2. Infection Model Flashcards
Outline the basic structure of a virus.
Nucleic acid (DNA or RNA) with a protein capsid coat Envelope - lipid bilayer 'Spikes' on the outside to aid attachment and entry into host cells.
Give an example of a common virus and its structure.
Adenovirus.
DNA, non -enveloped, icosahedral.
What are bacteriophages?
Viruses that infect bacteria and are able to transmit DNA between bacteria.
What are the 2 main bacterial shapes?
Cocci
Bacilli/rod-like
What is a bacterial capsule commonly made up of?
Polysaccharide
How can a bacterial capsule act as a virulence factor?
Poor immunogen - evades immune system and protects from phagocytosis.
What colour do gram-positive bacteria stain?
Purple
What colour do gram negative bacteria stain?
Pink
What is the main structural differences in the cell wall structure of gram positive and gram negative bacteria?
Gram positive have a thick outer peptidoglycan layer.
Gram negative have thin peptidoglycan inner layer.
Lipopolysaccharide on the outside.
What is lipopolysaccharide?
Virulence factor on the cell wall of gram negative bacteria.
Highly toxic and triggers inflammatory response.
What is an aerobe and an obligate aerobe?
Bacteria that can survive in the presence of oxygen.
Obligate aerobes have an absolute requirement for oxygen.
What is an anaerobe and an obligate anaerobe?
Anaerobes can survive in the absence of oxygen. Obligate anaerobes must have an oxygen-free environment to survive.
Give an example of an anaerobe.
Clostridium difficile
Are spores active or dormant?
Dormant form of the bacteria
What is an exotoxin?
Toxin that is released from the bacteria to cause host damage.
What is an endotoxin?
Toxin that is part of the bacterial structure and is only released during cell breakdown.
Give an example of an endotoxin.
LPS
Give an example of a virulence factor that aids adherence to host cells.
Pili
Give an example of a yeast fungi.
Candida albicans
How many cells are yeast fungi made up of?
1 (single-celled!)
Which 2 pathogens are eukaryotes?
Fungi
Parasites
Virus’ and bacteria are _________.
prokaryotes
Give examples of patient factors in the infection model.
- Age
- Gender
- Social factors
- Physiological state
- Pathological state
Why is place an important patient factor?
Current - local infections and outbreaks
Recent travel history
Why does pathogen interaction with the host defences result in host damage?
Causes inflammation.
interaction with cells such as neutrophils releases ROS and cytokines which can trigger local and systemic inflammatory response and host damage.
What are the categories of treatment?
Supportive
Specific
Give examples of commensal bacteria which is found on the skin.
Staphylocuccus aureus
Staph. epidermidis
Streptococcus species
What infections does adenovirus commonly cause?
Conjunctivitis
Respiratory treat infections
Gastroenteritis
What method could be used to identify adenovirus?
Viral PCR
How is adenovirus usually transmitted?
Inhaled - easily spread in large groups
What is the treatment for adenovirus?
Supportive as no anti-virals available.
Outline the steps involved in gram-staining.
- Crystal violet
- Rinse, add Iodine
- Rinse iodine, decolonize with acetone.
- Rinse, apply counterstain safranin
Why do gram positive organisms appear purple yet gram negative appear red?
Gram positive organisms retain the crystal violet stain due to the thick peptidoglycan layer. Gram negative organisms do not retain this, so take up the red colour of the counterstain safranin.
What are the benefits of the microflora in our bodies?
- Compete with invading pathogens for nutrients and space
- Some bacteria in bowel produce antimicrobials
- Stimulus for immune development
- In gut provide nutrients - Vit K
How can microflora become harmful and pathogenic?
- If they are displaced from their normal site and introduced to a n abnormal site.
- Bacteria can convert commonly ingested food into carcinogenic derivatives in colon
- Can overgrow in immunocompromised people
Outline the structure of bacteria.
DNA - circular Extra DNA elements - plasmids which are replicable and transferrable No membrane-bound organelles No nucleus Cell membrane and wall Pili and flagella Ribosomes Capsule (sometimes)
