Microbiology Flashcards
Do bacteria have mitochondria?
No
What is an important action that takes place in mitochondria (in eukaryotes)?
Electron transport chain
Where is the site of bacteria’s electron transport chain?
Plasma membrane
What is the source of protein synthesis?
Ribosomes
What is the shape of bacteria’s DNA? Is it double stranded or single stranded?
Circular double stranded DNA
Release of LPS can cause what major life threatening syndrome? What are the symptoms/signs?
Septic shock!
Signs: Fever, hypotension, tachycardia, altered mental status.
Endotoxins will cause the body to release what molecules? What do they do and what symptom does it cause in shock?
Endotoxins cause macrophages to release: TNF-alpha, IL-1, and nitric oxide. They are all major VASODILATORS –> the hypotension found in shock.
What is one major difference between hypovolemic shock and septic shock?
Hypovolemic shock patient feels “cool and clammy” b/c of increased peripheral vascular resistance due to inc. adrenergic response. REPLACE VOLUME.
Septic shock patients will feel warm (fever) and may have flushed skin b/c of the vasodilatory response (release of TNF-alpha, IL-1, and NO).
What bacteria completely lack a cell wall?
Mycoplasma (cannot gram stain)
What special stain is needed to identify mycobacterium and why?
Contains mycolic acid - fatty acid in cell wall, causes it to be only weakly gram positive –> Must use ACID FAST STAIN to identify
Acid fast stain is used for what organisms?
Mycobacterium and Nocardia (only weakly acid fast); Cryptosporidium oocysts (protozoa)
Which organisms cannot be identified via gram stain?
“These Microbes May Lack Real Color”
- Treponema pallidum (too thin –> darkfield microscopy or fluorescent antibody staining needed to be seen)
- Mycobacteria spp. (lipids in cell wall; mycolic acid)
- Mycoplasma pneumoniae (lacks cell wall)
- Legionella pneumophila (intracellular –> immunofluorescent staining or silver staining needed)
- Rickettsia spp. (intracellular –> immunofluorescent staining needed)
- Chlamydia spp. (intracellular –> immunofluorescent staining needed)
PAS stains what structures well?
Sugars (ie glycogen in bacteria’s cell wall).
“PASs the SUGAR”
Remember: T. whippeli that causes Whipple’s disease is PAS positive (will stain bright red). Symptoms: weight loss, arthritis, abdominal pain, diarrhea.
Ziehl-Neelsen stains is used to detect what kind or organisms?
Acid fast organisms. Particularly good for mycolic acid.
What does india ink stain? What bacteria is this especially diagnostic for?
India Ink outlines the capsule of crytptococcus neoformans
What is silver stain used for?
Stains fungi, legionella, and H. pylori (appear black)
Your patient has PAS-positive macrophages on a small intestinal biopsy. What diagnosis should you consider?
Whipple’s Disease
How does selective media work?
Contains antibiotics to prevent growth of bugs other than the one of interest (i.e thayer-martin media). Thus only thing that grows on the media is the single bacteria of interest.
Thayer-Martin media is selective or differential media?
Thayer-Martin media is selective media (it contains antibiotics to prevent contaminating growth of other bugs other than neisseria gonorrhoeae or meningitidis).
Thayer-Martin media plates for what single bacteria and what antibiotics does it contain?
Neisseria gonorrhoeae or meningitidis.
“Very Typically Cultures Neisseria”
Antibiotics: Vancomycin (inhibits gram+), Trimethoprim + Colistin (inhibits gram- except Neisseria), Nystatin (inhibits fungi).
How does differential media work?
Causes bacteria of interest to change color so it can be differentiated from other bugs plated with it (ie McConkey’s agar –> lactose fermenting bugs will grow as pink colonies, the rest are colorless)
McConkey’s agar can be used to distinguish what types of bacteria? What type of media is this?
Lactose fermenting bugs (such as E.coli) will grow as pink colonies on this agar, while all other will be colorless. This is differential media.
What organisms can be distinguished on Giemsa stain?
“Certain Bugs Really Try my Patience”
Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium.
What is an alternative screening stain that can be used instead of Ziehl-Neelsen (carbol fuchsin)? What bacteria is this used for? Why is it used for screening?
Alternative is auramine-rhodamine stain for screening (inexpensive, more sensitive but less specific). This is used for acid fast bacteria (mycobacterium, nocardia, Cryptosporidium oocysts (protozoan)).