tetracycline and aminoglycosides Flashcards
what kind of antibiotics target the 30S subunit in the ribosomes
tetracyclines, glycylcycline, aminoglycosides
how does tetracyline work?
it concentrates intracellularly in susceptible organisms, the drug binds reversibly to the 30s subunit of bacterial ribosomes. This action prevents binding of tRNA to the A site of the mRNA ribosome complex, thereby inhibiting bacterial protein synthesis
how is tetracycline administered, how is it absorbed
orally, adequately absorbed
what should you not administer tetracycline with
dairy products or other substance that contain divalent or trivalent cations, decrease absorption particularly for tetracycline due to the formation of non absorbable chelate
penicillins
How is the distribution of tetracycline?
Concentrates well in bile, liver, kidney, gingival fluid and skin, good CSF penetration.
Bind to tissues undergoing calcification or tumours that have a high calcium content.
Accumulates in dentin and gingival crevicular fluid
All tetracycline crosses placental barrier, concentrates in fetal bones and dentition
What kind of bacteria does tetracycline target
broad spectrum against a gram positive, gram negative and atypical bacterial
What bacteria does tetracycline have inadequate activity against
pseudomonas aeruginosa and proteus
What can tetracycline treat
infections caused by rickettsia, chlamydia, vibrio cholerae, mycoplasma pneumoniae
What Cat is tetracycline, doxycycline and minocycline is for pregnancy
cat D
what can doxycyline be used for
skin and soft tissue infection caused by MRSA
Acne
STD
Community aquired pneumonia, S. pneumonia
What can minocycline be used for
H. influenzae, klebsiella spp, mycoplasma pneumonia, yersinia pestis
how is minocycline metabolised
extensively metabolised by liver before excretion
what is the difference between glycycyline and minocycline
it is structurally related to minocycline, it is altered to have an expanded spectrum of activity, designed to overcome tetracycline resistance
how is glycylcycline administered
IV, poor oral bioavailability
How does glycycline distributes
penetrates into tissues, but has low plasma concentration
What is glycycline indicated for
MRSA, MDR streptococci, vancomycine resistant enterococci, esbl gram negative bacteria, useful against carbapenem resistant strain
what are the side effect of tetracycline
- gastric discomfort
- effect on calcified tissues that may cause discoloration and hypoplasia of teeth
- hepatotoxicity
-phototoxicity - vestibular dysfunction
- renal side effects
- superinfection that can lead to CDAD and pseudomembranous colitis
What are the contraindication of glycycyline
- pregnant or breast feeding women
- children less than 8 yo
- last half of pregnancy, affects primary teeth
What types of aminoglycosides are there
- gentamycin
- streptomycin
- tobramycin
- amikacin
-neomycin
how does aminoglycoside function
binds to the 30S subunit, blocks the formation of initiation complex.
Causes misereading of codons as wrong amino acyl tRNAs bind to the A site without matching the codon present in the mRNA at that position, inhibiting translocation
Why does aminoglycoside not target anaerobic bacteria
- because aminoglycoside is transported across the inner membrane via active transport
- therefore bug is anaerobic, aminoglycosides will be inhibited
- entry can be enhanced by cell wall synthesis inhibitors like beta lactams
what are the clinical indications of aminoglycosides
broad spectrum antibody, primarily effective against aerobic gram negative bacteria and microbacteria
typically used to treat g- infections caused by enterobacteriaceae spp like Klebsiella, E.coli
Treat MDR microbes like pseudomonas and acinetobacter
First line defence for MDR tuberculosis
What is the most frequent use for aminoglycoside
empiric therapy for serious infections like septicemia, complicated UTI, nosocomial respiratory tract infections, less effective in anaerobic environment
What is aminoglycoside often used in combination with
B-lactam
how are aminoglycosides administered
iv, im
which aminoglycoside is the best for pseudomonas aeruginosa
tobramycin
which aminoglycoside has the widest antimicrobial spectrum of aminoglycoside
amikacin
which is the most toxic aminoglycoside
neomycin
when is neomycin contraindicated
in the prsence of intestinal obstruction
What are the adverse effect of aminoglycosides
ototoxicity
nephrotoxicity
hypersensitivity
neuromuscular paralysis
What cat is the pregnancy for aminoglycoside
cat D
what is the concentration of aminoglycoside in CSF
inadequate CSF concentration even in the presence of inflamed meninges
