Exam 2 Review Flashcards
How does the BCG vaccine work?
Stimluates the cell mediate response. It can be live, or attentuated from M. bovis.
What is used to decontaminate the sputum specimen?
To decontaminate the specimen with NaOH
What is used to liquefy the sputum specimen?
NALC
What is used in a sputum specimen to eliminate pseudomonas and/or proteus?
Zephiran - Trisodium and oxalic acid
A mycobacterium is found to produce pigment in light and was collected from water. What runyon group does it belong to?
Runyon Group I
A mycobacterium colony produces pigment in dark or light. What runyon group does it belong to?
Runyon Group II
What runyon group does not produce pigment in light or dark conditions?
Runyon group III
What class of antibiotic is structurally similar to acyl-D-alanyl-D-alanine?
Beta Lactam; It targets cell wall synthesis by binding to PBP
Antibiotics have cillin, penem, and ceph in their names. What class do they belong to?
Beta Lactams
What antibiotic requires an anaerobic environment in order for it to be effective?
Metronidazole (anti- nucleic acid synthesis)
What specific antibiotic can cause aplastic anemia?
Chloramphenicol
What antibiotic class inhibits the enzyme at the first step of cell wall synthesis?
Fosfomycin
What class of antibiotics act as a detergent by interacting with the phospholipids of the membrane?
Polymyxin. There is severe renal toxicity as a side effect.
What antibiotic is able to insert a hydrophobic tail into the membrane causing leakage and eventually bacteria death?
Lipopeptides
Lipopeptides may be effective against bacteria however they should not be used in ____?
Respiratory infection because lung surfactant inactivates it.
When can macrolides / ketolides become bactericidal?
If bacteria concentration is low and antibiotic concentration is high.
Deleted
Deleted
Prescribing clindamycin increases the patient’s risk for…?
C diff infection
Chloramphenicol is effective against what kind of bacteria?
Gram negative
How does chloramphenicol kill bacteria?
Inhibits peptidyl transferase (protein synthesis).
Oxazolidinones target…?
23S ribosomal RNA of the 50S subunit (protein synthesis). This prevents the formation of the function 70S initiation complex preventing replication and translation
Dalfopristin targets…?
Ribosomal 50S subunit causing a change in conformation (antiprotein synthesis)
Tetracycline and glycylglycines work against bacteria by targeting
The 30S subunit. Tetracycline binds irreversibly and glycylglycine binds reversibly to the 30S subunit.
Quinolones kill bacteria by targeting…?
DNA Gyrase and topoisomerase
What is a side effect of quinolones?
Tendon rupture and tendonitis
What environment does metronidazole require in order to work?
anaerobic atmosphere
Rifampin targets
RNA polymerase and works best on gram positive
Bacteria colonies growing on a plate that look like bread crumbs. What could it be?
Fusobacterium nucleatum
Bacteria colonies growing on a plate that are black pigmented colonies or black halo. What could it be?
Prevotella melaninogenica or porphyromonas spp.
Bacteria colonies growing on a plate made pits in the plate. What could it be?
Bacteroides ureolyticus
Bacteria colonies growing on the plate. You take a UV light and they fluoresce red. What could they be?
Porphyromonas gingivalis
Ground glass colonies growing on a plate and fluoresce yellow green. What could they be?
Clostridium difficle
You look at a plate and they look like molar tooth and have sulfur granules. What could they be?
Actinomyces israelii
What bacteria grows on skin naturally and produce propionic acid?
Propionibacterium acnes
A blood agar plate is examined with two zones of hemolysis. The inner zone is clear and the outer zone is partial hemolysis. What could the bacteria be?
Clostridium perfringens
A bacteria growing on a plate looks like small gray-white colones and smells sweet. The biochemical tests are
1. Indole +ve
2. Bile esculin -ve
3. Glucose variable
What could this bacteria be?
Bacteroides fragilis
Pinpoint gray - white colones with black pigmented center is growing on the plate. The biochemical tests done are:
1. Indole +ve
2. Bile esculin -ve
3. Glucose +ve
What could this bacteria be?
Fusobacterium nucleatum
Bacteria colonies that look small, gray-black colonies with “halo”.
Biochemical tests are
1. Indole +ve
2. Bile esculin +ve
3. Glucose +ve
What could this bacteria be?
Prevotella, the halo is due to melanin pigment. (There is one other bacteria that shows a halo).
Bacteria colonies that are small, gray-white colonies and smell like ammonia. The biochemical tests results are:
1. Indole +ve
2. Bile esculin -ve
3. Glucose variable
What could this bacteria be?
Bacteroides ureolyticus
Bacteria colonies that look like small, gray - black colonies with a halo. The biochemical results are
1. Indole +ve
2. Bile esculin -ve
3. Glucose variable
What could this bacteria be?
Porphyromonas spp., Halo is made from porphyrin pigment
What is presumptive identification?
Based on phenotypic characteristics such as colonial morphology, Gram stain, and biochemical reactions. Tests used to provide preliminary identification of the organism and guide further confirmatory testing. (Ex. -> Bile esculin agar for detection of Enterococcus spp. and Bacteroides fragilis group)
What is definitive identification?
Based on specific tests that confirm identity of organism. (Ex. -> PCR testing or ELISA for detection of specific antigens or antibodies). Important for determining antimicrobial susceptibility and epidemiological studies.
Describe the gram stain characteristics of bacteroides include shape and pattern.
Gram -ve bacilli with tapered ends, possible bipolar staining, “school of fish”, “jigsaw puzzle” due to clumping
Describe the gram stain characteristics of fusobacterium include shape and pattern.
Gram -ve bacilli with pointed ends and often exhibiting “spindle” or “cigar” shape. May also appear as chains or filaments.
Describe the gram stain characteristics of Propionibacterium include shape and pattern.
Gram +ve bacilli that may be pleomorphic -> coccobacilli to filaments. Can exhibit branching and club-shaped morphology.
Describe the gram stain characteristics of actinomyces include shape and pattern.
Gram +ve bacilli often branching and filamentous, resembling hyphae. Can appear as clubs or rods with beaded or clubbed ends.
Describe the gram stain characteristics of clostridium include shape and pattern.
Gram +ve bacilli usually large and rectangular, with square ends. May appear as long rods or filaments with swollen or spindle-shaped ends.
What is clavulanic acid used for in?
Extended-spectrum beta - lactamases are inhibited by clavulanic acid; therefore, this property can be used as a confirmatory test in the identification process.
What is the purpose of Mcfarland standard?
(i.e., 1.5 3 108 CFU/mL) usually serve as the
starting point for dilutions ultimately achieving the required
final standard bacterial concentration of 5 3 105 CFU/mL
in each microtiter well.
Define intrinsic resistance
Antimicrobial resistance resulting from normal genetic, structural, or physiologic state of a microorganism
Why is there a natural resistance in anaerobic bacteria versus aminoglycosides?
Lack of oxidative metabolism
to drive uptake of aminoglycosides
Why is there a natural resistance in gram-positive bacteria versus aztreonam (beta lactam)?
Lack of penicillin-binding protein (PBP) targets that bind
this beta-lactam antibiotic
Why is there a natural resistance between gram-negative bacteria versus vancomycin?
Lack of uptake resulting from
inability of vancomycin to
penetrate outer membrane
Why is there a natural resistance between pseudomonas aeruginosa versus sulfonamides, trimethoprim, tetracycline, or chloramphenicol?
Lack of uptake resulting in
ineffective intracellular
concentrations of these
antimicrobials
Why is there a natural resistance between Klebsiella versus ampicillin targets?
Production of enzymes (betalactamases) that destroy
ampicillin before it reaches
its PBP target
Why is there a natural resistance between aerobic bacteria versus metronidazole?
Inability to anaerobically reduce drug to its active form.
Why is there a natural resistance between enterococci versus aminoglycosides?
Lack of sufficient oxidative metabolism to drive uptake of aminoglycosides
Why is there a natural resistance between enterococci versus all cephalosporins?
Lack of PBPs that effectively
bind and are inhibited by
these beta-lactam agents
Why is there a natural resistance between lactobacilli and leuconostoc spp. versus vancomycin?
Lack of appropriate cell wall
precursor target to bind
vancomycin and inhibit cell
wall synthesis
Why is there a natural resistance between stenotrophomonas maltophilia versus imipenem?
Production of enzymes (betalactamases) that destroy
imipenem before it reaches PBP targets
List methods for a bacteria to combat antibiotics.
- Enzymatic degradation or modification of the antimicrobial agent
- Decreased uptake or accumulation of the antimicrobial agent
- Altered antimicrobial target
- Circumvention of the consequences of antimicrobial action
- Uncoupling of antimicrobial agent–target interactions and subsequent effects on bacterial metabolism
- Any combination of mechanisms 1 through 5
