Poly-N-acetylglucosamine mediates biofilm formation and antibiotic resistance in Actinobacillus pleuropneumoniae

Abstract

Most field isolates of the swine pathogen Actinobacillus pleuropneumoniae form tenacious biofilms on abiotic surfaces in vitro. We purified matrix polysaccharides from biofilms produced by A. pleuropneumoniae field isolates IA1 and IA5 (serotypes 1 and 5, respectively), and determined their chemical structures by using NMR spectroscopy. Both strains produced matrix polysaccharides consisting of linear chains of N-acetyl-D-glucosamine (GlcNAc) residues in beta(1,6) linkage (poly-beta-1,6-GlcNAc or PGA). A small percentage of the GlcNAc residues in each polysaccharide were N-deacetylated. These structures were nearly identical to those of biofilm matrix polysaccharides produced by Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis. PCR analyses indicated that a gene encoding the PGA-specific glycoside transferase enzyme PgaC was present on the chromosome of 15 out of 15 A. pleuropneumoniae reference strains (serotypes 1-12) and 76 out of 77 A. pleuropneumoniae field isolates (serotypes 1, 5 and 7). A pgaC mutant of strain IA5 failed to form biofilms in vitro, as did wild-type strains IA1 and IA5 when grown in broth supplemented with the PGA-hydrolyzing enzyme dispersin B. Treatment of IA5 biofilms with dispersin B rendered them more sensitive to killing by ampicillin. Our findings suggest that PGA functions as a major biofilm adhesin in A. pleuropneumoniae. Biofilm formation may have relevance to the colonization and pathogenesis of A. pleuropneumoniae in pigs.

Effect of Farnesol on Planktonic and Biofilm Cells of Staphylococcus epidermidis

“…This bacterium has become the primary cause of nosocomial bloodstream infections, also of the eye, ear, nose, and throat as well as cardiovascular infections [15]. This is related, in part, to the organism's ability to adhere to surfaces and form biofilms [2,5,10,16]. In fact, the formation of biofilms has been considered the main virulence mechanism of S. epidermidis [10,15], and is the main cause of chronic infections [5].…”

“…This is related, in part, to the organism's ability to adhere to surfaces and form biofilms [2,5,10,16]. In fact, the formation of biofilms has been considered the main virulence mechanism of S. epidermidis [10,15], and is the main cause of chronic infections [5]. Biofilm formation requires the bacterial attachment to solid surfaces, the development of bacterial multilayers and their enclosing in a large exopolymeric matrix [10].…”

“…Biofilm formation requires the bacterial attachment to solid surfaces, the development of bacterial multilayers and their enclosing in a large exopolymeric matrix [10]. This structure impairs the action of phagocytic cells from the immune system and of antimicrobial agents [5,10,16], and releases planktonic cells from the outer layers, allowing the persistence of bacterial infections [10]. Biofilms are notoriously difficult to eradicate and are a source of many recalcitrant infections [16].…”

Structural Basis for the De-N-acetylation of Poly-β-1,6-N-acetyl-d-glucosamine in Gram-positive Bacteria

“…The conserved exopolysaccharide known as polysaccharide intercellular adhesin was originally identified in the biofilms of S. epidermidis (11) and Staphylococcus aureus (12) and has now been shown to be produced by various Gram-negative bacteria (13)(14)(15)(16)(17)(18)(19) and higher eukaryotes (20). Polysaccharide intercellular adhesin is synthesized as a ␤-1,6-linked poly-N-acetyl-Dglucosamine (PNAG) 5 polymer and subsequently modified by partially de-N-acetylation and/or O-succinylation.…”

The Structure- and Metal-dependent Activity of Escherichia coli PgaB Provides Insight into the Partial De-N-acetylation of Poly-β-1,6-N-acetyl-d-glucosamine

“…A wide variety of medically important biofilm-forming bacteria produce partially de-N-acetylated poly-␤-1,6-N-acetyl-D-glucosamine (dPNAG) 5 exopolysaccharides, also referred to as polysaccharide intercellular adhesin. dPNAG was first described in Staphylococcus epidermidis (8) but has now been determined to be a component of the biofilm matrices of Staphylococcus aureus (9), Escherichia coli (10), Acinetobacter baumannii (11), Bordetella bronchiseptica (12), Bordetella pertussis (13), Actinobacillus pleuropneumoniae (14), Yersinia pestis (15), and Burkholderia species (16).…”