Infection 6 Infection At Surface + Biofilms Flashcards
What is a surface?
Interface between a solid and either a liquid or a ags
What viruses are located on the skin?
Papilloma
Herpes simplex
What does papilloma virus cause?
HPV - Warts
What does herpes simplex cause?
Cold sores
Herpes
What gram positive bacteria is located on the skin?
Staphylococcus aureus
Coagulase negative staphylococci
Corynebacterium
What gram negative bacteria is located on the skin?
Enterobacteriaceae
What fungi are located on the skin?
Yeasts
Dermatophytes
What do dermatophytes cause?
Athletes foot
Ringworm
What parasites are located on the skin?
Mites
What is microbiota?
What is another name?
- Microorganisms carried on skin + mucosal surfaces
- Harmless normally
- Harmful if transferred to another site
Commensals
Methods of commensals causing infections
Invasion
Migration
Inoculation
Haematogenous - in blood
Examples of external body surfaces which infection can effect and the disease linked
- cellulitis - skin
- pharyngitis - throat
- conjunctivitis - eye
- gastroenteritis - GI tract
- UTIs - urinary tract
Examples of internal body surfaces which infection can effect and the disease linked
Septic arthritis - joints
Osteomyelitis - bones
Endocarditis - heart valves
Empyema - body cavity
What is empyema?
Pockets of pus that have collected inside the body cavity
Causative organism of prosthetic joint infection
Staphylococcus aureus
Coagulase negative staphylococci
Causative organisms of cardiac pacing wire endocarditis
Staphylococcus aureus
Coagulase negative staphylococci
Causative organism of prosthetic valve endocarditis under 1 year post op
How does it cause an issue?
Coagulase negative staphylococci
Enters site during surgery
Causative organism of prosthetic valve endocarditis over 1 year post op or naive heart valves
Viridans
Staph aureus
Candida
HACEK group
Streptococci
Enterococcus
Faecalis
What is the pathophysiology of infections at surfaces?
1- Adherence to host cell or prosthetic surface
2- Biofilm formation
3- Invasion + multiplication
4- Host response - pyogenic (neutrophil > pus)
- granulomatous
What are some prosthetic surface infections?
IV lines
Prothetic joints
Cardiac valves
Peritoneal dialysis catheters
Pacing wires
Why is Coagulase-negative staphylococci so infectious?
Strong adherence to host cells or prosthetic surfaces
Form biofilms
How do microbes adhere to host cells?
They have pili or fimbriae
What is a biofilm?
- A thin slimy film of bacteria that adhere to surfaces
often staph. aureus or epidermidis - Bacterial colonies grow on film - encased in extracellular polysaccharide matrix
Explain biofilm formation
- planktonic bacteria attach to prosthetic surfaces using pili/frimbriae
- they proliferate and produce extracellular polysaccharide matrix
- cells detach from colony > more planktonic bacteria
What are planktonic bacteria?
Free floating bacteria
What are the 2 host responses to pathogenesis of infection at surfaces?
- pyogenitor - neutrophils > pus
-
granulomatous - fibroblasts, lymphocytes
+ macrophages > nodular inflammatory lesions
What is quorum sensing?
Where bacteria in a biofilm communicate with each other and coordinate their activities
How do bacteria in biofilm communicate?
Quorum sensing
What 3 things does quorum sensing control?
Biofilm formation
Sporulation
Virulence factor secretion
How are surface infections managed?
Aim is to sterilise tissue and reduce bio burden
- give antibacterials
- surgery > remove prosthetic material
How are surface infections diagnosed?
Aim is to identify infecting organism + its antimicrobial susceptibilities
- blood cultures
- tissue/prosthetic material sonication and culture
Why are biofilms difficult to eradicate?
- low metabolic state of bacteria in biofilm > antibiotics only target actively dividing
- therefore poor anti bacterial penetration into biofilm
