Bacterial structure & Normal human flora

Kingdoms: Monera  Prokaryotes  Unpaired chromosomes  No nucleus  Eubacteria Protist  Eukaryotes  Paired chromosomes  Nuclear structure  Protozoa, algae, moulds

ProkaryoteEukaryote Nucleic acids Structured nucleus Mitochondria Ribosomes Cell Membrane Rigid Cell wall Mesosome ER/Golgi

Shape: Arrangement:  Coccus  Diplococci – Neisseria spp.  Tetrads – Micrococcus luteus  Chains – Streptococcus spp.  Clusters – Staphylococcus spp.  Sarcinae – Sarcina maxima  Rods  Individual  Diplobacilli – Bacillus aureus  V-shaped – Corynebacterium diptheriae  Cord – Mycobacterium tuberculosis

 Differentiates bacteria  Gram +ve - thick cell wall  Gram –ve – thin cell wall  1 st line test dx Bacterial infection  Method: 1.Crystal Violet 2.Gram’s iodine 3.Acetone (Decolouriser) 4.Safranin Red

Gram +veGram -ve Thick Cell wallThin cell wall Teichoic acidOuter membrane SporulationLPS (endotoxin) Capsule Lysozyme sensitive >penicillin susceptibility<penicillin susceptibility

 18month old male presents with 2/7hx of:  Fever  Vomiting  Rash  Irritable, crying  Photophobia  DDx???  Tests to confirm?

 Reside consistently in a specific site  Cause no damage to host  May be beneficial  Modify skin secretions/enhance digestion/defence against pathogens  Differ from Transients, Opportunists, Pathogens

 Colonisation:  Microorganism live on/in host  Does not invade tissues or cause damage.  Occurs at birth  Changes during puberty/menstrual cycle  Normal human flora:  mixture of organisms regularly found at any anatomical site  Influenced by tissue type, occupation etc.

Skin: Staphylococci Coryneforms (diptheroids) Yeast Mouth/Nasopharnyx: Oral streptococci Neiserria Anaerobic bacteria Fungi Nose: Staph. aureus Potential pathogens: Strep. Pneumoniae Neisseria meningitidis Female lower genital tract: Similar to gut flora but lower numbers. Large Bowel: Anaerobic bacteria  Bacteroides spp,  Clostridia Aerobic bacteria  Enterococci  E.coli  Proteus spp  Klebsiella  “Enterobacteria” Fungi (esp. yeasts) Lactobacilli Protozoa, helminths

 Incapable of invasion & damage to host unless:  Immunocompromised  Abx disrupt normal flora  Physical barriers breached  Impaired clearance mechanism

Aspergillus fumigatus – pneumonia Cryptococcus neoformans – meningitis Toxoplasmosis reactivation - meningoencephalitis

Surgery Immunosuppression failure/normal physical barriers (wound, instrumentation) Examples:  E.coli – Abdo surgery, UTI  S. epidermidis – Septicaemia (IV catheter)

 Skin - S. aureus/ β-haemolytic strep.  Mouth - C. albicans overgrowth.  Colon – C.difficile!/ Salmonella

 Prokaryotes/Eukaryotes  Microscopic morphology  Gram staining  Structural differences Gram +ve/-ve  Structure of cell wall  Case example  Normal human flora  Opportunistic pathogen  Examples of infection by both