week 13 Flashcards
What are the factors that increased life expectancy during the 20th century?
Sanitation, medical advances, nutrition, and antibiotics.
What is the difference between bactericidal and bacteriostatic antibiotics?
Bactericidal: Kills bacteria; used for severe/life-threatening infections; more likely to develop resistance.
Bacteriostatic: Inhibits bacterial growth; preserves microbiome; requires a functional immune system.
What factors should influence the choice between bactericidal and bacteriostatic antibiotics?
Patient’s immune status (immunocompromised or not).
Severity of the infection.
Potential for resistance development.
What is the temperature and time required for an autoclave to kill bacterial endospores?
121°C for 15 minutes.
Name two genera of bacteria with endospores killed by autoclaving.
Clostridium and Bacillus.
What is the purpose of pasteurization?
To heat milk and other liquids to kill bacteria associated with food poisoning, such as Coxiella.
What are the three types of pasteurization, and their characteristics?
LTLT (Low Temp, Long Time): Preserves flavor best, longest process.
HTST (High Temp, Short Time): Slightly longer shelf life.
UHT (Ultra-High Temp): Longest shelf life; no refrigeration needed until opened.
What particle size is filtered out during filtration?
Particles larger than 0.3 µm, including all bacteria and most viruses.
How does irradiation kill microbes?
By inducing DNA mutations and generating free radicals that cause catastrophic damage.
What are common chemical disinfectants and their mechanisms?
Alcohols, 10% bleach, phenols, and formaldehydes; break bacterial cell walls.
What are the common targets of antibiotics?
Cell wall, protein synthesis (ribosomes), cell membrane receptors, DNA synthesis, RNA synthesis, and channels/transporters.
What are beta-lactams, and how do they work?
Beta-lactams prevent peptidoglycan crosslinking in the bacterial cell wall. Example: Penicillin.
How do bacteria resist beta-lactam antibiotics?
By producing beta-lactamases, enzymes that inactivate beta-lactam antibiotics.
What are common resistance mechanisms in bacteria?
Natural resistance (absence of the targeted structure).
Destroying/modifying antibiotics.
Pumping antibiotics out of the cell.
Blocking antibiotic entry.
Mutating/protecting target structures.
How does protein synthesis inhibition by antibiotics avoid harming human cells?
Human ribosomes have a completely different sequence than bacterial ribosomes.
