Introduction to microbiology Flashcards
categories of micro-organisms that cause infection
- bacteria
- viruses
- fungi
- prions
- parasites
common specimen types collected for culture, sterile sites.
- Blood
- CSF
- Lung
- Bladder
common specimen types collected for culture, non-sterile sites.
- Skin
- Nasopharynx
- Urethra
- Gut
diagnosis of bacterial infections using microscopy
Light microscopy can be used, stain varies:
- no stain to see pus cells or parasites
- Gram stain to see bacteria and yeast/fungi
- ZN or Auramine stain for mycobactria
Pros and cons of gram stain microscopy for bacterial identification.
pros: rapid
cons: not sensitive, can’t usually identify particular species
Pros and cons of bacterial culture for identification.
pros: sensitive
cons: slow
selective bacterial growth media
only grows a specific bacteria or doesn’t grow some species of bacteria
non-selective bacterial growth media
grows all bacteria
methods for identification of bacterial species
use observable characteristics:
- morphological (shape) using miscroscopy
- physiological (normal functions of the bacteria)
- biochemical (chemicals within and excreted by cells)
DNA based tests
sterile site
site in body that should normally not contain microorgansims
non-sterile site
site in the body that normally contains micro-organisms
Methods for detecting viruses
- molecular methods, real time PCR
- antigen detection
- serology to determine immunity
diagnostic principles in parasitology
- microscopy, looking for parasites, cysts and ova in faeces. Blood films for malaria.
- culture rarely possible
- serology sometimes useful
basic infection control measures
- wash hands before and after patient contact aswell as contact with patient’s immediate environment.
- swab stethoscope between patients
- isolation of patients, barrier nursing or source isolation
prions
infectious agents composed entirely of protein
