week 1 - an introduction to infection Flashcards
what is infection?
invasion of a host’s tissues by micro-organisms & disease caused by: microbial multiplication, toxins, host response
How does an individual develops an infection?
Micro-organism transferred to other sites can be harmful (microbiota) e.g. e.coli UTI
Physical contact e.g. STD
Airborne e.g. chickenpox
Vector e.g. mosquito for malaria
Contamination of food or water
Inhalation of air contaminated by environmental organisms
Contact with contaminated surfaces e.g. medical devices
what are the modes of horizontal transmission?
a. Contact: direct, indirect, vectors
b. Inhalation: droplets, aerosols
c. Ingestion: faecal-oral transmission
what is vertical transmission?
mother to child, before or at birth
Describe how micro-organisms cause disease?
Exposure –> adherence –> invasions –> multiplication –> dissemination (spreading, widespread
what are virulence factors?
a. Exotoxins: cytolytic, AB toxins, superantigens, enzymes
b. Endotoxins
what are the different forms of host cellular damage?
direct, consequent to host immune response
what are disease determinants of a pathogen?
a. virulence factors: degree of damage
b. inoculum size: amount of material containing pathogen to begin with
c. antimicrobial resistance
what are disease determinants of a patient?
a. site of infection e.g. surgical site, neonates, elderly
b. co-morbidities e.g. diabetes
how do you identify if a patient has an infection from history?
- Symptoms: focal (neurological), systemic, duration
* Potential exposures
what type of examination do you carry out to determine if your patient has an infection?
organ dysfunctions
what are the types of investigations required to carry out?
specific
supportive
bacteriology
virology
what are supportive investigations?
o Full blood count: neutrophils, lymphocytes (lack of WBC)
o C reactive protein (high in infections)
o Blood chemistry: liver & kidney function tests
o Imaging: x-ray, ultrasound, MRI
o Histopathology
what are bacteriology investigations?
o Specimen types: swabs, fluids, tissues
o Microscopy: bacterial cells (gram stain), patient cells e.g. CSF
o Culture
o Antibiotic susceptibility
what are virology investigations?
o Antigen detection – the virus
o Nucleic acid detection (DNA/RNA)
o Antibody detection – patient’s response
