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Bacteriology II &III
| Question | Answer |
|---|---|
| Gram Positive bacteria | Cocci and Bacilli .. cocci is more common in the names .. In gram positive the cocci mostly end with coccus .. the bacilli mostly end with "llus" or "ium" |
| Gram negative bacteria | Bacilli(rods) enteric bacteria, cocci, coccobacilli .. many would end with "ella" |
| Define Microbial Flor | microorganisms usually found associated with human body tissues |
| what are benign microorganisms | few contribute to health and few pose direct threat to health |
| Resident Flora microorganisms | they are always present .. covers almost all our epithelial and mucosal tissue |
| Transient Flora | live in or on our body for a period of time then move on or die off |
| Mutualistic relationship | both organisms benefit e.g E. coli they synthesis vitamins K & B for us and we provide a warm, moist, nutrient rich environment for them |
| Commensalistic relationship | One organism benefits, while the other is neither helped or harmed. We do NOT have this with bacteria |
| Opportunistic/parasitic | under normal conditions, microbe does not cause disease. if condition become conductive, then it may cause disease. E.g : Escherichia coli is usually in our digestive tract, if it gets in the urinary tract it becomes pathogenic. |
| Another example of opportunistic/parasitic | staphylococcus aureus is normally found in the upper respiratory tract, but if it gets into a wound it becomes pathogenic |
| How do mutualistic bacteria help us | 1. synthesis and excrete vitamins 2. Prevent colonization by pathogens 3. keep other normal flora under control 4. stimulate production of cross-reactive antibodies |
| How much do humans have of human cells compare to bacteria cells? | 90% bacteria cells and 10% human cells |
| Organisms that RARELY cause disease include | 1. micrococcus species 2. Lactobillus species |
| organisms that ALWAYS cause disease | 1. Vibrio cholerae (Cholera) 2. Yersenia Pestis (plague) |
| organisms that are in between .. sometimes cause disease | 1. Escherchia coli 2. Staphylococcus aureus 3. steptococcus pneumonia 4. pseudomonas aeruginosa |
| does the skin support the growth of microorganisms ? | No, the skin is generally dry and acidic environment |
| what colonizes moist areas (e.g sweat and sebaceous glands) | gram positive and other normal flora of the skin |
| where would you find staphylococcus species like S.epidermis and S. aureus? | in the skin and eye |
| Where would you find propionibacterium species. e.g P.acne? | in deeper skin |
| Where would you find corynebacterium species | conjuctive of the eye (tears) |
| What promotes localized microbial growth near surfaces of the mouth? | high concentrations of nutrients |
| An example of a microorganisms that grow in the oral cavity | Streptococci which result in a thick bacterial layer (dental plaque) |
| what happens when dental plaque keeps growing | Anaerobic bacteria begin to grow |
| example of 2 bacteria present in dental caries | Lactobacillus (lactic acid producing bacteria) and streptococcus mutans |
| an example of a group of organisms colonizes the upper respiratory tarct-nasopharynx | streptococci (S. Pneumonia) |
| Does the lower respiratory tract have any microflora? | NO |
| Where would you find steptococcus ? | in the esophagus |
| Where would you find Helicobacter bacteria and what would it cause? | in the stomach and it cause ulcers |
| Where would you find enterobacteria and enterococcus | small intestines |
| Where would you find Klebsiella and lactobacillus | Large intestines - colon |
| Where would you find enterococci and lactobacilli | small intestines |
| The Vagina of the adult females is weakly acidic and contains significant amount of glycogen and it has | Thought I have to know it |
| Lactobaillus acidophilus | a resident organism in the vagina that produce lactic acid` |
| candida albicans | yeast like fungus is a minor member of the normal flora (vagina, mouth, intestines) |
| Factors to be considered when selecting an antimicrobial drug | 1. Type of microbe 2. sensitivity of the microbe 3. overall medical condition of the patient |
| Characteristics of an ideal antimicrobial medication | 1. Highly toxic to the microbe 2. Not toxic to host 3. not interfere with the ability of the host to fight the disease 4. not lead to development of drug resistance. |
| Therapeutic index | a ration of comparison between Lethal dose and effective dose. Ideally, the larger the ratio the safer the drug |
| Antibacterial medication | Cause low toxicity to humans because they interfere with prokaryotes. not eukaryotic and their structures and processes |
| Antifungal medications | Have higher toxicity to humans because both humans and fungi are eukaryotes |
| Antiviral medications | Have the highest toxicity on humans because they must damage the host cell to inactivate the virus |
| there are 2 categories of antibiotics | 1. Bacteriostatic - reversibly inhibit growth 2. bactericidal - kill bacteria |
| characteristics of bacteriostatics | - duration of treatment is sufficient for host defenses to eradicate infection - better therapeutic index than bactericidal antibiotics - inhibitors are used to immediately block synthesis of bacterial toxins |
| characteristics of bactericidal | - usually antibiotic of choice for infections in sites such as endocardium or the meninges where host defenses are ineffective - resistance develop faster than with bacteriostatic anibiotics |
| Minimum inhibitory concentration | used to determine the lowers concentration (dose) of the drug able to kill or inhibit the growth of the microbe |
| What is the Kirby-bauer antibiotic susceptibility test used for? | used to determine whether the antibiotic effective against a particular microbe |
| How do you measure the efficacy of the drug? | by determining the zone of inhibition. if the zone of inhibition large then the drug have high efficacy and and the microbe is sensitive to it and vice versa. |
| Combination therapy | 1- Prevents emergence of resistance strains 2- temporary treatment until diagnosis is made 3- take advantage of antibiotic synergism |
| which drugs inhibits cell wall synthesis | penicillins and a,imoglycosides |
| define Antibiotics | naturally occurring agents |
| define chemotherapeutic agents | synthesized in the lab (most antibiotic nowadays are like that) |
| broad spectrum drugs | effective against many types of microbes and tend to have higher toxicity to the host |
| narrow spectrum drugs | effective against a limited group of microbe and have lower toxicity to the host |
| Antibacterial drugs disrupt microbial growth and division by: | 1. Inhibition of cell wall synthesis 2. Inhibition of protein synthesis 3. inhibition of nucleic acid replication and transcription 4. injury of plasma membrane 5. inhibition of synthesis of essential metabolites |
| what drugs causes inhibition of the cell wall synthesis | Penicillins, cephalosporins, bacitracin, vancomycin |
| What drugs cause inhibition of protein synthesis | Chloramphenicol, erythromycin, tetracyclines, streptomycin, 30S ribosomes and aminoglycosides |
| what drug causes the injury of plasma membrane | polymyxin B |
| what drug causes inhibition of essential metabolites | sulfanilamide, trimethoprim |
| what do Beta lactem drugs do | interfere with the formation of the peptide side chain |
| what do vancomycin do | bind to the amino acids side chains of NAM molecules interfering withe peptidoglycon synthesis |
| what Bacitracin do | interferes with the transport of peptidolglycan precursors across the cytoplasmic membrane |
| beta lactam ring | is a 4 membered ring .. |
| beta lactams of the cell wall inhibitors | are all derivatives of penicillin |
| what is a beta-lactemase | bacterial enzyme that destroys natural penicillins |
| Cephalosporins 4 generation | Stage 1 : narrow spectrum - gram positive stage 2: extended spectrum include gram negative stage 3: includes Pseudomonas stage 4: most extended spectrum |
| Translation in protein synthesis | slow rate synthesis .. in bacteria translation and transcription are coupled .. in eukaryotic it's different because it occur in a different cellular compartment |
| Protein biosynthetic machinery is made of 2 subunits. what are they | bacterial 30S and 50S |
| cytoplasmic ribosomes are larger and more complex than mitochondrial and chloroplast .. but functions and properties are similar | :D |
| mRNA is associated with which subunit bacterial? | 30S |
| what are some antibiotics that are inhibitors of INITIATION | - 30S Ribosomal subunit (Aminoglycosides and Tetracyclines) - 50S Ribosomal subunit (Chloramphenicol, Macrolides) |
| what are some inhibitors of ELONGATION | elongation factor G (Fusidic acid) |
| Elaborate a little on Aminoglycosides | They are bactericidal protein synthesis inhibitors. E.g streptomycin and all the other "cins" .. Modes of Action it reversibly bind to proteins of the 30S |
| Spectrum activity for aminoglycosides | many gram-negative and some gram-positive bacteria. not useful for anaerobic bacteria or in anaerobic environment |
| Resistance of aminglycoside | Enzymatic modification |
| Synergy of aminoglycoside | They synergize with Beta-lactams and inhibit cell wall synthesis |
| True/False : Tetracycline is Bacteriostatic? | True |
| What is the mode of action of Tetracycline | Binds reversibly to 30S |
| Spectrum activity to Tetracycline | broad spectrum useful against intracellular bacteria such as Chlamydia, Mycoplasma, and Rickettsia |
| Resistance of tetracycline | common mode is active efflux |
| Adverse effects of tetracycline | staining and impairment of the structure of bone and teeth |
| Chloramphenicol mode of action | bind to 50S and inhibit peptidyl tranferase. no elongation |
| Chloramphenicol spectrum activity | broad range |
| Cholramphenicol resistance | Renders antibiotics incapable of binding to 50S |
| Macrolides are bacteriostatics E.g erythromycin | and other mycins |
| Mode of action of Macrolide | inhibit translocation of ribosomes. binds to 50S |
| Spectrum activity of macrolides | useful in treating gram positive bacteria in patients with penicillin allergies |
| Resistance of macrolides | Methylation |
| Fusidic acid is bacteriostatic .. mode of action is | Inhibit the release of EF-G from EF-G/GDP complex .. and inhibit translocation during tRNA and mRNA |
| spectrum activity of fusidic acid | gram positive cocci like staphylococcus |
| Rifampin is bactericidal .. Mode of action | binds to DNA-dependent RNA polymerase and inhibit initiation of mRNA synthesis |
| Spectrum of activity of Rifamprin | develop rapidly through the mutation of RNA polymerase |
| combination therapy of rifamprin | resistance is common .. used to treat tuberculosis |
| Quinolones is Bactercidal .. e.g names ending with xacin .. Mode of action | binds to alpha subunit of DNA gyrase (topoisomerase) |
| Spectrum activity of rifamprin | gram positive and gram negative bacteria |
| Resistance of rifamprin | mutation to topo genes |
| sulfonamides and sulfones are bacteriostatic .. Mode of action | Competitively inhibit pteridine synthetase, blocking the formation of dihydropteroic acid |
| spectrum activity of sulfonamides and sulfones | broad range activity againts gram positive and gram negative bacteria .. used in urinary tract infection |
| resistance of sulfonamides and sulfones | due to premeability barriers |
| Trimethoprim is bacteriostatic .. mode of action | inhibit the formation of tetrahydrofolic acid |
| Spectrum activity of trimthoprim | broad range activity against gram positive and gram negative bacteria |
| resistance of trimethoprim | due to decrease affinity for substrate |
| combination therapy of trimethoprim | combined with sulfonmides to block 2 distinct steps in folic acid metabolism and prevent emergence of resistance strains |
| Cross resistance definition | single mechanism -- closely related antibiotics are rendered ineffective |
| Multiple resistance definition | Multiple mechanisms -- unrelated antibiotics -- big clinical problem |
| Altered influx definition | Mutation in a transporter necessary to import antibiotics can lead to resistance |
| altered efflux | acquire transporter gene that will pump antibiotics out (tetracycline) |
| what are some ways do to inactivate antibiotics | Beta-lactamase and Chloramphenicol acetyltransferase |
Created by:
amiqnais
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