10 Microbial infection Flashcards
What are viruses?
Obligate parasites
Genetic material in viruses?
DNA or RNA
How do viruses replicate?
Using host-cell nuclear synthetic machinery
How do viruses divide?
By budding out of the cell or by cytolysis
What are some routes of infection?
- Faecal-oral
- Airborne
- Insect vectors
- Blood born
What type of virus is HIV?
Retrovirus
How do retroviruses work?
DNA makes RNA
RNA makes protein
What is the enzyme required for RNA genomes?
Reverse transcriptase
Why smallpox (variola virus) has been eradicated?
Very effective vaccine
Vaccine can be given easily after symptoms are seen
Bacteria internal membrane structure
No internal membranes
Exception: photosynthetic bacteria
Are bacteria diploid or haploid?
Haploid
Single copy of a chromosome
Bacterial cytoskeleton is…
Poorly defined
Bacterial cell wall structure
Contains peptidoglycan
- Determines shape (rod, coccus, spriochaete)
- Basis of stain
How do bacteria divide?
Binary fission
How are bacteria motile?
Have a flagellum
- Swim away from toxins and towards food sources
What is the vaccine target in bacteria?
Capsule
What is the antimicrobial target in bacteria?
Cell wall
What is Shigella?
An invasive bacterial pathogen
How is Shigella transmitted?
Faecal-oral route
Shigella mode of action
Phagocytosed into epithelial cells of GI tract
Replicated and spreads to other cells using host actin
Shigella symptoms
Bloody stools
Diarrhoea
What is a nosocomial infection?
A hospital acquired infection e.g. MRSA
Why are new drugs required?
To combat antimicrobial resistance and shorten treatment
Pathogenic E. coli…
is always present in gut
How does E. coli cause problems?
Can adhere and get into gut cells
Mutation rates in different organisms are…
similiar
More mutations occur when…
the generation time is short
Are fungi prokaryotic or eukaryotic?
Eukaryotic
What do fungi occur in?
Yeasts, filaments or both
What do fungi cause?
- Allergy (reactions to fungal product)
- Mycotoxicoses (ingestion of fungi and their toxic products)
- Mycoses (superficial, subcutaneous or systemic invasion and destruction of human tissue)
How do yeasts spread?
They bud or divide
What are hyphae?
Filaments which have cross walls or septa
Main mode of vegetative growth
What are protozoa?
Unicellular eukaryotic organisms
- Parasites
How do protozoa replicate?
In host by binary fission or by formation of trophozoites inside a cell (asexual)
How is infection acquired?
By ingestion or through a vector
Examples of pathogenic protozoa
Malaria and Leishmaniasis
How is plasmodium infection acquired?
Through a mosquito vector
How does plasmodium replicate?
Formation of trophozoites inside a cell
Protection against malaria
Sickle-cell and β-thalassaemia
What are helminths?
Metazoa with eukaryotic cells
Multicellular
Lifecycle of helminths
Outside of human host
Examples of helminths
Roundworms (Ascaris)
Tapeworms
Flatworms (Flukes)
What are the targets for anti-fungal therapy?
- Cell membrane (ergesterol not cholesterol)
- DNA synthesis
- Cell wall
What Gram negative organism causes hospital acquired pneumonia, burn wounds, particularly affects immunocompromised hosts (e.g. chemotherapy, individuals with cystic fibrosis), and survives on abiotic surfaces?
Pseudomonas aeruginosa
What is the abbreviation for extended spectrum beta-lactam resistant E. coli?
ESBL
What Gram Neagtive organism causes ITU infections, and survives on abiotic surfaces?
?
What Gram Positive organism colonises the nasopharynx, causes bloodstream infections, and disseminated spread (e.g. osteomyelitis & infective endocarditis)?
?
What Gram Positive organism is a commensal of gastrointestinal tract, but can cause bloodstream and urinary tract infections?
?
What Gram Positive organism is a major cause of antibiotic associated diarrhoea and mortality?
Clostridium difficile
