April 15, 2019Quiz
Bacteria's ability to develop antibiotic resistance is well known, but it turns out fungi are also evolving to withstand modern 1) ___. Now one such fungus is cropping up in hospitals all across the globe and killing half the people who contract it within 90 days. This is raising concerns about a new global epidemic, according to an alarming story by The New York Times (04/06/19).
To understand the enormous danger of fungi, look back 20 years, when many species of amphibians were literally wiped out by a strange 2) ___. Climate scientists speculated that global rising temperatures and vast increased moist areas, could be the cause. In 1999, a new species of chytrid (fungus) was described that infected the skin of amphibians and was named Batrachochytrium dendrobatidis or Bd for short. Although the name Batrachochytrium is hard for even many scientists to pronounce, it roughly translates to mean frog chytrid. Bd is unusual because it is the only chytrid that is a parasite of a vertebrate animal 3) ___ specifically. Bd is a very important chytrid fungus because it appears to be capable of infecting most of the world's approximately 6,000 amphibian species and many of those species develop the disease chytridiomycosis which is linked to devastating population declines and species extinctions. In fact, infection with Bd has been called the worst infectious 4) ___ever recorded among vertebrates in terms of the number of species impacted, and its propensity to drive them to extinction.
Amphibian population declines due to chytridiomycosis can occur very rapidly, sometimes over a period of just a few weeks and disproportionately eliminate species that are rare, specialized and endemic. Because of these characteristics, rapid progression of population declines and loss of very important amphibian species, urgent mobilization of efforts to preserve amphibian species are required. Fungi thrives in 5) ___ areas. Consider the devastating flooding, now occurring globally, due to climate change, and the new vast areas of moisture, that result.
Mycotoxins are fungal metabolites which when ingested, inhaled, or absorbed through the skin can cause disease or death in humans and domestic animals, including birds. By general agreement this definition excludes the toxins produced by macrofungi (the mushrooms), and compounds that cause disease only in plants or lower animals such as insects. Fungi produce a large number of metabolites, but only a few are classified as mycotoxins, meaning, they have been demonstrated to cause illness. Specific mycotoxins are produced only by specific fungi, usually by only a few species Despite a few excellent studies of disease caused by fungi in feeds and foods in the first half of the twentieth century, the significance of mycotoxins in human and animal disease came only more recently. The term mycotoxicosis was first used in 1952, in a study of animal disease. However, the discovery of aflatoxins, following the deaths of 100,000 young turkeys in the UK in 1960, was the start of modern mycotoxin research. Starting after this devastating epidemic, laboratory and field experiments showed that many common 6) ___ that cause both food spoilage and plant disease are able to produce a vast array of more or less toxic metabolites. Molecular structures of mycotoxins vary widely, so their effects on human and animal health also vary widely. The most commonly induced diseases include liver cancer, kidney failure, and effects on the brain or nervous system. Toxicity due to mycotoxins is almost always insidious, without any overt indication of effects on health in the short term. For this reason, the health effects of mycotoxins are among the most neglected areas of medical science. Although mycotoxin-induced diseases have been recognized for many years, even centuries, recognition of specific mycotoxins as causes of disease is a comparatively recent development. As a result, major knowledge gaps remain to be filled through research for many of the known mycotoxins, particularly the potential human health effects of low-level chronic exposure, identification of biomarkers of exposure, and the effects of mycotoxin interactions. Mycotoxins continue to attract worldwide attention because of their impacts on human and animal health, agricultural losses, and the potential effects of climate 7) ___change.
Medical focus on Candida auris began in 2009, when doctors in Tokyo swabbed the ear of a 70-year-old woman and found an unknown strain of fungus that can infect humans and, in severe cases, cause a blood infection in high-risk patients. This discovery was Candida auris. Now, according to the US CDC, 8) ___ ___ ___ ___, a decade after it was discovered, cases have been reported in more than 30 countries around the globe -- including the United States, Australia, India, Germany, Israel, Venezuela and South Africa. At this point, the origin of this fungus is still a mystery. While the fungus seems to have cropped up relatively recently, its genetics reveal distinct groups that evolved apart, on different continents. The CDC's Mycotic Diseases Branch is considering that Candida auris could go back thousands of years. And yet, when scientists went looking for C. auris in old samples -- knowing that earlier tests may have misidentified it or not picked it up -- it was hardly anywhere to be found.
Part of the mystery is why this particular fungus suddenly come to cause a problem at a similar time in different parts of the world? Could it be due to increased moisture due to climate change? Or, could it have to do with our use of antibiotics and antifungal drugs? Changes in the health care environment? Or perhaps it's some other evolutionary change. Or a combination of all of the above? There are an estimated 5 to 6 million different species of fungi. Only a few hundred cause human disease. This Candida fungus acts like a bacteria. The emergence of C. auris highlights the danger of antimicrobial resistance: the rise of superbugs that threaten to render many of our tried-and-true drugs powerless. But there's something different about this fungus. It's a yeast that acts like a bacteria. Other species of Candida already travel with us -- on our skin, in our guts -- and they don't tend to cause infections unless there's an imbalance. This can happen, for example, when antibiotics wipe out good bacteria with the bad, leaving a place for Candida to grow. When this happens in the mouth, it's commonly referred to as thrush. In the vagina, it's a yeast infection. But most Candida is not known to be transmitted in health care settings, and C. auris is.
According to the CDC, C. auris can travel through health care facilities by lingering on surfaces and medical equipment, or it can spread directly from one 9) ___ to another. In a study published in October 2018, British researchers found 70 cases of C. auris in Oxford University Hospitals over the course of roughly 2.5 years, from February 2015 to August 2017. All but a handful had been admitted to its neurosciences ICU. Until public health authorities put out alerts about the fungus and doctors began actively looking for it, no one was aware that Candida auris was so virulent. It was several months before medical professionals could contain the problem. They used protective gear, changed how they cleaned, scaled back on bedside equipment and took other measures to stop the spread. However, as they cleaned to stop the spread, they continued to see new cases. Scientists thought they had found the culprit: a probe for monitoring patients' temperatures. Doctors stopped using the probes, but the fungus lingered. Even though the main source was found, the fungus still remained for a few more months before the medical staff could get rid of it completely. Only a handful of patients had had invasive fungal infections, no deaths were directly linked to it, and they haven't had a problem since. However, it might not be as successful in the next location or hospital, especially if dealing with more resistant types of C. auris. Samples of the fungus sent to the CDC are often resistant to one or two key antifungal drugs, and it can develop resistance to another while a patient is being treated. When it becomes resistant, it stays resistant, even though other microbes may lose their resistance when those drugs are no longer used against it. C. auris is dangerous. It has become resistant to all three classes of antifungals, making it a superbug, making it really untreatable, because there is no drug that kills it. In the United States, 587 confirmed clinical cases have been reported in 12 states as of February 28, 2019, according to the CDC. Over 1,000 additional patients have been found to be colonized with the fungus through targeted screening in seven of these states. Most of the clinical cases have been found in New York, Illinois and New Jersey -- with 309, 144 and 104 confirmed cases, respectively.
C. auris is a hard-to-treat organism in a patient population that's already very challenging to treat the sickest of the sick. In Illinois, for example, in one facility, the patients are chronically ill people who acquired the fungus in long-term care facilities, where they received a number of other medical treatments. Fortunately, most of the cases seen have still been treatable with common antifungals, but the appearance of C. auris underscores why we need to use drugs like antibiotics and antifungals responsibly. It's not about using less antibiotics. It's about using the right antibiotic for the right diagnosis and for the right duration of time. When it comes to bacteria, drug-resistant infections affect 2 million people a year in the United States, killing at least 23,000. And drug-resistant infections more broadly could claim 10 million lives per year around the globe by 2050 -- up from today's 700,000, according to one estimate. Once the persistent pathogen, C. auris turns up, getting rid of it is incredibly difficult. According to the New York Times, the CDC claims that more than 90% of C. auris infections are resistant to at least one major antifungal drug, with 30% resistant to two or more, and some medical facilities have had to go to such extreme lengths as tearing out their floor and ceiling tiles to completely remove traces of the fungus from a hospital room. All though we live in a world that has been filled with antibiotics, WHO says that the global supply is running out; not to mention that we now have superbugs like Candida 10) ___, that are resistant to the strong drugs we do have.
READ MORE: A Mysterious Infection, Spanning the Globe in a Climate of Secrecy [The New York Times]
ANSWERS: 1) medicine; 2) fungus; 3) amphibians; 4) disease; 5) moist; 6) fungi; 7) change; 8) Centers for Disease Control and Prevention; 9) person; 10) auris