Infection Flashcards
Give three pathogens causing meningitis
Bact:
S. pneumoniae
N. meningitids
M. tuberculosis
Viral:
HIV
HSV
How is meningitis diagnosed?
Lumbar puncture (cauda equina, taken between L4 and L5 to avoid hitting nerves)
Check WBC count and type, gram stain
Most abundant WBC in viral and fungal infection?
Lymphocyte
Most abundant WBC in bacterial infection?
Exception and what is found?
Neutrophil.
TB - mix of lymphocyte and neutrophil
Most abundant WBC in parasitic infections or foreign body breach?
Eosinophils
What five patient factors are most important to establish in ED acute sepsis?
Age
Pathological State
Physiological State
Social Factors
Relative Time
Give two indicators and their values used to diagnose SIRS (systemic inflammatory response syndrome).
Heart Rate: >90
Temp: <36 OR >38
Respiratory rate: >20
WBC count: <4 x 10^9/L OR >12 x 10^9/L
How many indicators of inflammation need to be present for a diagnosis?
Two
What is the structure of Adenovirus?
Non-enveloped
Icosahedral
Double Stranded DNA
During what times in the year is adenovirus most prevalent?
Endemic: throughout the year
Give two common sites of adenovirus infection and the mode of access to the body.
Respiratory tract: droplet inhalation
GI: faecal-oral route
What are the two main interactions exhibited by adenovirus to host cells? (Hint: viral phases)
Lytic: replication cycle resultant in cytolysis and dissemination, no host genome integration
Lysogenic (aka latent phase): continuous replication, bypasses cell lysis, insertion of viral DNA into host cell genome.
Advice to reduce spread of viral infection?
Cover nose and mouth when sneezing/coughing
Don’t share towels/drink/food with anyone
Wash hands regularly and well with plenty of soap and hot water
Stay home when possible
Name a gram positive pathogen and an infection caused by it.
Name a gram negative organism and and infection caused by it.
Give one physical and one physiological barrier of the innate immune system.
Physical: Skin, Mucous membranes, Ciliated epithelia Physiological: Diarrhoea, vomiting, coughing, sneezing
What is meant by ‘biological barrier’ in the innate immune system? Give an example.
The biofilm of commensal bacteria that compete with pathogenic bacteria for growth and nutrients. Commensals also produce bactericidal chemicals preventing the growth of pathogenic microorganisms. Examples: Staph aureus on skin Bacteroides fragilis/ E. coli in colon Strep viridans in mouth
Asplenia/Hyposplenia increases risk of infection from what? Give an example.
Polysaccharide encapsulated bacteria/pneumococcus E.g: Strep pneumonia, H. influenzae (type B), N. meningitidis
The deficiency of what complement components increases risk of Neisseria infection?
C3 and C5-9 (MAC)
The two mechanisms of killing in a macrophage are?
Oxygen-dependent: hydrogen peroxide, oxide radicals Oxygen-independant: proteolytic and hydrolytic enzymes (lysozymes)
What is chronic granulomatous disease?
The absence of a respiratory burst and therefore oxygen-dependent killing mechanism in macrophages.
What is the function of a dendritic cell? What receptors are found on them?
Tissue-resident immune cells. First line of defence against barrier breach. Called Langerhans cells in the skin. These are primarily antigen presenting cells and therefore bridge the innate and adaptive immunity. TLR’s 2 and 4 responsible for Gram +ve and -ve detection.
What vascular changes might there be at the site of inflammation?
Vasodilatation - histamine, prostaglandin Increased vascular permeability - histamine, bradykinin
Name an opsonising complement component
C3b, C4b
What is the action of IL-8?
Neutrophil chemoattractant. Produced by macrophages.
Where is C-reactive protein produced? Give two functions.
Liver Measured to indicate inflammation. Monitored to check progress of inflammation/response to treatment.
Mean Arterial Pressure = Total Peripheral Resistance (TPR) x Cardiac Output (CO) Knowing this, how could severe sepsis lead to circulatory shock?
Inflammation due to sepsis leads to mass vasodilatation. Vasodilatation reduces total peripheral resistance. Mean arterial pressure drops. If this continues it could cause circulatory shock.
Why is tachycardia a symptom of septic shock? (cross modular: why are both CO and TPR not reduced in simple septic shock?)
Mean Arterial Pressure = Total Peripheral Resistance (TPR) x Cardiac Output (CO) Sympathetic response to a drop in mean arterial pressure due to drop in total peripheral resistance. Pressure drop detection in carotid sinus and aortic arch –> increased vagus stimulation of SAN to increase HR –> tachycardia to restore cardiac output. (Venous and arterial systems work in opposition. If TPR falls, more blood enters venous system so CO should not be affected unless there is a circulatory breach i.e trauma leading to haemhorraging)
