Abstract:
ABSTRACT:
Objective: To determine the diagnostic accuracy of CHROMagarTM COL-APSE, for detection of colistin resistance in clinical
isolates of multi drug resistant (MDR) gram negative bacilli (GNB).
Study Design: Cross-sectional validation study.
Place and Duration of Study: Department of Microbiology, Armed Forces Institute of Pathology (AFIP), Rawalpindi, Pakistan
from February 2019 to August 2019.
Methodology: Total 96 MDR-GNB in clinical isolates were included. Isolates were identified using gram stain, catalase, oxidase,
API 20E and API 20NE. After taking approval from Institutional Ethical Review Committee, colistin susceptibility was determined
simultaneously by CHROMagarTM COL-APSE (using 1x105 CFU/ml inoculum) and Broth Micro Dilution (BMD) Minimum Inhibitory
Concentration (MIC) method as per CLSI. EUCAST guidelines were followed for interpretation of susceptibility profile. Results
were validated with gold standard test, i.e. BMD.
Results: Out of 96 MDR clinical isolates, the distribution was K. pneumoniae n=63, E. coli n=18, A. baumannii n=11, C. freundii
n=3, and E. cloacae n=1. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy
of CHROMagarTM COL-APSE for detection of colistin resistance, keeping BMD-MIC method as gold standard, was 97.96%,
97.87%, 97.96%, 97.87% and 97.92%, respectively.
Conclusion: CHROMagarTM COL-APSE can be used as screening agar by direct streaking of specimen as well as diagnostic for
detection of colistin resistance by the use of standardised inoculum. It can be used as a critical time saving method for colistin
resistance detection in absence of expertise or manpower required for BMD as well as the cost required for genetic sequencing
to detect MCR genes.
