The Home Guard Flashcards
Define the ‘normal flora’.
The wide range of organisms that live on the body without causing disease (usually).
Define endogenous infection.
An infection whose source is within the body.
Define exogenous infection.
An infection whose source is a tranmitted organism.
What is the meaning of commensal or non-commensal?
Pathogen or non-pathogen
What is a pathogen?
An organism capable of causing disease.
Mucus and cilia capture organisms and remove them from the respiratory tract. This is part of the innate immune system What could compromise this?
- Loss of ciliary function (e.g. Kartagener’s syndrome).
- Thick mucus as in cystic fibrosis.
- BOTH lead to chronic bronchial sepsis.
- Some organisms which cause this are:
- S. aureus
- H. influenzae
- P. aeruginosa
- M. cattarhalis
- M. abscessus
- Intubation bypasses the system which is designed to prevent pathogens from entering so could also compromise this defence mechanism.
The flushing action of urinary flow removes organisms. This is part of the innate immune system. How could this immune defence be compromised?
- Many urinary pathogens have specialised adherence mechanisms.
- Obstruction to the urinary flow can lead to stasis and urosepsis.
- Obstruction can be caused by:
- Catheters
- Congenital malformations
- Pregnancy
- Prostatic enlargement
- Stones
- Tumours
- Cathaters damage the epithelial lining. A big bag of urine full of bugs which can eventually travel back up the cathater can compromise.
The skin is a physical barrier to pathogens. This is part of the innate immune system. How could this be compromised?
- Breaching the skin opens a route for infection.
- Some causes of this are:
- IV therapy
- Canulae
- Central venous lines
- Arterial lines
- Chest drains
- Post-operative drains
- This can take skin organisms into the body.
- They can use this as a route for invasion.
- It causes local sepsis and septicaemia.
The stomach acid kills infected pathogens. This is part of the innate immune system. How could this be compromised?
- The stomach acid reduces the infective dose making intestinal infection less likely.
- Reducing stomach acid allows colonisation and infection at lower infective doses.
- The impact varies depending on the organism’s infective dose.
- Some causes are:
- Antacids
- H2 antagonists
- Proton pump inhibitors
- Some relevant organisms are:
- Salmonella
- Shigella
- C. difficile
- Resistant gram negatives
The vagina has a low pH as a result of lactobacilli which prevents colonisation by pathogens. This is part of the innate immune system. How could this be compromised?
- Mixed flora in the vagina prevents colonisation.
- Replacement by potential pathogens leads to vaginitis.
- Some causes are:
- Antibiotic use
- Age-related - becomes more common with age because the flora depletes with age.
- Some relevant organisms are:
- Candida spp.
- Trichomonas vaginalis
Which patients will be affected by S. mitis?
S. mitis does not cause disease unless the patient is immunocompromised. These patients can become septic.
What can be caused by S. oralis?
Endocarditis
What can be caused by staphylococcus aureus?
- Skin sepsis
- Septicaemia
- Acute endocarditis
- Osteomyelitis
What can be caused by staphylococcus epidermidis?
- Endocarditis
- Local sepsis
- Septicaemia
What can be caused by candida albicans?
- Candidaemia
- Endocarditis
