Systems For Detecting Pathogens I Flashcards
- What are some important features that a pathogens name needs to have
- Needs to be descriptive eg what type of pathogen, what disease it causes
- Uses Systematic bacteriology and virulence
- What do names tell us in terms of pathogenicity or virulence?
Names only imply capacity for pathogenicity
They do not include an assessment of virulence
- What forms the name of the pathogen “Mycobacterium Tuberculosis”
So we can look at taxonomy and see that the domain is a eurobacteria, at the genus level its called a mycobacterium and it causes TB
- What are the three obligate pathogens in humans of the mycobacterial?
Mycobacterium tuberculosis (MTB)
M. leprae
M. ulcerans
- The typical definition of a pathogen is “A biological agent that causes disease or illness to its host” why is this not necessarily right?
what if it was present and not causing disease? Maybe its latent , maybe the patient is a carrier
- Whats a commensal non pathogen (in host) and give an example of one
e.g. E.coli = present but not capable of causing disease in the host
- Whats a Zoonotic Non Pathogen (in carrier) and give an example of one?
present but only capable of causing disease in another host e.g. E.coli 0157:h7 in cattle is subclinical , however if humans gets this E.coli they would be very ill
- What is a commensal opportunistic (host) and give an example?
present and capable of causing disease in the host but only in certain circumstances (immunocompromised) eg Bacteroides Fragilis
- Are all positive samples of a pathogen diagnostic of disease?
being presented with the organism is not always a guarantee that you’re going to get the disease
- What % of humans are infected with Mycobacterium Tuberculosis, what % have the latent disease?
30% of humans are infected : 18% have LATENT disease
- What % of humans are infected with Helicobacter pylori , what % have the latent disease?
50% of humans are infected : 25% have LATENT disease
- How should we define a pathogen?
A microbe CAPABLE of causing a specific degree of host damage
- What controls are important during a test to ensure accurate results?
- Sterile sites must be free from contamination eg. Skin flora in blood cultures
- Non sterile sites require decontamination of normal flora eg Faeces, Mouth, Skin
- Samples with high volume or relatively low infected pathogen load require concentration (centrifugation, filtering) eg CSF, Ascites, 24 hr Urine
- Do samples really need to be cultured?
It depends what you’re looking for
- You don’t really need to, we can amplify the sample for an identification of the organism inside
- Don’t necessarily need to as long as we think it’s there
- BUT you Need to have a rough idea of what you’re looking for
- Explain the difference if you do with culturing or directly?
Culture: Preparation Phase (Enrichment , Amplification and Purification)
Direct: Preparation Phase (Concentration, sample treatment)
Both have the same identification phase
Identification Phase (Molecular DNA/RNA
Gross morphology -Microscopy-
Chemical composition -HPLC MassSpec-)
- How can we detect pathogens using a light microscopy - what kind of pathogens can we detect and why?
- -We can use microscope for very large organisms – Trichomonas Vaginallis ( you can see very easily with a microscope, the most common STD in the world)
- Don’t need to do PCR, culture etc..
- Give some examples of pathogens that are large enough to be detected using light microscopy?
- -Strongyloides (threadworm) very easy to detect with a microscope
- -Entamoeba Histolytica
- -Schistisoma Mansomii