Abstract

A comparative evaluation of Neo-Sensiitabs^TM (Rosco, Taastrup, Denmark) and BBL paper discs (Becton Dickinson, Cockeysville, MD) according to the CLSI Performance Standards for Antimicrobial Susceptibility Testing was done. A total of 303 clinical isolates were included: 60 Enterobacteriaceae (including ESBLs isolates), 63 Pseudomonas aeruginosa, 63 Staphylococcus aureus, 33 Streptococcus pneumoniae, 51 Enterococcus faecalis and 33 Beta haemolytic streptococci. Strains were tested using the disc diffusion method, including both discs and tablets. minimal inhibitory concentrations (MICs) were determined by E test (AB Biodisk, Sölna, Sweden). The results were analyzed by linear regression and Pearson's correlation coefficient. The Pearson correlation coefficient of the inhibition zone diameter, related to the discs and tablets, had a high value (0.824 to 0.998). Based on the CLSI categorization of antimicrobial susceptibility (S-I-R), agreement was found within the range of 78.79 to 100%. Overall percentage of 3.31% of minor error and 0.38% of major error was observed. All of the 12 major errors occurred when there was no intermediate category. The major errors were found within isolates with SR discrepancies, and minor errors (1,64/1,67% for Neosensitabs and BBL, respectively) within isolates with IS-IR discrepancies. Antibiotic tablet sensitivity for ESBL detection was 97.14% compared to paper discs. Neo-Sensitabs™ tablets showed a high inter-correlation with BBL paper discs which indicated the possibility of using tablets as an alternative to paper discs.

Key words: Disc diffusion, paper discs, Neo-Sensitabs™ tablets.