Biofilm-forming capacity of blood-borne Candida albicans strains and effects of antifungal agents / Capacidad de formación de biopelículas de las cepas de Candida albicans de transmisión sanguínea y efectos de los agentes antifúngicos

Infections related to Candida albicans biofilms and subsequent antifungal resistance have become more common with the increased use of indwelling medical devices. Regimens for preventing fungal biofilm formation are needed, particularly in high-risk patients. In this study, we investigated the biofilm formation rate of multiple strains of Candida albicans (n = 162 clinical isolates), their antifungal susceptibility patterns, and the efficacy of certain antifungals for preventing biofilm formation. Biofilm formation was graded using a modified Christensen's 96-well plate method. We further analyzed 30 randomly chosen intense biofilm-forming iso lates using the XTT method. Minimum biofilm inhibition concentrations (MBIC) of caspofungin, micafungin, anidulafungin, fluconazole, voriconazole, posaconazole, itraconazole, and amphotericin B were determined using the modified Calgary biofilm method. In addition, the inhibitory effects of antifungal agents on biofilm formation were investigated. Our study showed weak, moderate, and extensive biofilm formation in 29% (n = 47), 38% (n = 61), and 23% (n = 37) of the isolates, respectively. We found that echinocandins had the lowest MBIC values and that itraconazole inhibited biofilm formation in more isolates (26/32; 81.3%) than other tested agents. In conclusion, echinocandins were most effective against formed biofilms, while itraconazole was most effective for preventing biofilm formation. Standardized methods are needed for biofilm antifungal sensitivity tests when determining the treatment and prophylaxis of C. albicans infections.

Las infecciones relacionadas con las biopelículas de Candida albicans y la consiguiente resistencia antifúngica se han vuelto fenómenos habituales con el uso creciente de dispositivos médicos permanentes. Son necesarios regímenes para prevenir la formación de biopelículas fúngicas, en especial en los pacientes de alto riesgo. En este estudio se investigó la tasa de formación de biopelículas de numerosas cepas de Candida albicans (162 aislados clínicos), sus patrones de sensibilidad a los antifúngicos y la eficacia de algunos de estos agentes para prevenir la formación de biopelículas. La formación de biopelículas se clasificó utilizando el método de Christensen modificado de 96 pocillos. Posteriormente se analizaron 30 aislados de formación intensa de biopelículas elegidos al azar, utilizando el método XTT. Se calcularon las concentraciones mínimas de inhibición de biopelículas (minimum biofilm inhibition concentrations, MBIC) de la caspofungina, la micafungina, la anidulafungina, el fluconazol, el voriconazol, el posaconazol, el itraconazol y la anfotericina B, utilizando el método modificado de biopelículas de Calgary. Además, se investigaron los efectos inhibitorios de los agentes antifúngicos sobre la formación de biopelículas. Nuestro estudio encontró una formación débil, moderada e intensa de biopelículas en el 29% (n = 47), 38% (n = 61) y 23% (n = 37) de los aislados, respectivamente. Encontramos que las equinocandinas mostraron los menores valores MBIC, y que el itraconazol inhibió la formación de biopelículas en más aislados (26/32; 81,3%) que otros agentes ensayados. En conclusión, las equinocandinas resultaron más eficaces frente a las biopelículas formadas, mientras que el itraconazol resultó más eficaz para prevenir la formación de biopelículas. Se necesita contar con métodos estandarizados para efectuar las pruebas de sensibilidad a los antifúngicos en términos de formación de biopelículas a la hora de determinar el tratamiento y la profilaxis de las infecciones por C. albicans.

Nosocomial Candiduria in Critically Ill Patients Admitted to Intensive Care Units in Menoufia University Hospitals, Egypt.

Aims: Detect the incidence of urinary tract infection caused by candida species and to determine their antifungal susceptibility, biofilm formation and its minimal biofilm inhibitory concentration. In addition, detect the importance of multiplex nested polymerase chain reaction (PCR) in detection of candidemia in serum of patients with candidurea. Methodology: Study was carried out by collecting urine samples from 200 patients admitted in the intensive care unit inMenoufia university hospitals and suspected to have hospital acquired urinary tract infection. Isolation, identification and antifungal susceptibility testing were done. Biofilm formation and Minimum biofilm inhibitory concentration testing were detected. Patients with positive candiduria were tested for the presence of candida in serum by multiplex nested PCR. Results: Candida spp. were isolated from urine of 38(19%) patients, 78.9% of them were catheterized, C. albicans was isolated from 18(47.3%) samples as detected by Analytical profile index (API system). Antifungal susceptibility show that Flucytosmine, Amphotericin B, Voriconazole were more effective antifungal agents against Candida spp (100%, 84.2% and 84.2% respectively). A total of 26 (%68.4) out of 38 Candida species isolates produced biofilm. 72.2% of the tested C. albicans, were resistant to fluconazole and had MBIC > 640 μg/mL while only 27.8% were sensitive to fluconazole and had MBIC < 10 μg/mL. 26.3% out of 38 patients with candiduria had candidaemia as detected by multiplex nested CR. Conclusion: Candida albicans is the most common Candida spp that show biofilm production. There is increased in the percentage of the resistance to fluconazole in candida isolates in this study. The incidence of candidemia among patients with candidurea was high in our study.

Time dependent enhanced resistance against antibiotics & metal salts by planktonic & biofilm form of Acinetobacter haemolyticus MMC 8 clinical isolate.

Background & objectives: Available literature shows paucity of reports describing antibiotic and metal resistance profile of biofilm forming clinical isolates of Acinetobacter haemolyticus. The present study was undertaken to evaluate the antibiotic and metal resistance profile of Indian clinical isolate of A. haemolyticus MMC 8 isolated from human pus sample in planktonic and biofilm form. Methods: Antibiotic susceptibility and minimum inhibitory concentration were determined employing broth and agar dilution techniques. Biofilm formation was evaluated quantitatively by microtiter plate method and variation in complex architecture was determined by scanning electron microscopy. Minimum biofilm inhibiting concentration was checked by Calgary biofilm device. Results: Planktonic A. haemolyticus MMC 8 was sensitive to 14 antibiotics, AgNO3 and HgC12 resistant to streptomycin and intermediately resistant to netilmycin and kanamycin. MMC 8 exhibited temporal variation in amount and structure of biofilm. There was 32 – 4000 and 4 – 256 fold increase in antibiotic and metal salt concentration, respectively to inhibit biofilm over a period of 72 h as against susceptible planktonic counterparts. Total viable count in the range of 105 -106cfu / ml was observed on plating minimum biofilm inhibiting concentration on Muller-Hinton Agar plate without antimicrobial agents. Biofilm forming cells were several folds more resistant to antibiotics and metal salts in comparison to planktonic cells. Presence of unaffected residual cell population indicated presence of persister cells. Interpretation & conclusions: The results indicate that biofilm formation causes enhanced resistance against antibiotics and metal salts in otherwise susceptible planktonic A. haemolyticus MMC 8.