Meningococcal biofilm formation: structure, development and phenotypes in a standardized continuous flow system

Area of Science:

• Microbiology
• Bacterial pathogenesis
• Biofilm formation

Background:

• Neisseria meningitidis is a significant human pathogen.
• Biofilm formation is crucial for bacterial survival and virulence.
• The role of pili and associated proteins in meningococcal biofilm development is not fully understood.

Purpose of the Study:

• To investigate biofilm formation by unencapsulated Neisseria meningitidis variants.
• To determine the antibiotic susceptibility of meningococcal biofilms.
• To elucidate the role of the pilE gene and PilX protein in microcolony formation within biofilms.

Main Methods:

• Standardized in vitro flow system for biofilm formation.
• Antibiotic susceptibility testing (penicillin, rifampin, ciprofloxacin).
• Genetic analysis including mutation and complementation of pilE and PilX.
• Microscopy to observe microcolony formation.

Main Results:

• Genetically diverse Neisseria meningitidis strains formed stable biofilms ( >96 h).
• Biofilm cells exhibited resistance to penicillin but susceptibility to rifampin and ciprofloxacin.
• Microcolony formation was observed in some strains and linked to pilE and PilX.
• Pilus expression was not essential for initial biofilm attachment and accumulation.
• PilX indirectly supported microcolony formation by enhancing pilus expression.

Conclusions:

• Neisseria meningitidis can form robust biofilms in vitro with strain-specific antibiotic resistance profiles.
• While pilus expression is not required for initial attachment, it plays a role in microcolony development.
• PilX contributes to biofilm architecture by promoting pilus expression and influencing microcolony formation.