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

Mahmoud M Sherif,Wafaa S Khalaf,Neveen A Abdelaziz,Walid F Elkhatib,Nooran S Elleboudy

doi:10.3389/fmicb.2021.716627

Mahmoud M Sherif, Wafaa S Khalaf + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2021.716627

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Abstract

Acinetobacter baumannii 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 A. baumannii were investigated, and the findings were confirmed with scanning electron microscopy (SEM). Among 90 A. baumannii 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 blaVIM and blaOXA–23 genes along with biofilm-related genes (ompA, bap, and csuE) was statistically associated with the biofilm-forming abilities. Impressively, both gallic and cinnamic acids could significantly reduce the MDR A. baumannii 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 A. baumannii biofilms.

Highlights

Acinetobacter baumannii is receiving considerable attention as a troublesome pathogen owing to its extensive resistance to most commonly used antimicrobials (Elkhatib et al, 2019), in addition to carbapenems, which are usually reserved to combat multidrug resistant (MDR) isolates (Xie et al, 2020)
Genetic determinants related to biofilm include the biofilmassociated protein encoded by the bap gene, the outer membrane protein A, the pilus-like bundle structure mediated by the csuE gene, and blaPER−1 belonging to the β-lactamase family (Yang et al, 2019)
Some researchers proved that A. baumannii expressed high levels of resistance to antibiotics despite producing weak biofilms (Qi et al, 2016), while others reported a positive correlation between antimicrobial resistance and biofilm-forming ability in multidrug resistance (MDR) A. baumannii isolates (Bardbari et al, 2017)

Summary

Introduction

Acinetobacter baumannii is receiving considerable attention as a troublesome pathogen owing to its extensive resistance to most commonly used antimicrobials (Elkhatib et al, 2019), in addition to carbapenems, which are usually reserved to combat multidrug resistant (MDR) isolates (Xie et al, 2020). Carbapenem-resistant A. baumannii (CRAB) is ranked first priority by the World Health Organization (WHO) as a critical pathogen that urgently needs novel antimicrobial therapeutic strategies (WHO, 2017). Biofilms offer protection to pathogens in the face of external stressors Such infections respond inconsistently to antimicrobial treatments (Vestby et al, 2020). Some researchers proved that A. baumannii expressed high levels of resistance to antibiotics despite producing weak biofilms (Qi et al, 2016), while others reported a positive correlation between antimicrobial resistance and biofilm-forming ability in MDR A. baumannii isolates (Bardbari et al, 2017)

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