Week 5 - Infections on Surfaces Flashcards
(31 cards)
State examples of normal mucosal flora present in the eye.
- Coagulase negative staphylococci
- Diptheroids
- Saprophytic Neisseria species
- Viridans group streptococci
State examples of normal mucosal flora present in the nares.
Staphylococcus aureus
State examples of normal mucosal flora present in the nasopharynx.
Streptococcus pneumonia, Neisseria meningitidis, Haemophilus influenzae
State examples of normal mucosal flora present in the mouth.
Viridans streptococci, Neisseria, Veillonella, Lactobacillus, Actinomyces, Bacteroides, Capnocytophaga, Eikenella, Prevotella, Fusobacteria, Clostridia, Propionibacteria, Candida, Geotrichium species
State examples of normal mucosal flora present in the stomach.
Helicobacter, Streptococci, Staphylococci, Lactobacilli
State examples of normal mucosal flora present in the intestine.
Bacteroides, Bifidobacterium, Eubacterium, Lactobacillus, Coliforms, Aerobic and anaerobic streptococci, Clostridium, yeasts
State examples of normal mucosal flora present in the urethra.
Enterobacteriaceae, lactobacilli, diptheroids, alpha and non-haemolytic streptococci, enterococci
State examples of normal mucosal flora present in the vagina.
Lactobacilli, diptheroids, micrococci, coagulase-negative staphylococci, enterococcus faecalis, microaerophilic and anaerobic streptococci, Mycoplasmas, ureaplasmas, yeast
What is the microbiota?
Microorganisms carried on the skin or mucosal surfaces that are typically harmless or even beneficial
State the ways in which an individual can become infected.
- Invasion, e.g. Strep pyogenes pharyngitis
- Migration, e.g. E. coli urinary tract infections
- Innoculation, e.g. coagulase negative staphylococcus prosthetic joint infections
- Haematogenous, e.g. viridans strep endocarditis
State some examples of external natural surface infections.
- Cellulitis
- Conjunctivitis
- Pharyngitis
- Gastroenteritis
- Pneumonia
- Urinary tract infections
State some examples of internal natural surface infections.
- Endovascular: endocarditis, vasculitis
- Osteomyelitis
- Empyema
- Septic arthritis
Define empyema.
Collection of pus in the pleural cavity
State the organisms commonly implicated in native endocarditis/prosthetic valve endocarditis > 1 year post-operation.
- Candida
- HACEK Group
- Viridans streptococci
- Enterococcus faecalis
- Staphylococcus aureus
State the organisms commonly implicated in prosthetic valve endocarditis < 1 year post-operation.
Coagulase-negative staphylococci
State the organisms commonly implicated in prosthetic joint infections.
- Coagulase-negative staphylococci
2. Staphylococcus aureus
State the organisms commonly implicated in cardiac pacing wire endocarditis.
- Coagulase-negative staphylococci
2. Staphylococcus aureus
Outline the processes involved in pathogenesis of infection at surfaces.
- Adherence to host cells/prosthetic surfaces
- Biofilm formation
- Invasion and multiplication
- Host response:
- Pyogenic: neutrophils –> pus
- Granulomatous: fibroblasts, lymphocytes, macrophages –> nodular inflammatory lesions
Which bacterial structures enable adherence to host cell membranes?
- Pili
2. Fimbriae
What substance when exposed in damaged heart valves is ideal for colonisation by virulent bacteria?
Fibronectin
How are bacteria in biofilms different from free-living vegetative bacteria?
- Much slower turnover
- Longer lifecycle
- Smaller in size
Outline the stages involved in biofilm formation.
- Starvation can induce bacteria to shrink and adopt a spore-like state known as ultramicrobacteria, which wait in water, soil, rock or tissue until conditions are suitable for favourable growth.
- Active bacteria can attach to almost any surface. Changes in gene expression transform “swimmers” to “stickers” within minutes.
- Attached bacteria multiply and encase the colonies with a slimy matrix.
- Nutrients diffuse into the matrix.
- Close proximity of cells in the matrix facilitates the exchange of molecular signals that regulate behaviour
- Chemical gradients create microenvironments for different microbial species or levels of activity
- Although antimicrobials damage outer cell layers, the biofilm community is resistant
- Propelled by shear forces, aggregated cells can become detached or roll or ripple along a surface in sheets and remain in their protected biofilm state
State examples of prosthetic surfaces that can become infected.
- Peritoneal dialysis catheters
- Endovascular grafts
- Pacing wires
- Cardiac valves
- Intravascular lines
- Prosthetic joints
- Ventriculo-peritoneal shunts
State the controls involved in biofilm formation.
- Biofilm formation
- Sporulation
- Virulence factor secretion
