Week 5 Notes Flashcards
What are the three key processes essential for bacterial survival?
- Generation of cell envelope
- Production of bacterial proteins
- Replication of bacterial chromosome
What is the function of the cell envelope in bacteria?
Protective layer surrounding bacteria
What distinguishes Gram-positive bacteria from Gram-negative bacteria?
- Gram +: Cytoplasmic membrane surrounded by rigid cell wall (peptidoglycan)
- Gram -: Cytoplasmic membrane surrounded by a thin cell wall (thin peptidoglycan; more layers than gram +)
Why is the bacterial cell wall a target for antimicrobial agents?
Humans do not have a cell wall
What are the colors associated with Gram staining for Gram-positive and Gram-negative bacteria?
- Gram +: blue/purple
- Gram -: pink
What structural component is created by peptidoglycan in the bacterial cell wall?
Long sugar polymers crosslinked to one another
What role do penicillin-binding proteins play in bacterial cell wall structure?
Aid in the crosslinking of peptide chains
What are the four shapes of bacteria?
- Bacilli: rods
- Cocci: spherical
- Coccobacilli: combination of rods and spheres
- Spirochetes: corkscrew
What is required for protein production in bacteria?
Energy and nucleoside triphosphates (ATP or GTP)
What are the two categories of bacteria based on their oxygen requirements?
- Aerobes: use oxygen for metabolism
- Anaerobes: do not use oxygen
What are facultative bacteria?
May use oxygen present but can replicate and survive without it
What is the oxygen requirement for microaerophilic bacteria?
Need small amounts of oxygen
What is the process of transcription in bacteria?
Bacterial DNA used to synthesize RNA molecule (mRNA) using RNA polymerase
What is the role of ribosomes in bacterial cells?
Synthesize proteins from the information on mRNA
How do bacteria replicate?
Continuously multiply to overwhelm host’s immune system
What is binary fission?
A parent bacterium divides to form two identical daughter cells
What enzyme is responsible for replicating the bacterial chromosome?
DNA polymerase
What is the function of topoisomerases in bacteria?
Enzymes that regulate supercoiling
What is supercoiling in DNA?
Twisting of DNA; extent of twisting can impact DNA replication and transcription as well as how interlinked ‘daughter’ chromosomes become
Supercoiling affects the accessibility of DNA for replication and transcription processes.
What are the two main classes of antibiotics?
- Bactericidal - kill bacteria
- Bacteriostatic - suppress bacterial growth so immune system can finish killing bacteria
Understanding the difference is crucial for selecting the appropriate treatment.
What does MIC stand for?
Minimum inhibitory concentration
MIC is the minimum concentration of antibiotic that can suppress growth of the bacterial isolate.
What is the significance of not using more antibiotics than necessary?
Can cause increased resistance or increased side effects
Overuse of antibiotics can lead to the development of resistant bacterial strains.
What does MBC stand for?
Minimum bactericidal concentration
MBC is the minimum concentration of antibiotic that results in killing of the bacterial isolate.
What is empiric therapy?
Antimicrobial agents frequently used before pathogen is identified; based on experience with a particular clinical entity
This approach is often necessary in urgent clinical situations.
What are the steps to formulate a clinical diagnosis of microbial infection?
- Obtain specimens for laboratory examination
- Formulate a microbiologic diagnosis
- Determine the necessity for empiric therapy
These steps are critical in ensuring appropriate treatment.
What are the four main types of antibiotic resistance mechanisms?
- Decreased permeability/limiting drug uptake
- Antibiotic efflux pump
- Drug inactivation
- Altered target site
Understanding these mechanisms helps in developing strategies to overcome resistance.
What does decreased permeability/limiting drug uptake involve?
Porin loss (alteration of cell wall)
Antibiotics normally enter bacterial cells via porin channels in the cell wall.
What is an antibiotic efflux pump?
Altered uptake of antibiotics; increased efflux
Once antibiotics enter bacterial cells, they are immediately excluded from the cells via active pumps.
What does drug inactivation refer to?
Enzymes destroy antibiotics or prevent binding to target sites
Example: beta lactamase.
What happens when there is an altered target site in bacteria?
Antibiotics are no longer able to bind to modified binding proteins on the bacterial cell surface
This alteration can render certain antibiotics ineffective.
What questions should be asked when prescribing an antibiotic?
- Is an antimicrobial agent indicated based on clinical findings?
- Have appropriate clinical specimens been obtained to establish a microbiologic diagnosis?
- What are the likely etiologic agents for the patient’s illness?
- What measures should be taken to protect individuals exposed to the index case?
- Is there clinical evidence that antimicrobial therapy will confer clinical benefit for the patient?
These questions guide the appropriate use of antibiotics.
