Bacteria II Flashcards
How does mupirocin work?
Analogue of isoleucyl tRNA and so inhibits isoleucyl tRNA synthetase - the role is to tether amino acids to their tRNA adapters
Selectivity - binds bacterial synthetase
Narrow spectrum
What is mupirocin specific for?
Gram positive
Outer membrane on gram negative restricts access
What does mupirocin treat?
Topical treatment of staphylococcus and streptococcal skin infections & eliminate nasal carriage of MRSA in hospital patients and staff
Why is mupirocin not applied systemically?
Broken down in the body
Normal - rapidly broken down in kidney and liver producing metabolites which are not antibacterial action
Why is linezolid activity restricted to gram positives?
Removed by efflux pump in gram negatives
What does linezolid bind to?
50S ribosome - interferes with binding or correct positioning of aminoacyl-tRNA in the ribosomal A site
What does linezolid treat?
Skin/soft tissue infections and pneumonia
What are the adverse side effects of linezolid?
Mild/moderate
Skin reactions, GI disturbances, mild and transient abnormalities of liver function
Are tetracyclines broad or narrow spectrum?
Broad
What do tetracycline bind to?
30S subunit and prevent association of aminoacyl-tRNA with the ribosome
What is the purpose of tigecycline?
Solves resistance problems to earlier tetracyclines
IV only - skin, soft tissue and intra-abdominal infections
What are the clinical uses of tetracyclines?
Chlamydia, Lyme disease, cholera, mycoplasma pneumonia
What are the adverse side effects of tetracyclines?
Deposition in bones
CNS effects
Photo sensitivity
GI disturbances for oral products
Are aminoglycosides bactericidal?
Yes
Which aminoglycosides bind to 30S subunit?
Streptomycin and spectinomycin
What aminoglycosides bind to 30S and 50S?
Kanamycin and tobramycin
What do aminoglycosides do?
Cause mid-reading of mRNA producing abnormal proteins
Insertion of abnormal proteins into the cytoplasmic membranes leads to membrane destabilisation and bacterial cell death
What do aminoglycosides treat?
Plague
Enterococcal endocarditis
Sever sepsis
Tuberculosis (combination)
What are the adverse side effects?
Nephrotoxicity
Neuromuscular blockade
Ototoxicity
What does chloramphenicol bind to?
50S subunit - inhibits peptidyl transferase activity
Oral and IV
What are the adverse side effects of chloramphenicol?
Bone marrow suppression and gravy baby syndrome
What are the two types of macrolides?
Azalides and ketolides
How does azithromycin work?
Binds to the 23S rRNA at the peptidyl transferase centre of the 50S ribosomal subunit - causes premature dissociation of the peptidyl tRNA from the P site
What are the two molecules acting synergistically in streptogramins?
Quinupristin (30%) and dalfopristin (70%) - enhances binding
Binds to 50S subunit - inhibit peptide bond formation
What does streptogramins treat?
Vancomycin resistance, skin and soft tissue infections caused by S.Aureus
What are the two lincosamids developed for clinical use?
Clindamycin and lincomycin
How do lincosamides work?
Inhibits peptidyl transferase but don’t share a binding site with chloramphenicol
What are lincosamids active against?
Gram positive aerobes but not gram negative aerobes
What are most antibacterial agents that affect protein synthesis?
Bacteriostatic
