Flashcards in FA - Micro - Basic Bacteriology (2016) Deck (41):
Outer membrane of Gram(-):
1. Endotoxin: Lipid A induces TNF+IL-1/ O polysaccharide component antigenic.
2. Most OMPs are antigenic.
3. Porins: Transport across outer membrane.
1st-line lab test in bacterial identification:
Gram stain - Bacteria with THICK PEPTIDOGLYCAN LAYER retain ...?
CRYSTAL VIOLET DYE (Gram(+)).
Gram stain - Bacteria with THIN PEPTIDOGLYCAN layer turn ...?
RED or PINK (Gram(-)) WITH COUNTERSTAIN.
Chlamydia lack classic peptidoglycan because of ...?
DECREASED MURAMIC ACID.
Ziehl-Neelsen stain (carbol fuchsin) - Alternative:
AURAMINE-RHODAMINE STAIN for screening = INEXPENSIVE, more sensitive, but LESS specific.
Fluorescent antibody stain - Used to identify ...?
Many BACTERIA + VIRUSES.
Example of fluorescent antibody stain:
FTA-ABS FOR CONFIRMING SYPHILIS.
Properties of growth media:
1. Selective media.
2. Indicator (differential) media.
--> The SAME type of media can possess BOTH (or NEITHER) of these properties.
Favors the growth of particular organism while preventing growth of other organisms.
Indicator (differential) media:
Yields a color change in response to be the metabolism of certain organisms.
--> MacConkey agar contains a pH indicator; a lactose fermenter like E.coli will convert lactose to acidic metabolites --> Color change.
Special culture requirements - E.coli:
Eosin-Methylene blue (EMB) agar --> Colonies with green metallic sheen.
What serves as an antigen in vaccines?
Capsular polysaccharides + Protein conjugate.
Asplenics have ...?
DECREASED OPSONIZING ABILITY and thus INCREASED RISK for severe infections.
--> Give S.pneumo + H.flu + N.meningitidis vaccines.
Encapsulated bacteria vaccines:
Some vaccines containing polysaccharide capsule antigens are conjugated to a carrier protein, enhancing immunogenicity by promoting T-cell activation and subsequent class switching.
Encapsulated bacteria vaccines - A polysaccharide antigen alone cannot ...?
BE PRESENTED TO T CELLS.
1. PCV = Pneumococcal conjugate vaccine, ie, Prevnar.
2. PPSV = Pneumococcal polysaccharide vaccine with no conjugated protein, ie, Pneumovax.
H.flu type B - Vaccine:
Catalase-positive organisms - Catalase degrades ...?
H2O2 into H2O + Bubbles of O2 --> Before it can be converted to microbicidal products by the enzyme MPO.
In vivo biofilm-producing bacteria:
2. Viridans strep = S.mutans + S.sanguinis.
4. Nontypeable (unencapsulated) H.influenza.
Biofim of S.epi:
2. Prosthetic device infections.
Biofilm of Viridans strep (S.mutans, S.sanguinis):
1. Dental plaques.
2. Infective endocarditis.
Biofilm of P.aeruginosa:
1. Respiratory tree colonization in CF patients.
2. Contact lens-associated keratitis.
Biofilm of Nontypeable (unencapsulated) H.influenza:
Protein M - Shares ...?
Similar epitopes to human cellular proteins (molecular mimicry).
--> POSSIBLY, underlies the autoimmune response seen in acute rheumatic fever.
Type III secretion system - Also known as ...?
Type III secretion system - What is it?
Needle-like protein appendage facilitating direct delivery of toxins from certain gram(-) bacteria to eukaryotic host cell.
Bacterial genetics - Transformation - DNA that can be used?
ANY DNA CAN BE USED.
What inhibits transformation?
Adding DEOXYRIBONUCLEASE to environment will degrade naked DNA in medium --> NO TRANSFORMATION SEEN.
Example of TRANSPOSITION:
vanA gene from vancomycin-resistant Enterococcus to S.aureus.
Spore-forming bacteria - When?
At the END OF STATIONARY PHASE when nutrients are limited.
Spores - Features:
1. Highly resistant to heat and chemicals.
2. Have dipicolinic acid in their core.
3. Have no metabolic activity.
4. Must autoclave to potentially kill spores (as is done to surgical equipment) by STEAMING AT 121C for 15min.
AB toxin - Examples:
1. Diphtheria toxin.
2. Exotoxin A.
3. Shiga toxin (ST).
4. Shiga-like toxin (SLT).
5. Heat-labile toxin (LT).
6. Heat-stable toxin (ST).
7. Edema toxin.
8. Cholera toxin.
9. Pertussis toxin.
11. Botulinum toxin.
AB toxin is a 2-component toxin. Exception?
3-Component toxin for anthrax.
A is for ...
B is for ...?
B = Enabling BINDING + triggering uptake (endocytosis).
A = Active A component.
The active A components of the AB toxin are usually ...?
Endotoxin - LPS found in ...?
Outer membrane of gram(-) bacteria (both cocci + rods).
Endotoxin - LPS composed of ...?
1. O antigen.
2. Core polysaccharide.
3. Lipid A (the toxic component).
Endotoxin is released upon ...?
Cell lysis or by living vells by blebs detaching from outer surface membrane (vs exotoxin, which is actively secreted).