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Multi-species Biofilms

Multi-species Biofilms. Biofilms. A biofilm is a community of microorganisms, associated with a surface, and encased in an extracellular polymeric matrix . Why is Biofilm Formation Important?.

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Multi-species Biofilms

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  1. Multi-species Biofilms

  2. Biofilms • A biofilm is a community of microorganisms, associated with a surface, and encased in an extracellular polymeric matrix.

  3. Why is Biofilm Formation Important? • Many, if not the majority of infections involve biofilm formation (particularly chronic infections) • Important in device-related infections • Biofilm formation can complicate therapy

  4. Dental Biofilms • Very complex community; multi-species, multi-kingdom • Develop in stages

  5. Acquired Pellicle Acquired Pellicle Acquired Pellicle Acquired Pellicle Acquired Pellicle Tooth surface Tooth surface Tooth surface Tooth surface Tooth surface Stage 1: Pellicle formation Stage 4: Maturation Stage 2: Initial Adherence Stage 5: Dispersal Stage 3: Aggregation

  6. Stage 1: Pellicle formation

  7. Stage 2: Initial Adherence Actinomyces Streptococci Acquired Pellicle Tooth surface Streptococci and Actinomyces are initial colonizers

  8. Stage 1: Adherence • Why is adherence important? • Adherence is a critical first step in pathogenesis. • All pathogenic bacteria produce adhesins • What is an adhesin? • ADHESIN: Bacterial macromolecule that binds to specific ligands or receptors on host cells and defines the tropism of the microbe for various cells or tissues.

  9. Role of adherence 1) To avoid physical removal by host defenses • Mucociliary escalator • Washing action of saliva tears, mucus • Blood and urine flow 2) To make intimate contact with host tissues • Nutrient uptake • Invasion

  10. Types of Adhesins • Pili / fimbriae • Non-pilus surface proteins • Polysaccharides

  11. Types of Adhesins; 1. Pili • Streptococcus pyogenes pilus promotes adhesion to pharyngeal epithelial cells. • This is necessary for streptococcal pharyngitis

  12. Types of adhesins; 2. Surface Proteins • S. gordonii: Amylase-binding protein, AbpA S. gordonii

  13. Types of adhesins; 3. Polysaccharides • e.g. S. mutans produces glucosyltransferases that convert sucrose into polysaccharides which; • 1. Act as receptors for adhesins on other bacteria • 2. Contribute to adherence of S. mutans to the tooth surface

  14. Approaches to reducing adherence • Physical disruption; oral hygiene. • Replacing sucrose with non-utilizable sugars. • Anti-adhesin vaccines

  15. Stage 3: Aggregation Acquired Pellicle Tooth surface

  16. Stage 4: Maturation • Increased species diversity; late colonizers Acquired Pellicle Tooth surface

  17. Co-aggregation • Mediated by interactions between lectins on one bacterial cell and sugar residues on another.

  18. Co-aggregation

  19. Bacterial Vaginosis (BV) • Most common vaginal disorder worldwide • Mixed species biofilm forms on the vaginal epithelium Normal vaginal secretions BV vaginal secretions

  20. BV Associated Risk Factors • Number of known risk factors including • Sexual activity and number of sexual partners • IUD usage • Douching • Antibiotic treatment • Smoking

  21. Diagnosis • Wet mount: prepared from vaginal sample and observed for presence of clue cells • Whiff test with KOH • Vaginal pH greater than 4.5 • Culture or Gram stain • Positive 3 out of 4 is indicative of BV, treatment with oral or topical Metronidazole

  22. Complications of BV • Preterm delivery, low birth weight • Complications during pelvic surgeries can lead to PID • Increased risk of infection with HIV and other STDs • Frequently relapses or recurs after treatment

  23. Etiology of BV • G. vaginalis is the predominant species in >= 90% of cases, but pure cultures don’t reliably cause infection • Koch’s postulates have not been satisfied • Is G. vaginalis necessary but not sufficient to cause the disease??

  24. Gardnerella vaginalis • Facultative anaerobe, Gram positive or variable, rod shaped • Non-motile, non-flagellated, non-spore forming, non-encapsulated, may produce pili • G. vaginalis forms a biofilm on the vaginal epithelium of women with bacterial vaginosis (BV) Electron microscopy of G. vaginalis

  25. Hypothesis • Similar to Streptococci in dental biofilms, G. vaginalis is an initial colonizer and forms a biofilm on the vaginal epithelium. Biofilm formation allows G. vaginalis and other anaerobic species to survive in the face of oxygen, acid, hydrogen peroxide, and immune factors in the vagina.

  26. How would a biofilm limit local O2 concentrations?

  27. Forces of diffusion and convection (mixing)

  28. Forces of diffusion and convection (mixing)

  29. Forces of diffusion and convection (mixing)

  30. Forces of diffusion and convection (mixing)

  31. Forces of diffusion and convection (mixing)

  32. Forces of diffusion and convection (mixing)

  33. Mathematical Modeling of Biofilms • Is our hypothesis valid? • Could biofilm formation by G. vaginalis sufficiently deplete local oxygen concentrations?

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