systemic bacteriology II.pdf

systemic bacteriology II 24/10/23, 12:47 PM systemic bacteriology II Key definitions • Virulence: the capacity of a microbe to cause damage to its host • Pathogen: a harmful organism that produces a pathology • Commensal: an organism that is part of the normal flora ◦ Often a mutualistic relations...

systemic bacteriology II 24/10/23, 12:47 PM systemic bacteriology II Key definitions • Virulence: the capacity of a microbe to cause damage to its host • Pathogen: a harmful organism that produces a pathology • Commensal: an organism that is part of the normal flora ◦ Often a mutualistic relationship ◦ Endogenous • Opportunistic pathogen: an organism that causes infection when opportunity/change in natural immunity arises • Coagulase test: use to differentiate between Staph. aureus and coagulase negative Staph. (including Staph epidermis) • Haemolysis: used to differentiate between Streptococci Sepsis • Small blood vessels become ‘leaky’ and loose fluid into tissues - decreased blood volume so heart has to work harder • • • Poor tissue perfusion means blood supply to less essential organs is shut down Blood clotting system activated - uses all clotting factors, increasing risk of haemorrhage Patients with Gram-negative sepsis get very unwell very quickly due to endotoxin released when Gram-negative bacteria die Fever 1. Antigen/LPS interacts with macrophages 2. Macrophages release cytokines into bloodstream 3. Cytokines travel to anterior hypothalamus 4. Prostaglandin E released - increases body’s thermal set point 5. Body perceives it as cold - starts to ‘shiver’ 6. FEVER Key gram-negative pathogens Gram-negative cocci • • Neisseria meningitidis: most common cause of bacterial meningitis Neisseria gonorrhoeae: gonorrhea Gram-negative cocci associated with GI tract • Gut commensal coliforms ◦ ◦ • Many are part of normal bowl flora Any coliform that gets into a normally sterile environment can cause infection e.g. UTI Gentamicin is the first line antibiotic for the treatment of infections caused by coliforms Key gram-positive pathogens Streptococcus spp. https://galvanized-borogovia-4fa.notion.site/systemic-bacteriology-II-b166f6e4d0f5427f9aab7729341b2ec7 Page 1 of 2 systemic bacteriology II 24/10/23, 12:47 PM • Identified by haemolysis (ONLY streptococcus) • • GAS: numerous associated diseases e.g. Scarlet fever, impetigo, β-haemolytic Streptococcus pneumoniae: pneumonia, ⍺-haemolytic Staphylococcus epidermis • • Nosocomial - associated with foreign devices e.g. catheters Coagulase negative Staphylococcus aureus • • • • • Nosocomial and community Most common cause of skin, soft tissue and wound infection Sepsis Coagulase positive (appears golden) Clump forming - looks like grapes Enterococcus • • • Enteric infections Part of normal bowel flora, can cause problems if they get into a normally sterile area 𝛾-haemolytic Clostridium spp. • • • Part of normal bowel flora Produce endotoxins that can cause severe tissue damage Clostridium difficile: causes antibiotic-associated diarrhoea, especially in the elderly ◦ Proliferates in the absence of normal flora https://galvanized-borogovia-4fa.notion.site/systemic-bacteriology-II-b166f6e4d0f5427f9aab7729341b2ec7 Page 2 of 2