47-Antibiotics I Flashcards
Bacterial Factors in Gram negative bacteria that affect antibiotic action
LPS
Lipid bilayer
Hydrophilic pores
Nutrient receptor proteins allow penetration of drugs similar to nutrients (sideromycins)
Bacterial factors in Gram positive bacteria that affect antibiotic action
Teichoic and Teichruonic acid
Lipid bilayer
Nutrient transport proteins allow penetration of drugs similar to nutrients (D-cycloserine, phosphomycin, tetracycline)
What are the ‘ESKAPE’ bacteria?
a. Enterococcus faecium
b. Staphylococcus aureus
c. Klebsiella pneumonia
d. Acinetobacter baumanni
e. Pseudomonas aeruginosa
f. Enterobacter species
How does resistance to Daptomycin develop?
Gene mutation of mprF which upregulates L-lysine residues to membrane lipids. This increases the overall positive charge of the membrane. Because Daptomycin has cationic properties it is repelled by this charged membrane.
How does resistance to Tetracycline develop?
Increase in efflux pump in cytoplasmic membrane. (Seen in N. gonorrhoeae, E. coli, Strep pneumoniae, and P. aeruginosa)
How does resistance to Metronidazole develop?
Because the drug needs to be “activated” by the bacterium, mutation in the reducing enzymes (rdxA gene) results in impaired drug activation.
How does resistance to streptomycin develop?
The organism can upregulate expression of enzymes that destroy or alter the drug. (Aminoglycoside-modifying enzymes.
How does resistance to Amoxicillin (beta-lactam) develop?
Expression of the enzyme beta-lactamase which can hydrolyze the lactam ring of amoxicillin (or other penicillins and cephalosporins) rendering it ineffective.
How does resistance to Trimethoprim and Sulfonamides develop?
Expression of drug-insensitive enzymes that bind less well to the drug and still work well (dihydropteroate synthase and dihydrofolate reductase)
How does resistance to Vancomycin develop?
Substitution on the peptidoglycan stem so that the agent can no longer bind to the target. (normally blocks proliferation of the peptidoglycan)
