Akademik Veri Yönetim Sistemi
28th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), Madrid, İspanya, 21 - 24 Nisan 2018, ss.136, (Özet Bildiri)
Background: Broth microdilution is considered as the only reliable method to determine the colistin
susceptibility, however it's time consuming and laborious and thus, cannot be used widely in routine
laboratories. The recently developed "rapid polymyxin NP test" (RPNPT) provides an easy and rapid
alternative to distinguish between colistin-susceptible and -resistant strains. In this study, the
performance of RPNPT for the detection of colistin resistance in Enterobacteriaceae directly from
positive blood cultures was evaluated.
Materials/methods: RPNPT was first performed for 19 spiked blood culture sets (BacT/ALERT,
bioMérieux) each including 3 mL (103 CFU/mL) suspension of colistin-resistant Enterobacteriacae
isolates (range of colistin MIC: 8 - >128 mg/L). Following the signal, 50 μl from a positive blood culture
was withdrawn, diluted 1:10 and 50 μl of this dilution was used to perform the RPNPT as originally
described by Nordmann et al. in 2016. Secondly, for a period of three months, positive blood cultures
demonstrating the growth of Gram-negative bacilli were subjected to rapid identification by running
MALDI-TOF MS after inoculation and 3-hour incubation on chocolate agar. Cultures yielding
monobacterial growth of an Enterobacteriaceae isolate (n=59) were included in the prospective
evaluation study and the RPNPT was performed from the positive blood cultures immediately following
identification. The colistin MIC values of isolates in the prospective study were determined by broth
microdilution method.
Results: Colistin resistance in all 19 colistin-resistant strains was detected with the RPNPT in 2–4
hours. Among the clinical isolates included in the prospective study, four Klebsiella pneumoniae
strains were detected as resistant to colistin by RPNPT and the resistance was confirmed with colistin
MIC values ranging between 4–16 mg/L. The remaining samples (n=55) were detected as negative by
RPNPT and colistin MIC values were found in the susceptible range (0.125–0.5 mg/L).
Conclusions: Our results indicate that RPNPT can distinguish between colistin-resistant and
susceptible Enterobacteriaceae strains directly from positive blood cultures within 4 hours with 100%
sensitivity and specificity. The use of RPNPT together with rapid identification methods such as
MALDI-TOF MS, might produce same-day results and prevent the inappropriate use of colistin by
rapid detection of colistin-resistant strains.