Multidrug Resistant Acinetobacter baumannii Biofilms: Evaluation of Phenotypic–Genotypic Association and Susceptibility to Cinnamic and Gallic Acids

Abstract

<i>Acinetobacter baumannii</i> armed with multidrug resistance (MDR) and biofilm-forming ability is increasingly recognized as an alarming pathogen. A deeper comprehension of the correlation between these two armories is required in circumventing its infections. This study examined the biofilm-forming ability of the isolates by crystal violet staining and the antibiotic susceptibility by broth microdilution method. The genetic basis of the MDR and biofilm-forming phenotypes was screened by polymerase chain reaction. The antimicrobial activities of cinnamic and gallic acids against planktonic cells and biofilms of <i>A. baumannii</i> were investigated, and the findings were confirmed with scanning electron microscopy (SEM). Among 90 <i>A. baumannii</i> isolates, 69 (76.6%) were MDR, and all were biofilm formers; they were classified into weak (12.2%), moderate (53.3%), and strong (34.5%) biofilm formers. Our results underlined a significant association between MDR and enhanced biofilm formation. Genotypically, the presence of <i>bla</i> _VIM and <i>bla</i> _OXA-23 genes along with biofilm-related genes (<i>omp</i>A, <i>bap</i>, and <i>csu</i>E) was statistically associated with the biofilm-forming abilities. Impressively, both gallic and cinnamic acids could significantly reduce the MDR <i>A. baumannii</i> biofilms with variable degrees dependent on the phenotype-genotype characteristics of the tested isolates. The current findings may possess future therapeutic impact through augmenting antimicrobial arsenal against life-threatening infections with MDR <i>A. baumannii</i> biofilms.