ID Flashcards
Cholera
Gm -ve rod
Diarrhoea - rice water stools
Enterotoxin => hypersecretion of water / chloride
Hypovolaemiic shock + metabolic acidosis + electrolyte disturbance
ABx shorten duration
Epi
Not common in Aus, endemic in some parts of the world
Transmission from contaminated water /(food)
Incubation few hrs to 5 days
Vaccine - not efficient - need booster every 6/12
Botulism
Rare and life threatening paralytic illness caused by neurotoxins produced by Clostridium botulinum inhibiting release of ACh at NMJ
Can lead to respiratory failure
Anaerobic, spore-forming bacillus found in soil
The D’s - diplopia, droopy eyes, dilated pupils, dry mouth, dysphonia, dysarthria
Symmetric descending paralysis - motor component only
TYPES of Botulism
- Food-borne botulism
- Ingestion of preformed heatlabile toxin rather than from the ingestion of spores or live bacteria
- One taste can expose a person to enough toxin to cause clinical illness
- Home-canning, mass produced foods, restaurants
- Infant botulism (the most common form of the illness now)
- Floppy baby syndrome - lethargy, poor feeding, weak cry, poor head control, loss of facial expression (bulbar palsy)
- Ingestion of spores with in vivo production of toxin
- Honey and to a lesser extent corn syrup
- Soil and vacuum ;ceaner dust ? cause
- Wound botulism
- IVDU using black tar heroin / dirty wounds / skin popping
- Inadvertent botulism / iatrogenic botulism
- Botox injection
- Biologic weapon of mass destruction
- Aerosolized form - Iraq
DDx
- GBS - ascending, sensory component, CSF protein raised
- MG - pupils spared, tensilon test, no autonomic Sx
- Tick paralysis - ascending, no bulbar Sx, TICK
- ACh- syndrome - pupils dilated + ACh delirium
- Infant
- Must have broad DDx - sepsis
- Other
- Brainstem CVA
- Infectious - Polio, Diptheria
- Med
Treatment
- Supportive ICU care
- Early Intubation - VC <30%
- Supportive care
- Ileus Mx
- Antitoxin
- Neutralises circulating toxin, effects of bound toxin irreversible
- Can cause anaphylaxis
- After skin testing for hypersensitivity, one 10-mL vial should be given IV.
- T1/2 - 5-8 days.
- Infant botulism - human botulism immune globulin (BabyBIG), which is pooled plasma from immunized adults with high titers of antibodies to toxins A and B.
- Antibiotics
- No recommended
- Used for prevention of secondary infection
Fever in the Returning Traveller
3 most important
Malaria - P. falciparum
Dengue Haemorrhagic Fever
Typhoid
Hx
Host Factors: past medical history, previous infections, diabetes, pregnancy, immunosuppression
Pre-travel Preparation: immunizations, malaria prophylaxis (type and compliance)
Specific Travel Itinerary: dates of travel, season of travel, destinations visited (regions, urban, rural), reason for travel, transportation
Exposure History: high-risk foods (local water, street food, uncooked meat), animal/insect exposure, bites, fresh water activities, blood and body fluid exposures (including sexual encounters, tattoos, IV drug use), sick contacts, health of fellow travelers
Examination
- Vital signs (paradoxical bradycardia is sometimes seen in Typhoid fever)
- Neurologic Exam: mental status, meningismus
- Dermatologic Exam: skin lesions (rose spots of Typhoid fever, “islands of white in a sea of red” Dengue rash, eschar associated with tick bites of Rickettsia), petechiae, jaundice
- GI: hepatospenomegaly
- Lymphadenopathy
Ix
- FBC & diff (look for anemia, lymphopenia, thrombocytopenia)
- UECs
- Liver enzymes (AST/ALT - viral hepatitis/malaria), Br and lipase
- Hypoglycaemia
- Blood cultures x 2
- Malaria Screen: thick and thin smears are required every 12 hours until there are three negative smears. Three negative smears are required to rule out Malaria as parasitemia is cyclical.
- Dengue serology
Tropical Infections - Incubation periods
< 7-10 days
- Dengue fever, 5-8 days
- Meningococcal disease, variable
- Japanese B encephalitis, 4-14 days
- Yellow fever, 3-6 days
- Zika virus
- Rickettsial diseases
- viral haemorrhagic fevers, Ebola, 2-7 days
7-30 days
- Hepatitis A, 15-45 days
- leptospirosis
- malaria, 2-8 weeks for Falciparum
- amoebic dysentery, 7-21 days
- enteric (typhoid) fever, 7-14 days
- giardiasis, 2 weeks
- Rickettsial disease
- Lassa fever, 7-18 days
1-6 months
- acute schistosomiasis, 4-8 weeks
- Strongyloides, weeks to years
- filariasis, weeks to years
- viral hepatitis, weeks to months
Malaria
Species:
P. falciparum 75%, most severe (Africa, SE Asia, SA America)
P. knowlesi - can be severe (SE Asia)
P. vivax, malariae (20%), ovale - less severe
Sickle cell trait, Thalassaemia, G6PD = protective
Transmission:
Mosquito, Blood Transfusion, Maternal- Foetal transmission, Dirty needles
Incubation: 8d-4 weeks, can be 12 months!!!!
Presentation:
The ‘classic triad’ is fever, splenomegaly, and thrombocytopenia
Symptoms/ Signs
* Fever > 90%
* Cyclical - every 2-3 days but not always
* Continuous fever
* Headaches
* Jt aches
* N/V/D
* Jaundice
* Splenomegaly
* Altered conscious state / seizures / coma
Ix
Blood film - parasite load >2% to confirm and> 5% = severe
Thick = parasite presence
Thin = species typing
Repeat smears every 12 hours until 3 x negative smears
Malaria antigen test
FBC - anaemia, thrombocytopaenia
UECs - deranged electrolytes
LFTs - high Br
Coags - DIC (rare)
Haemolysis (Coomb’s +ve)
Hypoglycaemia
LP to exlude bacterial meningitis
CSF - may be normal or elevated protein /opening pressures, low glucose
Rx
* Anti-malarial therapy
* IV therapy for severe
* organ dysfunction (ARDS, ARF etc), anaemia, cerebral malaria, hypotension
* Artesunate 2.4g IV (superior)
* Quinine 20mg/kg IV (beware longQT) + doxycycline (clindamycin for pregnancy or children < 8yrs)
Protective:
Chemoprophylaxis
Haem: Sickle cell, Thalassaemia, G6PD
Typhoid
Water/food borne
Incubation 7-14 days
Fever stepwise rising over the course of each day
Relative bradycardia
Rose spots
- 2-4mm blanching macules
- trunk / extremities
- resolve 2-5 days
The presentation can be divided into 3 weeks:
Week 1: diffuse abdominal pain and tenderness, constipation, dry cough, frontal headache, delirium, and an increasingly stuporous malaise
Week 2: Rose spots, progression of GI symptoms with abdominal distension, relative bradycardia
Week 3: weight loss, conjunctival injection, tachypnea, thready plulse, crackles over the lung bases, ‘pea soup’ diarrhea, apathy, confusion, and even psychosis, peritonitis
Ix
Positive BC - Gm -ve bacilli
Rx
* Ciprofloxacin
* Ceftriaxone
* Azithromycin
Prevention - vaccine
Dengue
Arbovirus, 4 known serotypes
Transmission: Mosquitos
Incubation: 3-14d
Reservoir: humans
Susceptibility: infection -> lifetime immunity form that serotype but no protection against other serotypes
Saddleback fever - a bimodal fever that persists for 3 days, resolves, and peaks again in 1-2 days
The WHO definition of Dengue includes:
- Fever
- Two or more of:
- Rash – petechia or “islands of white in a sea of red” (see image)
- Arthralgias
- Nausea/Vomiting
- Positive tourniquet test (inflate BP cuff and leave it inflated for 5 minutes, on deflation, look distally for petechiae).
- Leukopenia
Classic dengue - benign course
Dengue Haemorrhagic Fever
- small no - mostly children < 10yrs
- pharyngitis, cough, N+V,
- AP
- Hepatomegaly
- Bleeding and DIC
Dengue Shock Syndrome
- 20-30% of DHF cases
- Massive plasma leak = pl effusions, acsites, hypovolaemic shock, DIC + massive haemorrhage
- Rx supportive with PRBC and judicious fluids
Infective Rashes
Rose spots - typhoid
Islands of white in a sea of red - dengue
Eschar - tick bite
TB - Signs and Symptoms
Primary Disease
- Ghon focus = 1-2cm subpleural lesion w/ central caseation and fibrotic walling off lof lesion
- Ghon complex = Ghon focus + hilar lymphadenopathy
- Usually in chldren of those not previously exposed to TB
Secondary disease
- Re-activation of latent TB or re-infection
- Usual site apex of lung or apical segments of lower lobes
Complications
- Pulmonary
- Cavitation = high bacterial load
- Broncho-pneumonia
- Miliary TB
- Erosion of blood vessels => haemoptysis
- Laryngeal
- Renal = CRF
- GIT = obstruction/adhesions/perforation
- CNS = Tuberculous meningitis
- Lymph = scrofula
- Skeletal = spinal (Pott’s)
- Adrenal = chronic adrenal insufficiency
- GU = epididymitis or chronic PID
TB RF and Management
RF - highest to lowest risk
- Immigrants from high prevalence coutries
- HIV/AIDS
- Sub-standardliving, institutions i.e prison
- Immunosuppression
- Malnourished
- (DM/IVDU/elderly/alcoholics)
- Elderly NH residents
Rx
* Isoniazid
* Rifampicin
* Pyrazinamide
* Ethambutol
Above for 2/12, then isoniazid + rifampicin for 4/12
TB Diagnosis
Infectivity (highest to lwest)
1. +ve sputum smear AND +ve sputum culture
2. -ve smear AND +ve sputum cultre
3. -ve smear and culture
4. Extra-pulmonary disease
Diagnosis
1. Hx
2. Delayed hypersensitivity immunological testing
a. Mantoux - Tuberculin Skin Test (See attached)
b. Quantiferonin - Blood Test
Pro - Result w/in 24 hours, single visit, less reader bias,
Cons - Blood test, not differentiate active and latent infection
3. CXR/CT
- Consolidation upper and mid-zone prevelance
- Hilar lymphadenopathy
- Cavitating lesions
- Ghon focus - subpleural calcifcation remains after inital infection
- Fibrosis calcification
- Tuberculoma - well defined mass
- Miliar Pattern - small nodules throughout the lungs
- PCR
Notifiable Diseases
- Diphtheria
- Mumps
- Poliomyelitis
- Haemophilus influenzae Type b
- Meningococcal disease
- Rubella
- Measles
- Pertussis
- Tetanus
HIV / AIDs classifications
as per CDC
AIDS = A3, B3, C1, C2, C3
HIV Infection WHO case definitions
HIV + Fever DDx
- HIV infection itself
- Pneumocystis carinii pneumonia
- Mycobacterial disease
- Cryptococcal disease
- CMV infection
- disseminated Herpes
- drug fever
- lymphoma
- wide range of other infections
- Pneumococcus, Staph
- SBE
- other opportunistic agents
AIDS defining Illnesses
- Pneumocystis carinii pneumonia 60%
- cerebral Toxoplasmosis 15%
- encephalopathy 10%
- CMV retinopathy 5%
- Kaposi’s sarcoma 2%
- tuberculosis 2%
- cryptococcal meningitis 2%
- others 1%
Bloods HIV Testing
- FBC
- Anaemia / thrombocytopaenia
- CD4 count
- Antibodies
- Serology
- ELISA
- Western Blot
- Viral Antigen
- p24 antigen detects viral load
- Gp 41/120/160
- Monitor therapy
- PCR
Pertussis
(Notifiable disease)
General
Serious infant URTI - mortality 0.5-1% <6mo
- immunisations confer protection w/ >3 vaccines
- maternal AB not protective
Rx Macrolide antibiotics
- non-infectious 5d post therapy
Complications
Pneumonia
Apneoa
Severe dehydration
Encephalopathy
Attack rate of 80% for susceptible contacts
Transmission - resp droplet
Incubation - 6-20d
Reservoir - Humans
Infectivity - just b4 + 21 days after onset cough
Ix
Best wihtin 3 weeks of symptoms
PCR - most sensitive
Serology - IgA - natural infection, IgG - vaccination + infection
Phases
Catarrhal (1-2 weeks)
Paroxysmal (3 weeks)
Convalescent (up to 3 months)
Pertussis prophylaxis
No later than 2 weeks post close contact
Recommended ABx same as Rx = azithromycin
Close contacts:
Household
Overnight stay
F2F contact <1m distance for >1hr
High risk:
Pregnancy females esp last month (risk of transmission w/ birth)
Infants < 6mo
Childcare staff + no vaccine in last 10 yrs
Syhpilis
Proctitis
Sexually transmitted > radiation > autoimmune
Mumps
+ve Blood Culture Interpretation
EBV
HHV4
Transmission: intimate saliva contact
Incubation 4-6 weeks
Communicability: up to 1 year
Peak age: 15-25 yrs
Symptoms
Fever +/- constitutional
Pharyngitis
Lymphadenopathy
Splenomegaly
Jaundice
Rash
Ix
Diagnosis confidently made with triad of:
- typical clinical picture
- FBC findings
- +ve Monospot test
FBC - lyphocytosis exceeding 50%
LFTs elevated in 95%, jaundice rare
Monospot
- False negatives in kids < 4yrs, Early in clincial course
- False positives - CMV, HIV, SLE, Rubella
Other EBV tests
- Viral Capsid antigen - IgM persists for up to 8 weeks
- PCR
Mx
Must diagnose in pregnant pt
Supportive
No contact sports for 6 weeks risk of splenic rupture
Meningitis Chemoprophylaxis Criteria
- Household contacts / overnight stay in last 7 days inc hostel, dormitory or military
- Sexual and intimate contacts (sharing saliva)
- Family daycare attendees
- Travel contacts immeidately adjacent to index case for >8hrs
- HCW providing airway Mx if mask not worn
- Special Hib < 24 months old or 4 yrs + not immunised
Regimes:
1. Ciproflxacin 500mg single dose (30mg/kg up to 125mg < 5yrs)
2. Rifampicin 600mg PO q12h for 2/7 (10mg/kg kids)
3. Ceftriaxone 250mg IM - preferred in pregnant women
3. Hib
a. Rifampicin 600mg PO QID 4 days
b. Ceftriaxone 1g IM QID 2 days
c. Hib vaccination course when well
Meningitis Organisms Age Groups
Bacterial
< 3mo
* GBS
* E coli
* Listeria
* S aureus
* Pseudomonas
<6yrs old
* Hib
* N meningitidis
* S pneumonia
Adults
* N meningitidis
* S penumoniae
* Klebisella
* S aureus
* Listeria (> 50yrs)
* Ecoli (immuno comp)
Viral
Echo, ENtero, Coxsackie, HSV, CMV, VZV, EBV
Other
Mycobacterium tuberculosis
Crypotcoccus neoformans (Immunocompromised)
Aseptic
LP interpretation
SAH
Br + Xanthochromia from 4th tube
RBC > 1000 suggest not from traumatic tap
Contraindications to LP before CT in meningitis
Risk of herniation 5% in acute bacterial meningitis
Any concerns for Raised ICP:
Altered LOC / confusion
Severe headache
Vomiting ++
Brainstem signs - Papilloedma, ophthalmoplegia, posturing, irreg respirations
Seizure
Other:
Known SOL
Imunocompromise - HIV
VZV in Pregnancy
HHV 3
Transmission - direct contact w/ vesicular fluid, droplet
Incubation - 10-21d
Communcability - 48 hrs before rash, until all lesions crusted
High risj groups
1. Immunocompromised
i. Hameatological malignancy
ii. Chemotherapy
iii. HIV
2. Neonates < 1mo
3. Pregnancy females
Course
Rash evolves over 4-5/7
Macules → papules → vesicles → pustular type lesions → crusting lesions
Crusting scabs can then last 1-2/52
Complications
1. Viral Pneumonia
2. Infection in Pregnancy
3. Infection of newborn
4. Secondary skin infection
5. Reye’s Syndrome
6. Encephalitis / Meningitis
7. Rare Neuro - GBS, transverse myelitis, acute cerebellar ataxia
8. Hepatitis
9. Shingles
Infection in Pregnancy
Infection within 2/52 of delivery = greatest risk of developing neonatal varicella (fever + vesicular rash +/- pneumonia/meningoencephalitis/hepatitis.
Mortality = 25% and is higher in premature babies
Rx with acyclovir to reduce her risk 2 complications
NB treatment does not reduce risk of transmission to baby
If delivery occurs within 5 days of the patient
developing a rash, the neonate should receive
varicella-zoster immune globulin as PEP.
Congenital varicella syndrome
Infection between 8-20/40
Transmission risk is low (2%)
IUGR, Skin and ocular abN, hypoplastic extremities, DD
Pertussis Complications
EYE - peri-orbital oedema, Subconunctival haemorrhage
Pulmonary - Haemoptysis, PTx, Pneumomediastinum, SC emphysema, Diaphragm rupture
SKIN - petechiae
ENT - epistaxis
GI - umbilical and inguinal hernia, rectal prolapse
Severe Malaria
Dengue Case Definitions - WHO
Measles
Org: RNA virus
Highly contagious
Transmission: airborne resp droplet
Incubation: 10d, rash appears 14d
Reservoir: Humans
Communicability: 3-5d before rash until 4 days post rash
Clinical
Fevers
3 C’s - cough, coryza, conjunctivitis
Koplick spots (grains salt on red background)
Rash begin head and neck before becoming generalised
GIT Sx
Lymphadenopathy / Splenomegaly
DDx
Rubella
Parvovirus
Ix
Routine bloods - leucopaenia and thrombocytopaenia
IgM - anti-measles IgM increases to 100% betw/ 4-14d after onset rash
PCR
Rx
Infection control for droplet - N95, PPE, negative pressure
Vitamin A (deficiency predisposes to severe and complicated course
Complications
AOM
Pneumonia
Meningitis
Subacute Sclerosing Panencephalitis
Prevention
Vaccination
Exclusion for 4 days post rash
PEP - Chemoprophylaxis
Household / overnight / sharing accommodation / students of school
Waiting room contacts
Travel contacts up to 2 rows infront/behind
All HCW with contact
Rubella
Org: RNA virus
Potential to cause congenital abN pregnancy
Transmission: resp droplet or direct contact
Incubation: 2-3/52
Reservoir: Humans
Communicability: 7d before rash until 4 days post rash/
Susceptibility: infants born to vaccinated mothers confer protection for 6-9/12, life long immunity after infection
Clinical
25-30% Subclinical
Clinical illness usually mild
Constitutional symptoms
Mild URTI Sx
LN - post chain
Rash 50-80% - maculopapular
Ix
Rubella Specific IgM
PCR
Complications
Pregnancy related
1. Miscarriage
2. Stillbirth
3. Congenital Rubella Syndrome
a. < 25% pregnancies that acquire rubella 1st trimester
b. Risk falls > 16/40 gestation, Rare > 20/40
c. Sx: Cerebral Palsy, Deafness, Blindness / Cataracts / CHD
Uncommon: arthralgia, encephalitis
Toxic Shock Syndrome
Toxic shock syndrome = infection with S aureus or Gp A Streptococcus which release harmful exotoxins, which can function as superantigens.
Mortality up to 80% if not treated.
Pathophysiology:
Bacteria produce superantigens, which trigger T lymphocytes, which bypass normal immune checkpoints and lead to cytokine release and multiorgan injury.
Epidemiology:
Streptococcal TSS is more common and affects**
local, invasive infection** all ages. This usually starts as a **
local, invasive infection** like cellulitis, pharyngitis, pneumonia, or necrotizing fasciitis. Up to 20% of these patients with an invasive infection can experience TSS.
Staphylococcal TSS (due to MSSA or MRSA) is less common and usually affects those < 40 years. Usually occurs due to colonization and not invasive infection. May occur due to **menstrual related causes (50%) ** but is also associated with postsurgical, postpartum, burns, focal infections, soft tissue injuries.
Presentation:
Combination of two factors: 1) toxin production (rash, multiorgan dysfunction, flu-like symptoms) and 2) significant focus of infection.
Classic presentation: Diffuse red rash, hypotension, fever, organ dysfunction. Patients may also consitutional symptoms
May have mucosal involvement, and desquamation is late 1-3 weeks after initial Sx.
Rapid decompensation: shock, acute kidney injury, neurologic symptoms due to cerebral edema, cardiopulmonary complications.
Ix
One of the first findings is renal injury, which may precede hypotension.
Inc CK, electrolyte abnormalities, and liver function test abnormalities common.
LATE = Thrombocytopenia, anemia, and DIC
BC +ve in 60% of streptococcal cases but < 5% of staphylococcal cases.
Consider in anyone with** red flag** symptoms:
* Diffuse rash in a patient with systemic illness
* Known /suspected Strep/Staph infection + sepsis/hemodynamic instability
* Localized infection that appears minor cf patient hemodynamics.
* Patient with viral, GI, or flu like illness who is hemodynamically unstable with no clear etiology.
* Pregnant + septic shock = 20 x inc risk of TSS
Mx
1. Hypotension
* Resuscitate with IVF + early vasopressors
* Endothelial injury -> risk of edema with extensive IV fluid resuscitation
* Stress dose steroids (hydrocortisone) if hemodynamics refractory
2. Broad spectrum antibiotics - Taz / clinda / meropenem
* Clindamycin inhibits toxin production
3. Source control (remove foreign body, drain abscess, debridement for necrotizing fasciitis).
Other treatments:
IVIG can neutralize the toxin. Observational studies suggest mortality benefit. RCTs show no statistically significant benefit, but improved SOFA score.
CDC Criteria for TSS
TSS - Compare Staph vs Strep
Chlamydia
Gonorrhoea
Roseola Infantum
LGV
Genital Ulcers
HF&M
Hand, foot and mouth disease is a common,
infectious skin disorder most frequently affecting
infants and young children. It can affect older children
and adults occasionally. It is usually caused by
coxackievirus A16 but some cases are caused by
enterovirus 71.
Transmission: very contagious faeco-oral contamination
Incubation period is 3–5 days
Reservoir: Humans
Communicability: blister, nasal and throat secretions, virus persists in stool for weeks
Presentation
Small blisters appear on palms and soles
Painful ulcers appear in the oral mucosa.
Bottocks / nappy area
DDx
EM, pustular psoriasis and EBV
Rosh Review TB Summary
Caused by Mycobacterium tuberculosis
Risk factors: HIV, immigration from an endemic area, immunosuppression, malnutrition
Primary TB
Usually asymptomatic and progresses to latent TB with no intervention
CXR: often normal, hilar adenopathy, Ghon focus
Latent TB
Asymptomatic
Screening: tuberculin skin test (TST) or interferon-gamma release assay (IGRA)
Tx: rifampin for 4 months, INH-rifampin daily for 3 months, or INH-rifapentine weekly for 3 months. Alternative is INH for 9 months or 6 months.
Reactivation TB
Sx: fever, night sweats, weight loss, productive cough, hemoptysis
CXR: upper lobe infiltrates, apical cavitary lesions
Dx: sputum smears for acid-fast bacilli (AFB) x3, sputum or tissue culture for AFB (gold standard)
Tx: rifampin, INH, pyrazinamide, ethambutol (RIPE) for 6 months
Monitor LFTs, add vitamin B6 (prevent peripheral neuropathy due to INH)
Comment: Positive TST determined by mm of induration and risk factors
15 mm: people with no known risk factors
10 mm: immigration from high-prevalence countries < 5 years ago, injection drug use, residents/employees of high risk settings (homeless shelter, correctional facilities, hospitals, nursing homes), children < 4 years old or exposed to adults in high risk categories
5 mm: HIV infection, recent TB contact, CXR consistent with prior TB, organ transplant, TNF-α inhibitors or chronic steroids
