micro test 3 study guide
TRANSCRIPT
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 1/29
Microbiology Test – CH 6, 7, 8, & 34
Lipids, carbs, proteins, & nucleic acids:
• The nutrients they need in large quantities: CHONPS
○ Hydrogen-
found all over the place
main source is organic. (ex: CH4, H2O)
○ Nitrogen-
Find it in proteins, nucleic acids, cell wall
Source is atmosphere (which is 80% N)
○ Phosphorous-
found in cell membrane (in phospholipids) & N.A
major source of it is inorganic molecules
The E source that gives P is ATP
○ Sulfer-
Find it in A.A, some vitamins
Major source is inorganic, especially sulfates
Immunoglobulins; IGE is measured to find if you’re allergic
• Also, K, Ca, Mg, Fe
○ K= required for enzyme activity
○ Ca= required for heat resistance (give it to spores)
○ Mg= is a cofactor
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 2/29
○ Fe= (can be 2+ or 3+) Ex: hemeproteins, or cytochromes
Fe is very insoluble, but required for e- carrier molecules, cytochromes
Siderophores: bind to Fe & cross membrane in some bacteria, fungi (to deliver Fe)
• Co, Mo, Cu, Ni: Trace elements; use metabolic pathways
We can divide groups by Energy source :
• Phototrophs: use light
• Chemotrophs: use chemicals
○ Litotrophes: if chemical source is of inorganic nature
• Autotroph: use CO2 as their sole source of Carbon. (plants)
• Heterotroph: use preformed organic molecules as their sole C source (Humans & most bacteria)
Does every org on the planet require ____ to survive? Why?
• O2- no
• O atom- yes
○ Oxygen is required in organic compounds & inorganic salts like PO4, SO4
○ O mostly comes from the air
How would you define an organic compound?
• Ans: it has a Carbon.
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 3/29
• Except: CO2, CO, & HCN: they are part of elemental gases
○ Pseudomonas can utilize more than 100 organic compounds
Some organic molecules have to cross selective permeable membrane. In order to do this they can:
• 1)passive diffusion: high to low
• 2)facilitated diffusion: use permeases - carrier proteins imbedded in membrane
• 3)active transport: use E (from ATP); transport of solute molec to higher concentration
• 4)group translocation: actively transported & chemically altered when they go through the membrane
Endocytosis: engulfs nutrients and/or viruses; for uptake of nutrients into cell
Pinocytosis: cell drinking
Different types of Media :
• Some will be liquid:
○ Gets very fast growth bc you can shake it or add O2 to it
○ We can monitor growth to determine how fast it grows
• Some will be solid:
○ Main advantage is isolation to obtain pure culture & serial dilutions
• Some will be complex:
○ With many nutrients & chemicals
○ TSA
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 4/29
• Some will be enriched:
○ Special nutrients have been added
• Some will be differential:
○ Will help distinguish bw bacterial growths
○ EMB: lactose +/-
• Some will be selective:
○ Differentiates groups of orgs; it favors the growth of a particular microorg.
○ This may be accomplished by inhibiting growth of undesired microorg.
○ EMB: select for Gram –
○ PEA: select for Gram +
pH= -log [H+]
• Measures # of H atoms released
• Org able to grow at:
○ 1-5.5: Acidophile (ex: lactobacillus)
○ 6-8: Neutrophile (ex: most bacteria & protists)
○ 8.5-11:Alkalinophile / basophile (ex: bacillus)
According to O2 requirements, orgs can be divided into different groups :
• Aerobic: requires O2
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 5/29
○ TCA, e- transport system
• Anarobic: killed by O2
○ Don’t have any way to get rid of H2O2
○ Don’t have catalase or peroxidase enzymes, so don’t have e- transport system
○ Ex: clostridium
• Facultative: live with or without O2
○ Ex: E. Coli – does better with O2 present
If O2 present, it can produce 38 ATP
If no O2, only 2 ATP
• Aerotolerant: metabolically resemble anerobes but not killed by O2
○ All these orgs are fermentative & grow very slowly
○ Ex: streptococcus & enterococcus
• Microaerophilic: this group requires O2, BUT do it at reduced pressure
○ So we use candle jar
○ It does make CO2, but not completely anerobic
○ Ex: Neisseria, lipids
They need low pressure to make membrane lipids
3/25
Oxygen accepts e- & is reduced.
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 6/29
(Singlet Oxygen: O pulled to a higher state; it is a very reactive, powerful oxidizing agent that will quickly destroy a cell-p142)(it is probably the major agent employed
by phagocytes to destroy engulfed bacteria)
The result is reduction products: superoxide radical, H2O2, & hydroxyl radical.
These are toxic because they oxidize & destroy cellular constituents so an org must protect itself or it will be killed.
Phagocytic cells: use the toxic products to destroy invading pathogens
Superoxide radical: O-; is formed during aerobic respiration (Use O2 as final e- acceptor) End product of enzyme is H2O2 – detrimental to all cells
The enzyme Super Oxide Dismutase (SOD) & catalase- catalyze the destruction of superoxide radical & H202
Peroxidase- can also be used to destroy/neutralize effects of H2O2
• H2O2(w/ catalase)H2O + O2
○ If bubbles, catalase +
○ Strep is catalase NEG
• H202(w/ peroxidase) H20 (no O2)
Aerobe: able to grow in presence of O2
• Final e- acceptor: O2
• SOD + catalase – so able to get rid of toxic orgs
• Ex: pseudomonas, mycobacterium, corynebacterium
Anerobes: able to grow without O2 (O2 kills it?)
• No enzymes to get rid of toxic orgs
Facultative Anaerobes: Better with O2, but don’t need it
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 7/29
• SOD + catalase
• Ex: enterobacteria
Aerotolerant Anaerobes: ignore O2; grow same with or without it.
• Ignore glycolysis; fermentative
• SOD – no catalase
• Ex: strep, lactobacillus
Microaerophiles- Damaged by normal levels of O2 & require 2-10% for growth
• SOD – yes or no catalase
• Candle jar
• Ex: Neisseria
Temperature
Cardinal temperature: Minimum: 10°C; Optimal: 30°C; Maximum: 45°C
Narrow temp range: Stenothermal; 30-38° (STD’s)
• Ex: Neisseria
Wide temp range: eurythermal 0-44°
• Ex: strepfaecalis
Low temps:
• Psychrophiles 0-20° (optimum 15°)
○ Ex: Pseudomonas, bacillus
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 8/29
• Mesophiles 15-45 (optimum 25-45)
○ Most all bacteria: specially pathogens
High Temps:
• Thermophiles 45-80° (optimum 55-80)
○ Ex: bacillus, stenothermophilus
More than 100°: hyperthermophiles
Osmosis
• In bacteria, regulated by cell wall
Physiological solution: same osmotic pressure as body fluid
Isotonic solution: same as above
• Animal cells & bacteria: no change to cell
Hypotonic: soln w lower concentration
• Animal cell- swell, burst
• Bacteria- no action due to cell wall
Hypertonic:
• Animal cells–shrink. Bacteria–stop growing
• Plasmolysis – (in prok, fungi, & algae bc has cell wall) membrane shrinks away from the cell wall
• Osmophilic (hypertonic): like to grow in high temps, like yeast
• Halophilic: (hypertonic) like to grow at high NaCl concentration
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 9/29
• Saccarophilic: like to grow at high sugar concentration
Water activity (WA): expresses the degree of H2O availability
• OAW – spores! They have no H2O
• Most orgs need 80-95% humidity to survive
○ Free H20 to vapor
○ Staph 85% humidity to survive
○ Molds 60% humidity to survive bc better at H20 extraction
Microbial Growth: growth increase in # cells or in mass
Binary fission:
Exponential growth: progressive doubling of # of cells or mass
• 1- LAG phase: the org adjusting to new environment. Not much growth.
• 2-log (aka exponential/ growth phase): org grows. Binary fission
• 3-transition phase: sporulation begins; stop making antibiotics
• 4-stationary phase: org is running out of media; cell division & death synchronized
• 5-death phase: too much toxic waste accumulated; die is also exponential
Microbial growth
• Viable cells – you can directly count the number of dead/alive cells
○ 2 methods to find them: (must use serial dilutions for both)
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 10/29
1) pour-plate, then count them.
Colonies on inside surface of plate
2) spread-plate, with hockey stick
dip in alcohol, flame hockey stick, spread org, incubate
colonies on surface only
advantages: very sensitive, viable counts
disadvantages: clumps, we have to do serial dilutions
3/29
Viable count: know what it is
• Only way to find it is spread plate & dilution technique (?)
Batch cultures – closed systems
• No fresh media is provided to org nor wastes removed
• Exponential growth is reached fast (quickly)
Direct Counting: don’t distinguish dead from alive cells
• Petrof Hausser counting chamber: used to count prokaryotes
○ Don’t get viable count bc cant tell whether cell is alive or dead
○ Has low density cells- won’t give good, accurate count
• Coulter counter: used to count larger orgs like protists & yeasts
○ Have optical eye that counts electrical resistance; counts the # of cells in a soln.
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 11/29
○ Only problem is don’t know if count is bc live/dead cells.
○ More expensive & No viable cells
Indirect measurement of microbial growth
• Spectrophotometry: measures cell mass by how concentrated your soln is; light scattering
○ Measures turbidity: higher concentration= less light transmitted=higher turbidity
○ no way to tell if cell is alive/dead; so no viable cell count
○ Standard curve
• Microbial dry weight: best for determining changes in cell mass
○ Use a centrifuge
○ Useful for growth of: filamentous fungi, large cultures
○ Cant tell if cells live/dead
Continuous Culture Systems: Open systems
• continual provision of nutrients & removal of wastes
• keeps microbial population at exponential growth phase for longer
Chemostat –
• Fresh media w/ limited qtys of essential nutrient being added
• Org grows at exponential rate always while you are feeding it fresh media.
• Can feed it more or less by how fast you want it to go
Turbidostat-
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 12/29
• Use photo cell to measure cell density/turbidity of the culture
• Can regulate flow rate of media by measuring how fast/slow is growing
CH 7: Control of Microorganisms
Sterilization: process all living cells, spores, & acellular entities are destroyed/removed;
• free of all orgs (spores, virus, prions – ALL)
• physical agents mainly
Disinfection: killing or removal of incubation of pathogens
• Primary goal: destroy pathogens, but also reduces whole population
• Lister was 1st
Disinfectant: used on inanimate, nonliving objects
Sanitation: microbial population reduced to safe levels for public
Antiseptic: something used on living tissue to prevent infection by killing pathogen growth
• Not as toxic as disinfectants. Stronger (?)
___-static: inhibit the growth of microorgs but doesn’t kill.
• Bacteriostatic
___-cidal: means it will kill
• bacteriocidal
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 13/29
Conditions that will affect use of antimicrobial agents:
• Kind of organism: Spore formers, older cells are harder to kill
• Surface: flat surface easier to keep clean (also, pop size, environment)
• Size: larger population takes longer to kill
• Amt: of your disinfectant; concentration – if it works better at high or low of chemical
• Temp: if it works better at high or low T
• pH: orgs don’t like acidic pH (except lactobacillus)
Autoclave: use moist heat to sterilize eqpt – it will be 100% sterile (kills spores)
• 15-20 psi – the high pressure increases the b.p of H2O to 120°
• leave it for 15-20 minutes
Pasteurization: used to kill the pathogen w/o harming the product
• Does not sterilize a beverage but reduces level of nonpathogenic spoilage microorgs.
• 63° C for 30 min
• TB decreases pathogenic viruses
High T short time flash pasteurization
• 72° for 15 sec
• lowers total microbial count
• milk refrigerator
Ultra high T
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 14/29
• Heat milk under steam. Reach 140°C for 3 sec.
• In Europe, served at room temp
Tyndalization
• 100°C for 30 min
• eventually free of microorganisms
Dry heat sterilization: put in oven. 170°C 2-3 hours.
• Incineration: you degrade everything to CO2 and H2O
Low temp: slow down growth or stop but doesn’t kill
• Liquid N2: 175°
• Dry ice: -70°
Freezing temp: fast (doesn’t kill) Vs. slow (kill it bc H2O expands & will rupture membrane)
Drying
• Most resistant to it: the more surface, the less resistant
• Cocci, rool, spiral
Alter osmotic pressure
• Make it hypertonic by adding salt or sugar
• Plasmolysis: shrinking. Used to preserve food
UV light: short wavelength & high E
• Noniodizing radiation
• Creates dimers (nitrogen bases bound together)
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 15/29
• Like to form thymine dimers (in DNA)so org cant grow: the primary mechanism of UV damage
Ionizing radiation: very short wavelength & high E which can cause atoms to lose e- (ionize)
• Extremely dangerous (kills spores)
• Rays; free radicals
• “cold sterilization”: doesn’t reach any kind of T whatsoever
• good for plastics, antibiotics, hormones, or anything heat sensitive
Filtration: removes bacteria; mostly for heat sensitive liquids
• o.45 Mfilters
• org w/o cell wall: microplasma (can get through this)
• 0.3 um 0.1 um
Positive pressure
Negative pressure
• keeps heat inside room (for isolation)
• try to remove as much of org as possible, so are clean rooms
3/31
Use of Chemical Agents in C ontrol: (mostly for disinfection & antisepsis)
• Phenolic compounds
○ Burns tissues, denatures proteins, disrupts cell membrane
○ Effective for organic material
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 16/29
○ Lysol contains phenol – gives strong odor
○ Hexachlorophene – antiseptic; compound found on phisohex, staph, strep
• Org compounds can only be used as antiseptics, not ______ bc……….?
• What org causes TB? Mycobacteria
• Alcohols
○ Disinfectant & fungicidal mostly. Occasionally a topical antiseptic.
○ 70-80% isopropanol; good for lipid containing viruses
○ will denature protein & dissolving membrane lipids
○ good against org that causes TB/ HIV; not sporicidal
○ if not organic material, alcohol is good for instrument disinfectant
○ don’t use internally, doesn’t kill hepatitis virus, kills epithelial cells
• Halogens: 7A; corrosive; denatures proteins; at high T, may kill some spores
○ CL- used to disinfect H2O; very strong oxidation agent; can cause allergies
○ F-
○ Br- “ “ H2O
○ I- used for antiseptic (oldest) for minor abrasions; binds itself to tyrosine; denatures proteins; at high T, it denatures spores
• Heavy Metals- denatures proteins, good for disinfect, not for use internally
○ 1% AgNO3- on eyes of newborns to stop/kill gonorrhea
○ silver sulfadiazine- burns to keep bacteria from infection; skin grafts
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 17/29
○ CuSO4- kill algae
○ ZnCl2- mouthwashes
• Quaternary Ammonium Compounds (Quats) - disinfectant
○ organic compounds added to detergents; serve as wetting agents or emulsifiers
○ Will disrupt cell membrane permeability
○ Anionic: some microbial activity
○ Cationic: disinfectants, esp on Gram+ orgs; no effect on acid fast orgs; no endospores
Ex: benzalkonium chloride
• Aldehyde – functional group is ______. Sporicidal & chemical sterilants.
○ Can be oxidized to an acid; reduced to an alcohol
○ Glutaraldehyde: considered a liquid sterilizer; kills spores (kills us); extremely toxic, denature, etc.
○ Cidex: 2% glutaraldehyde; 37% formalin (formaldehyde) disinfects.
• Sterilizing Gases:
○ Cl- H2O disinfectant
○ Ethelyne oxide: toxic; microbicidal & sporicidal; sterilizing agent
• Liquid:
○ H2O2- most effective against orgs that don’t produce catalase, so are anaerobic.
• Phenol coefficient: a disinfectant screening test in which the potency of a disinfectant is compared with that of phenol
○ Test organisms:
Staph aureus: G+
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 18/29
Salmonella typhi: G-
• Chemotheraputic Agents: chemicals that can be used internally to kill/inhibit the growth of microbes within host tissues. They can be used internally bc they have
selective toxicity.
○ Antimicrobial hemotherapy
○ Antimicrobial drugs: chemotherapeutic agents used to treat infectious agents
○ Selective toxicity: they target the microbe & do relatively little harm to the host.
○ (Understand well & how it relates to antibiotic)
○ Most chemotherapeutic agents are antibiotics: chemicals synthesized by microbes that effectively control the growth of bacteria.
• 2 Groups:
○ 1) antibiotics- naturally made. Made by fungi or bacteria
○ 2) synthetic drugs – lab made
CH 34- Antimicrobial Chemotherapy
Paul Ehrlich – father of ___ agents
• Found the dye trypan red could selectively destroy pathogens w/o harming human cells
• Discovered Salvarsan – used to treat syphilis
Alex Flemming: discovered penicillin
• Good selective toxicity against G+ orgs
Selman Waksman: discovery of streptomycin – filamentous bacteria found in soil. Treated TB.
• About 50% of all antibiotics are made by some species of Streptomyces
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 19/29
• Few made from bacillus
• Penicillium, ecphalosporium
The Therapeutic Index: the ratio of the toxic dose to the therapeutic dose.
• The larger the T.I, the better the chemotherapeutic agent.
• A drug has a low T.I if it inhibits the same process in host cells or damages host in other ways
Narrow-spectrum drugs: they are effective only against a limited # of pathogens
• Penicillin G+ (Breaks down bacterial cell wall peptiglycan but has little effect on host cells bc they lack cell walls; therefore, its T.I is high)
Wide- affect large spectrum of bacteria; attack many different types of pathogens
• G+ or G neg
• Bad, bc normalflora is affected/destroyed. This is disadvantage
• Antibiotics don’t destroy yeast. Why?
Super infections:
• Bc some orgs are resistant to……?
Kirby-Bauer
• -Muller Hinton agar
• R. I. S (resistance- antibiotics have no effect) (Intermediate) (succeptibility-good ag particular orgs)
• M.I.C (minimum inhibitory concentration) – this is the good one to use
• E Test – combines k.b & MIC together
• What is good against viruses? Antiviral drugs, NOT antibiotics
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 20/29
4/5
Cell Wall Inhibitors
• Penicillin & Cephalosporins
○ -both prevent final cross linking of peptidoglycan
○ “inhibit transpeptidation enzymes involved in cross-linking the polysaccharide chains of the bacterial cell wall peptidoglycan”
Penicillin:
penicillin contains B lactam ring (glues molecule ____ characteristic)
penicillium – known as penicillin G
• narrow spectrum (G+)(-cidal)
○ staph, strep, spirochetes
• injected, excreted/removed in 3-6 hrs by body
• orally, destroyed by stomach acid
• so came up with…….
○ Procaine penicillin – 24 hour
○ Penicillin V – resistant to stomach acids
Disadvantages – succeptible to ____ & penicillinases
○ Semisynthethic penicillin
Methicillin no B lactam ring
So now its been replaced by oxacillin
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 21/29
• Amoxicillin
○ Unfortunate patients can develop allergies to penicillin
Cephalosporins: cell wall inhibitors/ affect peptidoglycan
Have similar B-lactam ring
Given if patient is allergic to penicillin
Broad spectrum(G +, some G NEG) (more____ for G NEG orgs)
• Bacitracin & Vancomycin
○ –both: linear synthesis of peptidoglycan
○ “prevents transpeptidation of peptidoglycan subunits by binding to D-Ala-D-Ala amino acids at the end of peptide cross-bridges. Thus it has a different binding site
than that of the penicillins.”
Vancomysin (MRSA)
Narrow spectrum, (G+)
Has to be given intravenously, extremely painful
Toxic- blood levels must be monitored
Alter cell membrane permeability
Bacitracin
Made by bacillus
Effective against G+ orgs, but restrictive on topical applications
• Isoniazid (INH)
○ Good against mycobacteria, which causes TB & leprosy
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 22/29
○ Inhibits mycolic acid synthesis
○ Narrow spectrum – mycobacterial infections, principally TB
• Rifannpin
○ Is a nucleic acid inhibitor
Cell Membrane Inhibitors
• Bind to phospholipid, so will alter cell membrane permeability.
• Only used for topical application
• … so the therapudic index will not be as high
○ Polymyxin B (-cidal)
Produced by bacillus before they start sporulation
Very good against G NEG orgs, esp pseudomonas
“binds to plasma membrane & disrupts its structure & permeability properties”
narrow spectrum – G NEG only
Bacitracin & Polymyxin B – you can buy ointment w/o script. But if add neomycin: broad spectrum protein synthesis inhibitors
○ Aminoglycosides (-cidal)
“bind to small 30S subunit & interfere w protein synthesis by directly inhibiting synthesis & causing misreading of mRNA”
Neomycin- Broad spectrum (G NEG, mycobacterium)
Streptomycin- Narrow spectrum (aerobic G NEG)
○ Nystatin & Amphotericin
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 23/29
Both antifungal
Liver enzyme functions
Primary choice for histoplasmosis bird droppings (farmers) & also coccioliomycosis (found on soil)
Increase fungal membrane permeability
Nystatin – origin is NY state; extremely good for treatment of yeast
Protein Synthesis Inhibitors : happens on ribosome
on euk – ATP made on ribosomes
important- if you use too high of a therapeutic index on a proteins synthesis inhibitor, you will damage the ribosome (?).
be able to know if its index is too high, low, etc
Nitroaromatics
• Orally, naturally occurring antibiotics w/ benzene ring
Chloramphenicol (-static)
• Streptomyces
• 50 S subunit to inhibit peptide chain elongation during protein synthesis
• blocks peptide bond formation
• extremely toxic
• broad spectrum antibiotic ( some G +, some G NEG, rickettsia & chlamydia)
• bc of its small size, it diffuses into the cell
• spinal fluid
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 24/29
• meningitis, typhoid fever
• suppresses bone marrow activity
• a plastic anemia
Aminoglycosides (-cidal)
• Only account for about 3% of amino acids being used
• Also produce Streptomyces
• An example: streptomycin. (discovered 1944)
○ Attached to it are: tobramycin, gentamycin, karamycin, neomycin
Used as G NEG org, esp pseudomonas
Neomycin- ointment used for triple antibiotic ointment
Tobramycin- kids for cystic fibrosis
• 30S
• misreading of the genetic info carried by mRNA
Tetracycline (-static)
• Bind 30 S
• Prevent introduction of new amino acid
• Stop protein synthesis
• Streptomyces produces this
• Broad spectrum – inhibits most G+/G NEG orgs
• Penetrates tissues extremely well so very good
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 25/29
• Ag intracellular rickettsias or chlamyclias
• Good ag/ UTI & mycoplasma (no cell wall) pneumonia, syphillus, gonorrhea
• Candida- like to lead to super infections
○ Sensitive to UV light – avoid sun
○ Can cause yellow teeth (esp in kids)
Macrolides (-static)
• Binds to 50 S subunit to inhibit peptide chain elongation during protein synthesis
• Broad (aerobic & anaerobic G+, some G NEG)
• Ex: erythromycin
• Drug of choice for patients that are allergic to penicillim
• Good ag/ staph, strep, ear infections, whooping cough, mycoplasma, G + orgs
• Cannot penetrate wall of G NEG outer wall
Eukaryotic Protein Inhibitor
Cyclohexamide- antifungal
• Very dangerous – goes for the whole ribosome 80S
Nucleic Acid Inhibitors
• Inhibit n.a synthesis
• Not as strong
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 26/29
Rifampin (-cidal)has a limited mode of action; blocks RNA synthesis so cell cannot divide
• Gets produced by streptomycin
• For patients that have TB or leprosy
• Used as a simple antibiotic
• Good- it can reach high levels of the cerebral spinal fluid. If too much, can give liver problems.
• Recommended as a profylaxis.
• Ex: Neisseria, meningitis carriers
Quinolones (-cidal)
• Broad spectrum – like to inhibit DNA synthesis
• Block the enzyme DNA gyrase, therby blocking DNA replication & transcription
• Good for UTI treatment & traveler’s diarrhea
Cipro
• Synthetic antibiotic
• Braod spectrum
• Oral 40-50% gets secreted in urine
• Blocks DNA synthesis
Growth Factor Analogs
Sulfa drugs
• The action of it (the mode of it): competitive inhibition
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 27/29
• Able to synthesize its own folic acid (vit B), which is required for growth
○ Humans don’t synthesize their own, but e. coli can in order for it to grow.
• E. coli paraamino benzoic acid (PAB)
○ One of the precursers for folic acid synthesis
○ The org competes with PAB.
○ Sulfa drugs only work on orgs that make their own folic acid.
○ Ex: silver sulfa dyazine
Used for burns & eye infections
8/4/2019 Micro Test 3 Study Guide
http://slidepdf.com/reader/full/micro-test-3-study-guide 28/29
03/23/2011