Microbiology 3-4 Flashcards
What is bacteriostatic?
Antibacterial that prevents bacterial growth.
What is most widely prescribed family of antibiotics and give two examples.
Beta-lactams
Penicillin and methicillin
How do beta-lactams work?
Interfere with peptidoglycan synthesis in the cell walls of bacteria.
What is an antibiotic?
An agent that kills or inhibits the growth of a microorganism.
What is an antimicrobial?
Chemical that selectively inhibits microbes.
What is the minimal inhibitory concentration?
The lowest concentration of an antibiotic that is needed for the growth of an infection.
What are the three sources of antibiotic resistance?
Plasmids, transposons and naked DNA.
How do transposons work?
Integrate into chromosomal DNA.
What are the four mechanisms by which ABR works?
1) Change the metabolic profile of the bacterium
2) Change the binding or target site
3) Inactivate the antibiotic
4) Decrease drug accumulation so concentration to inhibit growth is not reached
What are aminoglycosides?
A group of antibiotics that target protein synthesis on the 30S ribosomal subunit in prokaryotes.
What is a downside of ahminoglycosides?
High toxicity so use is limited.
How does Rifampicin work?
Targets transcription of genes and blocks RNA polymerase. Turns tears and urine red so compliance is affected.
How does Vancomycin work?
Targets the integrity of the cell wall and biosynthesis.
How does Linezolid work?
Inhibits initiation of protein synthesis by binding to the 50S subunit.
How does Daptomycin work?
Targets the cell membrane.
What are quinolones?
The first synthetic antibiotics to be synthesised, targeting gyrase in gram-negative bacteria and topoisomerase in gram-positive bacteria.
How can ABR be reduced?
- Stricter control on antibiotic prescription
- Reduced use of broad spectrum antibiotics that suppress gut biota
- Combination therapy
- Knowledge of local strains
- Quicker identification
What increased risk of ABR?
- Crowded wards
- Immunosuppression
- Transmission by staff
- Broken skin (IV and catheters)
What are non-enveloped viruses surrounded by?
Protein capsule
What are enveloped viruses surrounded by?
Lipid capsule derived from previous host
What is the Baltimore classification system?
Virus classification system based on type of genome and type of replication. Grouped in families.
Why do RNA viruses and retroviruses have a high mutation rate?
Use their own polymerase to replicate so lose the ability to proof-read.
Why are RNA genomes limited in size?
Instability of genome in comparison to DNA genomes.
Which is the largest type of virus?
Coronavirus
How do viruses gain access to host cells?
Attach to the ‘viral receptors’ on the cell surface. These receptors were initially used for cell signalling and transportation but viruses have managed to take advantage of them for cell entry.
What is the cytopathic effect?
Structural changes to the host cell caused by a virus. As we cannot see viruses we rely on their effects on host cells to diagnose and differentiate between them.
What are syncytia?
Viruses with surface proteins that are able to fuse at neutral pH.
How is a virus diagnosed? (5)
- Viral genome detected by PCR
- Antigen detected by IFA or ELISA
- Virus particles detected by electron microscopy
- Detect cytopathic effect
- Detect antibodies
