exam 3 antibiotic Flashcards
Goal of antimicrobial chemotherapy?
administer a drug to an infected person that destroys the infective agent without harming the host’s cells
T or F - Antimicrobial drugs are produced naturally or synthetically
T
microbicidal
kills microbe
microbiostatic
inhibits the growth or multiplication of microbiota.
keep still, or stop growing → immune system
What are the ideal characteristics of a antimicrobial drug?
- Selectively toxic to the microbe but nontoxic to host cells
- microbicidal rather than microbistatic
- Remains potent long enough to act and is not broken down or excreted prematurely
- Is not subject to the development of antimicrobial resistance
- Complements or assists the activities of the host’s defenses (immune system)
- remains active even when diluted in body fluids and tissues
- readily delivered to the site of infection
- reasonably priced
- does not disrupt the host’s health by causing allergies or predisposing the host to other infectio
Define antibiotics
common metabolic products of aerobic bacteria and fungi
What bacteria genera are found in antibiotics?
- found in soil
- lot of bacteria in soil and kill competition
- not kill them = gene Ab^R
Streptomyces and Bacillus
What genera forms molds? by doing so they secrete antibiotics
Penicillium and Cephalosporium
By inhibiting the other microbes in the same habitat, antibiotic producers have less competition for____ and ____
nutrients and space
Antimicrobial drugs should be selectively toxic - meaning?
drugs should kill or inhibit microbial cells without simultaneously damaging host tissues
- remember microbiocidal
- microbistatis
Antimicrobial drugs should be selectively toxic - meaning?
drugs should kill or inhibit microbial cells without simultaneously damaging host tissues
- remember microbiocidal
- microbistatic
As the characteristics of the infectious agent become more similar to the vertebrate host cell, complete _____ _______ becomes more difficult to achieve and more side effects are seen
selective toxicity
List 5 major components that are useful drug targets in actively dividing cells
- Inhibition of cell wall synthesis
- Breakdown of the cell membrane structure or function
- Interference with functions of DNA and RNA
- Inhibition of protein synthesis
- Blockage of key metabolic pathways
why would be drug target for inhibition of cell wall synthesis be useful?
made of peptidoglycan
why would be drug target for breakdown of the cell membrane structure or function be beneficial?
the phospholipid bilayer
why would be drug target for interference with functions of DNA and RNA be beneficial?
look for differences
why would be drug target for Inhibition of protein synthesis be beneficial?
inhibition of ribosomes or tRNA
why would a drug target for blockage of key metabolic pathways be beneficial?
cell starves
define spectrum
range of activity of a drug
Narrow-spectrum drugs– effective on a
small range of microbes
Target a specific cell component found only in certain microbes
Medium or Broad-spectrum drugs has what type of range of activity?
greatest range of activity
Target cell components common to most pathogens
What antibiotic target cell with medium range?
ampicillin
What antibiotic target cell with broad range?
tetracycline ->targets all bacteria because they have 30S ribosome
A drug that targets lipopolysaccharides in a gram- negative cell would be considered:
- does not say specific LPS
a. Broad Spectrum
b. Narrow Spectrum
c. Selectively Toxic
d. Broad Spectrum and Selectively Toxic
e. Narrow Spectrum and Selectively Toxic
C. selectively toxic
Most bacterial cell walls contain peptidoglycan. Name bacteria that does not contain peptidoglycan.
Bacteria lacking peptidoglycan come into four main categories:
- Mycoplasmas
- bacterial L-forms
- halobacteria
- methanogenic bacteria.
What does penicillins and cephalosporins block the synthesis of? which causes the cell wall to lyse
peptidoglycan
doesn’t destroy block synthesis
cell wall needs maintenance
what type of cells are antimicrobial cell active on?
active on young, growing cells
w/ log phase
Some penicillins that do not penetrate the outer membrane. As a result they are less effective on what type of gram bacteria?
gram-negative bacteria because they are too big to move thru porins
what type of gram bacteria can broad spectrum penicillins and cephalosporins can cross the cell walls?
gram-negative bacteria
Describe Beta-lactam antimicrobials structure?
highly reactive 3 carbon, 1 nitrogen ring
What is the beta-lactam antimicrobial primary mode of action?
primary stop cross-linking of ppg
Greater than ½ of all antimicrobic drugs are what?
beta-lactams
what are the most prominent beta-lactams?
Penicillins and cephalosporins
what is the largest diverse group of compounds that could be synthesized in the laboratory?
pencillin and its relatives
What is an economical approach to obtain natural penicillin?
microbial fermentation and modify it to semi-synthetic forms
Pencillin contains 3 parts
- Thiazolidine ring
- Beta-lactam ring
- Variable side chain dictating microbial activity
what are the most important natural forms of penicillins?
Penicillins G and V
Penicillin is the drug of choice for what type of gram and morphology - there’s two
Penicillin is the drug of choice for gram-positive cocci (streptococci) and some gram-negative bacteria (meningococci and syphilis spirochete)
semisynthetic pencillins examples
ampicillin and amoxicillin have broader spectra – Gram-negative infections
Penicillinase-resistant examples
methicillin, nafcillin, cloxacillin
what is the primary problems of pencillin?
allergies and resistant strains of bacteria