DD - Practice Questions (Week 1 and 2) Flashcards
Components of Gram-positive bacteria
Peptidoglycan
Teichoic acids
Cytoplasmic membrane
Components of Gram-negative bacteria
Peptidoglycan Lipopolysacharide Cytoplasmic membrane Outer membrane Periplasmic space Porin proteins
Toxic portion of endotoxin
Lipid A: component of outer membrane in Gram-negative organisms
O and H antigens
O antigen: oligosaccharide antigen
H antigen: flagellar antigen
Why aren’t beta-lactams effective against bacteria in the stationary phase of growth?
Beta-lactam antibiotics target cell wall synthesis; bacteria in the stationary phase are not synthesizing cell walls and so can’t be targeted by beta lactams. Beta lactams are more effective against bacteria in the log phase.
Targets of quinolone antibiotics
DNA synthesis inhibitors: DNA gyrase and DNA topoisomerase
Immune defenses associated with Mycobacterium tuberculosis infection
T-cell mediated defense (M. tuberculosis is an intracellular pathogen)
Coagulase
Agent that inhibits spread of microbes by promoting the deposition of fibrin and helping to “wall off” and localize infections.
Infection
Process whereby a microbe enters into a relationship with the host
Pili
Most commonly involved in mediating adherence of bacteria to human cells - used in bacterial conjugation
Pediatric pneumococcal vaccine
Polysaccharide capsule-protein conjugate: used in children. Illicit help mechanism. Needed to elicit more than an IgM response, which is not protective in children
Rheumatic fever
Caused by production of an antibody against Group A Streptococci that cross-reacts with tissue in the heart
Bacteria causing catheter infections
Staphylococcus (aureus, epidermidis), Enterococcus faecalis
Bactericidal or bacteriostatic antibiotics (in terms of MIC/MBC)
Bactericidal: MBC/MIC < or = 4
Bacteriostatic: MBC/MIC > 4
Botulinum toxin
Cleaves a specific SNARE complex protein, preventing release of intercellular vesicular contents (neurotransmitters)
Phosphatases in Gram-negative bacteria
Most likely to localize in periplasm
Why is it difficult to become immune to Streptococcus pyogenes?
Immunity is related to formation of Ab against M-protein. But becoming immune to all 70 M-protein serotypes is virtually impossible.
Why is it difficult to become immune to Streptococcus pneumoniae?
Immunity is related to producing Ab against the polysaccharide capsule. But becoming immune to all different capsular antigenic types is very difficult.
Why is it difficult to become immune to Neisseria gonorrhoeae?
Immunity is related to producing Ab against the pilus. But you can’t become immune to gonorrhea because of intrastrain genetic variation or interstrain antigenic differences.
Metronidazole
Good for C. diff, C. perfringens, and Bacteroides (DNA inhibitor, only for anaerobes)
Organism most associated with production of coagulase
Staphylococcus aureus
Organism most associated with production of glycocalyx
Coagulase-negative Staphylococcus
Organism most associated with antiphagocytic capsule
Streptococcus pneumoniae
Organism most associated with production of dextrans (enhance adherence to damaged heart valves and teeth)
Viridans streptococci (can cause infective endocarditis)
Organism most associated with production of toxins transferring glucose from UDP-glucose to Rho family GTPases- altering cytoskeleton of enterocytes
Clostridium difficile
Gram-negative rod with intrinsic resistance to penicillin, ceftriaxone, and erythromycin
Pseuomonas aeruginosa
Gram-negative anaerobe frequently associated with abdominal infections and part of normal flora of colon
Bacteroides fragilis
Organism most associated with production of M protein
Streptococcus pyogenes (Group A Strep)
Organism most associated with antigenically distinct pili allowing repeated infection with different strains
Neisseria gonorrhoeae
Organism most associated with a lack of cell wall, precluding use of beta-lactam agents
Mycoplasma
Organism most associated with being an obligate intracellular pathogen
Chlamydia
Which organisms would not routinely be recovered from respiratory specimens from patients?
Chlamydia pneumoniae, Mycoplasma pneumoniae. Would not be recovered using ROUTINE culturing methods - need special methods
VanA mechanism of resistance
Vancomycin
erm mechanism of resistance
Macrolides
gyrA mutation mechanism of resistance
Fluoroquinolones
KPC mutation mechanism of resistance
Ceftriaxone and meropenem
TEM-1 mechanism of resistance
Amoxicillin
Why does amoxicillin have better activity against E. coli than penicillin?
Amoxicillin has a different structure to its R group than does penicillin, so it is more hydrophobic and able to pass through the porins of E. coli to get to the target.
Why does vancomycin work against MRSA?
Vancomycin inhibits stage 2 of cell wall synthesis (attacking precursor molecule) and MRSA is mutated in stage 3 (peptidoglycan crosslinking).
TL;DR vancomycin doesn’t target PBPs and so it doesn’t care if they’re altered or not
Cefazolin has spectrum of activity most like what antibiotic?
Amoxicillin
Diphtheria toxin
Irreversibly inhibits protein synthesis by inactivating EF-2 through ADP ribosylation
Anthrax edema factor
Increases intracellular cAMP. Requires activation by calmodulin
Pertussis toxin
ADP ribosyltransferase, causes increased intracellular cAMP.
Tetanus toxin
Inhibits release of NTs.
Organisms that express resistance to beta-lactams through alteration of PBPs
S. aureus
Coagulase-negative staphylococcus
Streptococcus pneumoniae
Enterococcus faecium
Bacteriostatic antibiotic categories
Protein synthesis inhibitors (except for aminoglycosides)
Intermediary metabolic pathway inhibitors
Bactericidal antibiotic categories
Cell wall synthesis inhibitors
Cell membrane function disruptors
DNA function/synthesis inhibitors
Aminoglycosides (protein synthesis inhibitors)
