The Automated Plate Assessment System (APAS®) is a novel system for the screening of cultures on agar plates. Using image analysis technology, it is able to detect and enumerate bacterial colony growth. It also provides an analysis of the different types of colonies present. The system also includes an expert system with standard microbiological rule sets for the preparation of summary reports and the sorting of each plate into groups for further processing.
In this study, cultures from 526 urine specimens from two separate laboratories were analysed by an APAS® device. The results obtained were compared with those generated by experienced microbiologists.
Microbiologists reported that 178 urines showed growth at >=10^5 CFU/ml, 164 at 10^4 CFU/ml, 116 at 10^3 CFU/ml and 68 with no growth. APAS® showed agreement with these counts in 512/526 (97%) of the cases. Preliminary colony identification on morphological and biochemical reactions for the main isolates showed agreement with 94% of isolates from the MacConkey agar and 98% from a Chromogenic UTI agar.
This study demonstrated the ability of image analysis technology to read and interpret cultures on agar plates. APAS® was able to detect and enumerate colonies and provided a preliminary identification for the primary isolates on the different agar combinations used by the two laboratories. The expert system incorporating standard reporting rules further enhanced the usefulness of the system.
In summary, APAS® was able to screen routine urine cultures with a diagnostic sensitivity of 97% and specificity of 95%.