week 4 medical microbiology

• What does "selective toxicity" refer to?


  The ability of a drug to target pathogens without harming the host
• What are the broad categories of antimicrobials?

  Bactericidal, bacteriostatic, sporicidal, virucidal, antiprotozoal, antifungal, antihelmintic
• Why are phenotypic methods important for determining antibiotic susceptibility?


  They help identify how bacteria respond to antibiotics in vitro
• What recent trends are observed in antimicrobial consumption?


  Increased resistance and changing patterns of usage
• What are some early treatments for infections mentioned?

  Oils, quinine, mercury, chaulmoogra oil
• What was the role of carbolic acid in early treatments?


  It was used to treat wound infections
• What was the efficacy of carbolic acid in treating infections?


  It had low efficacy and was damaging to healthy tissue
• What were arsenicals used for in the 1900s?


  As antiprotozoal agents and for treating schistosomiasis and syphilis
• What are sulfa drugs known for?


  Having a limited spectrum of activity
• What is the difference between bactericidal and bacteriostatic agents?


  Bactericidal agents kill bacteria, while bacteriostatic agents inhibit their growth
• What is the significance of Penicillium chrysogenum?


  It is the species used for penicillin drug production
• Why was the original species discovered by Flemming not effective for pharmaceutical use?


  It was not effective enough for clinical use
• Who is credited with the discovery of streptomycin?


  Selman Waksman
• What was the first drug to treat tuberculosis?

  Streptomycin
• How did the discovery of streptomycin differ from that of penicillin?


  Streptomycin was discovered through systematic screening of soil microbes
• What does "serendipitous discovery" mean?


  It refers to an accidental discovery that leads to significant findings
• What are the stages of how infections are established?

  1. Attachment to epithelial surface
  2. Penetration of epithelial surface
  3. Interference/avoidance of host defences
  4. Multiplication in host tissue
  5. Damage of host tissue
• Why do most antibiotics target stage 4 of infection establishment?


  Because they kill organisms or slow growth, allowing host defences to regain control
• What are the mechanisms of action of glycopeptide antibiotics?


  They bind to growing peptidoglycan chains and prevent transglycosylation
• What is the role of beta-lactam antibiotics?


  They bind to penicillin-binding proteins and inhibit cross-linking in the cell wall
• What is the significance of beta-lactamase enzymes?


  They hydrolyze beta-lactam antibiotics, leading to resistance
• What are ESBLs?


  Extended-spectrum beta-lactamases
• Why are beta-lactamase inhibitors important?


  They help restore the effectiveness of beta-lactam antibiotics against resistant bacteria
• What is the mechanism of action of polymyxins?


  They disrupt inner and outer cell membranes, causing cell lysis
• What are the side effects of colistin?


  Nephrotoxicity and neurotoxicity
• How does renal function affect colistin metabolism?


  Poor renal function can lead to higher levels of colistin and increased toxicity
• What are the differences between Gram-positive and Gram-negative bacteria in terms of cell wall structure?


  • Gram-positive: thicker peptidoglycan layer, teichoic acids
  • Gram-negative: thinner peptidoglycan layer, outer membrane as a barrier

  
• What is the role of autolysins in bacterial cell wall synthesis?


  They break peptide bonds but do not create new bonds
• What is the significance of the pentapeptide in peptidoglycan?


  It links NAM and NAG in the bacterial cell wall structure
• What is the function of transpeptidase enzymes?


  They bind NAM-NAG monomers and facilitate cross-linking in the cell wall
• What happens when vancomycin binds to NAM-NAG monomers?


  Transpeptidase is inhibited, preventing cell wall synthesis
• Why is vancomycin considered an antibiotic of last resort?


  Due to the emergence of vancomycin-resistant organisms
• What is the role of clavulanic acid in co-amoxiclav?


  It inhibits beta-lactamase, restoring the effectiveness of amoxicillin
• What is the significance of side chain variations in beta-lactam antibiotics?


  They determine the spectrum of activity and resistance profile
• Why are there fewer antibiotics available for obligately parasitic bacteria?


  Because they have complex life cycles and specific host requirements
• What is the Svedberg unit for bacterial ribosomes?


  70S
• What is the Svedberg unit for eukaryotic ribosomes?


  80S
• What are the subunits of the bacterial ribosome?


  30S and 50S
• What are the subunits of the eukaryotic ribosome?


  40S and 60S
• How does mRNA enter the ribosome during protein synthesis?


  It enters via the small subunit.