Infectious Diseases

Question 1

Needle Stick Injury

Answer 1

Hep B
Risk of transmission post percutaneous exposure in unvaccinated source is 22-31% (if source is positive for Hep B surface antigen and Hep B e antigen)

Risk is 1-6% if the source is positive for Hep B surface antigen but negative for Hep B e antigen.

Mx:
Hep B vaccine (if unvaccinated)
Hep B immunoglobulin ASAP - effectiveness is unknown

Hep C:

• risk post percutaneous exposure is 1.8%
• Immunoglobulin and antivirals are not recommended for PEP after exposure to hepatitis C virus–positive blood.

HIV:
If the source patient is HIV infected, the estimated risk of transmission is 0.3% after a percutaneous exposure and 0.09% after a mucous membrane exposure.

Initiate PEP as soon as possible after the exposure; if later testing determines the source to be HIV negative, discontinue prophylaxis. PEP is less effective if started more than 24 to 36 hours after exposure.

MANAGEMENT

Expedite medical evaluation.

Wash wounds with soap and water.

Obtain history/Risk assessment:
- exposure circumstances - percutaneous, mucous membranes, bodily fluid, volume
- source patient
- Hep B & Hep C status
- HIV status
CD4+ T-cell count
viral load
antiretroviral therapy
history of antiretroviral resistance (optimise PEP)
- vaccination history of exposed person

Bloods in exposed person

• Bhcg
• Hep B serology
• anti Hep C & ALT at baseline
• Hep C RNA at 4 & 6 weeks
• HIV serology at baseline, 6wks, 12wks, 6 months

Bloods in the source patient (with consent)

Assess need for tetanus, Hep B vaccination or immunoglobulins or HIV PEP

Counsel

• risk of specific bloodborne pathogens
• discuss risks/benefits of available treatment options
• advise not donate blood, plasma, organs, tissue, or semen.
• barrier protection or abstinence
• avoid pregnancy and breastfeeding (discuss contraception while on PEP)

Arrange follow up through employee occupation health clinic within 72h, require repeat testing in 6wks and 3months

Meticulous documentation of events and incident reporting

Question 2

Measles

2020.1 Registrar Interaction Station

Most infectious virus known to humans

Suspect in unvaccinated child with fever, rash, coryza, conjunctivitis

Teratogen in pregnancy

MMR vaccine

Mortality high in infants (20-30%) second to pneumoniae

Answer 2

INCUBATION:
10 days to onset of prodromal symptoms
14 days to the appearance of the rash
Infectious period - 5 days before the rash appears until 4 days after the rash appears

CLINICAL FEATURES:
Starts with Cough, Coryza, Conjunctivitis

Then Morbiliform rash starting at the head then spreading to rest of body - even affects palms and soles of feet
Fever at the onset of rash

Koplik spots (small white spots on buccal mucosa)

Koplik spots and rash are pathognomonic for measles

INVESTIGATIONS:

measles IgM antibodies will be present when rash starts

throat swab and urine for measles PCR (will differentiate between measles vaccination and infection)

INFECTIVITY:

*Highly infectious - most infectious virus known to humans

*Virus lives in mucous in nose and throat of an infected person

*Aerosol spread

*Can stay in the air for 30min

*90% of close contacts will become infected

MANAGEMENT OF MEASLES IN ED:

apply a face mask to infected patient

place them into an isolated negative pressure room as soon as possible

all staff who enter the patients room must be in full PPE with P2/N95 face mask, eye wear, long sleeved gowns, gloves

exclude pregnant or non-immune staff and family

use portable xrays if required

Handling of specimens:

• double bag specimen, ensure there is no contamination of the external bag
• specimens will be walked to the lab and not sent via pneumatic tube delivery as the measels can contaminate the entire system

when vacated, the room must be left for 30min then cleaned with detergent before it can be used again

COMPLICATIONS:

*Otitis media

*Pneumonia

*Measles encephalitis
- permanent neurological damage in 40%
*Subacute sclerosing pan encephalitis (SSPE)
- may occur 4-10 years following infection
- always results in death

*Myocarditis
*Pericarditis
*Hepatitis
*Nephritis

treatment is supportive

Complications:
- pneumoniae
- encephalitis

Face mask
Negative pressure room
Notify public health
Contact tracing
MMR vaccine for contacts if unvaccinated
Testing of contacts
Isolation/quarantine

Question 3

HIV

2016 history taking station

26y Male with HIV who is non-compliant with ART and follow up since being diagnosed, presents with headache suggestive of an opportunistic CNS infection.

Benefits of antiretroviral therapy
- reduce viral load and maintain CD4 count (prevents infection and prolongs life)
- stops disease progression
- prevents transmission to sexual partners

Immune reconstitution inflammatory syndrome (IRIS) when starting anti-retroviral therapy

Cryptococcal meningitis:
- hydrocephalus, need to check opening pressures, may need CSF shunting or drainage

• antifungal amphotericin B 4mg/kg IV daily for 6-10 weeks then fluconazole 400-800mg daily for 12-18 months

A flare in disease activity may occur in patients with HIV infection after starting antiretroviral therapy (immune reconstitution inflammatory syndrome [IRIS]

Answer 3

History:
headache:
- onset (sudden, thunderclap)
- location (retro-orbital, unilateral)
- character (pulsatile, throbbing)
- radiation (eyes, neck)
- aggravating/alleviating factors
associated symptoms:
- fever
- nausea/vomiting
- photophobia
- rash
- neck pain or stiffness
- visual disturbance
- weakness, numbness, tingling
- syncope
- seiures
- confusion/disorientation
- trauma
- anticoagulation
- tearing, nasal congestion (cluster headache)

Analgesia taken and response

HIV
- when diagnosed
- why not taking ART and following up with ID
- CD4 count/viral load
- sexual partners
- IVDU

PMHx:
- malignancy
- aneurysms
- migraines

Meds: (many drug interactions with ART)

Allergies:

Social:
- alcohol
- IVDU
- employment
- partner/home life

AIDS defining illness

Lung:
- Pneumocystis jiroveci pneumoniae
- Tuberculosis
- Mycobacterium avium complex

Brain:
- toxoplasmosis encephalitis
- cerebral abscess
- cerebral lymphoma
- cryptococcal meningitis/cryptococcomas

CMV retinitis with loss of vision

GI tract:
- cryptosporidium gastroenteritis
- oral/oesophageal candidiasis

Oncology:
- non-hodgkin’s lymphoma

Dermatology:
- karposi’s sarcoma

Differential Diagnosis:

HIV related:
- cryptococcal meningitis
- cerebral abscess
- cerebral lymphoma
- toxoplasmosis encephalitis

Investigations:
Bloods:
- HIV antibody/antigen (if previous results are not available)
- CD4 cell count
- plasma HIV RNA (viral load)
- HIV genotype resistance testing (will need expert advice on what ART regimen)
- Hepatitis C serology
- Hepatitis B serology
- Syphilis
- Serum cryptococcal antigen if CD4 <100
- UEC & LFT’s (ART)

UEC - hyponatremia
FBC - WCC
Inflammatory markers CRP

Lumbar puncture
- openning pressures
- xanthochromia
- cell count
- gram stain, microscopy and culture

Imaging:
CXR - Pneumocystis Jervoceri Pneumoniae

Non-contrast CT brain - ICH, vasogenic oedema, cytotoxic oedema, masses

CT brain with contrast - tumours/abscesses

INFECTIOUS DISEASE SPECIALIST CONSULTATION:
- which drug regimen to start
- when to start in light of opportunistic infection
- arranging follow up

Question 4

Fever in Returned Traveller

Malaria

Dengue

Salmonella Typhoid

Chikungunya

HIV seroconversion

Acute hepatitis A, B, C, E

Shistosomiasis

Amoebic infection

Rickettsia

Measles

African trypanosomiasis

Answer 4

HISTORY:

Travel history - countries visited in the last year, duration of stay
- Immunisations
- Antimalarial prophylaxis and compliance
- Mosquito nets, repellents, screens
- Known mosquito bites
- Sexual contact
- Contact with animals – animal bites
- Swimming? (schistosomiasis)
- Medical treatment abroad ?blood transfusions
- IV drug use
- New tattoos piercings

EXAMINATION:

Altered mental status
Tachycardia
Tachypnoea
Hypoxia
Hypotension

Jaundice

Pulmonary oedema - ausculation + B-lines on POCUS

Hepatosplenomegaly

LABORATORY FINDINGS MALARIA

FBC – anaemia, thrombocytopenia

LDH - raised in haemolysis

LFTs - transamintis (raised ALT/AST)

Thick and thin blood films - 3 consecutive every 12-24hrs - show parasitaemia %

Coags - DIC

UEC - Acute renal failure

BSL - Hypoglycaemia

blood cultures for typhoid

Serology:
- dengue fever
- chikungunya
- rickettsia
- HIV
- Hepatitis A
- Hepatitis B
- Hepatitis E
- Hepatitis C

Sexually transmitted infections:
- chlamydia
- gonorrhoea
- mycoplasma genitalium
- trichomoniasis
- syphylis

TREATMENT:
artesunate 2.4 mg/kg (child up to 20 kg: 3 mg/kg) IV on admission, repeat at 12 hours and 24 hours, then once daily

OR

quinine loading dose: 20 mg/kg intravenously over 4 hours, 10 mg/kg intravenously over 4 hours, and then Q8H

PLUS
Ceftriaxone 2g IV daily (secondary infection is common)

PLUS
paracetamol 1g Q6H for 3 days (to reduce the risk of haemolytic acute kidney injury)

COMPLICATIONS OF MALARIA
- cerebral malaria (high mortality)
- black water fever - severe haemolysis and haemaglobinuria
- severe anaemia (requiring blood transfusion)
- hypoglycemia
- secondary infection (sepsis, pneumoniae)
- acute pulmonary oedema
- acute renal failure (acute tubular necrosis)

Question 5

Sexually Transmitted Infections

2022.1 History taking: STI management

Take a history from a patient and
to discuss an assessment and management plan.

Medical Expertise: Assessment and management (50%)
* Elicits a focused history and identifies important historical details diagnostic of an important
condition
* Generates differential diagnoses
* Creates a focused investigation plan to confirm or exclude time critical diagnoses
* Outlines a treatment plan for the patient
* Outlines a clear discharge plan for the patient including safety net return advice.

Communication (25%)
* Demonstrates a professional and respectful approach
* Uses language appropriate to the patient’s level of health literacy to explain the treatment
and management plan
* Summarises the encounter and confirms the patient’s understanding.

Health Advocacy (25%)
* Demonstrates the ability to use medical expertise to protect and advance the health and
well-being of the patient
* Demonstrates the ability to integrate the broad range of factors that affect this patient
beyond the ED encounter
* Proactively engages in health promotion using available resources to intervene in order to
improve the health outcomes of this patient and those within his social circle.
Candidates were required to:
* take a focused history from the patient (role player)
* provide their differential diagnoses
* advise the patient of the investigation and management plan.

Answer 5

Genital Ulcers/Lesions DIFFERENTIAL:
- Herpes Simplex Virus
- Syphilis
- Lymphogranuloma venerium - chlamydia
- Chancroid - Haemophilus ducreyi
- Granuloma inguinale - Donavanosis

SYPHILIS:
- on the rise among men who have sex with men
- associated with HIV infection

Primary Syphilis:
- painless ulcers to genitals, anus, mouth

Secondary Syphilis:
- painless lymphadenopathy
- non-puritic maculopapular rash that also affects the palms and soles of feet
- condylomata lata
- aseptic meningitis
- nephrotic syndrome
- moth eaten allopecia
- ocular manifestations (uveitis, optic neuritis)

Latent phase (asymptomatic)

Tertiary phase

Ix:
Swab lesions - treponema pallidum NAAT or PCR
Syphilis serology

LYMPHGRANULOMA VENEREUM:
- chlamydia
- may have proctitis or rectal bleeding
- Untreated can lead to tenesmus, fistulas and strictures

CHANCROID:
- haemophilus ducreyi
- diagnosis of exclusion of syphilis and HSV
- treat with ceftriaxone 500mg IM

Granuloma inguinale - Donavanosis
- caused by klebsiella granulomatis
- requires punch biopsy

Question 6

Necrotizing Fasciitis

IBCC podcast 118 - necrotizing fasciitis

EM rapid bombs - ep 23 necrotizing fasciitis

Answer 6

CLASSIFICATION:

Type 1 - Polymicrobial
- mixed aerobic and anaerobic bacteria
- often gas forming - Fournier gangrene
- E. coli
- Bacteroides fragilis
- Clostridium perfringes
- Steptococci
- Staphylococci

Gas gangrene refers to clostridial myonecrosis

Fournier gangrene - gangrene of the genitalia. Can occur after trauma (post partum), UTI, bacteria from perianal

Type 2 - Monomicrobial
- usually Group A strep pyogenes
- Clostridium perfringens
- Staphylococcus aureus
- Vibrio vulnificus
- Aeromonas hydrophilia

RISK FACTORS:
- IVDU
- immune compromise
- diabetes
- trauma/post operative
- crush injury or penetrating injury
- recent varicella infection
- NSAID use

CLINICAL FEATURES:
- severe pain out of proportion to clinical lab findings
- conjunctivitis
- echymoses, purple discolouration which represents skin necrosis/gangrene
- levido reticularis
- bullae/blisters
- tense oedema (skin may feel hard or “woody”)
- oedema beyond the margin of erythema
- crepitus with gas forming bacteria
- localised cutaneous anaesthesia (due to destruction of local nerves)
- rapidly spreading erythema
- overwhelming sepsis

INVESTIGATIONS:

This is a clinical diagnosis
Lab and radiological findings can support your diagnosis
They cannot exclude nec fasc

Coagulopathy - high INR
thrombocytopenia or thrombocytosis
high WCC and CRP
hypoalbuminaemia
metabolic acidosis with high lactate
high CK - myonecrosis

subcutaneous emphysema on imaging

POCUS:
- thickened fascia
- turbid fluid in the fascia plane
- oedema out of proportion to skin findings

“The finger test”
- anaesthetise
- 2-3cm incision
- insert finger down to fascia
- Lack of bleeding and/or “dishwater pus” (grey-colored fluid) in the wound are very suggestive of necrotizing fasciitis.
- If the deep tissues dissect easily with minimal resistance, the finger test is positive

MANAGEMENT:

Urgent surgical consultation
Surgical debridement of devitalised tissue - may need multiple surgeries
Broad spectrum antibiotics
- Meropenam 1g tds or Piptaz
- Vancomycin 30mg/kg IV
- Clindamycin 600mg IV QID (reduction in bacterial toxin - Group A Strep)

Immunoglobulins 2g/kg IV
Hyperbaric oxygen