BASIC MICRO Flashcards
Which spirochete can you identify with a Giemsa stain?
Borrelia
What stain uses carbol fuschin?
Zeehl Neelsen for acid fast organisms
What are the 7 catalase positive organisms?
Pseudomonas, Listeria, Aspergillus, Candida, E. coli, S. aureus, and Serratia
What 5 bugs have AB toxins?
C. diphtheriae (tropic for heart/nerves), Pseudomonas (exotoxin A), ETEC heat labile toxin (heat stable is NOT AB toxin), Vibrio cholerae, B. pertussis (the pertussis toxin)
Which bacteria contains a toxin that cleaves phospholipid C causing myonecrosis and hemolysis?
Clostridium perfringens; Alpha toxin
What lab test is used to test for Rheumatic fever?
Antistreptolysin O antibodies = “STREP WAS HERE”
What is the difference between F(+) plasmid and Hfr?
In F(+) ONLY plasmid (i.e. extrachromosomal DNA) can be transferred? In Hfr, BOTH plasmid and nearby CHROMOSOMAL DNA can be taken up by the copulating bacteria
What is generalized transduction?
When a lytic phage infects a cell and accidentally packages some bacterial DNA into its capsid and then transfers that to another bacterium
What type of transduction is a “packaging event” which type is an “excision event”?
Packaging event = generalized; Excision event = specialized
What toxin does Staphylococcus aureus use to cause food poisoning?
Enterotoxin
What agar do you grow fungi on?
Saboraud dextrose agar
Where will you find genes for A) endotoxin B) exotoxin
A = bacterial genome as LPS is an essential gene B) on plasmid or bacteriophage because these are accessory genes
What is the 100 day cough?
Pertussis
Which ETEC toxin decreases water and NaCl reabosorption from the gut?
Heat stable (activates guanylate cyclase)
How does Lipid A (of LPS) cause DIC?
by activating tissue factor
What general kind of bacteria will have a positive quellung reaction?
Encapuslated bacteria (Quellung test is an anti-capsular antibody)
What toxin overactivates adenylate cyclase BY INHIBITING Gi?
Pertussis toxin
What 4 bacteria contain virulence factors that inhibit protein synthesis?
Pseudomonas and Corynebacterium (inhibit EF-2) and Shigella nad EHEC (“nick” the ribosome by blocking addition of adenine into rRNA)
What phase of the bacterial growth curve do penicillins and cephalosporins affect? WHY?
The exponential/log phase; this is where peptidoglycan is actively being made, since these are Beta-lactams, this is the only time they can actually kill bacteria (when they are dividing)
What effect will adding deoxyribonuclease to a medium have on the process of transduction?
Nothing. Transduction involves the transfer of DNA via bacteriophages, thus the DNA will be located within the viral capsid, NOT in the media as in transformation and therefore it will not be degraded
What agar do you use for Neisseria species?
Thayer Martin agar (VPN agar: vancomyin, polymyxin, and nystatin)
On what agar will E. coli grow in metallic green colonies?
EMB = Eosin methylene blue
Where are you likely to find beta lactamases in a gram negative bacterium?
In the periplasm which is a space between the cytoplasm and the outer membrane
What enzyme can you add to a medium to prevent transformation from occuring?
Deoxyribonuclease (cuts up DNA); transformation = uptake of free DNA
What is the dye in a Ziehl Neelsen stain?
Carbol fuschin
How do you know if a bug is a lactose fermenter based on its growth on ___________ agar?
Pink colonies on MacConkey agar
What cytokines are induced by LPS?
TNF and IL-1
What is Regan-Lowe agar used for?
Bordatella pertussis
Where will you find endotoxin?
Endotoxin is contained in the outer membrane of gram negatives
What is Loffler’s media used for?
Corynebacterium diphtheriae
What 2 toxins does ETEC possess?
HEAT LABILE: activates adenylate cyclase and secretes chloride and H20 from gut. HEAT STABLE: overactivates guanylate cyclase and decreases H20 and NaCl resorption from gut
What toxin has a similar, and more severe, action to exotoxin A from Streptococcus pyogenes?
TSST-1; both are superantigens
What 2 bacteria contains toxins that inactivate elongation factor 2?
Corynebacterium diphtheriae and Pseudomonas aeruginosa
Which 2 toxins overactivate adenylate cyclase in the gut and promote water and chloride excretion? What is similar about their structure?
Cholera toxin (permanently activates) and ETEC heat labile toxin (both are AB toxins)
What bacteria has yellow granules?
Actinomyces israelii (they arent really made of sulfur)
Why do you use conjugated vaccines?
Because if you only use the polysaccharide the only antibody produced would be IgM because a polysaccharide cannot be presented to Th cells
What 2 toxins cleave SNARE proteins?
Tetanospasmin and Botulinum toxin
What are pili and fimbrae made of?
glycoproteins
What are 8 urease positive organisms?
Cryptococcus, H. pylori, Ureaplasma urealyticum, Proteus, Nocardia, Klebsiella, S. epidermidis, S. saprophyticus
What are 5 bugs that have received their virulence factors via specialized transduction?
Shiga-like toxin of EHEC, Botulinum toxin, Cholera toxin, Diphtheria toxin, and Erythrogenic toxin of Strep pyogenes
What is Eaton’s agar used for?
Mycoplasma pneumoniae
What is specialized transduction?
When a lysogenic phage infects a bacterium and upon re-excision, accidentally takes some bacterial DNA along with it to transfer to another bacterium
What is the function of catalase for a bacteria?
It breaks down H202 before it can be used by myeloperoxidase to make bleach as part of O2-dependent killing by MO
What do you use to grow Legionella?
Buffered Charcoal Yeast Extract agar buffered with cysteine and iron
What is Bordet-gengou agar (potato) agar used for?
Bordatella pertussis
What agar do you use to grow Mycobacterium tuberculosis?
Lowenstein-Jensen agar
What toxin causes scalded skin syndrome? What is another name for this syndrome? What is the localized form called?
Staphylococcal exfoliative toxins (S. aureus); Ritter’s disease; Bullous impetigo
What is the screening stain for TB?
Auramine-Rhodamine
Which toxin in B. anthracis increases cAMP by mimicking adenylate cyclase?
Edema factor (edematous borders of the black eschar)
What 2 bacteria contain toxins that inactivate 60S ribosome by removing adenine from rRNA?
Shigella spp. and EHEC (shiga toxin and shiga-like/verotoxin)
To say that a bacteria is “competent” means that it is able to undergo ________-
transformation, take up naked DNA
What agar is used for Bordatella pertussis?
Regan-Lowe and Bordet-gengou (potato agar)
What kind of vaccine is the pneumovax? Prevnar?
Pneumovax = polysaccharide; Prevnar = conjugated (Strep pneumo)
What is the function of M protein? Who expresses it?
Inhibits phagocytosis; used by Streptococcus pyogenes
What is the primary toxin for Clostridium perfringens?
Alpha toxin; essentially = phospholipase C
What 2 stains can be used to identify Cryptococcus neoformans?
India ink and Mucicarmine
Which bacteria has an atypical capsule? What are most others made of?
Most are made of polysaccharide. Bacillus anthracis has a poly-D-glutamate capsule (amino acid capsule)
What 5 bugs can you identify with Giemsa stain?
Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium
What media do you culture H. influenzae on?
Chocolate agar (Factor V = NAD and Factor X = hematin)
Name 2 toxins that block the release of a neurotransmitter
botulinum toxin (blocks Ach release) and tetanospasmin (blocks GABA and glycine release)
What toxin is responsible for the edematous borders of the black eshcar in anthrax? What is the MOA?
Edema factor, increases cAMP by mimicking adenylate cyclase
What hardy structure in some bacteria is made of dipicolinic acid?
Spores
What plasmid contains the genes necessary to make a sex pilus?
The good old bacterial penis can be encoded for on the F(+) plasmid
What kind of vaccine can be used for bacterial exotoxins?
Toxoid vaccine
What is bacterial transformation?
The ability to take up naked DNA i.e. as in cell lysis
What 2 agars can you use to grow C. diphteriae?
Tellurite agar and Loffler’s media
Which bug expresses protein A? What does it do?
Staphylococcus aureus; binds the Fc portion of IgG which prevents opsonoization and phagocytosis
Which infectious disease do you use PAS to identify? What molecule does PAS stain?
Whipple’s disease; Glycogen
Which aspect of the cell wall is unique to gram positive organisms?
Lipotechoic acid
How are Quellung positive bugs handled by the immune system? Which kind of disease might lead to ineffective clearance?
Opsonized and removed by the spleen; asplenia, sickle cell anemia (autoinfarction)
Why are Chlamydia and Rickettsial species obligate intracellular?
They cannot make their own ATP
What kind of phage is involved in A) Generalized transduction and B) Specialized transduction
A) lytic phage B) lysogenic phage
What bug has a red pigment?
Serratia marsescens
Name 6 encapsulated bacteria (typical capsule)
Group B strep, Neisseria meningitidis (NOT gonorrhea), Haemophilus influenza B, E. coli, Salmonella, and Klebsiella
What 3 bugs can you identify with a silver stain?
Fungi, Legionella pneumophila, and H. pylori
Why does reactivation of TB tend to go to the apices of the lung?
They have the highest V/Q ratio because there is more ventilation. Since TB is an obligate aerobe, this is a good spot for them
What is Lowenstein-Jensen agar used for?
To grow Mycobacterium tuberculosis
Which kinds of bacteria have a periplasm?
Gram negative since they have an outer membrane. The space between the cytoplasmic and outer membrane is the periplasm
What kind of vaccine is likely to be used against a quellung positive bacterium?
Conjugate vaccine; Quellung positive = “has a capsule”
Name 3 bugs that possess IgA protease
S. pneumoniae, H. influenza, Neisseria
What is another name for VPN agar? What is V, P, and N?
Thayer Martin agar: V = vancomycin to inhibit gram positives, P = polymyxin excludes gram negatives aside from Neisseria, N = nystatin which excludes fungi (same MOA as amphotericin B)
What kind of transduction occurs when a lytic phage infects a bacteria and packages some of the bacterial genome into its capsid and (possibly) transfers this to another bacterium?
Generalized transduction (a PACKAGING event)
Which toxin from group A strep is a major contributor to its beta hemolytic activity?
Streptolysin O
What kind of transduction occurs when a lysogenic phage infects a bacterium and upon reexcision, takes some of the bacterial DNA with it?
Specialized transduction
Where does bacterial oxidative phosphorylation take place?
Cell membrane (they have no mitochondria)
What stain identifies H. pylori?
silver
Which ETEC toxin increases Cl and water excretion from the gut?
Heat labile: activates adenylate cyclase
What cytokines are induced by lipotechoic acid?
TNF alpha and IL-1
What is the difference between exotoxin A in Strep pyogenes and Pseudomonas?
P. aeruginosa’s exotoxin A is an AB toxin that inhibits elongation factor 2 = cell death; Streptococcal exotoxin A is a superantigen responsible for the sandpaper rash in Scarlett fever.
Why can’t you use aminoglycosides on anaerobic bacteria?
Aminoglycosides require oxygen to be taken into the cell
What occurs in bacterial transposition?
i.e. transposons or “jumping genes”, the genes excise themselves and may take flanking bits of DNA with them and reintegrate in other areas of bacterial genome
T/F: a polysaccharide vaccine would not produce antibodies
False. A polysaccharide vaccine would not be presented to T cells to facilitate class switching, HOWEVER, IgM antibodies could still be produced
What kind of bacteria would you expect to lack catalase and superoxide dismutase?
anaerobic–can’t handle the ROS generated from OX PHOS
Name 8 facultative intracellular bacteria
Salmonella, Brucella, Francisella, Legionella, Nesseria, Yersinia pestis, Listeria, Mycobacterium tuberculosis (anything ending in -ella is facultative intracellular and requires cysteine!)
