Explain the diagnostic methods used in identifying unknown organisms (i.e., microscope, metabolic, etc.). (USLO 11.1)
List differences between pathogens (fungi, bacteria, protozoan, etc.) that could be a selective target for drug treatment. (USLO 11.2)
Describe the modes of action of antimicrobial drugs (ie: cell membrane, cell wall, protein synthesis, etc). Please provide an example drug for each. (USLO 11.3)
Explain how antiviral drugs work and how do they differ from other organisms' treatment? (USLO 11.4)
Discuss antimicrobial resistance. Be sure to include the mechanisms used by organisms and the implication on treatment options. (USLO 11.5)
Discuss the methods used to select appropriate drugs (ie Kirby Bauer). Why is it important for the clinician to select the most appropriate drug? (USLO 11.6)
Discuss the misuse of antibiotics in the clinical setting. How does this misuse play a role in antibiotic resistance? (USLO 11.7)
Metabolic and Biochemical Tests: These tests are used to identify an organism by its metabolic characteristics. They involve culturing the organism in media containing specific substrates and then observing for chemical reactions. Examples include the catalase test to see if a microbe produces the enzyme catalase, or a fermentation test to determine if it can metabolize specific sugars.
Genetic Analysis: This is a more modern and highly accurate method. Techniques like polymerase chain reaction (PCR) can detect a microbe's DNA or RNA directly from a sample, even in tiny amounts. This method is particularly useful for identifying viruses and other organisms that are difficult to culture.
Differences Between Pathogens for Drug Treatment
Differences in the cellular structures and metabolic processes of pathogens provide selective targets for drug treatment, allowing drugs to harm the pathogen without damaging human cells.
Bacteria: They have a cell wall made of peptidoglycan, which is absent in human cells. Drugs like penicillin specifically target and inhibit the synthesis of this cell wall, causing the bacterial cell to lyse. They also have ribosomes that are structurally different from human ribosomes, which is why drugs like tetracycline can inhibit bacterial protein synthesis without affecting human cells.
Fungi: Fungi have a cell wall made of chitin and a cell membrane that contains ergosterol, which is not found in human cells. Antifungal drugs like amphotericin B target and disrupt the ergosterol in the fungal cell membrane, leading to cell death.
Protozoa: These are single-celled eukaryotes, and their structures are more similar to human cells, making selective targeting more challenging. Drugs often target unique metabolic pathways, such as quinine targeting the parasite's ability to digest hemoglobin.
Viruses: Viruses are non-living entities that require a host cell to replicate. They lack their own metabolic machinery and cellular structures, which is why they cannot be treated with antibiotics. Antiviral drugs must target specific stages of the viral life cycle.
Modes of Action of Antimicrobial Drugs
Antimicrobial drugs work by interfering with essential processes in the target organism.
Cell Wall Synthesis Inhibitors: These drugs prevent the formation of a rigid cell wall, leading to cell lysis.
Example Drug: Penicillin.
Cell Membrane Disrupters: These drugs damage the cell membrane, leading to the leakage of cellular contents.
Example Drug: Polymyxin B.
Protein Synthesis Inhibitors: These drugs bind to bacterial ribosomes, blocking the production of essential proteins.
Example Drug: Erythromycin.
Nucleic Acid Synthesis Inhibitors: These drugs interfere with the replication and transcription of DNA and RNA.
Example Drug: Rifampin.
Metabolic Pathway Inhibitors: These drugs block specific metabolic pathways that are essential for the microbe's survival.
Example Drug: Sulfonamides.
How Antiviral Drugs Work and Their Differences
Antiviral drugs work by targeting specific steps in the viral replication cycle, from entry to exit. Unlike antibiotics, which kill or inhibit bacteria, antivirals focus on preventing the virus from using the host cell to make copies of itself.