Candida parapsilosis: an emerging fungal pathogen

Sir,

Candidemia is the most common invasive mycotic infection across India. It is most commonly seen in immunosuppressed or immunocompromised patients. The important risk factors include the use of immunosuppressive drugs, and/or broad-spectrum antibiotic therapy, abdominal surgery, parenteral nutrition, haemodialysis, haematological disorders, HIV infections, solid tumours, mucosal or cutaneous barrier disruption, extremes of age, prolonged ICU stay and central venous catheter use1–5. Candida albicans is of the foremost importance as opportunistic pathogen in immunocompromised hosts, which may cause life threatening infections. In the recent years, an increase in opportunistic infections caused by other Candida species, viz. C. tropicalis, C. parapsilosis, C. krusei and C. glabrata, has been increasingly reported2–5. The epidemiology of systemic Candida infections varies in different regions, and frequently from one hospital to another within the same region2. Further, C. glabrata and C. krusei have been noted to have decreased susceptibility or resistance to fluconazole6,7. In India, mortality in candidemia varies from 28 to 71.4 per cent1. Rapid and accurate species identification is necessary to optimize the choice of antifungal therapy. The aim of this study was to assess the candidemia profile in clinically diagnosed consecutive cases of fungemia at Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, by germ tube production, morphology on corn meal agar (CMA) and colour production on Hichrom candida agar8,9. Antifungal susceptibility of the isolated Candida species was tested by disc diffusion method against amphotericin B (10 U) and fluconazole (25 μg) on Mueller-Hinton Agar supplemented with 2 per cent glucose and methylene blue (5 μg/ml). Zone diameter endpoints were read at 80 per cent growth inhibition and were interpreted as per approved Clinical and Laboratory Standards Institute (CLSI - M44-A) guidelines10.

Candida species were isolated from 31 patients (50%) from the 62 blood samples received in the mycology section, Department of Microbiology, JIPMER, Puducherry, during October 2009 to March 2010. Of the 31 isolates, 19 (61.3%) were isolated from females and 12 (38.7%) from males; 80.6 per cent (n=25) were isolated from patients admitted in intensive care units (ICU); 61.3 per cent (n=19) isolates were obtained from patients with age ≤10 yr, 12.9 per cent (n=4) from ≥51 yr, 6.5 per cent (n=2) each from 21-30 and 41-50 yr, and 9.7 per cent (n=3) from 31-40 yr.

Species identified by morphology on corn meal agar (CMA) and Hichrom candida agar were the same. Most common isolate was C. parapsilosis (64.5%) followed by C. tropicalis (19.4%), C. albicans (9.7%) and C. glabrata (6.5%). Only two species of C. albicans were isolated and both were germ tube test positive. Twenty nine isolates (93.5%) were sensitive to amphotericin B and 24 (77.4%) to fluconazole by disc diffusion method.

Candida was isolated more from female subjects as compared with male subjects in our study whereas it was isolated predominantly from male subjects in similar study from Brazil2 and Kerala11. Extremes of age are important risk factor for candidemia4. Candida was isolated most frequently from children ≤10 yr and those ≥51 yr of age group in our study. Candidemia is growing problem in intensive care unit (ICU) patients, as shown in our study also. The results coroborated with the other studies from India11,12. A surveillance programme (SENTRY) of bloodstream infections (BSI) in the United States, Canada, Latin America, and Europe from 1997 through 1999 detected 50 per cent isolates from ICU admitted patients13.

Most of the laboratories use germ tube test for the rapid and cost-effective presumptive identification of C. albicans14,15. It has been reported that up to 5 per cent of C. albicans isolates are germ tube negative15. Reporting time can be further reduced by using the germ tube test directly from the positive blood culture bottle with 87.1 per cent sensitivity and 100 per cent specificity16. Germ tube method, although simple, requires a microscope and a skilled microscopist familiar with mycology methods14. Species identification is most commonly done by chromogenic agar or corn meal agar morphology method. We used both the methods and observed 100 per cent concordance between the two methods.

The epidemiology of systemic Candida infections varies in different regions2, but the change in the pattern of yeast profile has been observed globally in recent years. C. albicans isolation is decreasing and non-albicans Candida especially C. parapsilosis isolation is increasing2–5,11–13,17–22. The most common pathogen is still C. albicans in USA, Europe, Spain and Brazil2,4,13,18,19 while C. tropicalis was isolated predominantly from India3,11,17. C. parapsilosis was the most common isolate in our study similar to another study from New Delhi17. It may be because 61.3 per cent of the isolation was from children (≤10 yr) and C. parapsilosis is a predominant pathogen amongst children18,19,21,22. It is mandatory to monitor the fungal spectrum in a particular geographical area to obtain relevant epidemiological data and the Candida susceptibility profile to anti-fungal drugs to assist in the management and treatment of hospitalized patients with Candida infection.