Physician

Yeast - C. albicans PNA FISH

For in vitro diagnostic use.

C. albicans PNA FISH™ (Cat. No. KT002) is a qualitative nucleic acid hybridization assay intended for identification of Candida albicans from blood cultures.

C. albicans PNA FISH provides rapid identification of C. albicans on smears made directly from Yeast-positive blood culture bottles and is compatible with all major blood culture media.  The 2.5 hours fluorescence in situ hybridization (FISH) assay uses fluorescently labeled peptide nucleic acid (PNA) probes that target the species-specific ribosomal RNA (rRNA) of C. albicans.  Results are visualized using fluorescence microscopy.  Green fluorescing cells indicates C. albicans while no fluorescence indicates another species is present in the positive blood culture.

Features and Benefits

Results Reporting - Rapid Identification of Yeast+ Blood Cultures

Once a blood culture turns positive, a Gram stain is performed.  If the Gram stain reveals Yeast, C. albicans PNA FISH is performed and within a few hours, results are available and can be reported to the attending physician.  A positive result identifies C. albicans, while a negative result indicates non-C. albicans. 

Optimizing Antifungal Therapy for Candidemia
- Ensure Appropriate Therapy for non-C. albicans species
- Reducing Unnecessary and Expensive Antifungal Use  

Candidemia is an infection of the bloodstream that is initially diagnosed when a blood culture turns positive with Candida species.  It is one of the most serious hospital-acquired infections that is on the rise due to the increasing population of immuno-compromised patients such as transplantation, oncology and AIDS patients.  The infection is associated with a high mortality rate and can be difficult to treat due in part to increasing resistance to antifungal agents in such species as Candida glabrata.  While antifungal therapy can be based on species identification, conventional laboratory identification can take up to 5 days or more.  As a result, patients are often treated empirically with broad-spectrum agents which are known to be nephrotoxic, expensive or both.(1)

According to “Guidelines for Treatment of Candidiasis” published by the Infectious Diseases Society of America, “knowledge of the infecting species, however, is highly predictive of likely (antifungal) susceptibility and can be used as a guide to therapy”. The guidelines also state that for candidemia due to C. albicans without prior azole exposure, fluconazole is appropriate as first-line therapy while for non-C. albicans species, broad-spectrum agents may be considered due to the risk of fluconazole resistance.(2,3) 

C. albicans PNA FISH provides rapid identification of C. albicans directly from Yeast-positive blood cultures.  Results are available in hours, instead of days, allowing labs to quickly report results to physicians and pharmacists, helping ensure optimal therapy for patients with candidemia.  Studies show that implementing C. albicans PNA FISH can lead to (4):

• Development of straightforward hospital specific treatment algorithms to ensure appropriate antifungal therapy for patients with candidemia
• Reduction of unnecessary use of broad-spectrum and expensive agents
• Reduction of antifungal drug costs
• Correct identification of Candida dubliniensis as a non-C. albicans species.  Conventional identification methods, such as germ tube testing, tend to mis-identify C. dubliniensis as C. albicans

Studies on Treatment Algorithms for Candidemia, based on C. albicans PNA FISH

In 2004, UMMC implemented C. albicans PNA FISH in order to report C. albicans and non-C. albicans results from Yeast-positive blood cultures.  A treatment algorithm, based on PNA FISH, was developed and implemented to ensure appropriate antifungal therapy for patients with candidemia and reduce the unnecessary use of broad-spectrum and expensive agents, such as caspofungin.  After a full year of implementation, a retrospective study was performed comparing candidemia therapy data from before C. albicans PNA FISH was implemented, to after the test was implemented.

According to the data from the study, implementation of the treatment algorithm based on C. albicans PNA FISH results led to a reduction in antifungal drug costs of $1,800 per candidemia patient, without affecting mortality.  The greatest reduction in drug costs came from a reduction in caspofungin use for patients with C. albicans.  During the study, UMMC discovered a sharp increase in the number of candidemias due to C. dubliniensis, from 0/76 (0%) cases in 2003 to 6/72 (8%) in 2004.  Further analysis revealed that conventional methods, such as germ-tube testing used in 2003, misidentified C. dubliniensis as C. albicans, whereas after the implementation of PNA FISH in 2004, C. dubliniensis was no longer misidentified as C. albicans.(4)

A paper published by physicians at Duke University Medical Center in April 2006 concludes that, “incorporating the C. albicans PNA FISH test as part of the initial identification algorithm for yeasts recovered in blood can result in substantial cost savings for hospitals.”(5) 

1. Fridkin et al.  The changing face of fungal infections in health care settings.  Clin Infect Dis. 2005 Nov 15;41(10):1455-60. Epub 2005 Oct 13. - Link
2. Pfaller et al. Trends in Antifungal Susceptibility of Candida spp. Isolated from Pediatric and Adult Patients with Bloodstream Infections: SENTRY Antimicrobial Surveillance Program  J. Clin. Microbiol. 2002 Mar.;40(3)852-63. - Link
3. Pappas et al. Guidelines for treatment of candidiasis. Clin. Inf. Dis. 2004 Jan. 15;38(2):161-89. - Link
4. Forrest et al.  Peptide nucleic acid fluorescence in situ hybridization-based identification of Candida albicans and its impact on mortality and antifungal therapy costs. J. Clin. Microbiol. 2006 44: 3381-3383. - Link
5. Alexander et al.  Cost savings with implementation of PNA FISH testing for identification of Candida albicans in blood cultures.  Diagn Microbiol Infect Dis.  April 2006;54(4):277-82. Epub 2006 Feb 8 - Link