1 - Introduction to Infection Flashcards
What is an infection and why does it cause disease?
Invasion of a host’s tissues by micro-organisms
Caused by: Toxins, Host Response, Microbe Multiplication
What are the general ways a patient can get an infection?
What are the two types of transmission for a disease and how does transmission occur?
How do microorganisms cause disease?
Virulence Factors: Exotoxins (release deliberately) and Endotoxins (part of bacterial structure released when disintegrated)
Host Response: Host damages bacteria to kill it, also damage own tissues. Immune response
What are some examples of exotoxins?
- Enzymes
- Superantigens
- AB toxins
- Cytolytic toxins
RELEASED TO AID VIRUSES SURVIVABILITY IN HOST
What are disease determinants?
Pathogen:
- Virulence Factors (different strains)
- Inocculum size (NORO, small inocculum causes disease though)
- Antimicrobial resistance
Patient:
- Site of infection
- Comorbidities and immune system
When a peatient presents with an infection what questions need to be answered?
- Where is it?
- What is causing it?
- What is the best treatment?
How do we know a patient has an infection?
History: potential exposures and symptoms
Examination: Organ dysfunctions
Investigations: Specific and supportive
When looking at history of symptoms for an infection what do you need to consider?
- Focal/Systemic
- Duration
- Severity
What is a supportive investigation?
- Identifies severity of infection, locate it, point towards prognosis and what may be causing
e. g blood tests, imaging, histopathology
What is a specific investigation?
Determines the organism causing the infection so you know how to manage it
Bacteriology: Microscopy, Antigen detection, Nucleic acid detection and Gram staining. All from swabs, fluids, tissues
Virology: Antigen/Antibody detection, detect viral nucleic acid
What is the microbial world made up of in ascending size order?
- Viruses
- Bacteria
- Fungi
- Parasites
What can cause infection and disease but is not classed as a microorganism?
Prions - can be passed on through surgical instruments
What microorganisms are difficult to treat and why?
Fungi and Yeast as they are eukaryotic so difficult to kill them selectively without killing own cells
Describe the structure of a virus.
Genetic material can be RNA/DNA SS/DS
What is the relevance of knowing whether viruses are enveloped or not and name some examples of enveloped and non-enveloped?
Enveloped are easier to kill
ssDNA non enveloped: Parvovirus 19
ds non-enveloped: Adenovirus, HPV
ds enveloped: Hep B, molluscum contagiosum
What are bacteriophages?
Type of virus that infects bacteria, can transmit information between bacteria
Describe the structure of a bacterium
What are the different bacterial shapes and arrangements?
How do you name bacteria?
- Genus then species, e.g Ashton leah
- Names sometimes suplemented by how they grow and what they are resistant to
Label some medically important bacteria in terms of gram positive/negative and cocci or bacilli.
What is the difference in the cell membrane of prokaryotes and eukaryotes?
Prokaryotes only have carbs, eukaryotes have carbs and sterols
What are the two types of fungi?
- Yeast = single celled e.g candida albicans
- Molds = multicellular e.g athlete’s foot and ring worm
What are the two types of parasite?
- Protozoa = single celled
- Helminths = worms, multicellular
What is the point of chocolate agar and enriched agar?
If a patient appears to have this and the blood culture has no growth what do you do?
Still give them antibiotics as infection may be in tissues not blood. Treat patient not test
What is the difference between gram-positive and gram-negative staining?
Gram-negative more susceptible to attack as thin cell wall
What is the capsule of a bacteria?
- Polysaccharide that helps bacteria to adhere to surfaces, protects bacteria from antibodies, phagocytosis and antibiotics. Prevents bacteria drying
- Spleen normally detects these bacterias so splenectomy must be vaccinated against bacteria
How do you do a gram stain?
What is the MCV and MCH of a full blood count?
MCV: Measures size of RBC
MCH: Measures amount of Hb in each RBC
What are obligate anaerobes and how do they survive?
They can only survive in absence of oxygen, they can form spores which are problematic as they can survive toxic and extreme environments that humans cannot
If you saw this and was told they had a fever what are some differentials you would think of?
- Childhood virus MMR
- Infectious mononucleosis EBV/CMV
- Acute HIV
- Rickettsia
- Dengue
