The new yeast superbug, let me introduce you to Candida auris

Nov ,29 2016

As we are becoming aware of the danger coming from antibiotic-resistant bacteria and the
urgency to invest in the development of novel antibiotics and alternative antibacterial
therapies, new threat is rising – multi-drug resistant fungi causing hospital-outbreaks.

Fungi are well-known causative agents of diseases ranging from mild vaginal infections or
athlete’s foot to life-threatening invasive whole –body infections (called candidiasis). In these
cases, importantly, people are the source of their own infection. In other words, fungi live
benignly inside of humans, but sometimes, either after antibiotic treatments that deplete
commensal bacteria in the gut, or when some other illnesses or infections weaken the immune
system, they can become pathogenic.

Unfortunately, in the case of this new yeast superbug, Candida auris, we are talking about
out-of-the-patient source of infection – it seems that infection is hospital-acquired, through
surgical equipment, counters, bed rims, etc. Even more worrying is that this yeast causes
outbreaks, which is a feature of antibiotic-resistant bacteria such as Klebsiella or Clostridium,
but not fungi.



A strain of Candida auris cultured in a petri dish at CDC.
Photo Credit: Shawn Lockhart, CDC

Candida auris was first identified in Japan, in 2009. Since then, the pathogen was found in
several hundred cases in South Asia, Middle East, South America, South Africa, in the United
Kingdom and United States of America. The center for disease control and prevention (CDC)
reported on 4th of November 2016 that thirteen cases of C.auris infection were described in
the last three months, and that four of those people died. C.auris is considered now to be an
emerging pathogen as increasing numbers of cases have been identified in different countries,
from the moment it was recognized as a threat.

C.auris is causing serious wound and systemic infections in hospitalized people; it can be
transmitted in the hospital from one person to the other through hospital equipment and it is
not responding to anti-fungal drugs available on the market. As pharmaceutical industry was
never considering anti-fungal drugs to be an attractive investment, at the moment only three
classes of anti-fungal drugs are available on the market, and C.auris is showing resistance to
all of them. Until the source of C.auris is determined or some therapy proves to be helpful,
strict precautions for health-care workers and extra-thorough cleaning of hospitals are the
only means of protection.

Interesting question is how did C.auris infection spread globally. Whole genome-sequencing
of the pathogen isolated from specimens coming from different countries where disease was
detected (regions of eastern Asia, southern Asia, southern Africa, and South America),
revealed that there is a great similarity between isolates coming from the same region, but that
they are relatively different across regions. This suggests that C.auris emerged independently
in multiple regions, approximately at the same time. Another important question is why this
fungus behaves more like antibiotic-resistant bacteria, than as other fungi; it is clear there
must be a factor or factors that elicited emergence of multiple resistant strains. It is hard to
hypothesize on what could be a cause, giving limited information available on the cases and
strains. The most probable causatives are increased usage of fungicides in agriculture as well
as overuse of antibiotics; not directly, but through killing of bacteria that might keep fungi in
check.

Reference:
1. http://www.cdc.gov/fungal/diseases/candidiasis/candida-auris-qanda.html