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susceptibility
Culturing specimens, antimicrobial agents, susceptability and Quality control
| Question | Answer |
|---|---|
| Beta-lactam drugs includes penicillins, penicillinase resistant penicillins, extended-spectum penicillins, cephems, __________, and __________. | Carbapenems and monobactam |
| Which drugs are included in the natural penicillins? | Penicillin G & V |
| Which drugs are included in the penicillinase resistant penicillins? | Methicillin, oxacillin & nafcillin |
| Which drugs are included in the extended-spectrum penicillins? | Aminopenicillins, carboxypenicillins, & ureidopenicillins |
| Which drugs are included in the aminopenicillins? | Amoxicillin & ampicillin |
| Which drugs are included in the carboxypenicillins? | Carbenicillin & ticarcillin |
| Which drugs are included in the ureidopenicillins? | Azolocillin & mezlocillin |
| The extended-spectrum penicillins differ in their range of activity. Place the following drugs in order of their activity starting with least effective and ending the most effective: azlocillin, ticarcillin, ampicillin | Least-Ampicillin, ticarcillin, Most-azlocillin |
| Which drug is included in the carbapenems? | Imipenem |
| Which drug is included in the monobactam group? | Aztreonam |
| Antibiotics which inhibit cell wall synthesis include penicillins, carbapenems, monobactam, __________, and ____________. | Cephems & vancomycin |
| Antibiotics which inhibit protein synthesis include tetracyclines, erythromycin, azithromycin, clindamycin, __________, and _____________. | Aminoglycosides & chloramphenicol |
| Which drugs inhibit DNA synthesis? | Quinolones and metronidazole |
| Which drugs inhibit folic acid synthesis? | Sulfonamides & trimethoprim |
| Which drugs act on the cytoplasmic membrane? | Bacitracin & polymyxins |
| Which drug damages DNA and bacterial enzymes? | Nitrofurantoin |
| Name the 1st generation cephems. | Cephalothin & cefazolin |
| Name the 2nd generation cephems. | Cefamandole, cefaclor & cefoxitin |
| Name the 3rd generation cephems. | Ceftizoxime, cefoperozone, ceftriaxone & cefotaxime |
| Name a 4th generation cephem. | Cefepime |
| Which organisms are intrinsically resistant to vancomycin? | Most gram-negative MOs & strep-like MO |
| Which organisms are intrinsically resistant to aminoglycosides? | Anaerobes |
| Which organisms are intrinsically resistant to clindamycin? | Gram negative organisms |
| Which genus is intrinsically resistant to sulfonamides & trimethoprim? | Enterococci |
| Which drugs are included in the aminoglycosides? | Gentamicin, amikacin, tobramycin & streptomycin |
| What are the adverse effects of aminoglycosides? | Nephrotoxic & ototoxic |
| What is the adverse effects of tetracyclines? | Discolored teeth |
| What is the adverse effect of quinolones? | Damaged cartilage |
| What are the adverse effects of chloramphenicol? | Bone marrow suppression, aplastic anemia, & gray baby syndrome |
| What is the adverse effect of rifampin? | Red-orange body fluids |
| Which drugs are included in the macrolides? | Erythromycin & azithromycin |
| Which drugs are included in the quinolones? | Nalidixic acid, ciprofloxacin & levofloxacin |
| If a patient was diagnosed with an anaerobic infection, which antibiotic would most likely be prescribed? | Metronidazole |
| Which drug is used to treat only urinary tract infections? | Nitrofurantoin |
| Is this information correct for the broth dilution method? Final concentration=5x10*5 15 minutes to place inoculum in tube Endpoint is tube with highest drug concentation with no visible growth | No-should be lowest drug concentration w/ no visible growth |
| What is the final concentration of MOs when using the agar dilution method? | 10 to the 4th |
| What is the final concentration of MOs when using the disk diffusion method? | 1.5 x 10*8 |
| What is the final concentration of MOs when performing the following tests: MIC, MBC & Schlichter? | 5 x 10*5 |
| Place the following steps of the KB procedure in the correct order: 1. Incubator plate w/in 15 minutes; 2. Read plates against black background; 3. Prepare inoculum & streak MH plate w/in 15 minutes; 4. Apply disks w/in 15 minutes | 3, 4, 1, 2 |
| Is the beta-lactamase test appropriate for the following organisms? H. influenzae, N. gonorrhoae, Staphylococci, M. catarrhalis, K. pneumoniae, Enterococci & Bacteroides | It is appropriate for all except K. pneumoniae. |
| A positive (red) beta-lactamase means the patient can not be treated with _______ & ________. | Ampicillin & penicillin |
| Susceptibility tests are incubated at ____ degrees. | 35 |
| What is the purpose of using ampicillin & sulbactam together? | Sulbactam binds to beta-lactamase which allows ampicillin to be effective |
| What is the purpose of testing cefoxitin disk on staphylococci isolates? | Detect oxacillin resistance |
| How long is the cefoxitin disk incubated when testing Staphylococcus? | 24 hours |
| How is high-level aminoglycoside resistance determined for Enterococci? | Isolates are tested against high levels of gentamicin/streptomycin |
| How are serious infections of Enterococci treated? | Pen, amp, or van + gent or strept |
| What is one advantage to having community acquired MRSA vs hospital acquired MRSA? (not that we want either one) | Community acquired MRSA is usually not multi-resistant |
| Why is the "D" test performed? | To determine if clindamycin resistance can be induced |
| How long is vancomycin incubated when testing Enterococci? | 24 hours |
| What enzyme is detected in the Modified Hodge test? If the enzyme is present, which drugs cannot be used to treat the patient? | Carbapenemase is the enzyme; none of the beta-lactam drugs can be used |
| Define antibiotic. | Substance produced by MO which kills or inhibits other MO. |
| Define antimicrobial agent. | Substance which kills or inibits MO - may be natural, semisynthetic or synthetic |
| Define bactericidal agent | Agent that kills bacteria |
| Define bacteriostatic agent. | Agent that inhibits bacteria |
| Define spectrum of activity. | The range of MOs adversely affected by drug - narrow or broad spectrum |
| Define mechanism of action. | The way a drug harms MOs - may be inhibition of cell wall synthesis |
| Define plasmid. | Extrachromosomal DNA - can replicate & transfer resistance to other MOs |
| Define transposons ("jumping genes"). | DNA segments that move between chromosome & plasmid - may carry resistance |
| Describe the antimicrobial effect of an additive drug interaction. | Sum of the activity of the individual antimicrobials (2+2=4) |
| Describe the antimicrobial effect of an synergy drug interaction. | Effect of two drugs is greater than the sum (2+2=>4) |
| Describe the antimicrobial effect of an antagonism drug interaction. | One drug interferes w/ the activity of another drug (<2) |
| Describe the antimicrobial effect of an indifferent drug interaction. | Drugs work independent of one another - combined equal to most effective drug |
| What is the difference between intrinsic and acquired resistance? | Intrinsic is present at birth - acquired due to mutation/transfer of resistance |
| Bacteria can become resistance due to enzyme inactivation. What is an example of enzyme inactivation? | Staphylococci is resistant to natural penicillins due to penicillinases |
| Bacteria can become resistance due to permeability barriers. What is an example of a permeability barrier? | Most GNBs are resistant to vancomycin - the drug is too big to enter the MO |
| Bacteria can become resistance due to drug efflux. What is an example of drug efflux? | Some bacteria are able to pump tetracycline outside the cell |
| Bacteria can become resistance due to low affinity target sites. What is an example of an altered target site? | Altered penicillin-binding sites have caused resistance in pneumococcus |
| Bacteria can become resistance due to bypass mechanisms. What is an example of a bypass mechanism? | Enterococci resistance to SXT - MO finds folic acid outside of cell |
| How did Staphylococcus become resistant to natural penicillins? | Production of penicillinases |
| How did Staphylococcus become resistant to penicillinase-resistant penicillins? | Altered penicillin-binding proteins |
| How did S. pneumoniae become resistant to penicillin? | Altered penicillin-binding proteins |
| Antimicrobial susceptibility tests are performed on rapid growing organisms including staphylococci, enterics, & P. aeruginosa. Which medium is generally used when testing these organisms and what is the required media pH? | Mueller-Hinton agar or broth; pH 7.2-7.4 |
| What special susceptibility media are required for more fastidious organisms? | Haemophilus test medium; supplemented GC agar; MH w/ blood for pneumo |
| Which antimicrobial susceptibility tests are appropriate for enterics and P. aeruginosa | Broth dilution, agar dilution, disk diffusion, & E-test |
| Which antimicrobial susceptibility tests are appropriate for Staphylococcus species? | Broth dilution, agar dilution, disk diffusion, E-test, & beta-lactamase |
| Which antimicrobial susceptibility tests are appropriate for Enterococcus? | Broth dilution, agar dilution, disk diffusion, E-test, & beta-lactamase |
| Which antimicrobial susceptibility tests are appropriate for S. pneumoniae? | Broth dilution, agar dilution, disk diffusion, & E-test |
| Which antimicrobial susceptibility tests are appropriate for Haemophilus? | Broth dilution, disk diffusion, E-test, & beta-lactamase |
| Which antimicrobial susceptibility tests are appropriate for N. gonorrhoeae? | Agar dilution, disk diffusion, E-test, & beta-lactamase |
| Oxacillin is in the same class of drugs as methicillin and nafcillin. If a staphylococci isolate is resistant to oxacillin, can the patient be treated with methicillin or nafcillin? | Resistance to oxacillin means resistance to all the drugs in the class |
| What happens to susceptibility tests results when too many organisms are placed in the inoculum? OR too few organisms are placed in the inoculum? | Too many MOs = false R; too few MOs = false S |
| What happens to susceptibility tests results when tests are incubated too long? Or not incubated 16-18 hours? | Extented incubation = false R; shortened incubation = false S |
| Lose of disk potency in the disk diffusion test method can cause false _________ . What is one way disks can lose their potency? | Resistance; not allowing the disk cartridges/dispensers to warm to RT |
| Special tests are performed on Enterococci isolates from serious infections. These tests include susceptibility testing of penicillin, ampicillin & vancomycin AND testing for ____________________________? | High level resistance to aminoglycosides |
| When testing vancomycin susceptibility on Enterococci, the test should be held for ___ hours. | 24 |
| Special testing performed to detect methicillin resistant Staphylococci includes cefoxitin disk screen, latex agglutinatin test for PBP2a (altered penicillin-binding protein), and ______________________. | Oxacillin salt screen plate |
| What test is performed on community acquired methicillin resistant S. aureus that is erythromycin resistant & clindamycin susceptible? | D-test |
| Which drugs cannot be reported if Staphylococci is resistant to cefoxitin? | The beta-lactam drugs cannot be reported EVEN if they appear sensitivity |
| What is the disk and test method used to screen for penicillin resistance in S. pneumoniae isolates? If the isolate is resistant, what is the next step? | Disk diffusion (KB) using OX disk; if resistant, perform penicillin MIC |
| What are two special tests that are performed on enterics to detect resistance to certain beta-lactam drugs? | Confirmation test for ESBLs & Modified Hodge test |
| Using disk diffusion (KB) method to detect ESBLs includes testing 3rd generation cephalosporins alone and with clavulanic acid. If ESBLs are produced, which drugs can not be used to treat the patient? | None of the beta-lactam drugs can be used except carbapenems |
| New susceptibility equipment is tested daily for either 20 or 30 days against specific strains of bacteria. If the QC testing is successful, the next step is _______ testing. | Weekly |
| If weekly QC susceptiblity testing is out-of-range, the technologist must run daily QC tests for _ days. If the test results are in range for this period of time, the technologist returns to _______ testing. | 5; weekly |
| True or False Klebsiella is typically resistant to ampicillin & 1st generation cephalosporins. | False: Klebsiella is "R" to ampicillin & carbenicillin/ticarcillin |
| True or False Enterobacter is typically resistant to ampicillin & 1st generation cephalosporins. | True |
| True or False Stenotrophomonas is typically resistant to SXT (trimethoprim-sulfamethoxazole). | False: Stenotrophomonas is typically sensitive to SXT |
| Which of the following organisms is NOT considered normal flora? Listeria, S. aureus, GBS, GAS, N. meningitidis, E. coli, Haemophilus influenzae, Pneumococcus, P. aeruginosa, & Actinomyces israelii | GAS |
| What is the ratio of anaerobes to enterics in the colon? | 1000 anaerobes to 1 enteric |
| All clinical specimens should reach the microbiology lab area within ___ hours of collection. | 2 hours |
| Transport media is used to transport swabs to the clinical lab. What is the purpose of transport medium? | Holding medium to preserve MOs wlo allowing multiplication |
| Which specimens are refrigerated if they cannot be set-up as soon as they arrive in the laboratory? | Specimens that contain normal flora like urines and sputums |
| How should normally sterile body fluids be stored if they cannot be set-up immediately on arrival to the laboratory? | They should be stored at room temperature |
| What are some common pathogens associated with otitis media? | S. pneumoniae, GAS, & H. influenzae, not gp b |
| What are some common pathogens associated with sinusitis? | S. pneumoniae & H. influenzae, not gp b |
| What are some common pathogens associated with meningitis? | S. pneumoniae, N. meningitidis, H. influenzae, type b & GBS |
| How are cells enumerated on gram-stained smears? | Use 10X objective; w/ 10X eyepiece the total magnification is 100X |
| How are bacteria enumerated on gram-stained smears? | Use 100X oil objective; w/ eyepiece the total magnification is 1000X |
| Below are Gram stain results from a sputum: 3+ PMNs 3+ GPC in pairs 1+ GNB Is this specimen acceptable for culture? | Yes, the large number of PMNs indicate it is a quality specimen |
| Below are Gram stain results from a wound: 2+ WBCs (blue in color) 2+ GPB Can the stain results be trusted? Why or why not? | The results cannot be trusted because the cells are underdecolorized |
| Why is a calibrated loop used to inoculate urines? | Because the colony count defines a UTI - generally >10 to the 5th |
| Which calibrated loop is used to inoculate a midstream clean catch urine sample? Which loop is used to inoculate a suprapubic urine aspirate? | .001 loop for midstream; .01 loop for suprapubic |
| Jane Doe's clean catch urine was sent to the lab for culture. It was set-up with a .001 loop. The next day it grew the following organisms: BA - 250 colonies of GNB EMB - 235 colonies of GNB Are these results significant? Why or why not? | >10 to the 5th is considered significant |
| Which specimen is acceptable for culture - IV catheter or urine catheter (Foley catheter)? | IV catheter is acceptable for culture |
| What is considered significant growth from a IV catheter? | >15 colonies |
| Match the following bacteremia patterns with bacterial sources: Transient A. Abscessed tooth Intermittent B. Endocarditis Continuous C. Vigorous toothbrushing | Transient-C; intermittent-A; continuous-B |
| Which anticoagulant is recommended for blood culture bottles? | SPS |
| For many years Bactec blood culture instruments have detected bacterial growth by measuring CO2 production. The instruments have measured CO2 by using radioactivity, ___________, & _____________. | spectrophotometry, and fluorescence. |
| How does the BacT/Alert blood culture machine detect bacterial growth? | Detects color change on blood culture bottle |
| How does the ESP/Trek blood culture machine detect bacterial growth? | ESP/Trek machine detects pressure changes |
| Two sets of blood cultures were obtained from John Doe in the ER. At 24 hours all the blood cultures bottles were positive with GPC (probable staphylococci). Is this a significant result? | Multiple positive bottles typically indicate a significant result |
| Two sets of blood cultures were obtained from John Doe in the ER. At 24 hours one bottle was positive with GPC (probable staphylococci). Is this a significant result? | One positive bottle is most likely a contaminant |
| Blood cultures are sometimes contaminated skin flora including coag-negative staphylococcus, Propionbacterium acnes, ___________, & _____________. | Bacillus species, & Corynebacterium species |
| Which media is used to culture a joint fluid? | BAP, CHOC, & broth |
| Which media is used to culture a sputum? | BAP, EMB or MAC, CHOC |
| Which media is used to culture a urine? | BAP, EMB or MAC |
| Which media is used to culture a wound? | BAP, EMB or MAC, PEA or CNA |
| Which specimens are acceptable for anaerobe culture? | Aspirates & tissues |
| A physician request GC cultures on throat and rectal swabs? Are these acceptable culture requests? | Depending on the patient's sexual practices, GC can be isolated from these sites |
| The lab received a request for a throat Gram stain for GC. Is this an acceptable request? What about a request for a stool Gram stain for Salmonella? | Requests are not acceptable - normal flora looks like the pathogens |
| What is the principle of acridine orange stain? | Stains nucleic acids |
| What is acridine orange used for? | To detect organisms in blood cultures and body fluids |
Created by:
Mwortman
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