Biofilm Formation by Neisseria meningitidis

Abstract

Biofilm formation by the human pathogen Neisseria meningitidis was analyzed. Biofilm-forming meningococcal strains were identified and quantitated by crystal violet staining. Laser scanning confocal microscopy of the meningococcal biofilm revealed variable layers up to 90 m in thickness. A total of 39 meningococcal isolates were studied; 23 were nasopharyngeal-carriage isolates, and 16 were invasive-disease isolates. Thirty percent of carriage isolates and 12.5% of invasive-disease isolates formed biofilms proficiently on a polystyrene surface. Generally, the strains that formed biofilms showed high-level cell surface hydrophobicity, characteristic of strains lacking a capsule. The inhibitory role of capsule in biofilm formation was further confirmed by comparing the biofilm-forming capabilities of a serogroup B wild-type strain of a disease-associated isolate to those of its capsule-deficient mutant (ctrA). Some strains of meningococci form biofilms, and this process is likely important in menigococcal colonization.Bacterial biofilms are sessile bacterial communities that adhere to each other and solid surfaces and are enclosed in an exopolysaccharide matrix (6). Biofilms are the predominant communities of many bacterial species in numerous ecosystems. Formation of biofilms involves participation of the extracellular-matrix and cellular-surface molecules, including membrane proteins. Biofilm formation also requires considerable bacterial energy and resources. The formation of biofilms begins with the attachment of the planktonic cells to a suitable surface, followed by replication and spreading. Eventually, the biofilms mature to differentiated forms. Exopolysaccharides play a key role in the establishment of biofilm architecture (6).In clinical settings, bacteria in biofilms are less susceptible to antimicrobial agents and host immune responses, thereby becoming persistent colonizers or sources of chronic infections (8). Bacteria are released from biofilms as individual planktonic cells or as a result of the sloughing of the biofilms. While many biofilms form on abiotic surfaces such as medical devices, some also develop on living tissues, as in the case of endocarditis or cystic fibrosis (8).Studies of biofilm formation by the Neisseria species are very limited, and most of those species examined have been oral commensals (4,20,24,26,38). Biofilm formation by Neisseria meningitidis, an etiologic agent of epidemic sepsis and bacterial meningitis, has not been documented. Meningococci are isolated from 5 to 10% of the normal population, and the colonization of the human nasopharyngeal mucosal surface by meningococci is the first step of the host-parasite interaction.Successful meningococcal colonization requires initial attachment facilitated by pili and subsequent interaction of other secondary-surface molecules with the host mucosal surface (12,31,36,43).In this study, the formation of the biofilms by N. meningitidis was assessed. In addition, the roles of the bacterial-surface molecules (pilus, capsule, and ...

Enhanced Biofilm Formation and Loss of Capsule Synthesis: Deletion of a Putative Glycosyltransferase inPorphyromonas gingivalis

“…This bacterium is the causative agent of bacterial meningitis, and its ability to colonize the human nasopharyngeal mucosal surface is a key aspect of its pathogenicity. Non-biofilm-forming strains of N. meningitidis were encapsulated, and a capsule-transport mutant (ctrA) gained the ability to form a biofilm (89), similar to the phenotype we observed here with P. gingivalis. Also, it was shown that the expression of capsule, as well as pili, is repressed in N. meningitidis upon contact with host epithelial cells, and this down-regulation facilitated attachment (14).…”

“…According to TIGR annotation, the gene is predicted to be involved in the biosynthesis and degradation of surface polysaccharides and LPS, and therefore, the deletion could result in a strain that is defective in LPS synthesis. A defect in LPS synthesis (expression of a truncated LPS structure) has been shown to enhance biofilm formation in Salmonella enterica (60) and in Neisseria meningitidis (89). The altered biofilm phenotype could also be the result of inactivation of genes downstream of PG0106.…”

Structural and Biological Characterization of a Capsular Polysaccharide Produced by Staphylococcus haemolyticus

“…8B). Similar structures with N-acetyl-aspartate were described as constituents of the O-antigen polysaccharides of enterobacteria of the genera Providencia and Proteus (31). The NMR data were confirmed by composition analyses that showed the presence of GlcN, FucN, and Asp.…”

Biofilm Formation by Neisseria gonorrhoeae

“…These may encase the gonococci within sac-like structures into which a matrix is released. A recent study of biofilms produced by 39 Neisseria meningitidis strains showed that 30% of the carriage isolates and 12.5% of the invasive disease isolates formed biofilms in microtiter wells (25). Generally, the more hydrophobic the surface of the or- ganism, the more likely it was to form a biofilm, and encapsulation inhibited biofilm formation.…”