IAHI Block 2 Flashcards
(133 cards)
1
Q
Most species of bacteria use _____ for growth. Which ones don’t?
A
-glucose -clostridia, Legionella (amino acids) -leptospira (fatty acids)
2
Q
What are 7 important differences between prokaryotes and eukaryotes? Why does this make prokaryotes better at adapting to the environment?
A
- 30s/50s ribosomal subunits 2. extra-chromosomal DNA (plasmids) 3. single circular chromosome, non-membrane bound 4. Many genes can be encoded within a single operon (translation/transcription are coupled and translation of different proteins can happen at same time on single mRNA) 5. No mitotic apparatus/nuclear envelope 6. NO introns/exons 7. Only one type of RNA polymerase (as opposed to 3 for eukaryotes)
- easy to replicate and can horizontally share DNA
3
Q
Name 5 characteristics specific to gram positive bacteria.
A
- Thick, peptidoglycan outer layer, high amount of cross-linking 2. Can have flagellum (NO PILLI) 3. Teichoic acids in outer peptidoglycan layer (capsule) 4. Produces primarily exotoxins 5. More susceptible to antibiotics
4
Q
Describe the Gram Stain process:
A
(a) crystal violet; both purple (b) gram’s iodine; both purple (c) Decolorizer (alcohol/acetone); gram– will be transparent, gram+ will stay purple (d) Safranin Red; gram– will be pink, gram+ will stay purple
5
Q
Name 6 characteristics specific to gram negative bacteria.
A
- Thin, peptidoglycan middle layer, cross-liked to outer layer (little cross linking; more permeable); in periplasmic space 2. Can have flagellum or PILLI 3. Liposaccharides in capsule 4. Produces primarily endotoxins 5. Less susceptible to antibiotics 6. Double membrane layer (outer membrane is not very permeable due to porins/etc.)
6
Q
What is the basic unit of a peptidoglycan? What are the 5 amino acids, starting from the amino saccharide bond, that are on the subunit? Between which two amino acids does ___ cut for crosslinking?
A
- NAG-(ß1-4)-NAM
- penicillin binding protein (PBP)
- L-alanine, D-glutamine, L-lysine, D-alanine, D-alanine -Between D-ala-D-ala
7
Q
What does a lipopolysaccharide consist of (3 parts)? Which part elicits an immune response/used for diagnostics (due to its variability)? Which LPS is fever inducing?
A
(1) lipid (at outer membrane) (2) sugar with sugar core (polysaccharide) (3) O-antigen (polysaccharide) -O-antigen -Lipid A (binds TLR on immune cells; known as endotoxin; ex. P. aeruginosa)
8
Q
What structure stimulates innate immune response in gram+ bacteria?
A
lipoteichoic acid (PAMP)
9
Q
Pili and Fimbriae are polymers of ________, specific to the pathogen, and their function is to _____. They are found in gram _____ bacteria.
A
-proteins -adhere to eukaryotic cells and between bacteria (important for virulence) -negative
10
Q
Flagella are polymers of proteins and their function is to _____. They are found in gram _____ bacteria. Name 2 types of flagella.
A
-provide motility -G+ and G- (1) Pseudomonads = single polar flagellum (2) enteric bacteria - flagella over entire surface of cell
11
Q
Name the three types of secretion mechanisms. How do these virulence factors evolve?
A
(1) Type II = secrete protein across inner membrane (toxins out) (2) Type III = deliver toxins directly into host cells (3) Type IV = deliver DNA into host cells -gene duplication of flagellum genes
12
Q
What does a capsule consist of and what is its function? How can the virulent function of a capsule be used in medicine?
A
-polysaccharide (very virulent) or protein -function = to prevent host cell phagocytosis/opsonization by increasing size -to produce vaccines!!
13
Q
Before the vaccine was developed, what bacteria caused meningitis in the younger demographic? What does the vaccine consist of?
A
-Haemophilus serotype B (HiB); type of influenza -capsular polyribosylribose phosphate
14
Q
Haemophilus: (a) What is its reservoir? (b) Pathogenesis (c) What causes virulence? (d) Can you have asymptomatic carriers?
A
(a) humans only (b) nasopharynx = uncomplicated; only bad when gets into blood stream to cause meningitis (c) Type B polysaccharide capsule (ribose and ribitol); 5 other serotypes don’t cause infections (d) YES!
15
Q
Why can’t a child under 3 months contract HiB? When is HiB most invasive? Why?
A
-Still has maternal Ab’s = protective -Between 3 months and 3 years because humoral immune system hasn’t matured yet to produce Ab’s
16
Q
Why was the 1st generation Hib vaccine not effective for children under 18 months? What did the 2nd generation vaccine do differently?
A
-used purified polysaccharide (PRP) capsule which were poor immunogens, stimulated T-independent antibodies and had poor immunologic memory (humoral immune system not developed) -PRP protein conjugates (diphtheria toxoid) as an adjuvent for T-dependent immune response for sustained Ab production
17
Q
Name the bacterial shape of each.
A
A = cocci
B = diplococci
C = streptococci
D = staphylococci
E = micrococci (tetrad)
F = baccili (coccobaccili)
G = diplobaccili
H = streptobaccili
I = vibrio
J = spirochete
18
Q
Name some targets for antimicrobial agents. Why are these targets?
A
- ribosomes
- cell wall (peptidoglycan)
- gene products
- selective toxicity for prokaryotes
19
Q
How do you classify the species of a prokaryote? What 2 methods can you use to identify a species?
A
- by genetic relatedness and possession of similar physiological functions (because horizontal gene transfer)
1. molecular identification (look at hybridization/amplification of DNA); rapid, high accuracy, decreased selectivity
2. conventional diagnostics based on morphology and biochemistry; rapid diagnostics (sometimes)
20
Q
What are two types of Molecular Diagnostics for bacteria? Describe a real-life application of each.
A
- PCR; for organism difficiult to grow and isolate/one that produces toxin, like Clostridium difficile (amplify toxin)
- RFLP (restriction fragment length polymorphisms); use to see whether bacterial is nosocomial (isolates identical between patient and personnel) or community based (isolates different between patient and personnel); use gel electrophoresis
21
Q
Suppose Lane 1 is the isolated RFLP from the doctor and Lanes 2-4 are those of various patients with similar clinical symptoms. Is this bacterial nosocomial or community-aquired? How do you know?
A
All the isolates have different ID markers, meaning that they are community-aquired. If they were nosocomial, the doctor would have the same ID pattern as at least one of the patients.
22
Q
Name the 3 morphological determinants in order to ID a bacteria. Name the 3 biochemical determinants.
A
Morphological:
- colony morphology
- cell shape/Gram stain/Motility
- Presence of a capsule
Biochemical:
- ability to metabolize specific substrates
- production of specific end products (aerobic = CO2, H2O and energy efficient [ATP, NADH2] ; anaerobic = reduce NO3 to organic end products [NO2+, N2], little energy production, unique to microbes)
- antibiotic sensitivity
23
Q
Define the following terms and give an example of each:
(a) Aerobes
(b) Microaerophiles
(c) Facultative anaerobes
(d) Aerotolerant
(e) Anaerobes
A
(a) metabolizes O2; only grows in O2 conditions; ex) Mycobacterium tuberculosis, Pseudomonas aeruginosa
(b) metabolizes O2; only grows in low O2 conditions; ex) Helicobacter pilori
(c) metabolizes O2 when available, otherwise undergoes fermentation; ex) Escherichia coli
(d) ferments/grows in presence/absence of O2; ex) Lactobacillus
(e) ferments/grows only in abscence of O2; ex) Clostridium difficile, C. perfringens, C. tetani, C. botulinum
24
Q
How would you tell the difference between an aerobic bacterium vs facultative anaerobic bacterium?
A
Aerobic bacteria use cytochrome C as terminal oxidase wherease facultative anaerobic bacteria use cytochrome D; the difference in redox potential allows bacteria with cytochrome C to turn BLUE with an OXIDASE TEST
25
What is the NITRATE TEST? List the steps.
Diagnostic of whether a bacteria is anaerobic
1. add nitrite reagent = anaerobe will be BROWN and aerobe will be red
2. add zinc to brown tube = anaerobe will remain BROWN (+) and aerobe will remain red (-)
26
Most pathogens undergo fermentation. Why is this? Which pathogens make these final fermentation products as follows: (a) Lactate (b) propionate + CO2 & Butanol/Iso-propanol (c) Formate (pH low)--\> CO2 (g) + H2 (g)
- Gives them a selective advantage in environment; when make pyruvate from glucose there's only a net +2 ATP to go to fermentation product, but these bacteria don't need much energy to replicate (a lot of potential energy stored in lactate)
(a) Streptococcus
(b) Clostridium
(c) Enterobacteriaceae
27
How would you tell the difference between E. coli/Salmonella and Shigella/S. typhi?
CARBOHYDRATE FERMENTATION TEST aka ACID/GAS TEST = Grow each in sugar and test for acid and gas due to production of formate dehydrogenase (E. coli/Salmonella); (+) test will show yellow bacteria and gas at bottom of test tube (see right tube)
NOTE: E. coli uses formate DH to decrease pH in stomach (Formate --\>CO2 + H2)
28
Define psychrophilic, mesophilic and thermophilic. Which class has the most human pathogens?
Psychrophilic = grows -5-10 degrees C
Mesophilic = grows 10-45 degrees C (MOST PATHOGENS)
Thermophilic = grows 25-80 degrees C
29
Most bacteria tolerate only _______ salt conditions. Wherease ______ bacteria require up to ______ salt for growth. For selective media, use ______ to select for G+ bacteria. Name a G- bacteria that needs high salt to grow.
- moderate
- halophilic
- 30% (5 NaCl M equivalent)
- Mannitol salt media (ex: G+ = Staphylococcus aureus)
- *Vibrio cholerae*
30
Sporulation is a unique property of ______ bacteria, such as [give examples and types of spores]. Spores will form in the absence of \_\_\_\_, and sporulation is an example of ____ differentiation.
- G+
- Bacillus (aerobe) = subterminal spore [endospore], Clostridium (anaerobe) = terminal spore
- C, N or P
- unicellular (due to asymmetric cell division)
31
How do you inactivate a spore?
Wet heat, 120 degrees C, 20 min (AUTOCLAVE)
32
What are disinfectants? Antiseptics? How are antibiotics different?
Disinfectants = toxic to humans AND bacteria (bleach); nonspecific; used for inanimate objects
Antiseptics = toxic to bacteria, but too toxic for systemic use in humans (peroxides, alcohols); nonspecific; OK for topical use
Antibiotics = selective toxicity and not toxic to humans
33
Define bacteriostatic and bactericidal. Which graph represents which term? List antibiotics that belong in each class.
**Bacteriostatic** = inhibit growth of bacteria by targeting protein synthesis (must rely on immune system to eradicate bacteria); left graph
ex) Sulfonamides, tetracyclines, chloramphenicol, erythromycin, ethambutol, clindamycin, linezolid
**Bactericidal** = kill bacteria directly by targeting replication, DNA synthesis and cell lysis; right graph
ex) penicilin, aminoglycosides, polypeptides, rifampicin, isoniazid, cephalosporins, ciprofloxacin, metronidazole
34
What factors must you consider when choosing an antibiotic? (Name 3)
1. pharmacology/bioavailability; antibiotic needs to get site of infection
2. Spectrum of activity = (a) **narrow spectrum** is effective against small group of bacteria {i.e. aerobic G+}; important for GI because we have lots of natural flora (b) **broad spectrum** is effective against wide range of bacteria {i.e. G+ and G-}; important because if don't know infection, can treat to cover all bases (but be careful with GI side effects)
3. Antibiotic resistance (lack of susceptibility); all isolates of given bacterial species are NOT susceptible to the same antibiotics (therefore must know straintype and **ANTIBIOTIC SUSCEPTIBILITY PROFILE**)
35
In the context of antibiotic resistance, define Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) and when each is used. Additionally, name a type of antibiotic susceptibility test.
MIC = defines lowest concentration of antibiotic that inhibits growth (ask: Did it grow?)
MBC = defines lowest concentration of antibiotic that kills a defined proportion of bacterial population after specified time; antibiotic must exceed MBC (ask: Did they die?)
DISK DIFFUSION TEST = qualitative measure of susceptibility due to zone of inhibition; use discs of different antibiotics on plate of bacterial strain
36
To which discs is the bacteria resistant? To which discs is the bacteria susceptible? What 2 factors can cause antibiotic resistance?
Resistant = 2/4
Susceptible 1/3
1. Horizontal gene transfer (MDR strains!)
2. Spontaneous mutations (strong selection for growth with rare resistant mutants)
37
What are some adverse effects of antibicrobials. List the drug associated with the effect if there is one.
1. Toxicity = discoloration of teeth in children (tetracycline), auditory damage (streptomycin), anemia (chloramphenicol)
2. hypersensitivity = anaphylaxis (penicilin)
3. Alteration of normal microflora = antibiotic-associated diarrhea (endogenous C. difficile [G+] grows and produces exotoxins A and B/Pseudomembraneous enterocolitis)
4. Selection for Ab-resistance = renders antibiotics useless
38
Name the 3 ways bacteria overcome inhibition by antibiotics and name examples.
1. **Modification (inactivation) of antibiotic itself**; ex) ß-lactamases; modification of aminoglycosides/chloramphenicol
2. **Modification (reporgramming) of antibiotic target**; ex) point mutation in *gyrA, rpoB*, ribosomes, PBPs; alternative peptioglycan structure for vancomycin resistance
3. **Reduction of antibiotic concentration/prevent access to target**; ex) efflux pumps [tetracycline, macrolides], some with broad substrate specificity; altered cell envelope permeability via mutations in porins
39
What are the 4 peptidoglycan synthesis-targeting antibiotics. What does each do? Which kind of bacteria do these target? When are these Ab most effective?
1. **ß-lactams (penicilin, cephalosporin)** = bind penicilin binding proteins (PBPs) at D-ala-D-ala active site to inhibit cross-linking; have ß-lactam ring that mimics D-ala-D-ala; different R groups change bioavailability but not mechanism of action
2. **Vancomycin** = binds D-ala-Dala on peptidoglycan subunit chains to prevent PBPs from binding
3. **Bacitracin** = inhibits flipping of lipid carriers, carrying peptidoglycan subunits outside the PM
4. **Cycloserine** = inhibits peptidoglycan crosslinking by inhibiting precursors to D-ala-Dala --\> D-ala-Cycloserine (competitive inhibition)
- **G+** because G- has permeability barrier (OM) with porins
- during **bacterial growth** (making new cell walls); high bacterial specificity and low host toxicity
40
Primarily _____ bacteria have primary resistance to ß-lactam antibiotics with an enzyme called \_\_\_\_\_\_. Describe the mechanism of the enzyme. Some bacteria, like ______ code this enzyme in their chromosome and other code it on their plasmids.
- G-
- ß-lactamase
- Mechanism = cleaves ß-lactam ring; allows PBPs to work
- Pseudomonas aeruginosa
41
Define ESBLs. Where are they found, mostly?
extended spectrum ß-lactamases can cleave a wide range of different ß-lactam antibiotics
-G- bacteria
NOTE: porin mutation can also prevent ß-lactam entri in some G- bacteria by decreasing pore size/chemical composition
42
Primarily ______ bacteria can resist ß-lactam antibiotics due to mutations in their \_\_\_\_\_\_. How does this mechanism confer resistance and which common organism uses this type of ß-lactam resistance?
- G+
- Penicilin binding proteins (PBPs)
- ß lactams cannot mimic PBP binding sites anymore and so they will not bind to inhibit PBP activity
- methicillin-resistant *Staphylococcus aureus* (MRSA)
43
What would you give to a patient with a G- infection in addition to a ß-lactam antibiotic to help cure her infection? What is the mechanism behind this decision?
- ß-lactamase inhibitor (clavulanic acid, sulbactam, tazobactam)
- share structural features with ß-lactams so that ß-lactamases bind these and are inactivated, allowing ß-lactam antibiotics to bind PBPs more readily
44
Glycopeptides, like _______ tend to be most effective on _____ bacteria. Describe why. When would this medication be prescribed?
- vancomycin (HUGE!!)
- G+
- too big to get through porins of OM of G- bacteria
- for ß-lactam-resistant infections like MRSA or ß-lactam hypersensitivity
45
What is the mechanism behind vancomycin resistance? Where is this resistance found? Which bacterial strain specifically is associated with vancomycin resistance? Why is VRSA incredibly dangerous and how does it occur?
- change peptioglycan structure from D-ala-D-ala to D-ala-D-lactate so that vancomycin will not recognize binding site (loss of H-bonding!! and thus low affinity)
- plasminds or transposons (easily transferred)
- Enterococci in hospitals (VRE)
- because vancomycin is the choice antibiotic for MRSA and VRSA is MRSA + vancomycin resistance, which is incredibly difficult to treat; happened due to catheter with VRE horizontally transferring VR gene to MRSA
46
Bacitracin must be administered ______ because it is \_\_\_\_\_\_\_\_\_. Describe bacitracin's mechanism. Which bacteria are particularly susceptible to bacitracin?
- topically
- too toxic for systemic use (cause killing of GI flora)
- binds **pyrophosphate on lipid carrier** to block recycling of lipid carrier for peptidoglycan precursors (bactoprenol-P)
- Group A Streptococci (GAS)
47
Which 2 antibiotics target the cell membrane? Which type of bacteria is each specific for and what is the mechanism of each?
1. **Daptomycin** = lipopeptide, bacteriocidal; binds to and disrupts PM by poking holes in it and losing Vm; targets **G+**
2. **Polymyxins** (polymyxin B, colistin) = lipopetide, bactericidal; binds LPS in OM of **G- bacteria**, leading to disruption of both OM and cytoplamsic membrane by poking holes; high host toxicity --\> topical use only
48
Name 5 antibiotics that inhibit protein synthesis. What are their mechanisms and which type of bacteria do they work best on?
1. **Tetracyclines** = inhibit **30s** ribosomal subunit to **block the initiation of protein synthesis** (binding of aminoacyl tRNA to ribosome); bacteriostatic, broad spectrum; **G+/G-**
2. **Aminoglycosides** = irreversibly binds **30s** ribosomal subunit via **enzymatic modification** **to cause** **misreading** (incorporation of incorrect aa into growing polypeptide) and **premature release of ribosome** from mRNA; bactericidal, **G-** mostly (because can't go through G+ wall); ototoxic and nephrotoxic
3. **Macrolides** (erythromycin, azithromycin, chloramphenicol) = binds **50s** ribosomal subunit to **block protein elongation**; **G+** mostly; bacteriostatic often used in patient allergic to ß-lactams
4. **Clindamycin** = binds 50s ribosomal subunit to block elongation of proteins; **G+** mostly (not effective against G- aerobes); useful for community-aquired MRSA Tx; to treat toxin-producing bacteria, like *S. aureus*
5. Oxazolidinone (**Linezolid**) = new class of antibiotic; binds **23S rRNA on 50s subunit (unique) to prevent 70s initiation complex**; bacteriostatic; **G+**; oral availability but high $
49
Describe the 2 mechnaisms of resistance to tetracycline.
1. tetracycline effux pump to reduce [tetracycline] in bacteria; most common
2. mutation on ribosome; less common
50
Describe the resistance mechanism of bacteria to aminoglycosides.
emzymatic modification of antibiotic (aceyl, phosphoryl, etc. group) to prevent binding to 30s structure of ribosome; genes on plasmids/transposons
51
Describe the mechanism for macrolide resistance in bacteria.
1. enzyme modification (methylation) of 50s rRNA on **ribosome**; ***erm* methylase gene; erythromycin/clindamycin can't bind** (cross-resistance of different macrolides!!)
2. efflux pumps expel macrolides from cells
52
Describe the mechanism of resistance to chloramphenicol (macrolide).
Addition of acetyl group (via chloramphenicol acetyltransferase) to **antibiotic** in order to prevent ribosome binding
53
Describe the mechanism of linezolid resistance.
Point mutation in ribosomal components to prevent linezolid binding; **no cross-resistance** because binds different sit than either erythramycin or clindamycin
54
Which antibiotics target DNA replication, RNA synthesis and DNA repair?
1. **Nalidixic acid** (synthetic quinolone; 1st generation) = binds bacterial **DNA gyrase/topoisomerase** to inhibit replication and repair; PROBLEM: narrow anti-microbial spectrum and selective for resistant mutants
2. **Fluoroquinolones** (norfloxacin, ciprofloxacin, levofloxacin, 2nd generation) = bactericidal; broad-spectrum with binding **DNA gyrase/topoisomerase** to inhibit replication and repair
3. **Metronidazole** (\*prodrug) = in anaerobic environment, **radical is produced** to lead to toxic metabolite, damaging DNA; **anaerobic bacteria** (*C. difficile*!!)
4. **Rifampin** (rifampicin) = bactericidal; binds **ß-subunit of bacterial RNA polymerase** to inhibit RNA synthesis; PROB: rapid selection for resistant mutants
5. **Fidaxomincin** = bactericidal; **noncompetitive** inhibitor of RNA synthesis by binding **bacterial RNA polymerase**
55
Describe the 2 mechanisms of resistance to nalidixic acid (1st gen) and fluoroquinolones (2nd gen).
1. **point mutation in bacteral DNA gyrase** prevents antibiotic from binding
2. efflux pump
56
Describe the mechanism of rifampin resistance.
acquisition of **mutation in ß-subunit of RNA polymerase** that prevent antibiotic from binding
57
Which antibiotics target the tetrahydrofolate biosynthesis pathway? Describe the mechanism. What is a mechanism for resistance?
1. **Sulfonamides** = p-Aminobenzoic acid analogs in THF biosynthesis pathway to inhibit pathway
2. **Trimethoprim** = metabolic analog of dihydrofolate that **inhibits dihydrofolate reductase**
Resitance to Trimethoprim = acquisition of another gene encoding dihydrofolate reductase; the more DHFR copies, the more antibiotics you will need to overcome enzyme activity
58
Name 4 times when you should use antibiotics in combination.
1. Undetermined pathogen, like bacterial meningitis or bactermeia
2. Mixed infection caused by bacteria with different susceptibility profiles
3. To avoid delay emergence of resistant strains during long-term antibiotic therapy with slow-growing bacteria (like TB!)
4. Synergistic effects
59
Name two synergistic drugs that will block an essential metabolic pathway. Name the pathway.
- Sulfonamides and trimethoprim
- THF pathway
60
Name a drug that enhances the uptake of another drug; when would you use this?
penicillin (vancomycin) enhances uptake of aminoglycosides; G+ mostly (especially endocarditis)
61
Name a drug that may prevent the inactivation of another drug; for which type of bacteria would you use this?
Clavulanic acid inactivates ß-lactamase, allowing for ß-lactam antibiotics to work; usually for G- bacteria
62
Antibiotic antagonism can occur mostly with _______ and _______ antibiotics in general, as well as with two different _____ antibiotics due to general effect of AmpC ß-lactamases. Antibiotic \_\_\_\_\_, on the other hand, is when 2 agents together work the same as one alone.
- bactericidal
- bacteriostatic
- ß-lactam
- indifference
63
\_\_\_\_ cause antibiotic tolerance due to a physical barrier, growing mostly on exogenous devices, like heart valves. Which type of chronic infection is most common due to this phenomenon? What are 3 specific mechanisms for this antibiotic tolerance? Standard antibiotic susceptibitily measurements, like \_\_\_\_\_\_, doesn't work for this type of antibiotic tolerance.
- biofilms
- endocarditis
1. antibiotic therapy only kills planktonic (free-swimming) bacteria
2. fail to eradicate biofilm bacteria
3. after antibiotics withdrawn, bactera can disperse from biofilm and cause recurring infection
- MIC (minimum inhibitory concentration)
64
Bacterial chromosomes have only ONE origin of replication, called the \_\_\_\_\_. Bacteria can begin a second round of replication before the cell beings to divide. (T/F)
- Ori
- True!
65
On a plate, antibiotic resistant clones tend to be due to ______ rather than \_\_\_\_\_\_, which is more common in the human body. Why do there tend to be more replication errors in bacteria? Do most mutations confer a selective advantage?
- point mutation
- horizontal gene transfer
- less proofreading ability (about 1 mutation per 300 chromosome replications)
- NO!!! because could code for redundant amino acid codon (dif nucleotide) or not protein-codingn sequence of DNA
66
There is no natural species boundary for prokaryotes. Why is this?
1. promiscuous with DNA via transformation, conjugation, transduction
2. only need single organism in population to survive
3. certain genes provide selective advantage in particiular environments to outcompete or kill other organisms
4. Rapidly spread antibiotic resistance (ex. VRE to VRSA)
**\*\*\*Exchange of genetic material between bacteria ocurs with great frequency/efficiency outside and/or within a host\*\*\***
67
What are the 3 types of exchangeable genetic elements (MGE = mobile genetic elements) and what 2 types of genes do they usually encode?
1. **plasmids** = ds/ss; replicates independently of chromosome; circulsar/linear; single plasmids = F plasmids
2. **insertion sequences/Transposons** = linear DNA segment; jump from one site to another (cannot replicate on own) on bacterial chromosome/plasmid; have inverted terminal repeats (ITR) and transposase (tnp) enzyme
3. **Pathogenicity islands** = large segment of bacterial genome carried by plasmid/bacteriophage; need Type III secretion system; high G/C content, which differs genetically from majority of chromosome (can also encore adjerence factors, invsion genes, iron uptake systems, proetin secretion systems, toxins); cannot replicate by itself (host chrom/plasmid)
- encode virulence factors and antibiotic resistance determinants
68
Describe the 4 types of transposable elements and the mechanism they use to jump from place to place.
1. **Insertion sequences** = inverted repeat
2. **Composite transposons** = insertion sequences on either end + gene in the interior; (a) left island can transpose by itslef (b) right island can transpose by itself **(c)** TWO = both L and R islands can be cleaved and cary with it a gene
3. **TnA Family** = transposase expression gene regulation
4. **Mu Bacteriophage** = can carry transposable element
69
Explain how transposons can cause phase variation in Escherichia coli responsible for UTIs (UPEC). What is the advantage to having fimbriae and an advantage to having no fimbriae.
-UPEC: ther promotor sequence of fimbriae is located between two inversion sequences; if placed one direction, will transcribe fimA gene (advantage = adheres to epithelial cells of UT); if inverted, will not transcribe gene (advantage = avoid immune response); site-specific inversion--\>spontaneous
70
What does the F plasmid code? For what process is this used?
- sex pillus
- conjugation
71
What process, occuring in both G+ and G- bacteria, was illustrated in Griffith's S. pneumoniae experiement and Avery's S. pneumoniae experiment? Describe.
Transformation
- Griffith = Type R (nonvirulent) + heat-killed Type S (virulent) --\> Dead mice with Type S
- Avery = Type S + proteinases --\> +Type R = Type S; Type S + DNAases---\> +Type R = Type R only
72
T/F:
(a) In transformation, dsDNA is bound and processed to ssDNA before internalization
(b) Bacteria are naturally competent during G1 phase
(c) Stable inheritance of transformed DNA requires homologous recombination
(d) In conjugation, the donor loses its original genetic material that it donates.
(a) True!
(b) False--during growth
(c) True!
(d) False--donor copies its genetic material before it donates it
73
Define (a) lytic (b) lysogenic and (c) temperate phage. What is a transducing phage/transductant?
(a) **Lytic** = infects bacterium and genome is replicated independently of host genome; new progeny are made and lyse cells
(b) **Lysogenic** = phage genome integrated and replicated with bacterial genome; vertical transmission of phage due to binary fission
(c) **Temperate phage** = switch between lytic and lysogenic due to stresses causing excision of genomic material from host genome
- **Transducing phage** = during lytic replication, fragment of bacterial genome packaged into phage by accident; when this transducing phage inserts bacterial DNA into another bacterial host, stable recombination of different bacterial genetic material = **transductant**
74
Two virulence factors carried on a bacteriophage are ______ and \_\_\_\_\_. These are NOT examples of transduction because they are endogenous in the viral genome.
- cholera toxin (CTXø = Chloera toxin phage)
- Shiga toxin (Stxø = Shiga toxin phage)
75
What does Chloera toxin phage infect? Describe the toxin and effect on the host.
- ***Vibrio cholera***
- **Ctx = 5B:1A**
- B = binding to **ganglioside GM1**; A = internalized enzymatic activity to bind and **constituitively acitvate GPCR Gs∂ (AC on!!)** to enhance secretion of water and electrolytes in human host
- Other toxins: **Ace** = increases fluid secretion; **Zot** = involved in Vibrio cholerae invasion by acting to decrease intestinal tissue resistance
76
What does Shiga toxin phage infect? Describe the toxin and effect on the host.
Large, temperate bacteriophage that infects ***Shigella dyenteriae*** and enterohemorrhagic E. coli (**EHEC**)
- **Stx1 = 5B:1A** (also Stx2 = Shiga-like toxin)
- B = binding **G3b** glycolipid on PM of bacterial cell; A = translocated into cytosol from phagosome to RER and modifies ribosome acceptor site to **block protein synthesis**, killing the host cell
- clinical: severe diarrhea, hemorrhagic colitis, hemolytic-uremic syndrome (**HUS**)
77
How do EXTRACELLULAR bacteria resist killing by phagocytes? (7 ways)
1. invade regions not accessible to phagocytes (skin)
2. minimize inflammatory response
3. inhibit phagocyte chemotaxis (minimize recruitment of immune cells)
4. hide antigenic surface (capsule)
5. evade opsonization by complement antibodies via Ab or complement-cleaving enzymes
6. inhibit engulfment via capsule
7. kill/damage phagocytes via enzymes
78
How do INTRACELLULAR bacteria resist killing by phagocytes? (4 ways) List advantages/disadvantages and corresponding bacteria.
1. **secrete proteins that block phagosome maturation** (alter phagosome trafficking); ADVANTAGE = hide from immune system; DISADVANTAGE = must uptake nutrients from cytosol; ex. *Mycobacterium, Salmonella*
2. **survive inside phagolysosome** with low pH and produce enzymes to counteract reactive oxygen/nitrogen species; ADVANTAGE = hide from immune system; DISADVANTAGE = must uptake nutrients from cytosol; ex. *Coxiella*
3. **Secrete enzyme that degrades phagosomal membrane** to escape before it fuses with lysosyme; ADVANTAGE = access to nutrients; DISADVANTAGE = more susceptible to immune response, secretion of IL1/TNF∂; ex. *Rickettsia, Shigella, E. coli, Listeria*
4. **Alternative trafficking pathway** causes different destination of phagosome (like to RER to block protein synthesis--Chlamydia); ex. *Legionella, Brucella, Chlamydia*
79
What are the 5 functional steps of phagocytosis?
1. **Recognition** = TLRs recognize LPS (G-) or LTA (G+), or immune system components (complement, antibodies)
2. **Uptake via reorganization of PM**
3. Maturation via series of steps that cause fusion with endosomal vesicles (level of pH declines from early to late endosomes; phagolysosome has pH of 4-5)
4. **Killing by lysosomes**; via oxygen dependent and oxygen independent killing
5. Antigen presentation on MHC II
80
How do bacteria evade host cell recognition? Give some examples of mechanisms and corresponding bacteria.
(a) change antigen presentation (outer surface proteins); Borrelia recurrentis, Borrelia burgdorferi
(b) phase variation of pili; **FimA** expression with EHEC
(c) mask epitopes/ability to evade certain receptors (ex. mannose receptor) via capsule (G- and some G+)
81
What are the 3 ways intracellular bacteria are phagocytosed? Give corresponding example pathogens.
(a) usually **passive with Mø**; ex. *Rickettsia*
(b) unless **actively elicited by some bacteria with nonphagocytic (EC) cells** via Type III enzymes; ex. *Salmonella typhimurium*-major membrane perturbations (G-),* Listeria monocytogenes*-minor membrane perturbations (G+)
(c) or **special active phagocytosis of Mø**; ex. *Legionella pneumophila*- coiling (G-), *Francisella tularensis*-looping
82
\_\_\_\_\_ phagosomes have more H+ ATPases/Rab7/LAMPs. _____ are the cytoskeletal components that allow maturation of phagosome from periphery to perinucler region.
- Late
- Microtubules
83
Name 3 oxygen-dependent lysosome killing mechanisms and 3 oxygen-independent killing mechanisms.
**O2-DEPENDENT:**
1. iNOS to generate nitric oxide radical
2. NADPH oxidase (NOX) to generate superoxide radical
3. MPO (in neutrophils) to general HOCl (bleach)
**O2-INDEPENDENT:**
1. H+ ATPases, causing low pH
2. Lysozymes
3. Defensins to poke holes in bacterial membranes
84
What are some consequences of bacterial ingestion by macrophages?
1. Tissue injury (hydrolytic enzymes, radical-producing enzymes, damaging own tissues)
2. TNF∂/IL-1 lead to fever, wasting and septic shock
3. Chronic inflammation/autoimmune disease
4. Mø can act as "Trojan Horse" where bacteria hide in them then disseminate in other tissues
85
Activated macrophages are amenable to bacteria-induced modulation. (T/F)
FALSE!!!
## Footnote
**Activated macrophages are NOT amenable to bacteria-induced modulation!!!**
86
Define (a) saprophyte (b) commensal (c) opportunistic pathogen (d) pathogen; list corresponding bacteria
(a) **Saprophyte** = no associated with disease (most bacteria); ex. *Bacillus*
(b) **Commensal** = lives in association with host, mutually beneficial; ex. *Staphylococcus*
(c) **Opportunistic** = causes disease in an immune/physical/chemical compromised host; ex. *Pseudomonas, Staphylococcus*
(d) **Pathogen** = organism capable of causing disease in immunocompetent host (virulence factors); ex. *Bacillus anthracis, Corynebacterium diphtheriae*
87
What are the 4 proprties of a sucessful pathogen?
1. Gain access into host (insult, ingestion, etc.)
2. Colonize specific host tissue (tropism)
3. Resistant host defense system (either nonspecific or adaptive immunity-evading, like a capsule)
4. Damage host via (a) **invasiveness** at site where enters host or (b) **toxigenicity**, most of the time systemically
\*\*\*\*Pathogen may be toxic but not invasive (*Corynebacterium diphtheriae*), insvasive but nontoxic, or invasive AND toxic\*\*\*\*\*
88
What is a toxoid? Why is it important medically? If a bacteria produces a toxin, how do you treat the patient? Name a couple strains of bacteria whose pathology is due to toxins only.
Toxoid = chemically (formalin) inactivated toxin that retains immunogenicity; ex. Diphtheria
- important to generate a vaccine for that particular toxin, creating anti-toxin antibodies
- Goal of Tx is to neutralize the TOXIN (rather than the bacteria); treat with protein synthesis inhibitors (aminogycosides)
- Pertussis, cholera, ulcers (H. pylori), Shiga, botulinum, tetanus
89
At what ages do children get the DTaP vaccine? What does DTaP stand for? What other combinations of the vaccine are there and when are they used?
- FIVE TIMES = 2 months, 4 months, 6 months, 15-18 months, 4-6 years
- **DTaP** = Diphtheria toxoid, Tetanus toxoid, acellular Bordella pertussis
- **DT** = diphtheria toxoid, tetanus toxoid; used for children with allergies/reacivity to pertussis (DTaP)
- **Td** = Tetanus toxoid, diptheria (reduced dose); used as booster shot every 10 years or after exposure to tetanus
- **Tdap** = tetanus toxoid, diphtheria (reduced dose), acellular B. pertussis (reduced dose); used for pertussis booster (11-18 yo and 19 yo+ should get this) and 3rd trimester in pregnancy to boost maternal antibodies
90
Why is toxoid diphtheria used as a carrier for *Haemophilus influenzae* type B polysaccharide protein?
Conjugated vaccine causes the immune system to make a **T-CELL DEPENDENT IMMUNE RESPONSE** (IgM--\>IgG) by activating plasma cells for longer period of time
91
What were the causes of the diphtheria outbreak in the Newly Independent States of the former Soviet Union after the Cold War? How was this situation ameliorated? What is the moral of the story?
- Originally Russia vaccinated everyone for diphtheria; when Soviet Union broke up into separate states, (a) less vaccination (deterioration in health infrastructure) caused (b) increased amt of susceptible individuals in population due to migration
- WHO stepped in to vaccinate people in these states in 1995
**MORAL: CONTINUED VACCINATION IS REQUIRED TO CONTROL DISEASE!!**
92
Anaerobes have low amounts of superoxide dismutase (resulting in H2O2) to remove O2 radicals and thus low amounts of ______ (making H2O and O2 gas). Anaerobes generally lack \_\_\_\_\_\_\_\_, using fermentation metabolisms instead.
- Catalase
- Cytochromes
93
Which (above/below) is *Bacteriodes fragilis* and which is *Clostridia perfringens* in this catalase test? How do you know?
Bacteriodes fragilis = above because G-, catalase +
*Clostridia perfringens* = below because Clostridia are G+, catalase -
94
Where do **anaerobic G-** pathogens infect? Why are they foul-smelling? Give an example of a G- bacili that is a common inhabitant of the bowel. What is special about this bacterium?
infection sites = colon, mouth, skin
foul-smelling due to short chain, aromatic fatty acids produced during fermentation
-ex. *Bacteriodes fragilis*; **aerotolerant**!!, so it encodes catalase and superoxide dismutase
95
*Bacteriodes fragilis *is often isolated in mixed bacterial infection with a G+ anaerobic cocci (especially in intra-abdominal abscesses). Name this bacterium.
*Peptostreptococcus*
96
What kind of selective medium is this that the bacterium can produce a black precipitate (medium contains bile and gentamicin)?
Bacteroides bile-esculin agar
(hydrolyzes esculin to produce black precipitate)
97
What are the two types of *Clostridia botulinum* toxins used in medical therapies? Which serotypes are they? What are they used for and why?
1. Botox = Serotype A
2. Myoboc = Serotype B
- used for neurological spasms and cosmetics because have specificity to SNAREs on neurons
\*\*BOTULINUM IS MOST POTENT TOXIN FOR HUMANS!\*\*
98
A patient comes in with an abnormal eyelid twitch and functional blindness. You treat them with BoNT to stop spastic paralysis. What disease do they have?
Blepharospasm
99
An immunocompromised patient on antibiotics is complaining of perfuse diarrhea and general GI pain. The endoscopy reveals this and PCR tests positive for Toxin A and Toxin B. Which bacteria is this?
*Clostridia difficile*
100
A small kid stepped on a sharp stick and punctured his heal. Not thinking it was a big deal, he put a bandaid on it and went about his way. A couple hours later, the kid comes to the ER with the following (see picture). Which pathogen is this? What is the toxin causing this clinical showing?
*Clostridia perfringens*
∂ toxin
101
Instead of LPS, what does the G- *Neisseria meningitidis* have? What does this virulence factor, specifically, cause in the host? What can antibodies to normal flora do?
lipooligosaccharide (LOS)
- vascular damage, inflammation of vessel walls, thrombosis, intravascular coagulation, meningitis
- protect against N. meningitidis
102
Where is the Meningitis Belt? What bacteria and serotype is most associated with these epidemics? When do these epidemics usually occur?
- sub-Saharan Africa
- N. meningitidis; serotype A
- Dry season (June-Dec); every 8-12 years
103
A 6 yo female comes into the ER complaining of headache, neck stiffness and previously tiny red dots on her legs. Upon examination, she has hyperreflexia and purpura on her legs (petechiae that have coalesced--see picture). What caused the purpura? What is your diagnosis and treatment?
- Sloughing off of LOS (lipooligosaccharide) caused inflammatory reaction
- Meningitis due to N. meningitidis
- Tx with penicillin (broad range antibiotic)
104
Why was it difficult to create a vaccine for N. meningitidis serotype B? What is the new vaccine called?
because the group B polysaccharide is a homopolymer of sialic acid, which is antigenically similar to fetal neuronal tissues, so there would be cross-reaction!! (greater serotype B meningitis in children/infants!)
-4CMenB (Bexsero)
105
What are the 3 properties of N. gonorrhae's PorB? What other virulence factors have antigenic variation?
1. interferes with neutrophil degranulation
2. facilitates bacterial invation (transcytose to subepithelium)
3. resistance to complement (serologic variation)
- pilli & Opa proteins (localized infections) that bind non-ciliated epithelial cells
106
What is ophthalmia neonatorum? What can you do to prevent it?
it is a purulent ocular infection acquired by neonate at birth due to maternal N. gonnorhea; cornea is an epithelial surface and N. gonnorhea infects epithelium, causing inflammation and damage
-you can prevent this by treating prophalactically with antibiotics
107
What is the #1 transmitted STI? #2? How would you definitively tell these two STIs apart?
#1 = Chlamydia
#2 = Gonnorhea
-PCR!! Very difficult to tell apart otherwise
108
About _____ of women have asymptomatic *C. trachomatis* infections and ____ of men have asymptomatic *C. trachomatis *infections. Why is this a problem?
- 80%
- 20%
- easily transmitted because people don't know they have it
109
A young caucasian male (IMPORTANT) comes into the orthopedist's office complaining of polyarthritis. After asking some questions, the orthopedist realized the patient had unprotected sex recently and has been complaining of "discharge" coming out of his penis. You diagnose him with Reiter's Syndrome. What is the bacterial pathogen?
*Chlamydia trachomatis*
110
What pathogen can cause chronic conjuctivitis that can eventually lead to loss of vision? Where is this endemic?
* Chlamydia trachomatis* (Inclusion conjunctivitis); serotypes A, B, Ba and C
- endemic in developing world with poor hygiene and overcrowded areas
111
What is the disease name of the clinical presentation (picture) caused by Chlamydia trachomatis?
Lymphogranuloma venereum (LGV) = swollen inguinal lymph nodes
112
What is the major genetic difference between Intermediate Vancomycin Resistant S. aureus (VIRSA) and VRSA?
- VIRSA is due to prolonged treatment of MRSA with vancomycin, causing point mutations in the CHROMOSOME of MRSA, causing change in cell wall physiology; this results in **vertical antibiotic-resistance gene** transfer
- VRSA is due to the **horizontal transfe**r of VR-gene on Enterococcus (VRE) plasmid; Enterococcus is indogenous flora
113
What is the name of this test? What does this test show?
**Antibiogram** = analysis of antibiotic sensitivity locally
114
What is Lancefield typing in the context of Streptococci?
It classifies carbohydrate cell wall antigens for ß-hemolytic Strep strains (pyogenes, agalactiae, dysgalactia, anginosus)
115
Define the 3 hemolytic patterns of bacteria that grow on agar containing red blood cells. Which is most virulent?
1. ∂-hemolytic = partial hemolysis, "greening" (S. pneumoniae)
2. ß-hemolytic = compete clearing; MOST VIRULENT (S. pyogenes)
3. gamma-hemolytic = no change in RBCs
116
What is the cause of glomerulonephritis and rheumatic fever with a S. pyogenes infection? When would these clinical symptoms occur?
Host adaptive immune system response; occurs weeks after primary infection
117
A 20 yo patients comes into the ER with a poitive Nikolsky sign (picture shown), severe pain due to large bullae and erythroderma. Patient says she just began a new medication (allopurinol) 3 days ago. Why would you diagnose this patient with TEN (toxic epidermal necrolysis)? If the patient had not been taking new meds, but instead had fallen and scraped her knee, how would your diagnosis change?
The two diagnoses in the Dxx would be TEN and Staphylococcal scalded skin syndrome (caused by exofolatin proteins ETA/ETB = degrade desmoglein-1 in kaeratinocyte-epidermis layer); TEN does not need an epidermal insult because it is an allergic reaction (1st scenario); However, if patient fell and scraped her knee AND was not on new meds, it is most likely due to Staphylococcus aureus, which would produce ETA/ETB (2nd scenario)
118
What is Panton Valentine Leukocidin (PVL) toxin and what type of infection is it associated with? What are the clinical symptoms?
PVL is a ß-pore forming toxin that causes necrotizing fasciitis, usually correlated with **community acquired MRSA**
-Other symptoms: pneumonia, **thrombolitis**, spetic arthritis, abscesses, heart murmurs, endocarditis, etc.
119
Which part of the GI system absorbs the most water in digestion? What causes diarrhea? Would you want to use anti-motility drugs to help cure GI infections? The ____ the pH of the stomach, the more infections you are prone to get.
Small intestine!! (about 90%)
- when water is not absorbed due to disruption of GI physiology
- NO!!! would increase susceptibility of infection to spread to other parts of the body and/or prolong infection
- higher (more alkaline)
120
What drives the maturation of the mucosal immune system? What is the most powerful host defense mechanism in the GI tract?
- The normal GI flora = teaches the immune system which bacteria are good and which are bad
- The normal GI flora!! To outcompete pathogenic bacteria
121
A pregnant lady eats a canteloupe that she cut and stuck in your refrigerator 4 days ago. She develops gastroenteritis, which she thinks is just an awful bout of morning sickness at first, but she deveops a fever and flu-like symptoms. What bacterial strain was she infected with and how many months pregnant is she?
* Listeria monocytogenes*
- in her 3rd trimester (cellular immunity impaired)
122
There once was a cook named Mary, Typhoid Mary. She carried with her *Salmonella typhi* and gave it to anyone she served food to. Upon autopsy (after a lengthy excommunication/isolation/prison scenario), where was the *S. typhi* located and how did this cause chronic infection w/o antibiotic treatment?
Typhoid Mary had a chronic infection in her gall bladder, causing her to shed *S. typhi* in her feces. Clearly she wasn't hygenic because she passed on the bacteria to those she served food to. She wouldn't necessarily have "typhoid fever" symptoms if bacteria was isolated in gall bladder
123
E coli has many different types (EHEC, ETEC, EPEC, UPEC, etc.). These strains are \_\_\_\_\_\_% different from each other. Describe how EHEC attaches to the epithelial layer of the GI tract. What secretion system(s) does it use?
25%
- EHEC uses Type III secretion system to inject Tir receptor protein into host enterocyte; it can then bind Tir on enterocyte via intimin (EHEC membrane protein)
- EHEC also has a Type II secretion system, excreting Stx1, Stx2 or both (most virulent)
124
What is HUS? What bacteria causes this and by what mechanism?
HUS = hemolytic uremic syndrome; *Enterohemorrhagic E. coli* causes this due to production of Shiga toxins (Stx1/Stx2), which bind GB3 proteins on host cells. GB3 receptors are abundant in the kidney, and so a systemic EHEC infection could cause permanent renal failure
125
A 58 yo male comes into clinic complaining of bloody diarrhea about 3 days after eating BBQ chicken during a 4th of July celebration. A colonoscopy reveals the following picture of flat mucosal ulcers and stool sample showed S-shaped bacteria and RBCs/WBCs. (The bacteria was difficult to culture due to its higher incubation temperatures.) Which bacterial strain is this and what toxin does it produce? As a physician, what autoimmune disorders would you be on the lookout for following this infection?
* Campylobacter jejuni*
- toxin = cytolethal distending toxin (**Cdt**), which stops cell division in host cells
* -*Guillain-Barre syndrome and reactive arthritis
126
What two gene loci does *H. pylori* have to have in order to produce peptic ulcers? What percentage of infected individuals are asymptomatic for *H. pylori*? Why? What kind of cancer(s) is associated with *H. pylori* infection?
First locus: **Type IV secretion** = injects **CagA** (big protein) into host cells to induce/enhance txn of IL8 release; also induces pedestal formation that disrupts GI epithelium
Second locus: **VacA** = exotoxin that forms anion-specific channels and large vacuoles in host cells that alter tight junctions and increase GI erosion
- 70-80%; because their *H. pylori* strains have either one locus, the other locus or no loci
- gastric adenocarcinoma/gastric B-cell lymphomas
127
The earthquake in Haiti caused the destruction of infrastructure in Port au Prince. Devasting, many people became violently ill with an osmotic diarrhea, excreting over 20L of fluid per day about 2-3 days after eating food containing fecal matter. This rice-stool diarrhea is indicative of which strain of *V. cholerae*? Be specific. Also, describe the mechanism of the toxin causing this terrible disease. If you were to culture this bacteria, what type of plate would you grow it on?
- Serotype O1--El Tor biotype
- Cholera toxin = A:5B toxin that ADP-ribosylates GCPR to constiuitively activate AC--\>the increase in cAMP causes excretion of Cl- from the CFTR channel in the GI tract and thus massive water efflux
- Mannitol agar because it needs NaCl to grow!
128
Why is it difficult to control TB infections? (Name 4 ways) What causes a latent infection to be reactivated? The majority of reported cases of TB are thought to be a cause of reactivation rather than newly acquired infections (T/F).
1. Movement to metropolitan areas causes more exposure
2. increase in MDR and XDR strains (also TDR strains)
3. Difficulty supporting those infected
4. Lack of new antibiotics for treating TB, especially LATENT TB (antibiotics tend to work of bacteria that are growing)
- Immunocompromised/decrease in cytokines--especially HIV!! (entanercept = TNF∂ inhibitor)
- **TRUE!!!**
129
What is the Mantoux test? What bacteria is it testing for and what happens if it is positive?
- intradermal PPD test (cell wall components) for M. tuberculosis
- If it is positive, that means you have either an active or latent infection, or you have been vaccinated for TB. An x-ray will determine if you have an active infection.
130
The following are pictures of acid-fast staining procedures. Identify the three types of staining for *Mycobacterium tuberculosis*. Why do you need to use this procedure instead of a Gram stain?
(a) Carbol Fuschin
(b) Ziehl-Neelsen
(c) Auramine Rhodamine (immunofluorescene)
- Because lots of mycolic acids (long FA chains) make it difficult to Gram stain; must visualize with another technique
131
The bacteria being identified is *Legionella pneumophilia*. What are the two methods of identification (be sure to describe the TYPE of media on the right).
(LEFT) DFA = differential fluorescent antibody
(RIGHT) agar with buffered charcoal yeast extract; selective culture plate
132
What is a "professional multisystem pathogen"? Define (a) biological transmission and (b) vector competence.
Pathogen that can cause disease in immunocompetent hosts (most are vector-borne)
\*\*OVERCOMING PHYSICAL BARRIERS AND DISSEMINATION ARE ESSENTIAL TO THE BIOLOGY OF THE ORGANISM
(a) when a pathogen has a specific life stage in a vector
(b) the ability of a vector to acquire, maintain and transmit a pathogen
133
Define (a) transstadial and (b) transovarial transmission. Give examples of each.
(a) **Transstadial** transmission = when a pathogen is transmitted or maintained in the different life stages of the same individual vector; ex) Lyme disease, Anaplasmosis, Ehrlichiosis
(b) **Transovarial** transmission = when a pathogen is transmitted from one vector generation to the next; ex) Rocky Mountain Spotted Fever (transovarial *and* transstadial)
