Diagnosis Of Infectious Disease Flashcards
What are the 7 types of cultures?
- blood cultures
- throat cultures
- sputum cultures
- cerebrospinal fluid cultures (CFS)
- stool cultures
- urine cultures
- genital tract cultures
When are blood cultures most often performed?
When sepsis, endocarditis, osteomyelitis, meningitis or pneumonia are suspected
When are throat cultures primarily used?
To detect the presence of:
- group A beta-haemolytic streptococcui (Streptococcus pyogenes)
- diphtheria
- gonococcal pharyngitis
- thrush
What usually causes an acute sore throat?
Viruses - 90% of the time
When are sputum cultures performed?
When pneumonia, tuberculosis or lower respiratory infections are suspected
When are cerebrospinal fluid cultures performed?
When meningitis, primarily meningococcal meningitis, or other central nervous system diseases are suspected
When are stool cultures performed?
Primarily for diarrhoeal disease
If doing a culture for parasites may need to collect into a special container with PVA (polyvinyl alcohol) fluid to preserve the parasite
When are urine cultures performed?
Collected for symptoms of urinary tract infections or pyelonephritis. Culture can be tested immediately on a dipstick.
When is a genital tract culture performed?
When Neisseria gonorrhoea, Chlamydia trachomatis, Trichomonas vaginalis or Candida vaginitis is suspected.
- can be taken via speculum with a swab or by a self taken vaginal swab
What is an obligate anaerobe?
An organism that is able to, or can only, live in the absence of oxygen
What is an obligate aerobe?
An organism that grows in the presence of oxygen or requires oxygen for growth
What is an aerotolerant organism?
They do not require oxygen to grow however they can tolerate its presence and are not poisoned by oxygen
What is a facultative anaerobe?
Can grow with or without the presence of oxygen because they metabolise energy aerobically and anaerobically
What is a microaerophile?
Need oxygen because they cannot ferment or respire anaerobically however they are poisoned by high concentrations of oxygen.
What are some characteristics of anaerobes?
- smell bad
- cause some of the worse infections
Name 4 types of selective media?
- sheep’s blood agar
- chocolate agar (cooked blood)
- Eosin methylene blue agar, bacteria change colour on agar so no need for a microscope (E.coli is yellow and P.aeruginosa is green)
- Mannitol salt agar
What are ways to identify bacteria? (7 points)
- growth on media
- morphology and staining
- oxygen requirements
- nutritional requirements
- biochemical activities
- antibiogram
- pathogenicity
- genetics
What does immunoassay mean?
A biochemical test used to detect the presence or quantity of a specific substance by binding antibodies to antigens
Name 3 non-culture diagnostic methods?
- immunologic tests
- sandwich Elisa (EIA)
- fluorescent antibody test
What does PCR stand for?
Polymerase chain reaction
What does PCR do?
Used to amplify a segment of DNA (multiply it exponentially)
What are the different ways of testing? (4 points)
- culture
- microscopy
- immunoassay
- molecular methods (PCR)
