Week 1 - Introduction to Infection and Microbes Flashcards
(24 cards)
Describe the function and characteristics of the red pulp of the spleen.
- Red pulp receives arterial blood which passes into the venous sinuses
- Lined by macrophages which remove old red cells and recycle iron
What is cellulitis?
Non-necrotising inflammation of skin and subcutaneous tissue
State two organisms that are commonly implicated in cellulitis.
Staphylococcus aureus
Streptococcus pyogenes
Define exotoxins.
Bacterial toxins that can cause local or distant damage
Define endotoxins.
Stimulate macrophages to produce cytokines such as interleukin-1 and tumour necrosis factor that cause fever and shock
State the functions of the lymphatic system.
- Fat absorption
- Fluid balance
- Defence
Describe the structure of a lymph node.
Cortex: follicles with germinal center - contains dividing lymphocytes
Medulla: contains phagocytic macrophages
Define lymphadenitis.
Swollen painful lymph node responding to a foreign antigen
State two functions of the thymus.
- Produces lymphocytes
2. Produces a protein hormone thymosins
State the two tissue types present in spleen and outline what each of them contain.
Red pulp: red blood cells and macrophages
White pulp: contains lymphocytes
Outline the structural features of adenovirus.
DNA
Capsid
No envelope
Which parasitic protozoan can cause diarrhoea?
Cryptosporidium
State Koch’s postulates.
- The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
- The microorganism must be isolated from a diseased organism and grown in pure culture.
- The cultured microorganism should cause disease when introduced into a healthy organism.
- The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
What is infection?
Invasion of a host’s tissues by microorganisms
How is disease caused by microorganisms?
- Microbial multiplication
- Host response
- Toxins
How is chicken pox spread?
Airborne
What are the ways in which people can get infected?
- Physical contact, e.g. STIs
- Airborne, e.g. chicken pox
- Vector may be necessary, e.g. mosquito for malaria
- Ingestion of contaminated food or water
- Inhalation of air contaminated with environmental organisms
- Contact with contaminated surfaces, e.g. medical devices
Outline the modes of horizontal transmission.
- Contact: direct, indirect, vectors
- Inhalation: droplets, aerosols
- Ingestion - faecal oral transmission
Outline the disease determinants related to the pathogen.
- Virulence factors
- Inoculum size
- Antimicrobial resistance
Outline disease determinants related to the patient.
- Site of infection
2. Co-morbidities
Outline supportive investigations that can be carried out for a patient with infection.
- Full blood count: neutrophils, lymphocytes
- CRP
- Blood chemistry: liver and kidney function tests
- Imaging: X-ray, ultrasound, MRI
- Histopathology
Outline the specific investigations that can be carried out for a patient with bacterial infection.
- Specimen types: swabs, fluids and tissues
- M, C &S: Microscopy - bacterial cells (e.g. Gram stain), patient cells, e.g. cerebrospinal fluid, culture, antibiotic susceptibility
- Antigen detection
- Nucleic acid detection
Outline the specific investigations that can be carried out for a patient with viral infection.
- Antigen detection: the virus
- Antibody detection: patient’s response
- Detecting viral nucleic acid (DNA/RNA)
Why are asplenic patients susceptible to infection by encapsulated bacteria?
- Encapsulated bacteria are more likely to produce overwhelming sepsis/meningitis in asplenic patients since without a spleen, the patient is deficient in macrophages
- Responsible for clearing opsonised, encapsulated bacteria
