> See also: > - [[Cell Cultures]] # Antimicrobial Chemotherapy Antimicrobial agents are chemicals that kill or inhibit the growth of microorganisms - `-cidal` or `-cide` → “to kill” (*Bactericidal*) - `-static` → “to inhibit” (*Bacteriostatic*) There are three major types of antimicrobials: 1. **Disinfectants** - Chemical agents *used on inanimate surfaces* - Not as effective as steri - Ex: Lysol, Bleach 1. **Antiseptics** - Chemical agents that may be safely *applied to living tissue* - Ex: Hydrogen Peroxide, Rubbing Alcohol 1. **Antibiotics** - a - a ## Discovery/Sources of Antibiotics > See also: > - > [!info] History of Antibiotics > > **Alexander Fleming** (1881) accidentaly > - The exact events are uncertain, although it is speculated that a Penicillium > > **Florey, Chain, and Heatley** built off of Fleming’s research and successfully *isolated and studied* the first true antibiotic, *penicillin*. > > The modern era of chemotherapy began with the work of **Paul Ehrlick** (1854) who defined the theory of *selective toxicity* and obs > - “Dyes can attach to cells, can they also kill them?” Anything that kills bacteria is known as an **antibiotic** Anything that neutralized viruses is known as an **antiviral** The vast majority of antimicrobial chemotherpeutics are antibiotics, meaning that they target bacteria. However, there are several that target viruses and can’t be called > [!important] **Sussy Streptomyces** !> ![[Chair Conformations-2.png]] > - Chloramphenicol, terramycin, neomycin and tetracycline are all true antibiotics isolated from Streptomyces > a > True antibiotics ## Main Modes of Action **Minimal Inhibitory Concentration (MIC):** How much do you need of this drug to inhibit growth of bacteria Minimal Lethal Concentration (MLC): How much do you need to kill the bacteria completely ![[Screenshot from 2023-10-01 17-15-39.png]] ### Selective Toxicity **Selective Toxicity:** The ability to kill or inhibit microbial pathogens while causing minimal damage to the host (typically humans) Anti ![[Chair Conformations-1.png|300]] ### Inhibitors of Cell Wall Synthesis > [[Bacteria Cell Envelope]] the most specific type Transpeptidation penicillin inhibits the enzyme that allows DAP from making a peptide bond https://www.osmosis.org/learn/Antibiotics_-_Beta_lactam_&_beta_lactamase_inhibitor_combinations:_Nursing_Pharmacology A B-lactam ring is common in antibiotics that inhibit synthesis of the bacterial cell wall > [!info] **Penicillins** > inhibits the enzyme that allows DAP from making a peptide bond > > [!info] **Cephalosporins** > Contents > [!info] **Carbapenem** (& Other $\beta$-lactam) > Contents > [!info] **Vancomycin** > Contents Vancomycin does not contain a B-lactam ring - inhibits transpeptidation but by preventing the terminal alanine from being removed - previously considered the “drug of last resort” however bacteria exist today that are resistant ### Protein Synthesis Inhibitors Many antibiotics bind specifically to the bacterial ribosome Other bacteria inhibit a step within the [[Translation|protein synthesis]] process 1. preventing peptide elongation **Aminoglycosides** - bactericidal - cyclohexane ring and amino sugars bind to small subunit *30S protein and rRNA* **Tetracyclins** - four ring structure - bacteriostatic ![[Chair Conformations-3.png|200]] **Macrolides** - 12-22 carbon lactone ring - binds to and inhibits 23S rRNA - erythromycin - azithromycin (chlamydia) **Lincosamides** - aaa **Chloramphenicol** - frist broad spectrum antibiotic - bacteriostatic (bactericidal to sensitive bacteria) - binds to 23S rRNA (can also bind to mitochondrial ribosome) **Oxazolidinones** - bacteriostatic synthetic drugs - binds to 23s rRNA - work against bacteria that are resistant to many broad antibiotic ### Metabolic Antagonists structural analogs “its not sug” ![[Chair Conformations-4.png|300]] > [!info] Sulfonamides/Sulfa Drugs > a > Structurally related to sulfanilamide > doesn’t affect humans as we do not produce folic acid > > [!info] Trimethoprim > a > ### Nucleic Acid Synthesis Inhibition contain several antiviral drugs - viruses aren’t alive and thus don’t last resort drugs > [!INFO] Fluoroquinolones > synthetic drugs containing the 4-quinolone ring amanrtadine herpes: - acyclovir - adenine arabinoside hiv - HAART - nucleoside reverse transcriptase inhibitors (NRTIs) - PrEP (preexposure prophylaxis) anti fungal drugs - ergosterol is often main target - ampho antiprotozoan drugs - mechanism not precisely known - chloroquine and mefloquine () ## Sources of Antibiotics Most true antibiotics Streptomyces is one of the leading maker of true antibiotics Penicillin V & G - Penecillin ## Mechanisms of Drug Resistance ![[Pasted image 20231003223908.png]]