Association of carbapenem resistance levels with the presence of carbapenemase coding genes among Acinetobacter baumannii strains isolated from some hospitals

Abstract

In addition to virulence factors, antibiotic resistance
has helped strains of Acinetobacter baumannii become
one of the most common agents of hospital-acquired
infections. In A. baumannii, carbapenem resistance is
mainly mediated by carbapenemase. In this study, 144
strains of A. baumannii isolated from 9 hospitals in
representing 3 regions of Vietnam were studied to detect
the minimum inhibitory concentration (MIC) and find
an association between carbapenem resistance levels and
the appearance of some carbapenemase coding genes.
Results: more than 70.8% of the isolated were resistant
to 7/9 antibiotics tested; 83.3% strains were resistant to
3 carbapenem antibiotics with MIC50, and MIC90 values
were 32-64 µg/ml and ≥64 µg/ml, respectively; 100%
strains were susceptible to colistin (MIC50=0.25 µg/ml
and MIC
90=0.5 µg/ml). Strains with only blaOXA-51 showed
much lower rates of antibiotic resistance and MIC than
those with ≥2 carbapenemase genes (p<0.01). 100%
strains carrying blaOXA-23 and blaNDM-1 were resistant to
carbapenem with very high MIC values. Conclusion:
there is an association between carbapenem resistance
and the appearance of gene blaOXA-23 and blaNDM-1. Colistin
is the last resort for the treatment of multidrug-resistant
A. baumannii.