Antimicrobial Susceptibility Testing – Flashcards
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| Define Antimicrobial Susceptibility Testing |
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| use of chemical compounds to treat diseases caused by microorganisms |
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| How are antimicrobials different from antibiotics? |
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| Antibiotics produced by another microorganism. Antimicrobials often synthetic or semi-synthetic. |
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| What determines the effectiveness of a drug on bacteria? |
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| What are some important factors to take into consideration when prescribing a drug for a bacterial infection? |
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| What are 2 ways antimicrobials can attack bacteria? |
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| What is important to consider when prescribing a bacteriostatic drug? |
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| Patient must have a competent immune system to complete the destruction of the microorganism. |
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| What is the principle behind the effectiveness of Beta lactams? |
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| Bind to enzymes (transpeptidases) critical in the production of the cell wall, inactivating the enzyme. |
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| What are the four types of Beta lactams? |
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| What is the common feature of all Beta Lactam drugs? |
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| Have beta lactam ring in their structure. |
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| What types of bacteria should Penicillin be used for? |
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| What types of bacteria should ampicillin be used for? |
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| What types of bacteria should carbepenem be used for? |
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| GNB including Ps. aeruginosa |
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| What types of bacteria should cephalosporins be given for? |
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| Which type of Beta Lactam affects the widest spectrum of organisms? |
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| Cephalosporins |
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| What type of bacteria should monobactams be given for? |
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| GNB |
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| What enzyme do bacteria produce that make them resistant to Beta Lactam drugs? |
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| Beta lactamase (hydrolyzes the beta lactam ring) |
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| What is a specific chemical that inhibits beta lactamase? |
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| Clavulanic acid |
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| Why is Augmentin effective in bacteria that are resistant to Beta Lactam Drugs? |
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| Combines a beta lactam (ampicillin) with a beta lactamase inhibitor (clavulanic acid). |
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| What is the principle behind Vancomycin? |
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| Disrupts cell wall at an earlier stage of its synthesis |
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| What types of bacteria is Vancomycin used for? |
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| Only gram-positive cocci (Staph aureus) |
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| What are the 3 types of drugs that inhibit protein synthesis in bacteria? |
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| What is the principle behind aminoglycosides? |
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| Bind to the 30S causing a misreading of the genetic code |
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| Are aminoglycosides bacteriocidal or bacteriostatic? |
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| Bacteriocidal |
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| What type of bacteria are aminoglycoside drugs used to combat? |
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| What is an example of a widely used aminoglycoside drug? |
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| Amikacin |
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| What are 2 disadvantages to Aminoglycoside drugs? |
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| What is the principle behind the drug, Tetracycline? |
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| Resversibly binds to the 30S spot on bacterial ribosome. |
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| Are Tetracylclines bacteriostatic or bacteriocidal? |
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| Bacteriostatic |
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| What kinds of pathogens are tetracycline drugs used for? |
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| Intracellular pathogen |
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| What are some examples of Macrolide drugs? |
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| What is the principle behind macrolide drugs? |
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| Binds to 50S portion of bacterial ribosome. |
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| Are macrolide drugs bacteriostatic or bacteriocidal? |
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| Bacteriostatic |
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| What kind of infections is the drug azithromycin most commonly used for? |
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| Upper Respiratory Tract infections |
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| What kinds of bacteria is erythromycin most effective against? |
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| What types of bacteria is clindamycin used to treat? |
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| What is the principle behind drugs that inhibit essential metabolites? |
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| Inhibit essential enzymes that bacteria need to make folinic acid (which in turn is used to synthesize DNA). |
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| What type of drug was the first broad spectrum antimicrobial drugs developed? |
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| Sulfonamides |
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| What is the beginning of the folinic acid --> DNA pathway? |
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| para-amino-benzoic acid (PABA) |
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| What drug has the acronym SXT? |
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| trimethoprim |
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| What drug is used in conjugation with sulfonamides to produce a synergistic effect? |
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| Trimethoprim |
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| Are sulfonamides bacteriostatic or bacteriocidal? |
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| Bacteriostatic |
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| What types of bacteria is Bactrim used for? |
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| What types of infections is Bactrim used for? |
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| What are some examples of drugs that are inhibitors of nucleic acid metabolism? |
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| Are inhibitors of nucleic acid metabolism bacteriostatic or bacteriocidal? |
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| Bacteriocidal |
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| What is the principle of Rifampin and what bacteria is it used to combat? |
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| Affects RNA metabolism of M. tuberculosis |
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| What types of bacteria are quinolones used for? |
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| Gram positive and negative |
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| Why can't quinolones be prescribed to children? |
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| Affects cartilage production |
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| What is the principle behind quinolone drugs? |
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| Affect DNA metabolism |
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| What types of bacteria is Cirpofloxcin used to treat? |
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| What is the principle behind the activity of the metronidazole drug? |
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| Affects the actual DNA molecule |
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| What types of bacteria is metronidazole primarily used for? |
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| What is one bad side effect of metronidazole? |
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| Leaves a metallic taste in mouth. |
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| What are 3 mechanisms of bacterial resistance? |
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| Whether or not to do susceptibility testing depends on which factors? |
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| Approximately how many antimicrobials are there to choose from for susceptibility testing? |
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| ~50 |
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| What 3 factors determine which drug panel is chosen for susceptibility testing? |
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| What are the three most commonly used panels in an automated system? |
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| What are the types of susceptibility testing methods? (3 main ones) |
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| What type of media is used in the Kirby Bauer test? |
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| Mueller Hinton agar |
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| What is the principle behind the Microtiter test panels for susceptibility testing? |
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| Each panel uses a number of drugs with a variety of concentrations of each drug in each microwell of panel |
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| What are two ways microtiter plates for susceptibility testing can be stored? |
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| What is the MIC? |
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| There are automated microtiter test panels for susceptibility testing of which organisms? |
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| "Trailing" occurs when which drug is tested using the microtiter plate susceptibility test? |
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| Sulfa drugs |
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| Which result is considered the MIC when "trailing" is observed in microtiter susceptibility testing? |
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| The result that is 80% reduction in growth as compared to the growth control |
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| Which drugs can be used against Ps. aeruginosa? |
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| What is one of the only drugs useful for B. cepacia? |
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| Bactrim |
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| What is the principle behind the E susceptibility test? |
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| Strip with many concentrations of the drug set up on an MH plate. Read where the arc of inhibition intersects the strip. |
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| What kinds of bacteria is the E test commonly used for during susceptibility testing? |
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| All Staph spp that are resistant to penicillins produce what? |
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| Penicillin binding proteins (PBP) |
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| What gene codes for resistance to penicillins? |
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| mecA |
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| What is heteroresistance? |
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| All cells have the gene, but not all express it so some colonies will show resistance and some will show susceptibility |
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| What plate is used to screen for MRSA? |
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| Oxacillin screen plate |
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| Besides an oxycillin screen plate, what other test can be done for detecting MRSA? |
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Disk difusion test (KB) Gives better correlation |
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| A D test must be performed when? |
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| Staph shows resistance to erythromycin and susceptibility to clindamycin |
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| If the D test is positive, how should the result be reported out? |
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| Inducible resistance to clindamycin |
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| What media is used for screening for VRE? |
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| Vancomycin screening plate (BHI plus vancomycin) |
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| What are Extended Spectrum Beta Lactamases (ESBL)? What organisms are included in this catgegory? |
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Resistant to later generations of Beta Lactamases (ampicillin, cephalosporins, and aztreonam) Bacteria: K. pneumoniae, K. oxytoca, E. coli |
