RT Journal Article SR Electronic(1) A1 Abdul Momin, Muhd Haziq F. A1 Bean, David C. A1 Hendriksen, Rene S. A1 Haenni, Marisa A1 Phee, Lynette M. A1 Wareham, David W.YR 2017 T1 CHROMagar COL-APSE: a selective bacterial culture medium for the isolation and differentiation of colistin-resistant Gram-negative pathogens JF Journal of Medical Microbiology, VO 66 IS 11 SP 1554 OP 1561 DO https://doi.org/10.1099/jmm.0.000602 PB Microbiology Society, SN 1473-5644, AB Purpose. A selective chromogenic culture medium for the laboratory isolation and differentiation of colistin resistant A cinetobacter, Pseudomonas, Stenotrophomonas and E nterobacteriaceae spp. (CHROMagar COL-APSE) was developed, evaluated and compared to an existing selective bacterial culture medium (SuperPolymyxin). Methodology. The medium was challenged with 84 isolates, including polymyxin B (POL B)-susceptible and -resistant type strains and colistin (COL)-resistant organisms recovered from human and animal samples. Susceptibility to COL and POL B was determined by agar dilution and broth microtitre dilution. The lower limit for the detection of COL-resistant organisms was also calculated for both CHROMagar COL-APSE and SuperPolymyxin media. The ability to isolate and correctly differentiate COL-resistant organisms within mixed cultures was also assessed and compared using both media. Results. Using CHROMagar COL-APSE, Gram-negative pathogens (n=71) with intrinsic (n=8) or acquired COL (n=63) resistance were recovered with 100 % specificity down to the lower limit of detection of 101 colony-forming units (c.f.u.). The growth on SuperPolymyxin was similar, but notably weaker for COL-resistant non-fermentative bacteria (Acinetobacter, Pseudomonas and Stenotrophomonas). CHROMagar COL-APSE was also more sensitive in supporting the growth of Enterobacteriaceae with COL resistance associated with the carriage of mcr-1. Conclusion. CHROMagar COL-APSE is a sensitive and specific medium for the growth of COL-resistant bacterial pathogens. Due to the low limit of detection (101 c.f.u.), it may be useful as a primary isolation medium in the surveillance and recovery of COL-resistant bacteria from complex human, veterinary and environmental samples, especially those with plasmid-mediated MCR-1 or novel mechanisms of polymyxin resistance., UL https://www.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.000602