Abstract
Objective: Pathogens resistant to ≥3 antimicrobial agents are referred to multi-drug resistant (MDR) pathogens. Although several antibiotics are available, antibiotics with broader spectrum of activity is required. The present study aimed to evaluate the in vitro susceptibility of minocycline against Carbapenem resistant gram-negative bacilli and its concordance sensitivity as compared to Tigecycline.
Methods: Non-repetitive, consecutive isolates carbapenem resistant gram-negative bacilli including MDR Klebsiella pneumoniae (K. pneumoniae) and Acinetobacter spp. were used for evaluation using Epsilometer test (E-test). The minimum inhibitory concentration (MIC) cut-off range for minocycline was based on Clinical and Laboratory Standards Institute (CLSI, 2016) and the interpretation (sensitive<4, intermediate=8, resistant ≥16) was considered valid for both, Enterobacteriaceae and Acinetobacter. Concordance susceptibility of minocycline was compared with that of tigecycline.
Results: Overall, 18 isolates from MDR Acinetobacter spp., 20 isolates from MDR Enterobacteriaceae (18 E. coli isolates and two Enterobacter, undefined), and 63 isolates of MDR Klebsiella spp. (58 K. pneumoniae isolates and 5 Klebsiella isolates) were evaluated. In vitro, sensitivity of minocycline was 50.0% (9/18) in Acinobacter species; 45.0% (9/20) in Enterobacter spp. and 36.5% (23/63) in Klebsiella spp., respectively. Of the 101 isolates used, concordance between tigecycline and minocycline was observed in 42 isolates (41.6%) and sensitivity to both minocycline and tigecycline was observed in 12 isolates (28.6%). The Cohen Kappa values showed that the overall concordance between tigecycline and minocycline was 0.11 (non-slight agreement).
Conclusion: Minocycline is effective against all the three carbapenem resistant gram-negative bacteria included in the study. J Microbiol Infect Dis 2018; 8(4):140-146.

Key words: Minocycline, Tigecycline, sensitivity, Carbapenem resistant gram-negative bacilli, in vitro susceptibility