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 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.

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

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

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

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

Gram Stain +ve cocci, clusteredS. Aureus (coag -ve) +ve cocci, paired or chainsStrep. Enterococci +ve bacilli (large + spores)Clostridium -ve cocci(intra-cellular)Gonorrhoea -ve rods, coliformE. Coli/Coliforms Pseudomonas -ve rodsAnaerobes Haemophilus spp

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

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

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

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 hostto be completed Shedding from body Leave body at a site and on a scale that ensures spread to fresh host- transmission Obligatory steps for infection

Relationship with humans We are sterile in utero Shortly after birth colonised Of 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?

1mm100µm10 µm1 µm100nm10nm1nm Light microscope Electron Microscope Plant and animal cells Bacteria Viruses Proteins Small molecules Size Matters

Bacteria Classification

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