Modulation of Resistance and Virulence of Acinetobacter baumannii using Some Selected Natural Products

Abstract

This study aimed to evaluate the resistance pattern and biofilm activity of A.baumannii clinical isolates and to estimate the correlation between these attributes and the role of β-lactamase and biofilm-related genes. Additively, we assessed the antibacterial and antibiofilm activities of cinnamic and gallic acids and their modulatory effect with the selected conventional antibiotics and the effect of gallic acid (½ MIC) on the expression of biofilm-related genes. Initially, Identification of the collected isolates (n=90) was verified by detecting blaOXA-51-like gene (intrinsic to A. baumannii) and the antibiogram of the isolates was determined against five selected antibiotics (colistin, imipenem, doxycycline, amikacin, and levofloxacin) by using microbroth dilution method. Resistance to levofloxacin (n = 81; 90%) was the most common, followed by resistance to amikacin (n = 65; 72.2%), imipenem (n = 62; 68.9%), doxycycline (n = 60; 66.7%) and colistin (n = 11; 12.2%). Next, 30 MDR isolates were selected for amplification of β -Lactamase genes by using conventional PCR and the results proved that coexistance of Ambler class B and A β-lactamases significantly affected the MICs of imipenem. Afterwards, the biofilm activity of all collected isolates (n=90) was evaluated by using microtiter plate method, and the amplification of biofilm-related genes (bap,csuE,ompA) was performed for the selected 30 MDR clinical isolates indicating a significant correlation between all biofilm-related genes and biofilm formation in the selected MDR isolates. Moreover, there was a significant association between antibotic resistance and biofilm-forming ability with an evidence of a significant correlation between resistance to amikacin (p=0.05) /or levofloxacin (p=0.0001) and biofilm formation. Similarly, there was a significant correlation between coexistence of blaVIM and blaoxa-23 and biofilm formation (p=0.0347). On the other hand, both cinnamic and gallic acids exhibited antibacterial activity against the selected 30 MDR A.baumannii with mean MICs = (1.2, 1.65) mg/mL respectively. Impressively, both Cinnamic and gallic acids (½MIC) exhibited a biologically significant modulatory