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20 Cards in this Set
- Front
- Back
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what are some factors that determine the effectiveness of antibiotics?
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1. susceptibility of the pathogen
2. drug reaching the site- what route of administration 3. concentration at site- which depends on absorption/metabolism, protein binding, excretion and presence of other bacteria |
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what are some antibiotics which inhibit cell wall synthesis of bacteria?
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penicillin, cephalosporins
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how do quinolones inhibit bacteria?
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inhibit DNA gyrase and topoisomerase so it blocks DNA replication and transcription- inhibit nucleic acid synthesis
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name some antibiotics that interfere with protein synthesis of microbes
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tetracycline, macrolides and aminoglycosides
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how does sulphoamides inhibit bacterial activity?
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sulphonamides have structural analogues of PABA. PABA is used in the synthesis of folate. when drug enters cells, it competes with PABA for enzyme that is involved in folic acid synthesis, causing a decline in folate concentration. it is detrimental to a bacterium because folic acid is a precursor of purines and pyramidines, the bases in construction of DNA and RNA . This leads to inhibition of protein synthesis and DNA replication.
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how is sulphoamides selective for bacteria
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many bacteria manufacture their own folate and cannot take up this cofactor but humans do not synthesize folate as we can obtain it from our diet
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why are aminoglycosides not frequently used?
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they can be toxic- deafness, loss of balance, renal damage
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why are quinolones not frequently used?
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expensive and develop resistance rapidly
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why are sulphoamides not frequently used?
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widespread resistance and hypersensitivity reactions are common
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how do antifungals prevent fungal growth?
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they bind to membrane sterols or prevent synthesis
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how do pathogens prevent entrance of drugs? give an eg.
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Gram -ve bacteria is unaffected by Penicillin G because it cannot penetrate envelope's outer membrane. pathogens can also prevent entrance of drug by genetic mutation of existing genes. these genes can be acquired by transformation, transduction, conjugation
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what are some methods of antibiotic resistance?
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1. the drug is pumped out of cell after it has entered- some pathogens have plasma membrane translocases (efflux pumps) that expel drugs eg E. coli
2. inactivating drugs through chemical modification eg hydrolysing the beta lactam ring of penicillin by penicillinase 3. use alternate pathways to bypass the sequence inhibited by agent and increase production of target meatbolite. for eg. some bacteria are resistant to sulphoamides simple bcos they use preformed folic acid from surroundings rather than synthesize it themselves. |
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what are viruses
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they are intracellular genetic elements and are obligate parasites
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name some viruses that have an icosahedral structure
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adenovirus, herpesvirus and papillomavirus
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what makes the rotavorus so hardy?
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double shelled capsid- it can survive passage through gut and even long periods in sewage despite stringest treatment
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what is the classification of viruses?
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1. kind of nucleic acid genome
2. strategy of replication 3. morphology of virion |
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what are arboviruses?
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they infect insects that ingest vertebrate blood. the virus is replicated in the insect and is transmitted by bite. eg togavirus
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amniotic and allantoic inoculation in chicken eggs can be used to cultivate which virus?
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Influenza
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which virus can be cultivated in yolk sac?
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herpes simplex virus
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what are some mammalian cell lines that can be used to cultivate virus?
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primary cells, diploid cell lines, continuous cell lines
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