title: Regression analysis and categorical agreement of fluconazole disk zone diameters and minimum inhibitory concentration by broth microdilution of clinical isolates of Candida.
abstract: OBJECTIVE
  Rampant use of fluconazole in Candida infections has led to predominance of less susceptible non-albicans Candida over Candida albicans. The aim of the study was to determine if zone diameters around fluconazole disk can be used to estimate the minimum inhibitory concentration (MIC) for clinical isolates of Candida species and vice versa. Categorical agreement between the Clinical & Laboratory Standards Institute (CLSI) recommended disk diffusion and CLSI broth microdilution method was sought for.
  
  
  METHODS
  Antifungal susceptibility testing by disk diffusion and Broth microdilution was done as per CLSI document M44-S3 and CLSI document M27-S4 for Candida isolates respectively. Regression analysis correlating zone diameters to MIC value was done. Pearson's correlation coefficient was calculated to determine correlation between disk zone diameters and MICs.
  
  
  RESULTS
  Candida albicans (33.3%) was clearly outnumbered by other non-albicans species predominantly Candida tropicalis (42.5%) and Candida glabrata (18.4%). Ten percent of the strains were resistant to fluconazole by disk diffusion and 13% by broth microdilution. MIC range for Candida albicans and Candida tropicalis ranged from≤0.25-64μg/ml while that of Candida glabrata ranged from≤0.25-128μg/ml. Categorical agreement between disk diffusion and broth microdilution was 86.8%. Pearson's coefficient of correlation was -0.5975 indicating moderate negative correlation between the two variables.
  
  
  CONCLUSIONS
  Zone sizes can be used to estimate the MIC values, although with limited accuracy. There should be a constant effort to upgrade the guidelines in view of new clinical data, and laboratories should make an active effort to incorporate them.
authors.affiliation: Department of Microbiology, ESIC Dental College, Delhi, India.
authors.forename: P
authors.initials: P
authors.lastname: Aggarwal
authors.affiliation: Department of Microbiology, University College of Medical Sciences & Guru Teg Bahadur Hospital, Delhi, India. Electronic address: dr_bineetakashyap@yahoo.co.in.
authors.forename: B
authors.initials: B
authors.lastname: Kashyap
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002175:Candida / Q000187:drug effects* / Q000254:growth & development* / Q000302:isolation & purification; D002177:Candidiasis / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D003470:Culture Media / Q000737:chemistry; D004058:Diffusion; D005260:Female; D015725:Fluconazole / Q000493:pharmacokinetics* / Q000494:pharmacology; D006801:Humans; D007201:Indicator Dilution Techniques / Q000706:statistics & numerical data; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D008875:Middle Aged; D012044:Regression Analysis; D055815:Young Adult
chemical_list: D003470:Culture Media; D015725:Fluconazole
keywords: Broth microdilution; CLSI; Candida; Disk diffusion; Fluconazole; La méthode de diffusion de disque; La méthode de microdilution en bouillon