In 2013, I took care of a gentleman who underwent surgery for what all his doctors, including me, thought was liver cancer. Surgery revealed that the disease was a rare but benign tumor rather than cancer. As you can imagine, he and his family were very happy and relieved.
However, two weeks after this surgery, he developed a liver abscess – an encapsulated tissue infection. Surgeons operated to remove the abscess. Two days later, test results revealed that the abscess was caused by a fungus called Candida which was resistant to echinocandins, our most powerful anti-fungal medicines.
The patient underwent several surgeries and received several antibiotics, but his abscess continued to grow. He died four weeks after the first surgery to remove the abscess. The cause of death was sepsis due to its resistance to echinocandin Candida infection, which at the time was uncommon in the US. This tragic case has shown me firsthand the devastating impact of drug-resistant fungal infections.
In the following years, I cared for more than a dozen patients who died of antibiotic-resistant fungal infections. On November 13, 2019, the Centers for Disease Control and Prevention released a report on threats to antibiotic resistance in the US, warning that drug-resistant fungi have become major public health problems.
The new report revealed that 18 microorganisms cause nearly 3 million antibiotic-resistant infections and 35,000 deaths annually. For the first time, this report includes several antibiotic resistant fungi: Candida auris, another drug resistant Candida (as in my patient above) and azol resistant Aspergillus fumigatus. These resistant fungi are especially threatening because currently only three classes of antifungal medications are available.
Antibiotic resistant fungi?
In recent years we have heard a lot about the public health crisis of antibiotic resistant bacteria, but less attention has been paid to antibiotic resistant fungi. In part, this is because fungi have become common causes of disease only in the last 30 years. During this period, the risk of serious fungal infections increased as more people suffered from weakened immune systems due to increased bone marrow and organ transplantation, new drugs to treat cancer and other diseases and complex surgeries. Widespread use of more potent antibiotics to treat resistant bacterial infections has also contributed, creating less competition for fungal growth in human tissues.
Fungi include yeast, which grow as spherical cells; and mold, which grow like elongated tubular cells. Yeast and mold are more closely genetically related to humans than to bacteria. Therefore, it is difficult to develop antibiotics that attack fungi without damaging human cells.
Candida These are yeasts that usually cause rash, urinary tract infections and vaginal infections. However, they are also the third leading cause of sepsis and other fatal infections in US hospitals.
Candida auris It was discovered in 2009, but was almost never found in a medical setting until 2015, when countless infections suddenly occurred on several continents. It is now one of the CDC's five "urgent threats" for two main reasons.
First, it demonstrates high level antifungal resistance. Ninety percent of strains are resistant to fluconazole, the frontline antifungal in many countries; 30% are resistant to two antifungal classes; and between 3% and 5% for all antifungals.
Another reason why the CDC is concerned C. auris It is that it has the unique ability to spread from person to person through contact with the hands and clothing of healthcare professionals or contaminated medical devices. It also persists outside humans in healthcare settings and causes major long-term infectious outbreaks. C. auris It is a remarkably robust organism that can survive the standard methods of disinfection, high temperatures and saline solutions that kill other microbes.
Since the first case in the US in 2016, C. auris caused over 800 infections in 13 states. Currently, the CDC and local health departments are working to contain numerous health care outbreaks. It is not clear why this fungus emerged now, although climate and other environmental changes may have played a role. Similarly, it is not clear how widely C. auris will be expanded in the US or worldwide.
It's not just C. auris we need to worry
Other drug resistant fungi in the Candida The family is also considered “serious threats” by the CDC. These strains cause more than 34,000 infections annually, more than those caused by C. auris, but they are less likely to spread from person to person and cause outbreaks. However, deeply invasive C. auris and other drug resistant Candida The infections are similar in severity, resulting in the death of 40% of patients.
Another species of dangerous fungus pointed out by the CDC is Aspergillus fumigatus, which is a mold found in soil and vegetation that releases spores that most people inhale daily without any problems. However, people with weakened immune systems – especially cancer or transplant patients – may develop lung or other organ infections that kill between 50% and 75% of infected patients.
Azole antifungals are the only drugs that kill A. fumigatus without causing serious side effects. Azoles are also widely used in agriculture. Azol Resistant A. fumigatus Infections are most common in Europe, where they have been associated with agricultural and patient use. Although these infections are still uncommon in the US, the CDC has placed azole resistant substances. A. fumigatus on their “resistance watch list” because azole use is widespread in this country and populations of vulnerable patients are large.
Combating antibiotic resistant fungi requires many strategies
How does the US fight antibiotic resistant fungi? CDC and health departments are leading the way in resistance surveillance and, in the case of C. auris, containment and prevention of outbreaks. Containment involves rapid and accurate diagnosis of C. auris infections and the use of hospital clothing, gloves, equipment and cleaning materials that reduce the likelihood of fungal spread.
Several US government agencies have funded research leading to new antifungal drugs and improved diagnostic tests.
Organizations that assess the quality of medical care for the public now require health services to have antibiotic administration programs that reduce inappropriate prescribing and the development of resistance.
Efforts are also underway to control antibiotic use in agriculture and animals, as resistance cannot be countered by focusing solely on human medicine. CDC and other US agencies are working closely with international partners, because antibiotic resistant microbes do not recognize geographical boundaries. Finally, the crucial first step in solving a problem is recognizing it, which is why the CDC report on threats to antibiotic resistance is so important.[[[[Deep knowledge, daily. Sign up for the conversation newsletter. ]
Cornelius (Neil) J. Clancy, Associate Professor of Medicine and Director of Mycology, Pittsburgh University
This article has been republished from The Conversation under a Creative Commons license. Read the original article.