Sayan Bhattacharyya

In-vitro Inhibition of Biofilm Formation in Candida albicans and Candida tropicalis by Heat Stable Compounds in Culture Filtrate of Aspergillus flavus

BACKGROUND Invasive candidiasis, caused mostly by Candida albicans and C. tropicalis is one of the most common causes of bloodstream infection with a substantial attributable mortality. This disease is associated with formation of structured, multilayered microbial communities known as biofilms over indwelling devices. Treatment is rendered difficult owing to factors like poor drug penetration through biofilms and high cost of the available antifungal drugs. Hence there is imminent need of developing low-cost natural compounds inhibiting Candidal biofilm formation in vitro. Organohalgen compounds derived from crude culture filtrate of Aspergillus flavus have been documented to impair in vitro Candidal survival. AIM We aimed to detect the effect of preheated and unheated crude culture filtrate of Aspergillus flavus on biofilm formation of Candida albicans and C. tropicalis in vitro. Setting and Designs: Ours was a laboratory-based observational study with clinical isolates of the microorganisms selected randomly. MATERIAL AND METHODS In this study, we showed for the first time by microtitre plate method that heat stable compounds which were present in preheated and unheated culture filtrates of Aspergillus flavus inhibited biofilm formation of Candida albicans and C. tropicalis and also lipase activities of these pathogens, and filtrate was non-toxic on human cell line as checked microscopically. STATISTICAL ANALYSIS USED Z-test of significance was used to calculate significant difference between Candidal biofilm formation in normal liquid medium and culture filtrate, respectively. RESULTS AND CONCLUSION Heat stable compounds present in culture filtrate of Aspergillus flavus inhibit biofilm formation of Candida albicans and C. tropicalis and also in-vitro lipase activity of these pathogens and could pave the way for development of low-cost alternatives to treat invasive candidiasis.

Comparative Analysis of Disc Diffusion and E-test with Broth Micro-dilution for Susceptibility Testing of Clinical Candida Isolates Against Amphotericin B, Fluconazole, Voriconazole and Caspofungin.

BACKGROUND Antifungal susceptibility testing remains an area of intense interest because of the increasing number of clinical isolates resistant to antifungal therapy. Clinical and Laboratory Standards Institute has proposed reference broth micro dilution (BMD) method for susceptibility testing. The reference method is time-consuming and poorly suited for the routine clinical laboratory setting. Agar-based susceptibility testing methods, disk diffusion (DD) method and the E-test method can be an easier, reliable and less time consuming alternative for the BMD method. AIM To compare the results of Amphotericin B, fluconazole, voriconazole, and Caspofungin susceptibility testing by DD, and the E-test method with the CLSI reference method for clinical Candida isolates. MATERIALS AND METHODS Broth Microdilution (BMD), E-test and Disk diffusion testing of the various clinical Candida isolates was performed in accordance with CLSI documents. The results obtained were analysed and compared. RESULTS The categorical agreement for Amphotericin B, fluconazole, voriconazole, and Caspofungin susceptibility results by E-test and DD method was 65.2%, 67.4%; 100%, 82.6%; 100%, 100%; 100%, 97.8% respectively. CONCLUSION The agar-based E-test and disk diffusion methods are reliable alternatives to the BMD method for Candida isolates when test susceptible to fluconazole, voriconazole, and Caspofungin, however the susceptibility testing results must be interpreted with caution in case of Amphotericin B.

Inhibition of biofilm formation and lipase in Candida albicans by culture filtrate of Staphylococcus epidermidis in vitro

Background: Candida spp. are fourth most common cause of bloodstream infection in developed countries and emerging agents of fungemia in developing countries, with considerable attributable mortality. Candidemia is associated with the formation of complex, structured microbial communities called biofilms. Biofilm formation makes treatment difficult due to improper drug penetration and factors like high cost and adverse effects of antifungal drugs available. Hence, low-cost alternatives are urgently required to treat device-associated invasive candidiasis. Objectives: To study the effect of culture filtrate of Staphylococcus epidermidis on biofilm formation and lipase expression of Candida albicans in vitro. Materials and Methods: Yeast cells isolated from clinical samples were suspended to a turbidity of 106 in (a) Yeast extract-peptone-dextrose (YPD) broth and (b) culture filtrate, and 100 μl of each were dispensed in separate wells of microtiter plate. After repeated washing and reloading with respective liquid media, readings were taken spectrophotometrically. To check for lipase inhibition, yeasts were incubated overnight in YPD and filtrate and subcultured on media containing Tween-80 and CaCl2. Positive lipase activity was denoted by haziness around colonies. Results: Mean reading of C. albicans in YPD broth was 0.579 while the same when yeasts were suspended in S. epidermidis culture filtrate was 0.281 (P < 0.05 by Z-test of significance). Lipase of C. albicans was inhibited by culture filtrate. Filtrate was found to be nontoxic to human cell line. Conclusions: Culture filtrate of S. epidermidis can hence pave the way for development of new strategies to inhibit biofilm formation in device-associated candidemia.

Spontaneous Bacterial Peritonitis (SBP) caused by Bacillus Cereus in an Alcoholic Patient: Case Report and Review of Literature.

Spontaneous bacterial peritonitis (SBP) is infection of peritoneal covering of the abdomen caused by bacteria, without any known etiology. Common known predisposing factors are cirrhosis of liver and old age among others. Bacillus cereus is an uncommon cause of SBP and often wrongly interpreted as a contaminant. We hereby report a case of peritonitis in chronic alcoholic, elderly male patient presenting in the outpatient department. Bacillus cereus is often regarded as contaminant but must be carefully identified and correlated clinically in case of isolation from peritoneal fluid.