20. Bacterial, fungal and protozoal infections in childhood

Question 1

Why do infections result in morbidity and mortality?

Answer 1

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

Question 2

What are exotoxins?

Answer 2

Toxin secreted by the loving bacterial cell into it’s surrounding

Question 3

Give examples of exotoxins and the typical symptoms

Answer 3

Cholera diarrhoea - diarrhoea and abdominal pain

Diphteria - sore throat, fever

Question 4

What are endotoxins?

Answer 4

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

Question 5

When are endotoxins released and what do they result in?

Answer 5

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

Question 6

What are the adverse effects of the inflammatory cascade?

Answer 6

Myocardial depression
Endothelial dysfunction - capillary leak and shock
Coagulopathy

Question 7

Why do infections develop differently in children compared to adults?

Answer 7

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

Question 8

What is the common global presentation of infections?

Answer 8

Fever

Question 9

Define ‘fever’

Answer 9

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

Question 10

What are the four major groups of infections?

Answer 10

Bacterial
Viral
Parasitic
Fungal

Question 11

Name some severe bacterial infections

Answer 11

a

Question 12

Name some common bacterial infections

Answer 12

a

Question 13

What organisms are responsible for septicaemia and meningitis?

Answer 13

Stretococcus pneumoniae
Neisseria meningitidis - mostly group B
haemophilus influenzae B

(All now vaccinated against in imm. schedule)

Question 14

What are the presentations of septicaemia?

What is the cause of these presentations?

Answer 14

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

Question 15

What are the three layers of the meninges?

Where does the inflammation occur in meningitis?

Answer 15

Dura mater
Arachnoid
Pia mater

Between the arachnoid and the pia

Question 16

What are the clinical presentations of meningitis?

Answer 16

High temperature 
Headache
Vomiting
Cannot tolerate bright lights
Drowsy 
Stiff neck

Question 17

How is meningitis diagnosed?

Answer 17

Lumbar puncture

Question 18

What are the changes in the CSF in meningitis?

Answer 18

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

Question 19

What is the problem with meningitis in infants?

Answer 19

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)

Question 20

What are the most common infections in neonates?

Answer 20

Group B streptococcus
E. Coli
Listeria

Question 21

Why are the common infections different in neonates to infants?

Answer 21

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)

Question 22

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?

Answer 22

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

Question 23

What is the difference between early onset and late onset sepsis?

Answer 23

Early onest - within 48 hours of life - more likely pneumococcus septicaemia
Late onset - after 48 hours - more likely meningitis

Question 24

What are the gram positive organisms? (Need to know)

Answer 24

Cocci:
Staphylococcus
Streptoccus
Enterococcus

Bacilli:
Corynebacterium
Listeria
Bacillus
Clostridium

Anything not on this list is likely to therefore be gram-negative

Question 25

What is the most common streptococcus infection?

Answer 25

Streptococcus pneumoniae - can be invasive or non-invasive

Question 26

What are the predisposing factors for a pneumococcal infection?

Answer 26

Absent/non-function spleen e.g. hyposplenism in sickle cell Hypogammaglobulinaemia e.g. low IgG or IgM HIV infection - T cell immunodeficiency

Question 27

How can these people in the predisposed groups be protected from a pneumococcal infection?

Answer 27

Vaccination | Lifelong peniccilin daily

Question 28

What are the clinical features?

Answer 28

Acute otitis media Sinusitis Conjunctivitis Pneumonia - lobar ``` Septicaemia Meningitis Peritonitis Arthritis Osteomyelitis ```

Question 29

What are the vaccinations for pneumococcal infections?

Answer 29

Two types PPV - pneumococcal polysaccharide vaccine PCV - pneumococcal conjugate vaccine - routinely to children at two and four months

Question 30

What is a conjugate vaccine?

Answer 30

``` 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

Question 31

What is serotype replacement?

Answer 31

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

Question 32

What is the bacterium responsible for TB infection?

Answer 32

Mycobacterium Tuberculosis

Question 33

What is the difference between TB infection and TB disease?

Answer 33

Infection - MT is present within the body | Disease - Presents with symptoms

Question 34

What is progressive primary disease?

Answer 34

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

Question 35

What is the bacterium responsible for Tetanus?

Answer 35

Clostridium Tetani - exotoxin Gram positive bacilli

Question 36

How can Tetanus present in neonates?

Answer 36

``` Weak Lethargic Poor such Spasms Fits ```

Question 37

What are the two different types of Fungi that can cause human disease? Give an example of each

Answer 37

Yeasts e.g. candida | Moulds e.g. Aspergillus

Question 38

What type of organism is Fungi?

Answer 38

Eukaryotes

Question 39

What are the two different types of fungal disease?

Answer 39

Superficial mycoses - normal, common (nothing wrong with the immune system) Invasive mycoses - rare - usually some problem with anatomical barriers or the immune system

Question 40

What are common superficial mycoses?

Answer 40

Candidiasis - nappy rash | Tinea corporis - ringworm

Question 41

What are the immune defects making you vulnerable to fungal infections?

Answer 41

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

Question 42

What are the different types of protozoa?

Answer 42

Sporozoa Amoebae Flagellates

Question 43

What are the most common types of Protozoa infection in children?

Answer 43

Sporozoa - Plasmodium and Toxoplasma

Question 44

What is the pathogen responsible for malaria?

Answer 44

P. Falcifarum - most severe P. Vivax P. Ovale P. Malariae

Question 45

What are the clinical presentations of malaria?

Answer 45

Non-specific - fever, lethargy, vomiting, diarrhoea

Question 46

What is the most common form of toxoplasma infection?

Answer 46

Congenital toxoplasmosis (cat oocytes)