Infectious diseases Flashcards
Inactivated vaccines
WHat is it
involve giving a killed version of the pathogen
Inactivated vaccines involve giving a killed version of the pathogen. They cannot cause an infection and are safe for immunocompromised patients, although they may not have an adequate response. Examples are:
- Polio
- Flu vaccine
- Hepatitis A
- Rabies
Subunit and conjugate vaccines only contain parts of the organism used to stimulate an immune response. They also cannot cause infection and are safe for immunocompromised patients. Examples of subunit and conjugate vaccines are:
- Pneumococcus
- Meningococcus
- Hepatitis B
- Pertussis (whooping cough)
- Haemophilus influenza type B
- Human papillomavirus (HPV)
- Shingles (herpes-zoster virus)
Live attenuated vaccines contain a weakened version of the pathogen. They are still capable of causing infection, particularly in immunocompromised patients. The following vaccines are live attenuated vaccines:
- Measles, mumps and rubella vaccine: contains all three weakened viruses
- BCG: contains a weakened version of tuberculosis
- Chickenpox: contains a weakened varicella-zoster virus
- Nasal influenza vaccine (not the injection)
- Rotavirus vaccine
Toxin vaccines contain a toxin that is normally produced by a pathogen. They cause immunity to the toxin and not the pathogen itself. Examples are ……
. Examples are the diphtheria and tetanus vaccines.
Vaccine Schedule
The HPV vaccine is ideally given to girls and boys before they become sexually active. The intention is to prevent them contracting and spreading HPV once they become sexually active. The current NHS vaccine is Gardasil, which protects against strains
6, 11, 16 and 18
The BCG vaccine is offered from_____ to babies who are at higher risk of ________ These are babies with relatives from countries of high TB prevalence or who live in urban areas with a high rate of TB. It may also be given to children arriving from areas of high TB prevalence or in close contact with people that have TB.
The BCG vaccine is offered from birth to babies who are at higher risk of tuberculosis. These are babies with relatives from countries of high TB prevalence or who live in urban areas with a high rate of TB. It may also be given to children arriving from areas of high TB prevalence or in close contact with people that have TB.
Who thought there was a link between MMR and Autism
Andrew Wakefield
Pathophysiology of Paediatric Spesis
The causative pathogens are recognised by_________, __________ and _____ cells. These cells release vast amounts of cytokines, such as ________ and tumor necrosis factor, to alert the immune system to the invader. These cytokines activate other parts of the immune system. This immune activation leads to further release of chemicals such as _____ ______ that causes _________. The immune response causes inflammation throughout the body.
Many of these cytokines cause the ________ ______ of blood vessels to become more ________. This causes fluid to leak out of the blood into the extracellular space, leading to ______ and a reduction in __________ volume. The oedema around blood vessels creates a space between the blood and the tissues, reducing the amount of oxygen that reaches the tissues.
Activation of the _________ system leads to deposition of ____ throughout the circulation, further compromising organ and tissue perfusion. It also leads to consumption of _______ and _______ _____, as they are being used up to form the blood clots. This leads to ____________, haemorrhages and an inability to form clots and stop bleeding. This is called __________ ________ ________ (DIC).
Blood _____ rises as a result of anaerobic respiration in the hypo-perfused tissues with an inadequate oxygen. A ______ _______ of anaerobic respiration is lactate.
The causative pathogens are recognised by macrophages, lymphocytes and mast cells. These cells release vast amounts of cytokines, such as interleukins and tumor necrosis factor, to alert the immune system to the invader. These cytokines activate other parts of the immune system. This immune activation leads to further release of chemicals such as nitrous oxide that causes vasodilation. The immune response causes inflammation throughout the body.
Many of these cytokines cause the endothelial lining of blood vessels to become more permeable. This causes fluid to leak out of the blood into the extracellular space, leading to oedema and a reduction in intravascular volume. The oedema around blood vessels creates a space between the blood and the tissues, reducing the amount of oxygen that reaches the tissues.
Activation of the coagulation system leads to deposition of fibrin throughout the circulation, further compromising organ and tissue perfusion. It also leads to consumption of platelets and clotting factors, as they are being used up to form the blood clots. This leads to thrombocytopenia, haemorrhages and an inability to form clots and stop bleeding. This is called disseminated intravascular coagulopathy (DIC).
Blood lactate rises as a result of anaerobic respiration in the hypo-perfused tissues with an inadequate oxygen. A waste product of anaerobic respiration is lactate.
WHat is Septic SHock
How should it be treated
Septic shock is diagnosed when sepsis has lead to cardiovascular dysfunction. The arterial blood pressure falls, resulting in organ hypo-perfusion. This leads to a rise in blood lactate as the organs begin anaerobic respiration.
Septic shock should be treated aggressively with IV fluids to improve the blood pressure and tissue perfusion. If IV fluid boluses fail to improve the blood pressure and lactate level, children should be escalated to the high dependency or intensive care unit where medication called inotropes (such as noradrenalin) can be considered. Inotropes stimulate the cardiovascular system and improve blood pressure and tissue perfusion.
Signs of Sepsis
Don’t underestimate observing the child from the end of the bed. Consider whether they look well or unwell.
Hard signs to look out for that can indicate sepsis are:
- Deranged physical observations
- Prolonged capillary refill time (CRT)
- Fever or hypothermia
- Deranged behaviour
- Poor feeding
- Inconsolable or high pitched crying
- High pitched or weak cry
- Reduced consciousness
- Reduced body tone (floppy)
- Skin colour changes (cyanosis, mottled pale or ashen)
Shock involves circulatory collapse and hypoperfusion of organs.
Risk Assessment
There are NICE guidelines from 2019 that cover the assessment of children under 5 year with a fever. They recommend using a traffic light system for the assessment of serious illness in these children. This categorises children as green (low risk), amber (intermediate risk) or red (high risk). Read through the table in the NICE guidelines describing the features of each to familiarise yourself with the signs to look out for. Patients are categorised based on examination findings in various systems:
- Colour: normal colour versus cyanosis, mottled pale or ashen
- Activity: active, happy and responsive versus abnormal responses, drowsy or inconsolable cry
- Respiratory: normal breathing versus respiratory distress, tachypnoea or grunting
- Circulation and hydration: normal skin and moist membranes versus tachycardia, dry membranes or poor skin turgor
- Other: other concerning signs, such as fever > 5 days, non blanching rash, seizures or high temperatures < 6 months
It is worth remembering that all infants under __ _______ with a temperature of ___ or above need to be treated urgently for sepsis, until proven otherwise.
It is worth remembering that all infants under 3 months with a temperature of 38ºC or above need to be treated urgently for sepsis, until proven otherwise.
Sepsis is a medical emergency and needs to be managed urgently. Call for senior help early for experienced support
- Give oxygen if the patient has evidence of shock or oxygen saturations are below 94%
- Obtain IV access (cannulation)
- Blood tests, including a FBC, U&E, CRP, clotting screen (INR), blood gas for lactate and acidosis
- Blood cultures, ideally before giving antibiotics
- Urine dipstick and laboratory testing for culture and sensitivities
- Antibiotics according to local guidelines. They should be given within 1 hour of presentation.
- IV fluids. 20ml/kg IV bolus of normal saline if the lactate is above 2 mmol/L or there is shock. This may be repeated.
Additional investigations may be performed depending on the suspected sepsis infection:
- Chest xray if pneumonia is suspected
- Abdominal and pelvic ultrasound if intra-abdominal infection is suspected
- Lumbar puncture if meningitis is suspected
- Meningococcal PCR blood test if meningococcal disease is suspected
- Serum cortisol if adrenal crisis is suspected
What is meningitis
Meningitis is defined as inflammation of the meninges. The meninges are the lining of the brain and spinal cord. This inflammation is usually due to a bacterial or viral infection.
Neisseria meningitidis is a _____ _____ _________ bacteria. They are circular bacteria (cocci) that occur in pairs (diplo-). It is commonly known as meningococcus.
Neisseria meningitidis is a gram-negative diplococcus bacteria. They are circular bacteria (cocci) that occur in pairs (diplo-). It is commonly known as meningococcus.
What is Meningococcal septicaemia
Meningococcal septicaemia refers to the meningococcus bacterial infection in the bloodstream. Meningococcal refers to the bacteria and septicaemia refers to infection in the blood stream. Meningococcal septicaemia is the cause of the classic “non-blanching rash” that everybody worries about. This rash indicates the infection has caused disseminated intravascular coagulopathy (DIC) and subcutaneous haemorrhages.
Meningococcal meningitis is when the bacteria is infecting the _____ and the _________ ______ around the brain and spinal cord.
Meningococcal meningitis is when the bacteria is infecting the meninges and the cerebrospinal fluid around the brain and spinal cord.
What is MC of Bacterial Meningitis
The most common causes of bacterial meningitis in children and adults are Neisseria meningitidis (meningococcus) and Streptococcus pneumoniae (pneumococcus).
Most common cause of bacterial meningitis in neonates
In neonates the most common cause is group B strep (GBS). GBS is usually contracted during birth from GBS bacteria that live harmlessly in the mother’s vagina.
Presentation of meningitis
Typical symptoms of meningitis are fever, neck stiffness, vomiting, headache, photophobia, altered consciousness and seizures. Where there is meningococcal septicaemia children can present with a non-blanching rash. Other causes of bacterial meningitis do not usually cause the non-blanching rash.
Neonates and babies can present with very non-specific signs and symptoms, such as hypotonia, poor feeding, lethargy, hypothermia and a bulging fontanelle.
NICE recommend a lumbar puncture as part of the investigations for all children:
- Under 1 month presenting with fever
- 1 to 3 months with fever and are unwell
- Under 1 year with unexplained fever and other features of serious illness
There are two special tests you can perform to look for meningeal irritation:
Kernig’s test
Brudzinski’s test
What is Kernig’s test
Kernig’s test involves lying the patient on their back, flexing one hip and knee to 90 degrees and then slowly straightening the knee whilst keeping the hip flexed at 90 degrees. This creates a slight stretch in the meninges. Where there is meningitis it will produce spinal pain or resistance to movement.
What is Brudzinski’s test
Brudzinski’s test involves lying the patient flat on their back and gently using your hands to lift their head and neck off the bed and flex their chin to their chest. In a positive test this causes the patient to involuntarily flex their hips and knees.
Children seen in the primary care setting with suspected meningitis AND a non blanching rash should receive an urgent stat injection (IM or IV) of __________ prior to transfer to hospital, as time is so important. The dose will depending on their age.
Giving antibiotics should not delay transfer to hospital. Where there is a true penicillin allergy, transfer should be the priority rather than finding alternative antibiotics.
Children seen in the primary care setting with suspected meningitis AND a non blanching rash should receive an urgent stat injection (IM or IV) of benzylpenicillin prior to transfer to hospital, as time is so important. The dose will depending on their age.
Giving antibiotics should not delay transfer to hospital. Where there is a true penicillin allergy, transfer should be the priority rather than finding alternative antibiotics.
Hospital management of meningitis
lumbar puncture for cerebrospinal fluid (CSF) should be performed prior to starting antibiotics,.
Send blood tests for meningococcal PCR if meningococcal disease is suspected. This tests directly for the meningococcal DNA.
There should be a low threshold for treating suspected bacterial meningitis, particularly in babies and younger children.
Always follow the local guidelines regarding the choice of antibiotic. Typical antibiotics are:
- Under 3 months – cefotaxime plus amoxicillin (the amoxicillin is to cover listeria contracted during pregnancy)
- Above 3 months – ceftriaxone
Vancomycin should be added to these antibiotics if there is a risk of penicillin resistant pneumococcal infection, for example recent foreign travel or prolonged antibiotic exposure.
Steroids are also used in bacterial meningitis to reduce the frequency and severity of hearing loss and neurological damage. Dexamethasone is given 4 times daily for 4 days to children over 3 months if the lumbar puncture is suggestive of bacterial meningitis.
Bacteria meningitis and meningococcal infection are notifiable diseases, so public health need to be informed of all cases.
The most common causes of viral meningitis are
herpes simplex virus (HSV), enterovirus and varicella zoster virus (VZV).
A sample of the CSF from the lumbar puncture should be sent for viral PCR testing.
Viral meningitis tends to be _____ than bacterial and often only requires supportive treatment. ______ can be used to treat suspected or confirmed HSV or VZV infection.
Viral meningitis tends to be milder than bacterial and often only requires supportive treatment. Aciclovir can be used to treat suspected or confirmed HSV or VZV infection.
A lumbar puncture involves inserting a needle into the lower back to collect a sample of cerebrospinal fluid (CSF). The spinal cord ends at the L1 – L2 vertebral level, so the needle is usually inserted into the L3 – L4 intervertebral space. Samples are sent for ________ _____, _____ _______, ____ ______, _____ and ______-.
A lumbar puncture involves inserting a needle into the lower back to collect a sample of cerebrospinal fluid (CSF). The spinal cord ends at the L1 – L2 vertebral level, so the needle is usually inserted into the L3 – L4 intervertebral space. Samples are sent for bacterial culture, viral PCR, cell count, protein and glucose.
Compare cerebrospinal fluid : bacterial and viral
Comment on Appearance, protein, glucose, WBC, Culture
