Question | Answer |
What kind of bacteria has metachromatic granules in its cytoplasm (polymerized phosphate)? | Diptheria |
Key difference between cytoplasmic and outer membrane of gram negative bacteria? | cytoplasmic membrane has selective transport proteins while outer membrane has porins that allow molecules to diffuse through. |
Name the bacteria that does not have a cell wall. | Mycoplasma |
What acid is unique to the cell wall of gram positive organisms? | Teichoic acid. |
What kind of antigen does flagella have? | H antigen |
What kind of antigen does LPS have? | O antigen |
What is located in the periplasmic space of gram negative bacteria? | betalactimases-can degrade penicillins. |
Why do gram positives stain purple? | higher peptidoglycan (mix of NAG and muramic acid) content in cell wall. |
Name two bacteria types that make spores | clostridia and bacillus, both large gram positive rods. |
What component of the spore coat is the source of resistance for the spore? | dipicolinic acid, proteinaceous outer coat. |
4 mechanisms of membrane transport-which one modifies the substrate? | passive, facilitated, active and sugar transports. Only sugar modifies the substrate. |
2 differences between bacterial and eukaryotic flagella? | In bacteria the flagella has no longitudinal fibers and no membrane coat. |
4 functions of cytoplasmic membrane | 1) oxidative enzymes
2)has enzymes for external cell wall synthesis.
3) pump nutrients from dilute external media
4) secrete toxins. |
Why won't vancomycin work against gram negative bacteria? | Too large, can't cross the outer cell membrane. |
Where is lipid A of endotoxin located? | embedded in the lipid bilayer of the outer membrane. |
What are common encapsulated bacteria? (6) | 1) Haemophilus influenzae
2) Streptococcus pneumoniae
3) Bacteroides
4) Strep A
5) Bacillus anthrax
6) Yersinia |
What is a glycocalyx and what kind of bacteria produce this? | Glycocalyx is a slime layer (carbohydrate polymers on surface of cell wall). made by gram positive bacteria only. |
What is happening in the lag phase of bacterial growth? | adaptation to host-metabolic activity with no increase in numbers |
Why are stationary phase bacteria often more resistant to antimicrobials? | Penicillins won't work if bacteria isn't growing/dividing. |
Give two exceptions to the rule that pathogenic bacteria like to grow at 37 degrees? | 1) mycobacterium leprae-likes to grow on extremities-slightly lower than body temps.
2) listeria monocytogenes-likes to grow at refrigerator temps. |
What is the best way to count viable #'s of cells? | Culture and look for Colony Forming Units. Plate Count divided by dilution factor. |
two things bacteria make to get iron from host. | 1)siderophores
2) hemolysins |
What kind of phosphorylations happen in glycolysis vs. fermentation? | glycolysis includes substrate level and oxidative phosphorylation as part of the ETC. Fermentation only includes substrate level. |
Give examples of obligate anerobes, aerotolerant anerobes, microaerophiles, facultative anerobes and obligate aerobes | 1) ob. anaerobes: b. fragilis, clostridium perfringes.
2) aerotolerant anearobes: strep, lactobacillus, some clostridia.
3) microaerophiles: campylobacter.
4) fac. anaerobes: e.coli, salmonella, staph.
5) obligate aerobes: nocardia, pseudomonas, TB |
Name 2 bacteria that can grow on lactose and 2 that can't. | 2 can: e.coli/klebsiella. (have galactosidase)
2 can't: salmonella and shigella. |
In glycolysis is glucose oxidized or reduced to become pyruvate? | oxidized (and NAD is reduced to become NADH) |
What process makes carbs from fats? | glycoxylate shunt (bacteria can do, humans cannot). |
Where does oxidative phosphorylation happen in the bacteria? | cytoplasmic membrane |
In fermentation is pyruvate oxidized or reduced? | reduced (and NADH is oxidized to NAD). |
Name first three of 6 different types of fermentation products. | 1) homolactic fermentation-lactic acid (lactobacillus, streptococus)
2) butyric acid fermentation-clostridia. protects from e.coli.
3) propionic acid fermentation (corynebacteria) Used in swiss cheese making. Also bacteria in acne. |
Name last 3 of 6 different types of fermentation products | 4)Mixed acid: enterobac. (e.coli, salmonella, shigella). Make acetyl COA, formic acid. Salmonella-H2 gas Shigella none.
5) Butanediol formation-acetoin made. non-fecal bacteria: Klebsiella, Enterobacter.
6) Ethanol fermentation-yeasts,C02 as well. |
what is the role of superoxide dismutase vs. catalase? | superoxide dismutase breaks down superoxide to hydrogen peroxide and oxygen. Catalase breaks down hydrogen peroxide to water and oxygen gas. (anerobes lack both enzymes). |
What is the strickland reaction? | special fermentation in clostridia, ferment amino acids. |
Describe body reaction to LPS | macrophages get activated, secrete TNF-alpha. Lead to increase of plasma proteins in tissue, increased permeability of blood vessels, lymphocyte/phagocyte migration and platelet adhesion. Leads to blood vessel occlusion. Systemic-hypotension and DIC. |
Does endotoxin get destroyed in autoclaves? | No--heat stable. |
Name 3 endogenous pyrogens. | IL-1, TNF-alpha, IL-6. Lead to release of prostaglandins, increase metabolic rate, vasoconstriction. Fever. |
What is the difference between functional and actual hypovolemia? | functional: space due to vasodilation.
Actual: space due to blood leaking. |
what pathway of complement does LPS activate? | alternative. (also lectin) Note also activates the coagulation cascade. |
What is the limulus test? | tests for LPS-horseshoe crab agglutination test. |
What is the toxic portion of LPS? the antigenic portion? | toxic=Lipid A (conserved, PAMP)
antigenic=O-antigen. (antibodies to O used to serotype strains). |
What is special about Sabouraud's agar that helps Fungi grow? | high acid environment--fungi are acid tolerant |
what are the two forms of growth for fungi and how do you describe the growth? | 1) yeast-polarized growth and then isotropic growth.
2) hyphae-always polarized from tip-penetrative. |
What are the 3 phyla that include pathogenic fungi? | 1) ascomyctes-includes candida, aspergillus
2) basidiomycetes-mushrooms, cryptococcus neoformans.
3) zygomycetes-including mucor. |
name of sterol in fungi cytoplasmic membrane? | ergosterol (amphotericin B binds to while the enzyme that makes it is the target for azoles) |
What is the major component of the fungus cell wall? | beta 1,3 glucan inner layer (PAMP) and chitin--crosslinked via glycosidic bonds. GPI anchors transfer carboyhdrates to beta 1, 6 glucans)-cross link with glycoproteins that protect the inner glucan layer. (MANNAN PROTEINS=outer layer) |
Are fungi motile? | no |
Which fungus does not use ergosterol in its cytoplasmic membrane? | Pneumocystis |
the antibody response of a host to fungus is directed at what? | the carbohydrate portion of glycoproteins (mannan, glactomannan, xylose) |
what is the only pathogenic fungus with a capsule? | cryptococcus neoformans. Capsule is made of polymers of glucuronoxylomannan (GXM). |
how is the geographic distribution of fungi determined? | delayed type hypersensitivity skin testing |
What is the difference between exogenous and endogenous fungi? | exogenous=free living, ecological niche is in nature.
endogenous=associated with human hosts, don't survive very long outside (candida albicans). |
name 2 examples of secondary metabolites of fungi. | 1) lovastatin-made by aspergillus terreus.
2) aflatoxins-toxic at low concentrations-concern in grain industry. (also with peanuts). |
What are two terms for hypha that don't have septa? | 1) aseptate
2) coenocytic-mass of protoplasm from repeated nuclear division, no cell fission. |
In C. albicans what dimorphic form is found in the host vs the environment? | host=hyphal, environment=yeast. (unique, other dimorphic fungi are opposite). |
What is auxotrophy? | inability to synthesize essential metabolites. (wild type is prototroph). |
What experiment showed that mutations are spontaneous and not induced by selective pressure? | Lederberg-replica plating with velvet (selective and non-selective media). Can show colony had resistance before put on the selective media. |
what test helps with ordering genes in a pathway? | Cross-feeding analysis. If precurser feeds a neighbor it means the precurser is at the end of the pathway. |
What is a good way to enrich your media for auxotrophs? | penicillin enrichment on minimal media. Get rid of any colonies that can grow, leaves behind those that can't (auxotrophs). |
What is a good way to get lethal mutations to examine? | Get temperature sensitive mutations-silent at low temps, denature protein at high temps. |
how do you determine the number of genes in a biosynthetic pathway? | genetic complementation test-chromosome and plamsid. If mutation in same gene then get no product, if in different genes, then they complement each other and can get product. |
How do you study commensals that can't be cultured? | look at small subunit RNA. (highly conserved) |
What are the two types of bacteriaphage? | 1) Lytic
2) Lysogenic-eg. Lambda, see site specific recombination to form prophage-viral DNA in bacterial DNA. C1 repressor stops viral DNA genes from being repressed until times of DNA damage/stress and then they are expressed and go into lytic cycle. |
What is a way bacteria protect themselves from phage? | restriction enzymes |
What kind of recombination do transposons do? | illegitimate recombination-nonhomologous. Use insertion sequences to insert at random locations. Transposons are often involved in antibiotic resistance. |
Name 3 mechanisms of gene transfer in bacteria | 1) transformation-bacteria get DNA from environment.
2) Transduction-viral transmission from phage. Can be generalized-random insertion, or specialized if lambda always inserts in same place).
3) Conjugation-bacterial sex (F pilus). |
3 examples of bacterial toxins that are transfered by phage? | 1) e.coli shiga like toxin.
2) diptheria toxin.
3) cholera toxin. |
What is an episome? | extrachromasomal DNA element that is capable of autonomous DNA replication but can also integrate into the chromosome. F is an example. |
how does the rapid chromogenic antibiotic resistance test work? | if bacteria is resistant will see color as nitrocefin is cleaved when beta lactamase is made (degrades beta lactam antibiotics) |
How does sulfonilamide work? | Anti-metabolite (anti folic acid metabolism-needed for DNA synthesis), used for urinary tract infection-broad spectrum. Bacteria static. |
Name 4 antimetabolite antibiotics. | 1) sulfonilamide.
2) trimethoprim-stops Dihydrofolate reductase.
3) bactrim-combo of 1/2.
4) isoniazid-affect mycolic acid-imp. for TB. cidal. |
Which penicillins are sensitive to acid? | Pencillin G (also sensitve to beta lactamase). Ineffective for gram negative enterics. Pen V. is acid resistant. |
Which penicillins are broad spectrum? | ampicillin/amoxicillin. Get high serum levels with amoxicillin. |
Which penicllins are best for enterics/pseudomonas? | tricarcillin, piperacillin. (less good for gram positives) |
which penicillins are best for staph (narrow spectrum) | oxacillin, dicloxacillin, nafcillin, methicillin. Why are these best? Becuase they are resistant to penicillinase. (unlike penicillin G/V or ampicillin groups). |
What bacteriocidal antibiotic class is similar to penicillin but with less allergic properties? | Cephalosporins. 3 generations. 3rd generation can handle pseduomonas better at cerebrospinal fluid penetration, others can't. |
What kind of beta-lactam antibiotic is good for aerobes but not anerobes? | monobactams-azetreonam. Also not good for gram positive. |
What is augmentin? | beta lactam with a beta lactamase inhibitor (clavulonic acid with amoxicilin). |
How does vancomycin work? | inhibits gram positive bacteria only- (too big to fit through the porins). R-D-ALA-D-ALA cross link binding-inhibit glycopeptides. |
Name 2 examples of drugs that affect membrane permeability (and thus bacterial energy source-cidal). | 1) polymyxin B and E-only topical. Gram negatives.
2) Daptomycin (cubicin)-gram positives only. |
3 examples of aminoglycosides and how they work. | 1) steptomycin
2) amicacin
3) gentamicin.
Work by interacting with small 30S ribosomal subunit--inhibit translation. Cidal-lead to bad proteins. |
Why do we see so much drug resistance for aminoglycosides? | Very specific binding to the 30S ribosome. (gentamicin has many binding sites and works much better). |
How do tetracyclines work? | tetracycline and doxycycine block tRNA and are bacteriastatic. Diable ability to synthesize more proteins. Great for intracellular parasites. Chlamydia, rickettsia. Bad for pregnant and kids teeth. |
How do macrolides work? 2 examples. | 1) azithromycin
2) erythromycin.
Both block chain elongation-50S subunit. |
Which antibiotic is particularly good for anerobes? | Clindamycin |
What is a limitation of the Kirby-Bauer Disc Diffusion? | Can't be used for determination of Minimal bacteriacidal concentration. (good for multiple testing of antibiotics). |
What are carbapanems (imipenem)? | antibiotic with beat-lactam ring, broad antimicrobial spectrum, restant to most lactamases, susceptible to renal dipeptidase so use with cilastatin. (Primaxin). |
Name 2 B-lactamase inhibitors | 1) Clavulonic acid
2) Sulbactam |
Name 3 glycopeptides and their coverage | 1) vancomycin-Gram positive
2) cycloserine-TB drug
3) Bacitracin-Gram positive Good for topical therapy only. Too toxic for systemic. |
What 2 conditions inhibit streptomycin? | 1) acidic
2) anaerobic
*note that aminoglycosides like streptomycin/genotmycin should only be used in patients with immune compromise as they can damage 8th cranial nerve/renal function. |
Name 5 antibiotics that inhibit 50S ribosomal function. (all static). | 1) erythromycin-static-chain elongation
2) azithromycin-static-chain elongation
3) Chloramphenicol-static-chain elongation-can get anemia. Good for bacteroides.
4) Clindamycin-good for anaerobes.
5) Streptogramins. |
How do oxazolidinones (linezolid) work? | inhibit translation-block tRNA translocation-interact with 16S and 23S rRNA. Great for gram positives. |
How does mupirocin work? | bind to tRNA synthetase and results in no charged Ile-tRNAs. Static at low concentrations, good for MRSA. |
What 3 drugs are good for inhibiting DNA replication? (one is particularly good for anaerobes) | 1 and 2 are both quinolones-ciprofloxacin and moxifloxacin. Broad range. Inhibit DNA gyrase. Bad for pregnant and children-hurt growing bone.
3) metronidazole-need anaerobic conditions. Binds to DNA and fragments it.
3) |
what antibiotic inhibits RNA synthesis? | Rifampin-broad spectrum |
Example of antibiotic antagonism? | agent needing growth (penicillin) and bacteria static drug (tetracyline) |
Example of antibiotic syndergism? | agent damging cell wall (polymxin or penicillin) and agent that is taken up poorly (aminoglycoside). |
5 important anti-fungal drugs: | 1) amphotericin B-bind to sterol
2) Nystatin-bind to sterol, can't be used systemically--too toxic. Static.
3) Fluconazole/ketoconazole-inhibit membrane synthesis.
4) Caspofungin-inhibit glucan synth. cidal.
5) Flucytosine-antimetabolite. replace urac |
How is fungal resistance conferred? | changes within the fungal genome itself. No resistance mechanisms have been discovered so far. (do see efflux pumps like bacteria have). |