Antibiotics Flashcards
Antibiotic
Antibiotic = naturally occurring compound that can kill a microbial organism (bacteria/parasite)
Antimicrobial
Antimicrobial = antibiotics as well as synthetic compounds
Multiple mechanisms of action including interfering with building of cell wall and synthesis of nucleic acids
Pharmacotherapy
Antibiotics are a different form of pharmacotherapy (Treatment) than drugs used to treat chronic diseases, in that they target bacterial receptors/proteins instead of patient’s proteins. This makes each patient’s treatment unique as organisms fight back, hide, etc.
Empiric therapy
When a bacterial infection is suspected but isn’t identified yet, a doctor can prescribe a general antibiotic until it is identified. This is called empiric therapy
Definitive therapy
Once the bacteria is identified by laboratory tests, they are supposed to describe an antibiotic that is specifically tailored to that pathogen, which is called definitive therapy.
Doctors don’t always transition from empiric to definitive therapy the way they should, which can be a driver of antibiotic resistance.
Pharmacodynamics
Pharmacodynamics is how antibiotics interact with both the bacteria and the patient. Pharmacodynamics can impact a lot of how effective an antibiotic is going to be. Some antibiotics may inhibit bacterial growth (bacteriostatic), while others kill the organism (bacteriocidal). For example, if the antibiotic interferes with DNA replication it is likely bacteriostatic. If it causes cell lysis, it is bacteriocidal. Usually both are effective, but some infections (like meningitis) require bacteriocidal antibiotics.
Interactions between pharmacodynamics and pharmacokinetics
Concentrations of antibiotics should be considered in the light of pharmacokinetic factors. In order to maintain an MIC or MBC, they have to be taken on a schedule. (more on this in class)
MIC
Whether or not a strain is susceptible to antibiotics is determined by the minimum inhibitory concentration (MIC), which is the minimum amount of antibiotic for inhibiting growth.
MBC
The minimum amount of antibiotic needed to kill a bacteria (if it is bacteriocidal) is the Minimum Bacteriocidal Concentration (MBC).
Pharmacokinetics
Pharmacokinetics is how the patient impacts the concentration of the antibiotic in the body. When an antibiotic is administered, it goes through three stages: absorption, distribution (concentrated differently throughout the body), and metabolism/excretion (most excreted in same form).
How quickly the antibiotic goes through each stage depends on a variety of factors. For example, it matters whether an antibiotic is hydrophobic or hydrophilic, how large the antibiotic is, and how it is administered.
Who discovered/popularized penicillin
Alexander Fleming formally discovered in 1928
Mold Penicillum notatum on petri dish
Purified by Florey and Chain (British researchers) and disseminated during WWII
Beta lactams, tetracycline, anti-metabolites (including how sulfanilamide works) and how they work
Beta lactams are a type of antibiotic that include penicillin and cephalosporin. They have a double-ring structure, and work by interfering with a protein that constructs bacteria cell walls. They are effective against many types of bacteria, but not against certain atypical organisms such as MRSA.
Antibiotics that interfere with ribosome function include tetracyclines. They are named for their 4 ring structure, and work by physically preventing binding tRNA to the ribosome.
Anti-metabolites function by mimicking something that the bacteria needs to metabolize to survive. An example of this is a sulfanilamide antibiotic. They interrupt the bacteria’s ability to take a chemical called p-aminobenzoic acid (PABA) and make folate (vitamin B9). The bacteria must make folate to survive (we get our B9 for our diet). The antibiotic is nearly identical to the structure of PABA but cannot be metabolized. The enzyme that is supposed to metabolize PABA is blocked by the sulfanilamide, like a key breaking off inside of a lock. (We’ll go through this all with pictures in class.)
The process of absorption, distribution, metabolism/excretion of antibiotics (try drawing it out), what impacts it and why it matters in conjunction with pharmacodynamics in determining dosage
How quickly the antibiotic goes through each stage depends on a variety of factors. For example, it matters whether an antibiotic is hydrophobic or hydrophilic, how large the antibiotic is, and how it is administered. DRAW IT OUT
Side effects of antibiotics
Antibiotics can alter microbiome composition and allow for opportunistic pathogens to infect. Patients can also have allergic reactions to antibiotics, or experience side effects due to cellular toxicity. This is true of many antibiotics used to treat TB. At very high doses, certain antibiotics can even cause seizures. Therefore, antibiotics should be very carefully prescribed.
