Hi, in my previous post I briefly discussed the bacterial pathogens that can contribute to HAI and that are found in the inanimate environment surroundings of the patients. In addition to bacterial pathogens, fungi also pose a significant risk to the patients. For example, among the pathogens reported to the National Healthcare Safety Network (NHSN) during 2009–2010 as the causative agents of HAI, 90% were bacteria and 10% were fungi.(1)
Candida albicans contributed 5.3% of the reported HAI and other Candida spp. contributed 4.2% of the reported HAI. (1)
C. albicans has been show to be able to survive for up to 4 months on surfaces. Persistence of other yeasts on inanimate surfaces is similar (Torulopsis glabrata: 5 months) or shorter (Candida parapsilosis: 14 days).(2)
Other fungi, in particular invasive molds such as Aspergillus spp.,can also contaminate the hospital environment and cause HAI. Indeed, one of the most common fungal infections of immunocompromised hematopoietic stem cell transplant (HSTC) individuals is aspergillosis. (3) The incidence rates of invasive aspergillosis have increased dramatically during the last two decades, and, despite all diagnostic and therapeutic efforts, outcome is often fatal. Aspergillus can remain viable for more than 30 days on inanimate surfaces, (2) during which spores are released into the air where they remain airborne for prolonged periods contaminating all immediate and non-immediate patient surrounding surfaces.(4)
Of increasing concern is the rise in resistance of fungi to the frontline antifungal agents-polyenes, pyrimidine analogs, echinocandins, and triazoles. Briefly these anti fungal agents work via a variety of mechanisms including binding ergosterol and blocking sterol destabilising the membrane (polyenes), blocking DNA replication and inhibiting growth (pyrimidine blockers), blocking glucan synthase and thus inhibit cell wall biosynthesis (echinocandins), and targetting a step in the biosynthesis of ergosterol that catalyzes lanosterol 14α-demethylation (triazoles).
Approximately 7% of Candida spp bloodstream isolates tested by the CDC (especially C. glabrata) (5,6) are resistant to fluconazole, and global prevalence of azole resistance in Aspergillus is estimated to be approximately 3 to 6 percent. (7)
In addition Echinocandin resistance,appears to be on the rise according to the CDC’s surveillance data. Resistance rates of up to 8% of Candida glabrata isolates were found in 2014 may not be susceptible to echinocandins; which has doubled from 4% in 2008. (7)
Not only can anti fungal resistant Candida not be readily treated, data is available that indicates a nti fungal resistant Candida infected patients have worse outcomes. (8, 9)
Recently the CDC has reported that an emerging Candida strain-Candida auris has caused severe illness in hospitalized patients worldwide, including the USA. This strain has some characteristics that make it concerning including some strains of Candida auris are resistant to all three major classes of antifungal drugs, and that there is evidence that Candida auris can persist in the environment and additional environmental cleaning is required. (10)
In conclusion, it is clear that pathogenic microorganisms, including both gram positive, and gram negative bacteria as well as fungi can be disseminated on environmental surfaces, remain viable on these surfaces for prolonged periods of time on inanimate surfaces, and be a source or reservoir of potential nosocomial pathogens.
We would like to hear your feedback or thoughts on bacterial and fungal environmental contamination!
References quoted
10) Candida auris CDC overview
Images taken from MicrobeWiki-(this is an excellent resource and I would urge anyone interested in microbes to check it out!), and the CDC.