Inhibition of Campylobacter jejuni Biofilm Formation by D-Amino Acids

Abstract

The ability of bacterial pathogens to form biofilms is an important virulence mechanism in relation to their pathogenesis and transmission. Biofilms play a crucial role in survival in unfavorable environmental conditions, acting as reservoirs of microbial contamination and antibiotic resistance. For intestinal pathogen Campylobacter jejuni, biofilms are considered to be a contributing factor in transmission through the food chain and currently, there are no known methods for intervention. Here, we present an unconventional approach to reducing biofilm formation by C. jejuni by the application of D-amino acids (DAs), and L-amino acids (LAs). We found that DAs and not LAs, except L-alanine, reduced biofilm formation by up to 70%. The treatment of C. jejuni cells with DAs changed the biofilm architecture and reduced the appearance of amyloid-like fibrils. In addition, a mixture of DAs enhanced antimicrobial efficacy of D-Cycloserine (DCS) up to 32% as compared with DCS treatment alone. Unexpectedly, D-alanine was able to reverse the inhibitory effect of other DAs as well as that of DCS. Furthermore, L-alanine and D-tryptophan decreased transcript levels of peptidoglycan biosynthesis enzymes alanine racemase (alr) and D-alanine-D-alanine ligase (ddlA) while D-serine was only able to decrease the transcript levels of alr. Our findings suggest that a combination of DAs could reduce biofilm formation, viability and persistence of C. jejuni through dysregulation of alr and ddlA.

Extracellular c-di-GMP Plays a Role in Biofilm Formation and Dispersion of Campylobacter jejuni

“…The assays were performed as previously described [ 50 ]. Briefly, overnight cultures of C. jejuni strains were diluted to an OD 600 (optical density at 600 nm) of 0.05, and 2 mL of cell suspension were dispensed into 24-wells plates (Geiner Bio-One, Monroe, NC, USA).…”

“…After that, the plates were gently rinsed with water, dried at 55 °C for 30 min and stained using the modified CV staining method as described previously [ 51 ]. The percentage of biofilm inhibition and dispersion (%) was calculated as described by [ 50 , 52 , 53 ]. Data are presented as mean ± standard errors.…”

“…The RT-PCR was performed as described previously in [ 50 ]. Briefly, C. jejuni 11168-O cells grown overnight at 42 °C with shaking at 50 rpm, under microaerobic conditions.…”

Campylobacter Biofilms: Potential of Natural Compounds to Disrupt Campylobacter jejuni Transmission

“…Moreover, DAs disrupted the ability of C. jejuni to form biofilm (up to 70%) by incorporating into peptidoglycan and inducing the disassembly of matrix-associated amyloid fibrils, or by a breakdown of EPS that surrounds the biofilm. DAs were also able to enhance the efficacy of D-Cycloserine (DCS) against C. jejuni by up to 32% [47]. DAs appear to be promising antibiofilm compounds and should be further investigated.…”

“…biofilm architecture is summarised in Figure 1. In the first stage of biofilm formation, planktonic cells attach to the surface via two types of interaction: cell-surface and cell-cell interactions using flagella, fimbriae, amyloid-like fibrils and outer membrane proteins [45][46][47]. This process is critical for bacterial adhesion and is influenced by the properties of both bacterial cells and the surface [48,49].…”