Evaluation of the OSIRIS video reader system for disk diffusion susceptibility test reading

• Published in: Clinical microbiology and infection Vol. 7; no. 7; pp. 352 - 357
• Main Authors: Sánchez, M.A., del Saz, B. Sánchez, Loza, E., Baquero, F., Cantón, R.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Elsevier Ltd 01.07.2001; Blackwell Science Ltd; Blackwell
• Subjects: Anti-Bacterial Agents - pharmacology; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; beta-Lactam Resistance; Biological and medical sciences; Diffusion; Disk diffusion; Enterobacteriaceae - drug effects; Enterobacteriaceae - growth & development; Enterococcus - drug effects; Enterococcus - growth & development; Humans; Image Processing, Computer-Assisted; Lactams; Medical sciences; Methicillin Resistance; Microbial Sensitivity Tests - methods; Pharmacology. Drug treatments; Prospective Studies; Reference Values; Reproducibility of Results; Sensitivity and Specificity; Staphylococcus - drug effects; Staphylococcus - growth & development; Vancomycin Resistance; video reader automatic system; Disk diffusion; video reader automatic system; Performance evaluation; Reading; Drug susceptibility test; Automatic analyzer; Video technique; Reader; Method; Diffusion; Disk; Test interpretation; Result
• ISSN: 1198-743X; 1469-0691
• DOI: 10.1046/j.1198-743x.2001.00274.x

The objective of this study was to compare the performance of the OSIRIS video-assisted reading system for disk diffusion susceptibility testing with conventional manual reading. Prospectively collected clinical isolates (n = 119) and isolates with well-characterised resistant mechanisms, including extended-spectrum (ESBL) or inhibitor-resistant TEM (IRT) β-lactamases producing Enterohacteriaceae (80), methicillin-resistant Staphylococcus aureus (MRSA) (16) and vancomycin-resistant enterococci (14) were studied using the National Committee for Clinical Laboratory Standards disk-diffusion technique. The OSIRIS reading (inhibition zone in mm) was compared with manual reading (reference value). Essential agreement (≤3 mm discrepancy with manual reading) was 91.6% in routine isolates and 94.8% in those with well-characterised resistant mechanisms, respectively. Overall agreement for susceptibility testing interpretation was slightly higher in the former (95.5%) than in the latter (93.2%) group. The presence of ESBL enzymes enhanced variations of measurements due to synergy among amoxicillin—clavulanate and cephalosporins, as a consequence of closer disk placement. The poor growth characteristic of enterococci affected the video reading; on the other hand, there was a high performance with MRSA isolates. Combining all interpretative results, 4.1% minor, 1.0% major and 2.8% very major errors were observed. The OSIRIS system is a useful tool for the reading and interpretation of inhibition zone sizes in disk diffusion susceptibility testing.