Infectious Diseases

Question 1

What are the complications of Parvovirus B19?

Answer 1

1. Aplastic crisis in chronic haemolytic diseases (sickle cell, thalassaemia)
2. Aplastic anaemia
3. Arthritis, myalgia more common in older children/adults
4. Congenital infection with anaemia and hydrops

Question 2

Parvovirus B19 incubates for 4-28 days (avg 16-17) and is transmitted in respiratory secretions and blood. It is no longer infectious once the rash has appeared.

What is the clinical presentation of this infection?

Answer 2

AKA erythema infectiousum, ‘slapped cheek’ or fifth disease. Affects red cell precursors and reticulocytes in the bone marrow.

The prodromal phase is mild and consists of low-grade fever in 15-30% of cases, headache, and symptoms of mild upper respiratory tract infection. The hallmark of erythema infectiosum is the characteristic rash, which occurs in 3 stages that are not always distinguishable.

• very erythematous cheeks, then erythematous maculopapular rash on trunk and extremities, which fades with central clearing giving the characteristic lacy or reticular appearance.
• Rash lasts 2-30 days

Question 3

What are the clinical features/diagnostic criteria of Kawasaki Disease?

Answer 3

Fever lasting at least five days without any other explanation combined with at least four of the five following criteria:

1. Bilateral bulbar conjunctival injection
2. Oral mucous membrane changes, including injected or fissured lips, injected pharynx, or strawberry tongue
3. Peripheral extremity changes, including erythema of palms or soles, edema of hands or feet (acute phase), and periungual desquamation (convalescent phase)
4. Polymorphous rash
5. Cervical lymphadenopathy (at least one lymph node >1.5 cm in diameter)

The inflammatory signs typically develop after a brief nonspecific prodrome of respiratory or gastrointestinal symptoms. These clinical signs are the basis for the diagnostic criteria for KD

Although not part of the diagnostic criteria, some finding support the diagnosis. Typical manifestations include elevation of acute phase reactants (eg, C-reactive protein [CRP] or erythrocyte sedimentation rate [ESR]), leukocytosis, and a left-shift in the white blood cell count. Platelet counts generally rise by the second week of illness and may reach 1,000,000/mm3 (reactive thrombocytosis) in the most severe cases.

Question 4

What is the clinical presentation of adenovirus?

Answer 4

Incubates for 2-14 days.

Clinical presentation

• URTI
• Conjunctivitis +/- pharyngitis
• Gastroenteritis (more common in <4 yrs)

Complications

• Severe pneumonia (infants)
• disseminated disease in immunocompromised

Treatment - supportive

Question 5

What are the clinical features of Enteroviruses including polioviruses types 1 to 3, coxsackieviruses A and B and echoviruses

Answer 5

Transmission by faecal/oral and respiratory droplets.

Clinical presentation:

• Non specific febrile illness: abrupt onset of fever and malaise +/- headache and myalgia, lasts 3-4 days.
• Respiratory: pharyngitis, tonsillits, nasopharyngitis, lasts 3-6 days.
• GI: diarrhoea, vomiting, abdo pain
• Skin: ‘hand, foot and mouth’
• Pericarditis and myocarditis
• Neurological: aseptic meningitis, encephalitis, cerebellar ataxia and Guillain-Barre

Treatment is supportive.

Vaccine for Polio

Question 6

What is the diagnosis?

Answer 6

Measles.

Image shows Koplik spots, raised white spots on a red background opposite the lower molars. These a pathognomonic of measles.

Question 7

What are the clinical features of measles?

Answer 7

Subdivided into Incubation,Prodrome, Exanthem, and Recovery.

Incubation: 8-10 days via respiratory mucosa or conjunctiva. Typically asymptomatic at this time.

Prodrome: 3-5 days, low fever, malaise anorexia, brassy cough, coyrza, conjunctivits, Koplik spots.

Exanthem: Maculopapular, blanching rash beginning on the face and spreading cephalocaudally and centrifugally to involve the neck, upper trunk, lower trunk, and extremities. The palms and soles are rarely involved. The cranial to caudal progression of the rash is characteristic of measles but is not pathognomonic.

Recovery: Cough may persist for one to two weeks after measles infection. The occurrence of fever beyond the third to fourth day of rash suggests a measles-associated complication.

Question 8

A 10 year old boy presents with the rash in the image below. It feels like sandpaper and blanches with pressure. He has a strawberry tongue and circumoral pallor. The rash started on his head and spread rapidly to his trunk and extremeties, sparing his hands and feet. It is now beginning to desquamate. You note the rash is more marked in the skin folds and at pressure points.

He reports having a sore throat recently.

What is the diagnosis and what complications should you consider?

Answer 8

Scarlett fever

A diffuse erythematous eruption that generally occurs in association with pharyngitis. Development of the scarlet fever rash requires prior exposure to S. pyogenes and occurs as a result of delayed-type skin reactivity to pyrogenic exotoxin (erythrogenic toxin, usually types A, B, or C) produced by the organism.

Scarlett fever with pharyngitis can predispose to Acute Rheumatic Fever.

Question 9

2008A Q12

A 13-year-old boy presents with right upper quadrant pain and vomiting. He lives on a sheep station. On examination he is afebrile and has hepatomegaly.
An ultrasound scan confirms the presence of a 12 x 12 cm cyst, with several internal membranes, in the right lobe of the liver. His chest X-ray was normal.
Which of the following medical treatments is indicated?
A. Albendazole.
B. Doxycycline.
C. Metronidazole.
D. Pentamidine.
E. Praziquantel.

Answer 9

A. Albendazole.

Question 10

In a non-immunised toddler with sepsis, what are the most likely organisms and what are the first line antibiotics?

Answer 10

S. pneumoniae

N. Meningiditis

less likely HIB

Rx Cefotaxime and vancomycin

Question 11

Why would you choose a cephalosporin over a penicillin in meningitis?

Answer 11

Penicillin has poor BBB penetration whereas cephalosporins have good penetration.

Question 12

How does pneumococcus develop penicillin resistance?

How would you manage your pt if this occured?

Answer 12

Pneumococcus alters the penicillin binding sites, but also encodes resistance to other antibiotics including 3rd generation cephalosporins.

Increasing dose of penicillin overcomes resistance, except in CSF.

Question 13

Can staph be treated with ciprofloxacin?

Answer 13

No, it mutates easily and becomes resistant quickly to cipro.

Question 14

What is main anti-staph antiobiotic?

Answer 14

Flucloxacillin.

nb. Absorption decreases with food.

Question 15

What are antibiotic options in treatment of MRSA?

Answer 15

• erythromycin
• clindamycin
• doxycycline
• cotrimoxazole
• vancomycin
• gentamycin

Question 16

What does fluclox cover?

Answer 16

staph and strep (skin bugs)

Question 17

In an ATSI pt with a skin infection who appears septic, what would you treat with (esp in Darwin)?

Answer 17

Vanc and fluclox for MRSA

Question 18

Why do we add amoxycillin to cefotaxime in neonates with suspected meningitis?

Answer 18

To cover for Listeria

Question 19

In a patient with neonatal herpes, after the acute infection has been treated should PO aciclovir suppression be commenced for improved neurodevelopmental outcomes?

Answer 19

yes

Question 20

What secondary infection is classically associated with chicken pox?

Answer 20

Strep Pyogenes (GAS)

Question 21

Typhoid fever is a severe systemic illness common in India. Caused by Salmonella typhi with onset of symptoms 5-21 days post ingestion of organism.

What are the clinical features and treatment of this illness?

Answer 21

• Stepwise fever
• chills
• Abdominal pain
• rose spots
• hepatosplenomegally
• perforation
• secondary bacteremia

Enteric fever requires antibiotic therapy

Question 22

Echinococcus granulosis is a zoonosis in which dogs are the prime host however some parts of the life cycle can be completed in humans, sheep and other animals.

What does this become in humans, what is the treatment and what treatment should you be cautious of?

Answer 22

Tapeworm which forms hydatid cysts which can occur in many organs in the body. Primarily liver, then lung.

Treatment with Albendazole.

Surgery is an option but with caution that the cyst does not rupture and cause spillage (overwhelming for body)

Question 23

10-30% of women will be colonised with GBS. 50% of these babies will become colonised. Of those babies, what percentage will develop invasive disease?

Answer 23

1-2%

Question 24

What is Ramsay-Hunt syndrome?

Answer 24

Reactivation of VZV from geniculate ganglion of CN VII.

Usually unilateral erythematous vesicular reaction eruption on face including ear canal, oropharynx, with unilateral facial palsy of variable severity.

Treatment - supportive, steroids, maybe aciclovir (not much evidence).

Monitor hearing loss

If eye involvement consider herpes zoster ophthalmicus.

Question 25

This 9 year old boy presented with the lesion below.

It was tender and boggy and had not responded to multiple courses of antibiotics over three months.

What is it and how do you treat it?

Answer 25

Kerion.

Take scalp scraping to confirm dx.

Fungal infection.

Prefers pre-pubertal children.

Note hair loss, and hair breakage.

Would flouresce under Woods lamp.

Treatment: Terbinafine OR itraconazole + fluconazole for 3-4 weeks

Ketaconazole 2% shampoo

Oral steroids if severe to reduce swelling and pain.

Question 26

What is the risk of developing congenital varicella zoster syndrome if a pregnant women develops chicken pox betwee 13 and 20 weeks gestation?

Answer 26

2%, before and after this gestation is much lower.

Question 27

Dengue Fever

Answer 27

Epidemic in Qld, south pacific.

• Fever
• Severe myalgia, arthralgia
• Fine macular rash, petechiae
• Leucopaenia
• Lymphadenopathy
• Headache, vomiting, retro occular pain.

Question 28

Dengue Haemorrhagic Fever

Answer 28

More common with second infections due to immune enhancement

Infants and young children highest risk

2-5 days into illness

Petechiae, bruises, ARDS, Hepatosplenomegally, thrombocytopaenia, seizures

20% progress to DIC/shock with 40% mortality

Question 29

In a discrete exposure to Hep B (ie needlestick injury with HBsAg status unknown) what would be the treatment in a child incompletely vaccinated for HepB?

Answer 29

The risk of transmission of viruses from community acquired needlestick injuries is low. HepB is the hardiest virus, which can survive for 5-7 days in dried blood spots

After a discrete exposure e.g. needlestick where the source’s HBsAg status is unknown, the Hepatitis B vaccine should be given. The vaccine will give a rapid rise in antibodies, which would be sufficient to protect against seroconversion if he has been exposed.

Question 30

Diptheria

Answer 30

Gram-positive bacillus Corynebacterium diphtheriae. Infection may lead to respiratory disease, cutaneous disease, or an asymptomatic carrier state.

The most common presenting findings are sore throat, malaise, cervical lymphadenopathy, and low grade fever.

In at least one-third of cases, local elaboration of toxin induces the formation of a coalescing pseudomembrane. This membrane can extend to any portion of the respiratory tract from the nasal passages to the tracheobronchial tree.