ANTIMICROBIAL AGENTS Flashcards
- Collectively referred as chemotherapeutic agent
- Commonly known as antibiotics
- Any substance from microorganisms or synthetically that are capable of inhibiting or destroying microorgansim even at a low concentration
- Any chemical (drug) used to treat an infectious disease
ANTIMICROBIAL AGENTS
- For bacteria
Antibacterial agents
- coined by Paul Ehrlich, German medical researcher.
- term to describe those chemical agents that kill pathogens without injuring the host.
Chemotherapy
- Example: albendazole, mebendazole, thiabendazole, fenbendazole, etc.
Antihelminthic agent
- substance produce by microorganisms that is effective in killing or inhibiting the
growth of other microorganisms-bacteria - produced by certain molds
- The mold Penicillium notatum, the source of penicillin.
- Example: penicillin
Antibiotic
- Fungal infections
- Local antifungal agents: administered topically
- Systemic antifungal agents: administered orally or intravenously.
- Example: butoconazole, clotrimazole, econazole, fenticonazole, isoconazole,
ketoconazole
Antifungal agents
- Protozoal diseases
- Example: eflornithine, furazolidone, hydroxychloroquine, melarsoprol, metronidazole.
Antiprotozoal agents
- For viral diseases
- Example: abacavir use for hiv, acyclovir (aciclovir) use for herpes, adefovir use for chronic hepatitis b, amantadine use for influenza, ampligen, tamiflu for influenza type a
Antiviral agents
When an antimicrobial agent used to treat any infectious disease is known as
antimicrobial chemotherapy
- Ex: penicillin, daptomycin, fluoroquinolones, metronidazole, nitrofurantoin, cotrimoxazole, telithromycin
Bactericidal antibiotics kill bacteria directly
- Example: penicillin G - effective at killing gram(+)tive bacteria, but not very effective against gram(-)tive bacteria.
Narrow-spectrum antibiotics are only effective against a narrow range of bacteria
- Example: Chloramphenicol, Clindamycin, Ethambutol, Lincosamides, Macrolides, Nitrofurantoin, Novobiocin
Bacteriostatic antibiotics stop/inhibit bacteria from growing.
- Many bacterial and fungal cells have rigid external cell walls - antimicrobial agents destroys
- Ex. penicillin and cephalosporin - w/B-lactam ring, which cross-linking/ interferes peptidoglycans in cell wall.
- Not for Fungi
Mode of Action: Inhibition of cell wall synthesis
- act against both gram (+) & gram(-) bacteria
- Example: Ampicillin, Tetracyclines, Amoxicillin/clavulanic acid
Broad-spectrum antibiotics are effective against a broad range of bacteria
- Function: Lipopolysaccharide, inner and outer membranes
- Example: Polymyxin B, colistin, daptomycin
- Example: Fungi - Polyene antibiotics (amphotericin B) act by binding w/ sterols of fungal cell membrane.
Mode of Action: Disruption of Cell Membrane
- Protein - important component of a cell which is required for DNA, RNA, and ribosome.
- 30S ribosomal subunit – Example: Aminoglycosides, tetracyclines
- 50S ribosomal subunit – Example: Macrolides, lincosamides, chloramphenicol, oxazolidinones
Mode of Action: Inhibition of Protein Synthesis
- Folic acid synthesis enzyme. Example: Sulfonamides, trimethoprim
- Mycolic acid synthesis enzyme. Example: Isonicotinic acid hydrazide
Mode of Action: Action as antimetabolites
- RNA- Example: Rifamycin
- DNA – Example: Fluoroquinolones
Mode of Action: Inhibition of nucleic acid synthesis
- occurs when bacteria, viruses, fungi and parasites change over time and no longer respond to medicines
- making infections harder to treat; increases risk of disease spread, severe illness and death.
Antimicrobial Resistance (AMR)
When a particular microorganism obtains the ability to resist a particular antimicrobial agent to which it was previously susceptible
Acquired resistance
- resistant to at least one antibiotic in three or more drug classes.
- MRSA: methicilluin-resistant Staphylococcus aureus
Multidrug-resistant (MDR)
Bacteria with resistance to several commonly used antibiotics.
Superbugs
- Treatment involving more than one drug.
- Rationale: lesser likelihood that
pathogen develops resistance to
multiple drugs.
Combination therapy
- A resistance gene may code for enzyme that can alter its structure leading to inactivation of the antibiotic
- Ex: some bacteria produce beta-lactamases which can hydrolyze the ß lactam bonds in the chemical structure of the antimicrobial agents
Drug modification or inactivation
Diagnosis or treatment base on clinical educated guess in the absence of complete or perfect information.
Empirical diagnosis and/or treatment
- Gram negative bacteria have developed the ability to change the lipid composition of their outer membrane, thereby preventing the antibiotic from reaching its cellular target
- Resistance to penicillin and cephalosporins
- There are gram positive and gram negative bacteria that have developed an efflux pump that can prevent the antibiotic to accumulate within the bacterial cell
Prevention of cellular uptake or Efflux
- Any change in the structure of the target structures of the antibiotics may lead
to inability to exert its action on the target bacteria
Modification of target sites
- Bacteria target specific enzyme that are essential to the metabolism of the organism
- Overproduction of the target enzyme of the antibiotic leads to enzymes free of antibiotics, allowing the organism to carry out essential enzymatic reaction
Overproduction or bypass of target enzyme
- Involves bacteria producing proteins that are similar in structure to the target site of the antibiotics
- Due to similarity in structure of the new proteins and the target proteins, the antimicrobials bind the new proteins and not the target protein
Target mimicry
- able to adapt to their environment survive and continue
to produce offspring
Natural occurrence
- taking medicines on one’s own initiative or on another person’s suggestion, who is not a certified medical professional”
Self medication
- prescribed antibiotics were unnecessary, duration of therapy
was incorrect
Clinical misuse
- inappropriate disposal of unused/ expired medication expose microbes in envt to antibiotics; trigger evolution of resistance
Environmental pollution
- Antibiotics are fed to livestock to act as growth supplements &
preventative measure to decrease infections.
Livestock
- overuse results in many of these microbes evolving a tolerance
against these antimicrobial agent
Pesticides
