Antimicrobial Agents Flashcards
define antibiotic.
products of microbes that, in dilute solution, inhibit or kill other organisms
describe antimicrobial agents
man made agents which include antibiotics and synthetic compounds that have the same effect - to inhibit or kill other organisms
what is the difference between agents being static or cidal
static - inhibits microbes
cidal - kills microbes
why may you use a static antimicrobial agent rather than cidal?
gives time for the immune system to eliminate the bacteria
- in case cidal can be more harmful
what test can you use to test the susceptibility of bacteria to drugs? describe it.
disc diffusion test
- grow bacteria on agar plate
- place antimicrobial onto them
- incubate
- observe the zones of clearing around the disc where bacteria has been killed
what is the MIC?
minimum inhibitory concentration
the lowest conc of antibiotic that prevents visible growth
what is the MBC?
minimum bactericidal concentration
the lowest concentration of antibiotic that kills particular bacterium
what is an accurate way of determining the MIC and MBC of a bacteriostatic drug?
using test tubes
- control with only bacteria
- control with only antibiotics
- test tubes with varying concentrations of antibiotics
state the concentration levels of test tubes if the concentration halves every time.
1
1/2
1/4
1/8
1/16
1/32
1/64
1/128
give an example of a bacteriostatic drug
erythromycin
give an example of a bactericidal drug
penicillin
why is selective toxicity important?
to not affect the human host, but just the bacteria
but acting upon bacterial reactions not found in human cells
how can you have problems with selective toxicity? give an example.
can develop allergies
penicillin allergy comes from presence of thiazolidine ring in penicillin
why can antiviral, antifungal and anti protist drugs be more toxic to humans?
closer cell structure to human cells
- can cause damage
how do antiviral drugs work?
inhibit transcription factors
ribozymes
- RNA molecules
- tertiary structure confers enzymatic activity
antisense RNA
- short sequence of RNA, complement of mRNA
- binds to specific mRNA
- prevents translation
give 10 examples of antiviral drugs.
AGARONZZLR
Acyclovir
- treat herpes
Gancyclovir
- treat cytomegalovirus
Amantadine and Rimantadine
- treatment and prevention of influenza A
- target viral entry and uncoating
Oseltamavir (Tamiflu) and Zanamivir (Relenza)
- inhibit neuraminidases
- prevent release of influenza virus from infected cells
Nelfinavir
- inhibits proteases
Zidovudine (AZT)
- inhibits reverse transcriptase
- slows down HIV when patient has developed AIDS
Lamivudine
- inhibits reverse transcripta
Ribavirin
- treat respiratory syncytial virus
heavy use of which drug during the influenza pandemic lead to resistant strains of this virus?
Oseltamivir
give 5 examples of antifungal agents.
NITTA - nitty having mushroom drugs
Nystatin
- a polyene
- treat oral and genital candida infection
Imidazoles and Triazoles
- the Azoles family
- inhibit ergosterol synthesis
= membrane leakage
- imidazole = too toxic for systemic infection but used topically
- triazoles - moulds and yeasts
Terbinafine
- treat skin and nail infections
- inhibits ergosterol biosynthesis
Amphotericin B
- treat systemic mycoses
- potentially toxic to humans
what drug is part of the Triazoles which some yeast species are devloping resistance against? give a fungi which IS resistant to it.
fluconazole
candida krusei
what is Amphotericin B (antifungal drug) also given with, to reduce the potential toxicity to humans?
5-flucytosine (5-FC)
describe 5-FC
5-Flucytosine
- synthetic pyrimidine
- metabolised in fungi to 5-flurouracil
- active against pathogenic yeasts
- how it works
- interfere with nucleic acid synthesis
describe a polyene?
bind with sterols in fungal eukaryotic membranes = destabilisation
what are protists?
unicellular eukaryotes
give examples of antiprotist drugs. (4) queens, pyramid and M
- chloroquine
- mefloquine
- pryimethamine
- metronidazole
what is metronidazole and how does it work? what does it treat?
an antiprotist agent
- induces strand breaks in DNA
- disrupts membrane integrity
treats anaerobic bacteria
- Trichomonas vaginalis
- Entamoeba histolytica
what antibacterial antibiotics target in bacteria? (6)
- cell wall
- membrane integrity
- protein synthesis
- DNA metabolism
- DNA packaging
- RNA polymerase
with antibacterial antibiotics, how do cell wall inhibitors work?
give 4 antibacterial antibiotics that interfere with cell wall.
which is a antibiotic that interferes with the cell wall but is also toxic to humans?
- bacterial cell wall has peptidoglycan
- with L and D amino acids
= targets for selective toxicity
antibiotics:
- cycloserine
- fosfomycin
- glycopeptides
- b-lactams - has a b-lactam ring
toxic antibiotic = bacitracin
what was the first antibiotic in clinical practise?
benzyl penicillin
give 3 types of b-lactam antibacterial antibiotics.
cephalosporins
monobactams
- mainly against gram-negative bacteria
carbapenems
give 3 antibacterial antibiotics that affect membrane integrity.
polymyxins
- against gram negative
metronidazole
- anaerobic bacterial infections
gramicidins
- topically, against gram positive bacteria
what antibacterial antibiotics affect DNA metabolism?
para-aminobenzoic acid
sulphamethoxazole
trimethoprim
folic acid
what antibacterial antibiotics affect DNA?
nalidixic acid
metronidazole
ciprofloxacin
moxifloxacin
levofloxacin
what antibacterial antibiotics affect protein synthesis?
ahminoglycosides
tetracyclines
chloramphenicol
macrolides
fusidic acid
lincosamides
mupirocin
linezoid
