<em>Acinetobacter baumannii</em> biofilms: effects of physicochemical factors, virulence, antibiotic resistance determinants, gene regulation, and future antimicrobial treatments

Abstract

Acinetobacter baumannii is a leading cause of nosocomial infections due to its increased antibiotic resistance and virulence. The ability of A. baumannii to form biofilms contributes to its survival in adverse environmental conditions including hospital environments and medical devices. A. baumannii has undoubtedly propelled the interest of biomedical researchers due to its broad range of associated infections especially in hospital intensive care units. The interplay among microbial physicochemistry, alterations in the phenotype and genotypic determinants, and the impact of existing ecological niche and the chemistry of antimicrobial agents has led to enhanced biofilm formation resulting in limited access of drugs to their specific targets. Understanding the triggers to biofilm formation is a step towards limiting and containing biofilm-associated infections and development of biofilm-specific countermeasures. The present review therefore focused on explaining the impact of environmental factors, antimicrobial resistance, gene alteration and regulation, and the prevailing microbial ecology in A. baumannii biofilm formation and gives insights into prospective anti-infective treatments.

Parallel evolution of tobramycin resistance across species and environments

“…These species are members of the Moraxellaceae and Pseudomonadeae families and the strains used differ in their genome sizes by 2.7Mb, or more than 40%. Infections with these two opportunistic pathogens are often associated with a biofilm mode of growth (Eze et al, 2018; Mulcahy et al, 2014), where the bacteria grow in aggregates on surfaces and are protected from antimicrobials by a number of mechanisms. This biofilm protection may occur from secreted substances like polysaccharides, proteins, or eDNA that limit diffusion or by slowing growth and rendering the bacteria less susceptible to an antibiotic (Hall and Mah, 2017; Høiby et al, 2010).…”

Biocide susceptibilities and biofilm-forming capacities of Acinetobacter baumannii clinical isolates from Malaysia

“…The ability to form biofilms is one of the important virulence factors that enable A. baumannii to survive in the harsh hospital environment by affording the bacteria greater protection against antimicrobials and survival in dry and desiccated conditions [16]. A. baumannii is known to form biofilm communities on most abiotic surfaces and thus contributes to medical-deviceassociated infections [17].…”

“…A. baumannii is known to form biofilm communities on most abiotic surfaces and thus contributes to medical-deviceassociated infections [17]. Biofilm formation is a complex process involving a repertoire of genes and although several factors that contribute to biofilm formation appear to be strain-dependent, some common factors have been identified [16][17][18]. A. baumannii produce biofilm-associated proteins (Bap), which are large surface-exposed proteins secreted through a type I secretion system (T1SS), and plays an important role in cell-cell adhesion and the development of higher order structures on medically-relevant materials [17,19].…”

Outer membrane protein A (OmpA) as a potential therapeutic target for Acinetobacter baumannii infection

“…Porins are only β-barrel proteins that have been found in outer membrane of GNB. AbOmpA is the most abundant porin associated with drug resistance, epithelial cells attachment and biofilm formation [60,61]. Smani et al first demonstrated the effect of AbOmpA on the phenotype of multi-resistant A. baumannii, and found that the depletion of OmpA gene decreased the MICs of chloramphenicol, aztreonam, and nalidixic by 8, 8 and 2.67 fold, respectively.…”