Introduction to Microbiology H GEE MD FRCOG Hon

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) – Fungi (Mycology) • Human, Animals, Plants

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

Objectives • By the end of the session you should be able to; – Distinguish between gram-positive and gramnegative 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.

Some definitions

Infection ‘the establishment of a microorganism within a host’

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

Virulence ‘ quantitative measure of the likelihood of causing disease’

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

Bacteria

Bacteria Description • 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

Prokaryote Eukaryote

Prokaryote vs Eukaryote

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

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

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

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

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

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

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

Genetic variability

Lateral gene transfer

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

Virulence factors 1. Aid colonisation 1. Adhesion proteins 2. Entry into cells 2. Aid survival 1. Immune avoidance eg. antiphagocytic 2. Immunosuppression 3. Damage host 1. Toxins 4. Obtain nutrition from host

Obligatory steps for infection Attachment +/- Evade natural protection and cleansing mechanisms Entry into body Local or general spread Evade 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

Relationship with humans • We are sterile in utero • Shortly after birth colonised • Of 10000 bacterial only 1000 are successful – Suggests highly evolved

Microbiome

Vaginal Flora • 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

Biofilms

Any Questions?

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

Bacteria Classification

Bacteria and Human body • Bacteria >10 x 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