Systemic Bacteriology II PDF

Summary

This document provides an overview of systemic bacteriology, covering key definitions, types of pathogens, sepsis, fever, and specific bacteria, such as Streptococcus and Staphylococcus species. The information appears suited for a university-level microbiology course.

Full Transcript

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

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