Introduction Flashcards
What is an infection?
An invasion of a host’s tissues by microorganisms.
What is disease caused by?
Microbial multiplication, toxins and the hosts response.
How may a patient get an infection?
Directly from the source, through an intermediary, from the environment, animals or themself.
What do microbiota and commensals mean?
A microbiota is the ecological community of commensal, symbiotic and pathogenic microorganisms that share our body space and commensals are microorganisms carried on the skin and mucosal surfaces, which are usually harmless/beneficial, but can be harmful when displaced in S. Pneumoniae.
In terms of transmission, how do infections differ?
Physical contact is needed for some (e.g. STIs where mucous membrane to mucous membrane contact is needed), but airborne spread may be sufficient for others (e.g. Chickenpox) or a vector may be utilised (such as a mosquito for malaria).
How may someone become infected from the environment?
Transmission due to ingestion of contaminated food/water, inhalation of air or contact with contaminated surfaces, including medical devices.
How do the modes of horizontal and vertical transmission differ?
Horizontal transmission includes: contact (direct, indirect, vectors), inhalation (droplets, aerosol), ingestion (foecal-oral transmission), whereas vertical transmission is from mother to child before or at birth.
What path do microorganisms causing disease take?
Exposure, adherence, invasion, multiplication and dissemination.
Name some disease determinants?
- Pathogen - virulence factors, inoculation size, antimicrobial resistance.
- Patient - site of infection, comorbidities.
How can you tell that a patient has a disease?
History taking determines symptoms (focal/systemic, severity, duration) and possible exposures (what, who, where, animals?).
Examination looks at organ dysfunctions.
Investigations can be specific (bacteriology & virology) or supportive.
Give some examples of supportive investigations.
Full blood count, C-reactive protein, blood chemistry (liver/kidney dysfunction?), imaging and histopathology.
What is done in a bacteriology investigation?
Specimen types (fluid, tissues, swabs) go through MC&S - microscopy, culture, antibiotic susceptibility and antigen detection along with nuclei acid detection (filtered urine?).
What happens in a virology investigation?
Antigen detection, antibody detection, detecting viral nuclei acid (from DNA and RNA).
Give an example of where it may become appropriate to relabel established diseases as infections.
Bowel cancer associated with bacterial infections.
