Microbiology Flashcards
What is meant by nosocomial infection and when can it be diagnosed?
An infection due to an organism which was acquired at hospital - can be diagnosed after 48 hours after admission to hospital
Name 4 important bacterial causes of nosocomial infection and state whether they are gram positive or negative. (4+4)
Enterococcus Faecium – G+ve
Staphylococcus Aureus – G+ve
Clostridium Difficile – G+ve
Acinetobacter Baumanii – G-ve
Some patient has a lung infection. List three ways to collect a sample from them
Bronchoalveolar lavage
Nasopharyngeal aspirtate
Lung biopsy
Sputum
List four bacteria that can be cultured from them (sample lung infection)
Mycobacterium
Streptococcus pneumonia
Haemophilus influenza
Klebsiella pneumoniae
Explain why looking at sputum and doing a tissue stain is useful
Sputum – easy to obtain and can test many diseases as the pathogens would be trapped in it
Tissue stain – Determines if gram negative or positive: so identifies appropriate treatment
Give an example of a gram positive infection, say what antibiotic it is resistant to and say how the antibiotic works
Staphylococcus Aureus – resistant to methicillin
Methicillin – works by inhibiting activity of penicillin binding proteins that inhibit peptidoglycan synthesis
Give examples of bacterial pathogens that can be vaccinated for
Haemophilus influenza Neisseria Meningitides Streptococcus pneumonia Clostridium diphtheria Bordetella pertussis Clostridium Tetani
Give examples of bacteria causing respiratory tract infections
Legionella pneumophilia (Gram -ve) Mycobacterium tuberculosis (mycobacterium)
Give examples of bacteria causing STIs
Chlamydia trachomatis (obligate intracellular) Neisseria gonorrhoeae (Gram -ve) Treponema pallidum (causes Syphilis)
Give examples of viruses causing STIs
HepB virus
HepC virus
HIV/AIDS
List some food- and waterborne diseases and zoonoses
Campylobacterosis (?)
Cholera (Vibrio cholera)
Listeriosis (Listeria monocytogenes)
Shigellosis (Shigella spp.)
Define an outbreak
When a greater number of individuals than what is normal or expected become infected or diagnosed with a particular infection in a given period of time or particular place or both
How are outbreaks measured, and why is it important?
Identified by surveillance with an established and timely reporting system
Important to identify early, quarantine to prevent further transmission, identify organism and treat
Name 4 types of protozoa and examples of each (4)
Amoeba – Entamoeba histolytic
Coccidia – Toxoplasma; Plasmodium spp.
Ciliates – Balantidium Coli
Flagellates - Trichromonas
What is the difference between protozoa and metazoan?
Protozoa are single celled organisms which do not cause eosinophilia while metazoa are multi-celled organisms which do cause eosinophilia
What are the two types of leishmaniasis and give features of each
Promastigote – in sand-fly vector. Can move in direction of their flagellum and can be cultured
Amastigote – In humans and other vertebrate hosts. No longer motile. Intracellular form of the parasite
What cell type do leishmania reside in?
Macrophage
What are endotoxins and exotoxins
Exotoxins – Toxins that are produced by bacteria and released extracellularly, e.g. neurotoxins and enterotoxins
Endotoxins – Lipid A moiety of lipoproteins produced by Gram negative bacteria which are shed in steady amounts from living bacteria
What are Pyrogenic toxins
Exotoxins which stimulate cytokine release and thus cause fever
Name the general term for the type of toxin that binds directly to both MHCII and T cell receptors.
Superantigens
Name some virulence factors other than toxins that are used by bacteria
Diverse secretion system – e.g. camplylobacter Flagella – e.g. camplylobacter Pilli – e.g Neisseria Capsule- e.g. streptococcus pneumonia Endospores – e.g. clostridium species Biofilms – e.g. pseudomonas aeruginosa
Name two examples of flagellates and the diseases they cause
Giardia Lamblia – Diarrhoea, greasy stools, stomach or abdominal cramps, nausea and vomiting and dehydration
Trichromonas – discharge and dysuria
Name two examples of coccidiae and the diseases they cause
Toxoplasma gondii – can cause toxoplasmosis
Cryptosporidium – diarrhoea, fever, nausea and vomitting
Name the 3 helminth infections
Ascariasis (Ascaris roundworms)
Schistosomiasis (flukes - Schistosoma)
Taenia = Flatworms => taeniasis
Two types of viruses with genetic drift and we have vaccines for them.
Influenza is one with genetic drift and vaccines available
Explain Genetic drift vs Genetic shift.
Antigenic drift = Continued rapid evolution driven by antigenic pressure from the host
Antigenic shift = Introduction of a new subtype from an animal source therefore existing as a different genetically stable serotype that co-circulates in humans
Talk about how viruses evade interferon detection
Hide PAMPS
Interfere globally with host cell gene expression and/or protein synthesis
Block interferon signalling cascade by destroying or binding to cascade components
Inhibit interferon signalling
Block activation of individual interferon induced antiviral enzymes
Activate SOCS suppression of interferon 1 induction
Have a replication strategy which is insensitive to interferon signalling
Give two examples of cytoplasmic sensors for viruses
cGAS senses viral DNA in cell - binds to DNA - forms cGAMP - binds to STING on endoplasmic reticulum -> transcription factor phosphorylation and movement to nucleus e.g. IRF 3 -> interferon transcription
RIG also intracellular detector - RIG-I binds to viral ssRNA or mRNA => RIG-I binds to MAVS => IR3 or IR7 is phosphorylation and translocated into nucleus => transcription of interferon beta
How does toll-like receptor (TLR) recognise viruses
Same way as RIG except it is membrane associated so only recognises endosomes or viruses outside of cell (RIG is intracellular sensor for viruses)
- detect viral RNA => IR3 or IR7 is phosphorylated => interferon transcription
Name two bacterial pathogens that use pyrotoxins
Staphylococcus aureus
Streptococcus pyogenes
