Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 9  |  Issue : 5  |  Page : 596-599  

Candidemia: Speciation and Antifungal susceptibility testing from a Tertiary Care Hospital in Maharashtra, India


Department of Microbiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, Maharashtra, India

Date of Web Publication13-Oct-2016

Correspondence Address:
Nageswari Rajesh Gandham
Department of Microbiology, Dr. D. Y. Patil Medical College, Pune - 411  018, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0975-2870.192165

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  Abstract 


Introduction: Invasive fungal infections are an important nosocomial health problem, candidal infections being the most common. Candidal bloodstream infections (BSIs) account for one-fourth of the nosocomial BSIs. Candida albicans once the most common has now been replaced by nonalbicans Candida, accounting for majority of cases of candidal infections. The knowledge and understanding of specific risk factors, epidemiology, prophylactic measures, and outcomes with relation to speciation are changing rapidly. Emergence of antifungal resistance is a cause of concern. With this background, a prospective study was undertaken. Aims and Objectives: To isolate Candida spp. from blood cultures of patients with clinically diagnosed or suspected septicemia; to identify and speciate Candida isolates and carry out the antifungal susceptibility test; to determine incidence of candidemia; to find out the crude mortality rate in candidemia patients. Materials and Methods: Blood cultures received in the Department of Microbiology from various critical care units over a 1-year period were included in this study. Samples were cultured on Sabouraud dextrose agar and routine bacteriological cultures. Speciation of suspected Candida growth was done by conventional and automated system. Results: A total of 225 out of 839 blood cultures were culture positive. A total of 196 were bacterial pathogens. Candida spp. were isolated in 29 samples. These included 10 cases of Candida tropicalis, 8 Candida parapsilosis, and three cases each of C. albicans and Candida krusei. Fluconazole resistance was seen (minimum inhibitory concentration ≥64 μg/ml) in 4 isolates, 2 of C. krusei and 2 of Candida haemulonii. Incidence of candidemia was 3.46%. Crude mortality rate in the present study was 24%.

Keywords: Bloodstream infections, candidemia, nonalbicans Candida


How to cite this article:
Gandham NR, Vyawahare CR, Jadhav SV, Misra RN. Candidemia: Speciation and Antifungal susceptibility testing from a Tertiary Care Hospital in Maharashtra, India. Med J DY Patil Univ 2016;9:596-9

How to cite this URL:
Gandham NR, Vyawahare CR, Jadhav SV, Misra RN. Candidemia: Speciation and Antifungal susceptibility testing from a Tertiary Care Hospital in Maharashtra, India. Med J DY Patil Univ [serial online] 2016 [cited 2024 Mar 28];9:596-9. Available from: https://journals.lww.com/mjdy/pages/default.aspx/text.asp?2016/9/5/596/192165




  Introduction Top


Bloodstream infections (BSIs) are always a cause of concern for clinicians and clinical microbiologists. In critical care units (CCUs), the severe patient condition and prolonged in-dwelling devices greatly increase the risk for such infections. In the etiology of these BSIs, Candida spp. are increasingly being implicated. Immunosuppression, extremes of age, changes in commensal flora, and cutaneous or gastrointestinal colonization from handlers along with zinc and iron deficiency are a few of the well-known predisposing factors for candidemias. There has been an increase in the incidence of candidemias worldwide. Candida spp. have emerged as a major opportunistic and nosocomial pathogen in BSI. They have been reported as the fourth leading cause of nosocomial BSI in the USA. Among the species of Candida, diverse species are increasingly reported in BSI.[1],[2],[3]

Candidemia often presents with nonspecific features of a septic state including fever not responding to antibiotics. In the absence of cutaneous or ocular involvement, clinical diagnosis can be difficult. Further, this candidemia can be due to a variety of species. These include Candida albicans, Candida tropicalis, Candida parapsilosis, Candida krusei, Candida glabrata, to name a few. Certain species have inherent resistance to some commonly used antifungals and some resistance is also being reported in other species in various studies A large range of antifungal drugs are available with different spectrum of activity against different species. The antifungal treatment for candidemia is often parenteral and prolonged.

With this background, a prospective study of candidemia in patients from CCUs was undertaken. The aims were to find out the occurrence of candidemia in CCUs, to culture and speciate Candida spp. from positive blood cultures, and to carry out the antifungal susceptibility test (AFST) of the isolates.


  Materials and Methods Top


This study was carried out in the Department of Microbiology of Dr. D. Y. Patil Medical College, Hospital and Research Centre, a Tertiary Care Hospital in Western part of Maharashtra, India. A total of 839 consecutive blood culture samples received from clinically suspected cases of septicemias from CCUs were included in this study. Blood cultures were carried out in BacT/Alert Plus bottles (pediatric) and BacT/Alert FA Plus bottles (adult) by the automated culture system BacT/Alert3D (Biomerieux) which support both bacterial and fungal blood isolates.

Bottles signaling positive were subcultured on blood agar, MacConkey agar for bacterial isolation, and Sabouraud dextrose agar for fungal follow-up. Subcultures were incubated at 37°C for 24 h and another 24–48 h as required. The growth obtained was identified by conventional phenotypic methods. Speciation of genus Candida was done by a combination of conventional and automated systems. The conventional tests employed included Gram-stain, germ tube test, growth on chromagar, and corn meal agar.[4],[5] The automated system used was Vitek-2 with YST-ID cards. The AFST was done using ASTYS01 and ASTYS06 cards. It included minimum inhibitory concentration (MIC) to flucytosine, fluconazole, voriconazole, amphotericin-B, and caspofungin. The isolates were considered resistant if they exhibited the following MICs: Fluconazole ≥64 µg/ml, voriconazole ≥4 µg/ml, flucytosine ≥32 µg/ml, amphotericin-B ≥1 µg/ml, and caspofungin ≥2 µg/ml as per CLSI guidelines.[6]


  Results Top


Out of the 839 consecutive blood culture samples received from CCUs, 225 were positive on culture. Identification of growth revealed that 196 of these were bacterial pathogens [Figure 1]. Among 196, Gram-positive cocci were isolated in 137 samples. These included Staphylococcus aureus, Streptococcus epidermidis, Streptococcus pyogenes, and Enterococcus. Gram-negative Bacilli were isolated in 56 samples and Gram-positive Bacilli in 3 samples.
Figure 1: Results of blood cultures

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Candida spp. were isolated in 29 samples. These included 10 cases of C. tropicalis and 8 of C. parapsilosis. C. albicans and C. krusei were isolated in three cases each. Two cases were of Candida haemulonii and one each of Candida famata, Candida lusitaniae, and Candida rugosa [Figure 2]. AFST of fluconazole showed higher MIC of ≥ 2 µg/ml in 4 isolates of C. tropicalis and 1 of C. parapsilosis, and 2 isolates of C. haemulonii and 2 of C. krusei were resistant. C. krusei is known to be inherently resistant to fluconazole [Table 1]. One isolate each of C. tropicalis, C. albicans, and C. krusei showed an MIC of 1 for amphotericin-B and were deemed resistant [Table 2]. All isolates were sensitive to flucytosine, voriconazole, and caspofungin.
Figure 2: Species distribution of candidal isolates

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Table 1:  Minimum  inhibitory  concentration  of  fluconazole (mg/ml)

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Table  2: Minimum inhibitory concentration of amphotericin-B  (mg/ml)

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  Discussion Top


BSIs refer to infections mostly occurring in hospital-based settings. The etiologies of which differ from bacteremias and septicemias from community-based settings. Intravascular catheterization, prolonged antibiotic exposures, long-term bedridden patients, and various immunocompromised conditions increase the chances of opportunistic pathogens and nosocomial agents to predominantly cause BSIs. These could be bacteremias or fungemias. Among the common nosocomial bacteremia agents are methicillin-resistant S. aureus (MRSA), Acinetobacter spp., Pseudomonas spp., to name a few. The opportunistic bacteremias include those due to S. epidermidis, Kocuria spp., and Streptococcus viridans. Among the opportunistic pathogens, the genus Candida is the most common fungal pathogen in CCUs.[2] They are commensals that normally colonize mucosal and skin surfaces. Candida infections commonly are mucocutaneous (oral thrush, vaginitis, or skin infections in moist folds). However, in hospital-based settings, they are responsible for invasive conditions such as candidiurias in catheterized patients, BSIs due to indwelling devices, and disseminated disease in severe immunocompromised conditions.[1],[3] The fungemias are increasing alarmingly. The single predominant group is the genus Candida. Candidemias are reported as the fourth common cause of BSIs in the Intensive Care Units (ICUs) and account for 10% of all BSIs.[1],[7] In another study, this statistic was 8–15%.[8] In the present study, candidemias accounted for 14.8% (29/225). Other studies have recorded varying percentages (6–9% and 15%).[1],[8] The incidence of candidemia among all blood cultures is reported between 1% and 5% in various studies. In the present study, the incidence was 3.4% (29/839) with a blood culture positivity of 23.3% (196/839) which compares well with most studies.

Previously, C. albicans accounted for 70–80% of candidal disease. However, in the last 10 years, infections due to nonalbicans species account for a majority of invasive candidal infections. Worldwide, C. tropicalis is now the most common.[9] More than 90% of invasive infections are attributed to five species: C. tropicalis, C. albicans, C. glabrata, C. parapsilosis, and C. krusei.[10] In the present study, C. tropicalis was the most common isolate, followed by C. parapsilosis and there was no isolate of C. glabrata, C. tropicalis, and C. parapsilosis, accounted for 62% of candidemias. This is comparable with various Indian studies.[2]C. albicans and C. krusei were isolated in 10% (3/29) each. Prior colonization with Candida spp. particularly of the gastrointestinal tract is a well-recognized risk factor for Candida BSIs, particularly with C. albicans and C. tropicalis.[1],[11] In contrast, invasive disease by C. parapsilosis can occur without prior colonization. It is transmitted via contaminated sources, most commonly hands (normal flora of subungual spaces) of health-care workers.[12],[13] Further, with prior empirical fluconazole therapy, C. parapsilosis and C. krusei are known to be more common causes of BSIs. Candida auris is a newly identified species. The first three reported cases of nosocomial fungemia due to C. auris were identified as C. haemulonii by the Vitek2.[14] There were two isolates identified as C. haemulonii by the automated system in the present study. Reports suggest that C. auris is identified as C. haemulonii in half of the cases. This is a species with higher virulence and increases mortality.[14],[15] The genus Candida encompasses more than 150 species. Of these, those causing human disease include C. albicans and few other species together commonly known as non-C. albicans (NAC).[16] Studies on the NAC show a marked difference in behavior between different Candida spp. This includes factors which affect the ability to cause disease and development of mechanisms of drug resistance. Therefore, to apply the findings in C. albicans to the NAC species would be a fallacy.[17]

The mortality rate in the present study was 24% (7/29). This is in the range of 10–49% reported in another study.[9],[16] However, this is much lower than a study from Northern part of India (60%).[18] The mortality in the present study was seen in four cases from neonatal ICU, two from road traffic accident in surgical ICU, and one case of acute pyelonephritis with uncontrolled diabetes mellitus.

Prophylactic antifungal therapy is used in patients at a high risk of acquiring candidal infections. Prophylaxis with fluconazole has been shown to be beneficial in low birth weight infants. Fluconazole is the antifungal most commonly used. However, C. krusei and Candida norvegensis are intrinsically resistant to fluconazole. Furthermore, different studies in India have reported fluconazole resistance between 4.9% and 37.5% among all Candida isolates.[1],[10] In the present study, all isolates of Candida were sensitive to flucytosine, voriconazole, and caspofungin. Four isolates were resistance to fluconazole (4/29), 12.6%. Of these, 2 isolates were of C. krusei and2of C. haemulonii. All of which are inherently resistant to fluconazole.[13],[15] Three isolates (1 each of C. tropicalis, C. albicans, and C. krusei) were deemed resistant to amphotericin B (3/29), 10.34%. These results are comparable with findings of Lockhart et al.[13] Other than voriconazole, statistically significant differences have been found when susceptibility of C. albicans and nonalbicansspp. to fluconazole and amphotericin B has been compared. These agents have been found to be more active against C. albicans.[19] Therefore, the need for speciation and AFST for correct antifungal therapy cannot be overemphasized.


  Conclusion Top


Among suspected BSIs in CCUs incidence of candidemia was 3.4%. In culture-positive BSIs, Candida spp. were responsible for 14.8% of the BSIs. The incidence of C. albicans was low. Non-albicans Candida accounted for a majority (89%) of Candida isolatesin fungemias. C. tropicalis was the most common isolate (34%) among the Candida isolates. Intraspecies variation in susceptibility is known. Resistance to test antifungal agents though not high was present and detected in this study. Therefore, speciation and AFST are necessary for the management of candidemias.

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Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

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    Tables

  [Table 1], [Table 2]


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