients,” McCormick said.

“The World Health Organization has recognised it as a widespread threat that has the potential to impact entire healthcare systems if left unchecked.”

Based on their findings, the researchers issued precautions and a “call to action” for the medical community to help protect people from multidrug-resistant fungi, starting with awareness and education.

“Healthcare providers must prioritise the use of diagnostic tests when faced with an unknown fungal infection,” Ghannoum said.

“Early detection can make all the difference in improving patient outcomes.”

Patients treated with medications to protect the immune system after cancer and transplant procedures are more vulnerable to fungal infections – making them especially more vulnerable to infections from drug-resistant fungi, the researchers said.

The emergence of multidrug-resistant fungal species, such as Candida auris and Trichophyton indotineae, is especially troubling and requires urgent attention, they reported.

In a study recently published in Emerging Infectious Diseases, Ghannoum’s research team and the Centers for Disease Control and Prevention (CDC), detailed a case that demonstrated Trichophyton indotineae, in addition to becoming drug-resistant, was also sexually transmissible.

To address the growing health concern, McCormick and Ghannoum suggest several measures:

  • Increased awareness and education: Raising awareness in the general healthcare setting to obtain a more accurate understanding of the rise of antifungal-resistant infections.
  • Diagnostic Testing: Routine use of diagnostic tests can guide appropriate treatment strategies.
  • Antifungal Susceptibility Testing (AST): Improving insurance reimbursement rates for AST and increasing the number of qualified laboratories with the capacity to perform these tests.
  • Call to Action: Addressing the emerging challenge of antifungal resistance involves concerted efforts from healthcare professionals, researchers, policymakers and the pharmaceutical industry to develop and implement strategies for managing and preventing antifungal resistance.

“The ultimate goal of these measures,” Ghannoum said, “is to improve the quality of patient care by ensuring effective treatment and preventing further escalation of the problem.”

Source: Case Western Reserve University

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Plant Compound could Prove to be a Potent Tool against Candida

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Photo by CDC on Unsplash

A new study published in the journal ACS Infectious Diseases has found that a natural compound found in many plants inhibits the growth of drug-resistant Candida fungi – including its most virulent species, Candida auris, an emerging global health threat.

Led by Emory University researchers, the study used in vitro experiments that showed that the natural compound, a water-soluble tannin known as PGG, blocks 90% of the growth in four different species of Candida fungi. The researchers also discovered the mechanism by which PGG inhibits the growth: It grabs up iron molecules, essentially starving the fungi of an essential nutrient.

By starving the fungi rather than attacking it, the PGG mechanism does not promote the development of further drug resistance, unlike existing antifungal medications. In vitro testing also showed minimal toxicity of PGG to human cells.

“Drug-resistant fungal infections are a growing healthcare problem but there are few new antifungals in the drug-development pipeline,” says Cassandra Quave, senior author of the study and assistant professor at Emory University. “Our findings open a new potential approach to deal with these infections, including those caused by deadly Candida auris.”

C. auris is often multidrug-resistant and has a high mortality rate, leading the Centers for Disease Control and Prevention (CDC) to label it a serious global health threat.

“It’s a really bad bug,” says Lewis Marquez, first author of the study and a graduate student in Emory’s molecular systems and pharmacology programme. “Between 30 to 60% of the people who get infected with C. auris end up dying.”

An emerging threat

Some species of Candida, a yeast commonly found on the skin or in the digestive tract, can cause infection, which can be invasive and life-threatening. Immunocompromised people, including many hospital patients, are most at risk for invasive Candida infections, which are rapidly evolving drug resistance.

In 2007, the new Candida species, C. auris, emerged in a hospital patient in Japan. Since then, C. auris has caused health care-associated outbreaks in more than a dozen countries around the world with more than 3000 clinical cases reported in the United States alone.

A ‘natural’ approach to drug discovery

Quave is an ethnobotanist, studying how traditional people have used plants for medicine to search for promising new candidates for modern-day drugs. Her lab curates the Quave Natural Product Library, which contains 2500 botanical and fungal natural products extracted from 750 species collected at sites around the world.

“We’re not taking a random approach to identify potential new antimicrobials,” Quave says. “Focusing on plants used in traditional medicines allows us to hone in quickly on bioactive molecules.”

Previously, the Quave lab had found that the berries of the Brazilian peppertree, a plant used by traditional healers in the Amazon for centuries to treat skin infections and some other ailments, contains a flavone-rich compound that disarms drug-resistant staph bacteria. They had also found that the leaves of the Brazilian peppertree contain PGG, a compound that has shown antibacterial, anticancer and antiviral activities in previous research.

A 2020 study by the Quave lab, for instance, found that PGG inhibited growth of Carbapenem-resistant Acinetobacter baumannii, a bacterium that infects humans and is categorised as one of five urgent threats by the CDC.

The Brazilian peppertree is a member of the poison ivy family. “PGG has popped up repeatedly in our laboratory screens of plant compounds from members of this plant family,” Quave says. “It makes sense that these plants, which thrive in really wet environments, would contain molecules to fight a range of pathogens.”

Experimental results

The Quave lab decided to test whether PGG would show antifungal activity against Candida.

In vitro experiments demonstrated that PGG blocked around 90% of the growth in 12 strains from four species of Candida: C. albicans, multidrug-resistant C. auris and two other multidrug-resistant non-albicans Candida species.

PGG is a large molecule known for its iron-binding properties. The researchers tested the role of this characteristic in the antifungal activity.

“Each PGG molecule can bind up to five iron molecules,” Marquez explains. “When we added more iron to a dish, beyond the sequestering capacity of the PGG molecules, the fungi once again grew normally.”

Dish experiments also showed that PGG was well-tolerated by human kidney, liver and epithelial cells.

“Iron in human cells is generally not free iron,” Marquez says. “It is usually bound to a protein or is sequestered inside enzymes.”

A potential topical treatment

Previous animal studies on PGG have found that the molecule is metabolised quickly and removed from the body. Instead of an internal therapy, the researchers are investigating its potential efficacy as a topical antifungal.

“If a Candida infection breaks out on the skin of a patient where a catheter or other medical instrument is implanted, a topical antifungal might prevent the infection from spreading and entering into the body,” Marquez says.

The researchers will bext test PGG as a topical treatment for fungal skin infections in mice.

Meanwhile, Quave and Marquez have applied for a provisional patent for the use of PGG for the mitigation of fungal infections.

“These are still early days in the research, but another idea that we’re interested in pursuing is the potential use of PGG as a broad-spectrum microbial,” Quave says. “Many infections from acute injuries, such as battlefield wounds, tend to be polymicrobial so PGG could perhaps make a useful topical treatment in these cases.”

Source: Emory University

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An Unexpected Ally: Pathogen Enhances Antifungal Drug

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Scanning Electron Micrograph of Pseudomonas aeruginosa.
Credit: CDC/Janice Carr

While pathogens usually work against drug treatments, sometimes, they can actually strengthen them, according to a new University of Maine study published in the journal Infection and Immunity.

Polymicrobial infections, which are a combination of bacteria, viruses, fungi and parasites, are challenging to treat because it is not well understood how pathogens interact during infection and how these interactions affect the drugs treating them.

In a study published in Infection and Immunity, University of Maine researchers examined two common pathogens that often occur at similar sites, particularly in cystic fibrosis and mechanically ventilated patients: Candida albicans and Pseudomonas aeruginosa.

Candida is the fourth most common hospital-acquired pathogen, and many antifungal agents only slow it rather than kill it outright. Meanwhile, P. aeruginosa infects 90% of all adult cystic fibrosis patients. Combined, C. albicans and P. aeruginosa cause more serious disease in cystic fibrosis and ventilated patients.

The researchers investigated the effectiveness of the antifungal drug fluconazole in vitro and then during infection of the zebrafish with both pathogens. Fluconazole slows fungal growth, but Candida can become tolerant to the drug and not only survive, but also evolve tolerance that leads to therapy failure and, potentially, death.

The results showed that P. aeruginosa in fact works with fluconazole to eliminate drug tolerance and clear the C. albicans infection in the culture and the zebrafish.

“Polymicrobial infections are challenging to treat not only because of the lack of understanding of how invading microorganisms interact but also because we don’t know how these interactions affect treatment efficacy. Our work demonstrates that polymicrobial interactions can indeed affect treatment efficacy and, most importantly, it highlights the importance of nutrient availability in the environment -; such as iron in our study -; and how it modulates treatment efficacy,” explained Siham Hattab, lead author of the study.

What’s more, the bacteria also enhance the drug’s ability against a second pathogenic Candida species that tends to be more resistant to the drug.

The increased effectiveness of the drug suggests to the researchers that there is still much more to learn about how current drugs work when targeting these dangerous and complex polymicrobial infections.

Senior study author, Robert Wheeler, associate professor of microbiology said: “We are really excited to have revealed that sometimes drugs against fungal infection can work even better in a more ‘real-world’ situation than in the test tube. There is still a lot to learn about how pathogens interact during infection, and it will be interesting to see how the bacteria manage to work with the drugs to target Candida.”

Source: University of Maine

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Candida Glabrata Genome Yields Secrets of Virulence and Drug Resistance

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Genetics
Source: Pixabay

A project sequencing the Candida glabrata genome has revealed insights into the pathogenic fungus’s virulence and resistance, which researchers found to have been enhanced by transmission through humans as they travel between continents. The project’s findings appear in Genetics. 

C. glabrata is an opportunistic human fungal pathogen that causes superficial mucosal and life-threatening bloodstream infections in individuals with a compromised immune system. It most commonly affects the urinary tract, genitals, mouth, and the bloodstream. If it is not caught, these infections can become deadly.  It is also very resistant to certain antifungal drugs, so understanding why resistance occurs is key to knowing how to treat it effectively. 

Using samples from eight hospitals in Scotland to sequence the genome of C. glabrata, new insights on the species were made. This includes information on how it reproduces and its genetic diversity. Genes increasing its infectivity also confer an advantage for survival, and the drug-resistance genes often evolve within patients.

These findings provide scientists with an advantage in treating fungus, allowing research to focus in ways that were not possible before. It also helps aid understanding on how the pathogen spreads, which is important to identifying infections.

Dr Rhys Farrer, one of the Principal Investigators at the MRC Centre for Medical Mycology at the University of Exeter, said: “Our study sheds new light on the genetic diversity of Candida glabrata. We have demonstrated that this deadly human fungal pathogen is being spread between continents, probably by humans, and recombining to form new populations, which is likely contributing to its high virulence and increasing drug resistance.”

Source: University of Exeter

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The Emerging Treatment-resistant Fungus Threat

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Professor Rodney E. Rohde, a public health and clinical microbiology expert at Texas State University, warned in article for The Conversation of the growing threat of fungal resistance — a problem drawing much less attention than antibiotic resistance. 

 Athlete’s foot, thrush, ringworm and other ailments are caused by fungi, and some are serious risks to health and life. Among these is Candida auris, a pathogenic fungus. Fungi generally have not caused major disease, so there is a lack of funding in this area and there are limited antifungal agents that can treat C. auris.

Most fungal infections around the world are caused by the genus Candida, particularly the species called Candida albicans. But there are others, including Candida auris, which gets its name ‘auris’, Latin for ear, because it was first identified from an external ear canal discharge in 2009.

Candida normally lives on the skin and inside the body, such as in the mouth, throat, gut and vagina, without causing any problems. It exists as a yeast and is thought of as normal flora, harmless microbes. However when the body is immuno-compromised, these fungi become opportunistic pathogens, something happening around the world with multidrug-resistant C. auris.

The threat of Candida auris

C. auris infections, or fungaemia, have been reported in 30 or more countries. They are often found in the blood, urine, sputum, ear discharge, cerebrospinal fluid and soft tissue, and occur in people of all ages. According to the US Centers for Disease Control, the mortality rate in the US has been reported to be between 30% to 60% in many patients who had other serious illnesses. In a 2018 review of research on the global spread of the fungus, researchers estimated mortality rates of 30% to 70% in C. auris outbreaks among critically ill patients in intensive care.

Recent surgery, diabetes and broad-spectrum antibiotic and antifungal use are risk factors. Furthermore, immuno-compromised patients are at greater risk than those with healthy immune systems.

C. auris can be difficult to identify with conventional microbiological culture techniques, which leads to frequent mis-identification and under recognition. This yeast is also known for its tenacity to easily colonise the human body and environment — including medical devices. People in nursing homes and patients with catheters, on ventilation etc seem to be at highest risk.

The CDC has set C. auris infections at an “urgent” threat level because 90% are resistant to at least one antifungal, 30% to two antifungals, and there are some resistant to all three available classes of antifungals. This multidrug resistance has led to outbreaks in health care settings, especially hospitals and nursing homes, that are extremely difficult to control.

The double threat of COVID and C. auris

For hospitalised COVID patients, antimicrobial-resistant infections may be a particularly devastating risk. The mechanical ventilators often used to treat serious COVID are breeding grounds and highways for entry of environmental microbes like C. auris. Further, according to a September 2020 paper, hospitals in India treating COVID have detected C. auris on surfaces including “bed rails, IV poles, beds, air conditioner ducts, windows and hospital floors.” The researchers termed the fungus a “lurking scourge” amid the COVID pandemic. Termed ‘white fungus’, these fungal infections typically arise a week to 10 days after being in the ICU.

The same authors reported in a November 2020 CDC article that of 596 COVID-confirmed patients in a New Delhi ICU from April 2020 to July 2020, 420 patients required mechanical ventilation. Of these, 15 were infected with candidemia fungal disease and eight of those infected (53%) died. Ten of the 15 patients were infected with C. auris; six of them died (60%).

How to deal with this?

With fewer and fewer antifungal options,  CDC is recommending a focus on preventing C. auris infections. This involves better hand hygiene and improving infection prevention and control in medical care settings, judicious and thoughtful use of antimicrobial medications, and stronger regulation limiting the over-the-counter availability of antibiotics.

Source: The Conversation

Journal information: Anuradha Chowdhary et al, The lurking scourge of multidrug resistant Candida auris in times of COVID-19 pandemic, Journal of Global Antimicrobial Resistance (2020). DOI: 10.1016/j.jgar.2020.06.003

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Antifungal Compound Discovered in Ant Farms

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Researchers in Brazil have discovered an antifungal compound by bacteria living in ant farms, which may have medical applications.

In the fungal farms where attine ants tend as their food source, Pseudonocardia and Streptomyces bacteria produce metabolites which shield the crop against pathogens. Curiously, these metabolites vary across geographic locations.

Attine ants are a type of ant which grow and harvest fungus for food, and are only found in the Western Hemisphere. They first evolved from a common Amazonian ancestor some 50 million years ago, giving rise to some 200 species of ants spread across South and Central America, which share common farming practices. The bacteria at these farms have a symbiotic relationship where they defend against fungi such as Escovopsis in exchange for food.

These metabolites vary considerably, suggesting a fragmented history. Searching a number of ant nests spread across a large geographical area, the researchers discovered that two thirds of the Pseudonocardia strains were producing the same metabolite. They named this newly discovered metabolite attinimicin.The study was the first one where a common, specialised metabolite produced by ant-associated bacteria was found across geographic locations.

Attinimicin inhibited fungal parasites while not harming the fungal crop, but only in the presence of iron. It proved as effective in treating Candida albicans infections in mice as a clinically used azole-containing antifungal. This means that the metabolite could have clinical applications. Attinimicin was shown to have a similar structure to two other metabolites produced by Streptomyces, suggesting the responsible genes have a common evolutionary origin.

Source: News-Medical.Net

Journal information: Fukuda, T.T.H., et al. (2021) Specialized Metabolites Reveal Evolutionary History and Geographic Dispersion of a Multilateral Symbiosis. ACS Central Science. doi.org/10.1021/acscentsci.0c00978.