Microbiology Lab Investigations Flashcards
Is it reliable to obtain a specimen from a catheter for urine dipstick?
No, once the urine was in the catheter long enough, the bacteria will be there (almost in every catheter)
* can be done for ketones/glucose but no for infection
Is catheter-associated bacteria the same as UTI?
No. Almost all catheter urine specimens will grow bacteria.
- therapy not usually required, unless patient unwell or manipulation, surgery planned
What is category 3 laboratory?
Category 4 lab?
High-risk specimens laboratory (safety cabinets etc)
Category 4 lab - infectious diseases w do not have meds to treat for e.g. Ebola
What are the benefits of having normal bacterial flora?
- defence against invasive pathogens
- aid in the maturation of the immune system
- assist digestion
- role in toxin degradation
What microbe causes tonsillitis with exudates?
Group A Streptococcus
Case: young female with pyelonephritis. Her obs look septic.
What investigations would we do?
- blood cultures
- Mid-Stream Specimen of Urine (MSU)
- MRSA screen (all hospital admissions) -> nose and groin swab
What’s gram reaction?
Stain used to identify the organisms as gram positive/gram negative
Types of gram-positive bacteria
Types of gram-negative bacteria
What does the lab look for in microscopy inflamed joint? (joint aspirate)
- gram stain bacterie e.g. septic arthritis
- crystals (monosodium urate, calcium pyrophosphate)
Examples of microscopy of stool specimens for parasites?
Giardia, Cryptosporidia
What special staining technique is used for TB?
Alcohol/acid stain -> e.g. Ziehl-Neelsen or Fluorescent stain (Auramine phenol)
What is the specific antigen for C. Diff?
Glutamate dehydrogenase (GDH) in stools
What urinary antigens can be found in pneumonia?
- Urinary Legionella antigen
- Urinary Pneumococcal antigen
Where can viruses reproduce?
Only in a host cell
Examples of viruses that may show latency and persistence
- herpes simplex
- varicella zoster
- HIV
*latency = once we have a primary infection, that virus will stay with us. It will be kept under immune check
Example of a virus that will induce lifelong immunity after natural infection
Measles
IgM and IgG
What do they tell us?
- IgM - immediate response antibody
- IgG - gradual response antibody (after some time)
What do we look at in terms of antibodies in a pregnant woman exposed to Parvovirus?
We look at IgG levels
- if low avidity -> IgG that is recently formed
- high avidity -> IgG that is longstanding
What does IgG avidity tells us?
Avidity /pl lapczywosc, chciwosc/ = eagarness, enthusiasm
Avidity testing:
- low avidity -> IgG are only recently formed
- high avidity -> IgGs are longstanding
What is PCR commonly used for?
PCR = Polymerase Chain Reaction
- it is used commonly in viral diagnostics (e.g. Influenza, Measles, Herpes encephalitis)
Do we need to inform the laboratory when an urgent specimen requires processing?
Yes e.g. in CSF
Do we need to inform the laboratory when blood cultures are taken - to process it urgently?
No, because their nature is that they need time to grow within culture medium -> therefore these are started being processed shortly after arrival
* take 8 hours, to ‘next day’
