Bacteria Flashcards
What are the features of bacteria?
Capsule Cell Wall Flagellum Membrane Ribosome Single chromosomes Spores
What is the function of the cell wall of a bacteria?
Prevents the cell wall from bursting (preventing lysis)
What are the two types of cell membrane
- Gram negative. Lipopolysaccharides are used to protect peptidoglycans from bile salts and lysozyme. They may prevent antibiotics from getting into the cell. They contain lipid A which if released causes endotoxic shock.
- Gram positive
What colours do the two types of cell membrane stain ?
Gram negative - Red
Gram positive - Purple
How do bacteria replicate ?
Binary fission
How is genetic variation created in bacteria?
Mutations and transfer of DNA.
How can bacteria be classified?
Phenotypically - Gram stain
Genotypically - Ribosomal RNA sequence or whole gene sequencing
How are bacteria named?
The first half is based on the genius of the bacteria and the second half is based on the species of the bacteria.
How can a strain of bacteria be identified?
DNA typing techniques
What are the different shapes bacteria can come in ?
Cocci (Spheres)
Bacilli (Rods)
Spirals
What are sensitive and resistant bacteria?
Sensitive means that the bacteria is killed or inhibited by X.
Resistant means that the bacteria is not killed or inhibited by X.
What does bactericidal mean?
A antimicrobial that kills a bacteria.
What is a MBC ?
Minimum concentration of a antimicrobial needed to kill an organism.
What does bacteriostatic mean?
A antimicrobial that inhibits a bacteria.
What is a MIC?
The minimum concentration of an antimicrobial needed to inhibit the growth of given organism.
In what ways can antibiotics be administered?
Topical (Onto the skin or mucous membrane)
Systemic (orally)
Parental (IV or IM and subcutaneously)
What are the three ways in which antibiotics work?
- Inhibition of the cell wall
- Inhibition of protein synthesis
- Inhibition of nucleic acid synthesis.
What two antibiotics can carry out inhibition of the cell wall?
B-lactams bactericidal antibiotics.
Glycopeptide bactericidal antibiotics
How do B lactams work?
They work on gram positive bacteria. They disrupt peptidoglycan synthesis by inhibiting enzymes responsible for cross-linking the carbohydrate chains.
How do glycopeptides work ?
They work on gram positive bacteria. They inhibit the assembly of the peptidoglycan precursors. Parental use only.
What are examples of Glycopeptides ?
Vancomycin - IV
Teicoplanin - Single daily dose.
What are the different types of antibiotics which inhibit protein synthesis?
Aminoglycosides bactericidal (Gram neg) Macrolides Bactericidal or bacteriostatic (gram pos) Tetracyclines bacteriostatic (gram pos) Oxazolidinones Bactericidal or bacteriostatic (gram pos) Cyclic lipopeptide strong bactericidal (gram pos)
What are aminoglycosides used for ?
Gram negative bacteria. Premature termination or misreading of RNA. Parental use only.
Example of aminoglycosides
Gentamicin (Cheap and effective) but you have to monitor serum levels.
What are macrolides used for?
Gram positive. Alternative to penicillin. Prevent adding of more amino acids and inhibit ribosomal translation.
Example of macrolides are ?
Erythromycin, azithromycin (good for single doses) and clarithromycin
What are tetracyclines used for?
Gram positive. Prevent tRNA attachment to the ribosome.
What are oxazolidinones used for?
Gram positive. No formation of initiation complex.
Example of oxazolidinones
Linezolid.
What are cyclin lipopeptide strong antibiotics used for?
Gram positive. Create holes in the membrane.
Example of cyclin lipopeptide strong
Daptomycin
What are the different types of antibiotic that inhibits nucleic acid synthesis?
Inhibition in purine synthesis. Bacteriostatic.
Fluroquinolones. Bactericidal.
How do inhibitors in purine synthesis work ? Quinolones.
Inhibit DNA synthesis.
Useful against gram negative
How do fluroquinolones work?
Gram negative
Inhibit DNA synthesis.
What are some adverse side effects to antibiotics?
Allergenic reactions (after to B lactams) Immediate hypersensitivity Delayed hypersensitivity Gastrointestinal Thrush liver toxicity Renal toxicity neurological toxicity Haematological toxicity (Bone)
How can you prevent adverse reactions to antimicrobials?
Only use when necessary
Use the minimum dose
Make sure it is safe to administer the dose i.e. Check if a women is pregnant etc
examples of antibiotics that are safe in pregnancy
Penicillin’s
What are the two types of antimicrobial resistance ?
- Inherent or intrinsic. When in every case that micro-organism is resistant to that antimicrobial
- Acquired. When resistant may be present in some strains but not in others.
Describe how some bacteria become resistant to B lactams
B-lactamases are enzymes that are produced by bacteria and which remove the B lactam ring from the antibiotics making it useless.
How can B lactamases be combated?
- Add a inhibitor i.e. clavulanic acid
- Add a component to prevent the action of the B lactamases. i.e. flucloxacillin
What are the three ways in which bacteria acquiring antimicrobial resistance?
Conjugation - DNA transferred through a join of bacteria
Transduction - Bacteria is transferred by viruses
Transformation - DNA is released from one bacteria and taken up by another
What are prophylaxis?
Antimicrobials given in anticipation of infection i.e. after surgery.
What is the delivery system of antimicrobials
Normally monotherapy but sometimes combinations are necessary.
What are the possible outcomes of antimicrobials being used in combination ?
- The effect is additive
- There effect is Synergistics (Greater than there sum)
What is a susceptibility test?
A test used to determine the MIC.
What antibiotics can be used against gram negative bacteria
Inhibition in purine synthesis. Bacteriostatic.
Fluroquinolones. Bactericidal.
Aminoglycosides bactericidal.
