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Introduction to Microbiology

Introduction to Microbiology. H. GEE. MD, FRCOG Hon. Assoc. Clinical Professor University of Warwick. Peter Gayo Munthali Consultant Microbiologist UHCW. What is Microbiology. The study of micro-organisms Bacteria (Bacteriology) Viruses (Virology) Parasites (Parasitology)

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Introduction to Microbiology

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  1. Introduction to Microbiology H. GEE. MD, FRCOG Hon. Assoc. Clinical Professor University of Warwick

  2. Peter GayoMunthaliConsultant MicrobiologistUHCW

  3. What is Microbiology • The study of micro-organisms • Bacteria (Bacteriology) • Viruses (Virology) • Parasites (Parasitology) • Fungi (Mycology) • Human, Animals, Plants

  4. Aim To introduce general principles in microbiology with an emphasis on bacteria and viruses

  5. Objectives • By the end of the session you should be able to; • Distinguish between gram-positive and gram-negative bacteria • Describe bacteria by their shape as either cocci or rods • Name some common bacterial and viral diseases linked to their causative organisms • Describe in broad terms, how antibiotics work on bacteria • Describe the difference between bacteria and viruses.

  6. Some definitions

  7. Infection ‘the establishment of a microorganism within a host’

  8. Pathogen ‘any microorganism that has the capacity to cause disease’

  9. Virulence ‘ quantitative measure of the likelihood of causing disease’

  10. Opportunistic • Principle pathogens regularly cause disease • Opportunistic pathogens require a defect in the immune defence • Eg Pseudomonas

  11. Bacteria

  12. BacteriaDescription • Unicellular • Prokaryotic • Primitive nucleus • No nucleus membrane • Genome • Single circular molecule double stranded DNA • Can harbour independent small circular DNA molecules called plasmids • Structure • Rigid wall which determines their shape

  13. Prokaryote Eukaryote

  14. Prokaryote vs Eukaryote

  15. Overall structure of bacterial cell walls Gram –ve cell wall Gram +ve cell wall

  16. Bacteria Classification • Cell wall classification by gram stain • Gram positive • thicker cell wall • Gram negative • thinner cell wall • Classification by shape • Spherical • Cocci • Cylindrical • Rods/bacilli

  17. Gram Stain Gram-negatives Gram-Positives Gram-negative rods Gram-positive cocci in clusters (Staphylococci) Gram-positive rods Gram-positive Cocci in chains (Streptococci) Gram-negative cocci

  18. Gram Stain - Importance • First stage of identification • (Culture) • Indicator for treatment • (Sensitivity)

  19. Gram Stain • +ve cocci, clustered S. Aureus (coag -ve) • +ve cocci, paired or chains Strep. Enterococci • +ve bacilli (large + spores) Clostridium • -ve cocci (intra-cellular) Gonorrhoea • -ve rods, coliform E. Coli/Coliforms Pseudomonas • -ve rods Anaerobes Haemophilus spp

  20. Culture & Sensitivity • Culture • Aerobic/Anaerobic • Haemolytic • Others (type of media) • Sensitivity • Antibiotics

  21. Bacterial Cell Division Super coiled DNA DNA relaxation and duplication Duplication of the DNA bacterial chromosome replicates leading to two identical chromosomes Enzymatic Cleavage Division Identical Daughter cells

  22. Genetic variability

  23. Lateral gene transfer

  24. Virulence ‘ quantitative measure of pathogenicity or the likelihood of causing disease’

  25. Virulence factors • Aid colonisation • Adhesion proteins • Entry into cells • Aid survival • Immune avoidance eg. antiphagocytic • Immunosuppression • Damage host • Toxins • Obtain nutrition from host

  26. Obligatory steps for infection Attachment +/- Evade natural protection and cleansing mechanisms Entry into body Local or general spreadEvade immediate local defences Multiplication Evasion of host defences Evade immune and other defences for growth in the host to be completed Shedding from body Leave body at a site and on a scale that ensures spread to fresh host- transmission

  27. Relationship with humans • We are sterile in utero • Shortly after birth colonised • Of 100000000 bacterial only 1000 are successful • Suggests highly evolved

  28. Microbiome

  29. Lactobacilli (Gram -ve) Gram +ve Atopobium spp. Peptostrep. spp. Staph. Spp. Strep. Spp. Bacteroides Fusobacterium spp. Gardnerella Vaginalis Mobiluncus Prenotella spp. Gram -ve E. Coli Others Candida albicans Mycoplasma Ureaplasma Vaginal Flora

  30. Biofilms

  31. Any Questions?

  32. Size Matters 1nm 10nm 100nm 1 µm 10 µm 100µm 1mm Light microscope Electron Microscope Proteins Viruses Plant and animal cells Bacteria Small molecules

  33. Bacteria Classification

  34. Bacteria and Human body • Bacteria >10x than human cells in the body (10¹ versus 10¹³) • Skin surface and in deep layers • Saliva and oral mucosa • Gastrointestinal tracts • Genital tract • Normal microbiota or microflora • Beneficial to human health • Opportunistic infections • < 10% culturable • Others not part of normal microbiota • Pathogenic • Opportunistic pathogens

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