20. Bacterial, fungal and protozoal infections in childhood Flashcards
Why do infections result in morbidity and mortality?
This is the result of the infective organism - toxins or as a result of the immunopathology of the host
The bacteria is generally not attempting to kill the host
What are exotoxins?
Toxin secreted by the loving bacterial cell into it’s surrounding
Give examples of exotoxins and the typical symptoms
Cholera diarrhoea - diarrhoea and abdominal pain
Diphteria - sore throat, fever
What are endotoxins?
AKA. Lipopolyacharide - A toxin present within the bacterial cell which is released when the bacterial cell disintegrates
Part of the outer membrane of the gram negative bacteria
When are endotoxins released and what do they result in?
Released during lysis of the organism
Leads to macrophage activation and a huge innate immune reaction and inflammatory cascade via release of IL-6 and TNF-alpha
What are the adverse effects of the inflammatory cascade?
Myocardial depression
Endothelial dysfunction - capillary leak and shock
Coagulopathy
Why do infections develop differently in children compared to adults?
Immune dysfunction - lack of memory, immature
Anatomical e.g. preterm baby- thinner skin, shorter airways, anatomy of Eustachian tube (more horizontal than angular like in adults) - from nasopharynx into the tube to cause ear infection
Increased exposure - hygiene, nursery/daycare
What is the common global presentation of infections?
Fever
Define ‘fever’
Abnormally high body temperature > 37.8 degrees celsius
NB. dependent on how you measure the temp - rectal temp is the most accurate for core temp
Mouth - will be 0.5 lower than core temp
Axilla - will be 1 lower than core temp
What are the four major groups of infections?
Bacterial
Viral
Parasitic
Fungal
Name some severe bacterial infections
a
Name some common bacterial infections
a
What organisms are responsible for septicaemia and meningitis?
Stretococcus pneumoniae
Neisseria meningitidis - mostly group B
haemophilus influenzae B
(All now vaccinated against in imm. schedule)
What are the presentations of septicaemia?
What is the cause of these presentations?
Tachycardia Tachypnoea Prolonged capillary refill Low BP - late sign Rash Fever
These are essentially signs of shock - the body’s way of responding to this e.g. shock due to myocardial depression
What are the three layers of the meninges?
Where does the inflammation occur in meningitis?
Dura mater
Arachnoid
Pia mater
Between the arachnoid and the pia
What are the clinical presentations of meningitis?
High temperature Headache Vomiting Cannot tolerate bright lights Drowsy Stiff neck
How is meningitis diagnosed?
Lumbar puncture
What are the changes in the CSF in meningitis?
Bacterial - cloudy CSF, low blood glucose, some neutrophils, high protein
Viral - clear CSF, high lymphocytes, normal protein and normal glucose - fewer clues
TB (extreme) - lymphocytes present, very high protein, very low glucose
What is the problem with meningitis in infants?
The younger the child, the more non-specific it will present - easier to be missed
Should therefore have a high index of suspicion in an unwell baby
Also that young babies are not fully vaccinated (apart from BCG)
What are the most common infections in neonates?
Group B streptococcus
E. Coli
Listeria
Why are the common infections different in neonates to infants?
They are likely to have been exposed to these during the brith process e.g. maternal colonisation of the pathogens in the vaginal canal (most commonly group B strep - third of women)
What are the most common antibiotics to administer to older children and then to neonates?
Why are these administered before you know the exact diagnosis?
Older children - Cefriaxone
Young infants (<3 months) - Combination of cefotaxime and amoxicillin (to cover listeria in the top three)
Because time taken for blood culture to return from the lab will allow disease progression
What is the difference between early onset and late onset sepsis?
Early onest - within 48 hours of life - more likely pneumococcus septicaemia
Late onset - after 48 hours - more likely meningitis
What are the gram positive organisms? (Need to know)
Cocci:
Staphylococcus
Streptoccus
Enterococcus
Bacilli: Corynebacterium Listeria Bacillus Clostridium
Anything not on this list is likely to therefore be gram-negative
What is the most common streptococcus infection?
Streptococcus pneumoniae - can be invasive or non-invasive
What are the predisposing factors for a pneumococcal infection?
Absent/non-function spleen e.g. hyposplenism in sickle cell
Hypogammaglobulinaemia e.g. low IgG or IgM
HIV infection - T cell immunodeficiency
How can these people in the predisposed groups be protected from a pneumococcal infection?
Vaccination
Lifelong peniccilin daily
What are the clinical features?
Acute otitis media
Sinusitis
Conjunctivitis
Pneumonia - lobar
Septicaemia Meningitis Peritonitis Arthritis Osteomyelitis
What are the vaccinations for pneumococcal infections?
Two types
PPV - pneumococcal polysaccharide vaccine
PCV - pneumococcal conjugate vaccine - routinely to children at two and four months
What is a conjugate vaccine?
The polysaccharide (make immune response against) is conjugated (joined) to a protein This is then engulfed by a B cell and broken up into many fragments and presents of MCII molecule Allows T cells to get engaged and there is antibody production against the polysaccharide
Under the age of two this is underdeveloped
The function of the protein is just to allow the pathogen to enter the B cell
What is serotype replacement?
Vaccination against certain strains of the pneumococcus means that these certain strains will no longer be present in the nasopharynx
BUT this results in other serotypes coming and settling in the nasopharynx which we do not vaccinate against
What is the bacterium responsible for TB infection?
Mycobacterium Tuberculosis
What is the difference between TB infection and TB disease?
Infection - MT is present within the body
Disease - Presents with symptoms
What is progressive primary disease?
The childhood infection of the TB does not result in a well developed immune response and reactivation of the TB will result in symptomatic TB and this has a high chance of ending in death
What is the bacterium responsible for Tetanus?
Clostridium Tetani - exotoxin
Gram positive bacilli
How can Tetanus present in neonates?
Weak Lethargic Poor such Spasms Fits
What are the two different types of Fungi that can cause human disease?
Give an example of each
Yeasts e.g. candida
Moulds e.g. Aspergillus
What type of organism is Fungi?
Eukaryotes
What are the two different types of fungal disease?
Superficial mycoses - normal, common (nothing wrong with the immune system)
Invasive mycoses - rare - usually some problem with anatomical barriers or the immune system
What are common superficial mycoses?
Candidiasis - nappy rash
Tinea corporis - ringworm
What are the immune defects making you vulnerable to fungal infections?
Reduced neutrophil counts
Impaired function of neutrophils e.g. leukocyte adhesion defect (cannot migrate to sites of infection), chronic granulomatous disease
Problem with the T cells, either congenital e.g. SCID or acquired e.g. HIV
What are the different types of protozoa?
Sporozoa
Amoebae
Flagellates
What are the most common types of Protozoa infection in children?
Sporozoa - Plasmodium and Toxoplasma
What is the pathogen responsible for malaria?
P. Falcifarum - most severe
P. Vivax
P. Ovale
P. Malariae
What are the clinical presentations of malaria?
Non-specific - fever, lethargy, vomiting, diarrhoea
What is the most common form of toxoplasma infection?
Congenital toxoplasmosis (cat oocytes)
