Antibiotics (Mar 2024)

The Use of CHROMID<sup>®</sup> Colistin R for the Detection of Colistin-Resistant Gram-Negative Bacteria in Positive Blood Cultures

  • Emma C. L. Marrs,
  • Olivia Milburn,
  • Gary J. Eltringham,
  • Danielle J. C. Fenwick,
  • Sylvain Orenga,
  • Gulsen Hazırolan,
  • Pinar Zarakolu,
  • John D. Perry

DOI
https://doi.org/10.3390/antibiotics13030246
Journal volume & issue
Vol. 13, no. 3
p. 246

Abstract

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The aim of this study was to assess the utility of CHROMID® Colistin R for direct detection of colistin-resistant Gram-negative bacteria from positive blood cultures. A total of 390 blood cultures from hospitalised patients containing Gram-negative bacteria were included in this study. These blood cultures were referred to clinical laboratories in the United Kingdom and Türkiye. A further 16 simulated positive blood culture bottles were included that contained a range of colistin-resistant strains as well as susceptible control strains. Fluid from each positive blood culture was diluted 1/200 in saline and 10 µL aliquots cultured onto cystine-lactose-electrolyte-deficient agar and CHROMID® Colistin R. All recovered bacteria were identified, and for Gram-negative bacteria, their minimum inhibitory concentration of colistin was measured using the broth microdilution method. From a total of 443 Gram-negative isolates, 57 colistin-resistant isolates were recovered, of which 53 (93%) grew on CHROMID® Colistin R within 18 h. Of the 377 isolates determined to be colistin-susceptible, only 9 isolates were able to grow, including 6 isolates of Pseudomonas aeruginosa. For positive blood cultures that are shown to contain Gram-negative bacteria, culture on CHROMID® Colistin R is a useful diagnostic tool to detect susceptibility or resistance to colistin within 18 h.

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