S1) Infection Overview Flashcards
What is an infection?
An infection is the invasion of a host’s tissues by micro organisms
How do people get infections?
Explain by means of a diagram
Identify 3 mechanisms that manifest as disease
- Microbial multiplication
- Toxins
- Host response
Identify and describe the modes of horizontal transmission
- Contact: direct, indirect, vectors
- Inhalation: droplets, aerosols
- Ingestion: faecal-oral route
What is vertical transmission?
Vertical transmission is transmission from mother to child, before or at birth
Describe how microbiota can cause infection
- Microbiota are micro-organisms carried on skin and mucosal surfaces
- Normally harmless / even beneficial unless transferred to other sites
Identify and provide an example for the different mediums for getting infections
- Physical contact e.g. STI
- Airborne spread e.g. Chickenpox
- Animal vector e.g. mosquito for malaria
Describe how one can get an infection from one’s environment
- Ingestion of contaminated food or water
- Inhalation of contaminated air
- Contact with contaminated surfaces
State the first 5 steps that lead to disease caused by micro-organisms
- Exposure
- Adherence
- Invasion
- Multiplication
- Disemmination
Virulence factors are involved in the second step that leads to disease caused by micro-organisms.
Identify some examples
Virulence factors:
- Exotoxins – cytotoxic, AB toxins, superantigens, enzymes
- Endotoxins
What is the last step that leads to disease caused by micro-organisms?
Direct host cellular damage
Identify the disease determinants for pathogens
Pathogen:
- Virulence factors
- Inoculum size
- Antimicrobial resistance
Identify the disease determinants for patients
Patient:
- Site of infection
- Co-morbidities
What 4 overlying questions should one ask when treating a patient with a potential infection?
- Is there an infection?
- Where is the infection?
- What is the cause of the infection?
- What is the best treatment?
What history should one take when treating a patient with a potential infection?
- Symptoms
I. Local / systemic
II. Severity
III. Duration
- Potential exposures
What examination should one perform when treating a patient with a potential infection?
Examine organ dysfunction
Which two investigations should one perform when dealing with a patient with a potential infection?
- Specific investigations
- Supportive investigations
Provide 5 examples of supportive investigations
- Full blood count
- C reactive protein
- Liver and kidney function tests
- Imaging: X-ray, ultrasound, MRI
- Histopathology
Which specimen types are used in bacteriology?
- Swabs
- Fluids
- Tissues
Identify the 5 steps involved in bacteriology
- Microscopy
- Culture (patient and bacteria cells)
- Antimicrobial susceptibility
- Antigen detection
- Nucleic acid detection
Outline the three steps involved in virology
- Antigen detection (the virus)
- Antibody detection (the patient’s response)
- Detecting viral nuclei acid (DNA or RNA)
Identify 4 key considerations regarding infection
- New pathogens
- Antimicrobial resistance
- Healthcare infections
- Re-labelling of established diseases as infections
All clinicians encounter patients with infections.
However, identify the specialities whose primary interest is infection management
- Infectious diseases
- Medical microbiology and virology
- Genitourinary medicine
- Health protection
Which measurements are included in a full blood count?
- WBC count
- WBC differential
- RBC count
- Haemoglobin
- Haematocrit
- Mean corpuscular volume
What is the white blood cell count?
WBC count is a measurement of the actual number of white blood cells per volume of blood
What is a white blood cell differential?
White blood cell differential looks at the types of white blood cells present:
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils
What is the red blood cell count?
RBC count: is a count of the actual number of red blood cells per volume of blood
What is the haemoglobin measurement?
Haemoglobin measures the amount of oxygen-carrying protein in the blood
What is the haematocrit measurement?
Haematocrit measures the amount of space red blood cells take up in the blood (reported as a percentage / a proportion)
What is mean corpuscular volume?
Mean corpuscular volume (MCV) is a measurement of the average size of your RBCs
Identify the circumstances where one can expect increases/decreases in WBC
- Increases: infections, inflammation, leukaemia, cancer
- Decreases: splenomegaly, bone marrow failure, liver disease, some autoimmune conditions
Identify the circumstances where one can expect increases/decreases in lymphocyte%
- Increases in conditions like chronic lymphocytic leukaemia
- Increases/decreases by viral infections
Identify the circumstances where one can expect increases/decreases in neutrophil%
Varies daily:
- Increased in bacterial infections (support diagnosis)
- Decreased in certain infections
