INFECTIOUS DISEASES Flashcards
What is the difference in location between congenital CMV and Toxoplasmosis CNS lesions?
CMV: periventricular calcifications
Toxoplasmosis: calcifications scattered throughout cortex
What are clinical features of congenital CMV infection?
Cataracts Purpuric rash ("blueberry muffin") Seizures from CMV CNS lesions Hepatosplenomegaly IUGR Microcephaly Prolonged neonatal jaundice
What cells are involved in humoral immunity? What cells are involved in cellular immunity?
Humoral: B-cell
Cellular: T-cell
Testing for HIV in child < 18 months?
Testing for HIV in child > 18 months?
Child < 18 months: cannot do HIV ELISA looking for antibodies against HIV since will still have maternal antibodies in system. Need to perform HIV DNA PCR which needs to be positive on two separate occasions
Child > 18 months: HIV ELISA (enzyme linked immunosorbent assay to look for HIV IgG: 99% specificity and sensitivity); if positive, confirm diagnosis with Western Blot (direct visualization of antibodies against the virus)
What is a soft tissue complication of varicella infection?
GAS invasive soft-tissue infection: necrotizing fasciitis, myositis, cellulitis, toxic shock syndrome
Treatment: Penicillin and clindamycin
What is the classical triad of Wiskott-Aldrich syndrome?
- Complications (2)
- mode of inheritance
Classic triad (in 1/3 of patients):
- Eczema
- Thrombocytopenia
- Immunodeficiency
Complications:
- Immunodeficiency:
- T and B cell function is reduced
- recurrent pneumonia/otitis media/sepsis/meningitis/sinusitis
- progressive
- can have hepatomegaly - Risk of malignancy (10-20%)
- leukemia/lymphoma
Mode of inheritance:
-X-linked
How do neonates with Wiskott-Aldrich usually first present?
Present at birth with thrombocytopenia features: bruising, petechiae, bloody diarrhea
Eczema by 1st month of life, recurrent infections by 3 months of life
In Wiskott-Aldrich, describe the levels of immunoglobulins seen.
IgA & IgE: elevated
IgM: reduced
IgG: normal, reduced or elevated
What investigations should be ordered for 1-3 mo febrile infants meeting clinical criteria for low risk SBI?
- CBC + diff
- Blood culture
- Bag for urine –> cath if positive
In febrile patients, when should a UA always be ordered? (5)
- All boys age < 6 months
- Uncircumcised males
- All females < 2 years old
- Prior diagnosis of UTI
- Known renal abnormality
What is the definition of a UTI?
- Urine with > 10 wbc/hpf
- Colony count of single organism > 50,000/ml
- **Remember that if child has been symptomatic < 48 hrs, may have absence in WBCs
- absence in WBCs in urine does not rule out UTI!
In children 3-36 months, what percentage of fevers are viral in origin?
> 95%
Clinical presentation of lyme disease (6)?
- Arthritis
- Erythema migrans: painless, annular, central clearing, minimum size 5 cm
- Aseptic meningitis
- Cranial nerve palsies
- Heart block
- Ocular involvement
What are the most common clinical presentations of urethritis (2)?
-What is the most common etiology of urethritis?
- Dysuria
- Penile discharge
Most common etiology: Chlamydia trachomatis (3x more common than Neisseria gonorrhoeae)
What is the best test for chlamydia and gonorrhea?
Urine PCR
What is the management of a patient diagnosed with urethritis?
- medical therapy
- advice to give patients (ie. how long to abstain from sex)
- Empiric treatment for chlamydia and gonorrhea
- Azithromycin 1 g PO x 1 for chlamydia
- Ceftriaxone 250 mg IM x 1 for gonorrhea - Instruct patients to abstain from sexual intercourse x 1 wk after single-dose therapy and until all partners are treated to prevent reinfection
- Test for other possible STIs (syphillis, HIV, hepatitis, etc.)
What is a possible GI side effect of ceftriaxone?
Increased gallbladder sludge and subsequent cholelithiasis
What is the pathophysiology of retropharyngeal cellulitis/abscess?
The retropharyngeal nodes that drain the mucosal surfaces of the upper airway and digestive tracts (between the pharynx and the cervical vertebrae, extending down into the mediastinum) become infected
- once infected, the nodes progress through 3 stages: cellulitis, phlegmon, abscess
- most patients have history of recent ear/throat/nose infection
What are the possible causes of retropharyngeal abscess?
- Localized infection of oropharynx extending to the retropharyngeal lymph nodes
- Penetrating trauma
- Vertebral osteomyelitis
- Dental infection
Retropharyngeal abscess are most common in what age group and why?
Most common in children < 5 years old
-after the age of 5, retropharyngeal nodes involute and thus infection is much less common in older children and adults
What are clinical manifestations of retropharyngeal abscess? (7)`
Think upper airway obstruction!
- Respiratory distress
- Stridor
- Drooling
- Fever
- Refusal to eat
- Obstructive sleep apnea
- Neck stiffness/torticollis
What is the differential diagnosis of retropharyngeal abscess? (5)
- Acute epiglottis
- Lymphoma
- Meningitis (if neck stiffness present)
- Foreign body aspiration
- Vertebral osteomyelitis
What is the underlying bacterial etiology of retropharyngeal abscess?
Polymicrobial! Most commonly:
- GAS
- Staph aureus
- Oral anaerobes
What is the treatment for retropharyngeal abscess?
- abx choice
- indications for surgical drainage (2)
Intravenous antibiotics until clinical improvement, then switch to PO abx (ideal duration of treatment unknown)
- 3rd generation cephalosporin + clindamycin
- studies have shown that > 50% of children can be successfully treated without surgical drainage
Indications for surgical drainage:
- Respiratory distress
- Failure to improve with IV abx
What are 4 complications of retropharyngeal abscess?
- Significant upper airway obstruction
- Rupture leading to aspiration pneumonia
- Extension into mediastinum
- Thrombophlebitis of internal jugular vein
What is Lemierre disease?
-causative organism
Infection from the oropharynx extending to cause septic thrombophlebitis of the internal jugular vein and embolic abscesses in the lungs
- causative organism: fusobacterium necrophorum (oral anaerobe)
- most commonly seen in pharyngitis where peritonsillar abscess forms (ie. with GAS) and this allows the oral anaerobes to flourish within the abscess and then spread to the IJV
- infected clot forms within the IJV and can throw off emboli
What is the Rochester Criteria?
- 4 clinical criteria
- 4 laboratory criteria
Used for management of febrile infants 1-3 months of age: if ALL criteria are present, then the risk of having occult bacteremia is < 1% and only have to do PSWU
Clinical criteria:
- Well appearing infant
- No evidence of skin, soft tissue, bone, joint or ear infection
- Term infant
- No prior illness (ie. hospitalizations, not hospitalized longer than mom after delivery, no prior antibiotics, no jaundice, no chronic illness)
Laboratory criteria:
- WBC 5-15 x 10^9
- Bands < 1.5 x 10^9
- Urine WBC < 10
- Stool WBC < 5
What are the live vaccines?
BOY LoVe The crIME
- BCG
- OPV
- Yellow fever
- Live vaccines
- Varicella
- Typhoid
- Influenza (intranasal)
- Measles/mumps
- Epidemic typhus
A septic baby is born preterm to a mother with a febrile, flu-like illness. The placenta was noted to have white nodules. On later imaging, the infant’s organs was noted to have microabscesses. What infectious organism is the most likely culprit?
Listeria monocytogenes
What is the chance of acquisition of neonatal HSV infection for:
- an infant born via SVD to a mother with primary HSV genital infection?
- an infant born via SVD to a mother with recurrent HSV genital infection?
Infant born to mom with primary HSV infection: 50%
Infant born to mom with recurrent HSV infection:1-3% (due to less viral shedding and presence of maternal neutralizing antibody)
You scrape the base of a vesicle found on an infant and send it for the Tzanck test. You see multinucleated giant cells. What is the differential diagnosis? (3)
- HSV
- Varicella
- CMV
What are the clinical features of infantile botulism?
- which organism and found from which sources (3)?
- why are infants affected but not older children?
- diagnosis?
- treatment?
Clostridium botulinum: intestinal colonization occurs from ingestion of spores from honey, dust, soil
- spores secrete neurotoxin that irreversibly prevents acetylcholine, thus see anticholinergic effects
- clinical features: constipation, urinary retention, symmetric progressive weakness (paralysis), ptosis, diplopia, respiratory failure, poor feeding
- in older children, they have to ingest the actual neurotoxin itself (may be present in foods) to cause disease; eating spores alone does not result in disease since the spores cannot germinate and produce neurotoxin in the gut of a child > 1 yo
- in infants <1 yo, they have lower levels of gastric acid, decreased immune system function, and decreased normal intestinal flora and thus, spores can germinate in their intestines and secrete neurotoxin
- diagnosis: presence of botulinum toxin in stool
- treatment: supportive care & human-derived botulinum antitoxin
Which medications are contraindicated in infantile botulism?
Aminoglycosides! Worsen neuromuscular blockade
What are the clinical features of infectious mononucleosis?
- infectious etiology?
- complications (4)
EBV infection = infectious mononucleosis
- clinical features: fever, exudative pharyngitis, fatigue, lymphadenopathy, hepatosplenomegaly, tonsillar hypertrophy
- complications:
1. Splenic rupture
2. Encephalitis
3. Hemolytic anemia/thrombocytopenia
4. Airway obstruction
5. Malignant association: Burkitt lymphoma, Hodgkin disease, etc.
What is the utility of a Monospot to diagnose infectious mononucleosis?
Monospot = looks for heterophile antibodies produced by the immune system to EBV
- sensitive test in children > 4 yo (present in >90% if has infection)
- in children < 4 yo, NOT a sensitive test; thus, specific serologies should be drawn (IgM & IgG for EBV)
What is the organism causing cat-scratch disease?
-what are the clinical features? (1 predominant, 3 less common, 1 particularly in immunocompromised patients)
Bartonella Henselae (gram negative bacillus)
- clinical features:
1. Regional lymphadenopathy (predominant)
Less common:
- Parinaud oculoglandular syndrome: inoculation of eyelid conjunctiva –> conjunctivitis and ipsilateral preauricular lymphadenopathy
- Liver and spleen granulomas
- Encephalitis
Immunocompromised:
5. Bacillus angiomatosis: proliferation of blood vessels –> tumor like masses in skin and organs
How do you diagnose cat-scratch disease?
-treatment for: mild disease? Severe disease?
Serology
- mild disease: supportive care; self-limited with resolution in 2-4 mo, no need for abx
- severe or systemic disease: 5 d course of azithromycin to treat severe, painful lymphadenopathy but does not shorten duration of symptoms
What are the classic clinical features of roseola?
- infectious etiology?
- treatment?
3-5 d of high fever followed by macular papular rash which appears on TRUNK first, then spreads to extremities/neck/face as the fever resolves.
- associated with febrile seizures
- infectious etiology: Human herpes virus 6
- treatment: supportive care
What is the definition of AIDS?
- CD4 count 200 or less in a patient with HIV
OR - The presence of an opportunistic infection in a patient with HIV
For a newborn born to HIV positive mom, what testing do you perform and when do you perform it?
-treatment until results are back?
- HIV PCR at 14-21 d; if negative, repeat at 2 and 6 mo.
- If still negative, HIV antibodies assay (ELISA) at 18 mo.
- treatment: zidovudine is given to mother prenatally, during L&D. Then start zidovudine for infant x 6 wks or until HIV PCR is back.
In general terms, what are the different classes of antiretroviral agents? (4)
-when initiating therapy, what is the principle?
- Nucleoside reverse transcriptase inhibitors (NRTI)
- Non-nucleoside reverse transcriptase inhibitors (NNRTI)
- Protease inhibitors
- Fusion inhibitors
- use combination of 3 or 4 agents from at least 2 classes
What are the complications of influenza infection? (5)
- Pneumonia with staph aureus, strep pneumo, GAS
- Otitis media
- Myocarditis
- Encephalitis
- Guillain Barre syndrome
How is malaria transmitted?
- which species of parasite causes the most severe disease?
- clinical features?
- diagnosis?
By the saliva of a female Anopheles mosquito - carries plasmodium protozoa (intracellular)
- most severe disease is seen with plasmodium falciparum
- clinical features:
1. High fever
2. Chills
3. Hemolysis (anemia, jaundice, splenomegaly)
4. Cerebral malaria: increased ICP, seizures, coma, death - diagnosis: thick and thin blood smears several samples per day x 3 days to identify parasite (thick is better to identify that parasite is there, thin is to identify species)
The treatment of malaria is guided by which 3 main factors?
- Clinical status of patient: non-severe vs. severe
- Plasmodium species
- Drug susceptibility of the infecting parasite
What is the treatment for malaria?
- ie. which patients should receive oral vs. IV antimalarials?
- how long to continue treatment?
For patients with non-severe, uncomplicated malaria, can treat with PO antimalarial (chloroquine = main one, other choices include primiquine, atovaquone proguanil or quinine sulfate plus doxycycline/tetracycline/clindamycin or mefloquine)
Patients with the following factors should receive IV antimalarials (IV quinidine plus doxycycline/tetracycline/clindamycin):
- Severe hemolysis: severe anemia, bleeding, jaundice, hemoglobinuria
- ARDS
- DIC
- Renal failure
- Impaired consciousness
- Parasitemia > 6%
-continue therapy until parasite level < 1% (usually within 48 hrs) and patient can tolerate PO antimalarial
Which malaria species can result in relapse due to their latent hepatic stages?
-which malaria species can cause chronic asymptomatic parasitemia that can persist for several years?
- Latent hepatic stages: Plasmodium vivax and ovale
- chronic asymptomatic parasitemia: Plasmodium malariae
When is a person with measles contagious?
5 days prior to onset of rash to 4 days after
What are the clinical features of measles? (3 Cs)
- what is the characteristic rash seen with measles?
- how do you diagnose measles?
Measles (paramyxovirus):
- Cough
- Conjunctivitis
- Coryza
- also see fever and Koplik spots
- Morbilliform rash starting from head and spreading downwards (happens on day 5 of illness)
- diagnose measles with IgG and IgM serology
What are the complications of measles? (4)
-which is the most scary?
- Pneumonia
- Croup
- Otitis media
- Subacute sclerosing panencephalitis
- rare degenerative encephalitis characterized by dementia and intellectual deterioration with seizures occurring many years after initial infection (11 yr on average)
What is the treatment for measles?
-who should receive prophylactic treatment after exposure to measles? (3)
Supportive treatment
- prophylactic treatment with IVIG within 6 days of exposure REGARDLESS of immunization status should occur for:
1. Pregnant women
2. Immunocompromised
3. Infants < 1 yo
What are the 3 main areas of the world where malaria is found?
- Africa
- Asia
- South America
Which population of people resist are immune to malaria?
Hemoglobin S - sickle cell anemia patients
What is the life cycle of a plasmodium parasite?
- Exoerythrocytic phase:
- inoculation of parasite into bloodstream by female Anopheles mosquito
- enters hepatocytes and multiplies asexually
- hepatocytes burst releasing thousands of parasites into blood stream - Erythrocytic phase:
- parasites then enter the erythrocyte and multiplies asexually
- erythrocyte bursts releasing parasites (this is what causes the high fevers) that then develop into male and female and then are sucked up by mosquito during a blood meal to be transmitted to the next victim.
GROSS.
What is chemoprophylaxis recommended for travellers going to areas with malaria?
In Chloroquine sensitive areas: give chloroquine
-in chloroquine-resistant areas, use atovaquone, mefloquine
What do you see on gram stain for Neisseria meningitidis?
Gram negative diplococci
What 2 age groups are most commonly affectd by Neisseria meningitidis?
-which are the common serotypes causing disease?
Children < 5 yo and adolescents
- common serotypes: A, B, C, Y, W-135
- serotype B most common in Canada
What is the treatment for meningococcemia?
- mortality rate of meningococcemia?
- postexposure chemoprophylaxis?
Pen G x 5-7 d
(remember that meningitis with N meningitidis is also treated with IV abx x 5-7 d only)
-mortality rate: 10%, most within 1st 48 hrs due to fulminant septic shock/DIC secondary to endotoxins
-postexposure chemoprophylaxis should occur for anyone who came into contact with oral secretions of an infected patient = use rifampin
What is Waterhouse Friederischsen syndrome?
Diffuse adrenal hemorrhage secondary to meningococcemia infection
What 6 groups are at increased risk of invasive meningococcal disease?
- Anatomical or functional asplenia
- Children with primary antibody deficiency disorders
- Children with complement, properdin or factor D deficiency
- Travellers to areas endemic for meningococcus
- Lab personnel with exposure to meningococcus
- Military
What are complications of mumps? (5)
Mumps = paramyxovirus, mainly causing parotitis (inflammation of salivary glands)
- Meningoencephalitis
- Orchitis
- Arthritis
- Myocarditis
- Pancreatitis
What are the clinical features of Parvovirus B19 infection? (ie. two types)
- period of infectivity for parvovirus B19?
- other clinical features
- treatment
Two types of infection:
- Erythema infectiosum: -fever, headaches, myalgias, polyarticular arthritis followed by slapped check facial rash followed by lacy, reticular rash on trunk and extremities
- period of infectivity occurs BEFORE the onset of rash (ie. once rash has developed, the child is no longer contagious). - Aplastic anemia:
- those with RBC aplasia ARE infectious at presentation and should be isolated for at least 1 wk or until resolution of fever
- seen especially in children with hemoglobinopathies
- treatment: supportive care, possible RBC transfusions
What are the 4 stages of pertussis?
-do you see this in infants?
ICPC: “I caught pertussis coughing”
- Incubation stage x 7-10 d
- Catarrhal stage: most infectious stage, mild upper resp prodrome x 1 wk (catarrhal means INFLAMMATION OF MUCOUS MEMBRANES)
- Paroxysmal stage: severe cough with inspiratory whoop x 1-3 mo, post-tussive vomiting
- Convalescent stage: gradual resolution of symptoms
- infants < 3 yo usually do not have classic stages and infants < 3 mo usually don’t have whoop but can have post-tussive apnea/cyanosis
How do you make the diagnosis of pertussis?
- what is the treatment of pertussis?
- does treatment change severity or duration of disease?
Pertussis PCR or culture
- may see leukocytosis with lymphocytosis
- treatment: azithromycin x 5 d
- treatment after paroxysmal stage begins does NOT change severity or duration of disease but does decrease infectivity
What is the immunization strategy to prevent pertussis?
- Immunize infants with DTaP vaccine at 2, 4, 6, 15 mo with booster at 4 yo
- Immunize adolescents with booster with single dose of Tdap
What is the chemoprophylaxis for contacts of pertussis positive individuals?
Azithromycin x 5 d regardless of immunization status in order to prevent spread
In a patient previously infected with pertussis OR previously immunized for pertussis, how long do their protective antibodies last?
Usually last 3-5 yrs only - this is why booster is needed in adolescence/adults
What are the complications of pertussis? (5)
- Secondary pneumonia
- Apneas
- Pulmonary hypertension
- Acute otitis media
- Physical sequelae from forceful coughing: scleral hemorrhage, petechiae, laceration to frenulum
What animal bites may transmit rabies?
Dogs, cats, skunks, raccoons, foxes, coyotes, bats (any exposure to bats, even being asleep in the same room since bites/scratches can be tiny and not noticed!)
-first the single stranded RNA virus replicates in the tissue at the site of the bite/scratch and over weeks-months, moves along peripheral nerves until it reaches the spinal cord (concentrated in brain stem) and spreads rapidly to the brain
What are the clinical features of rabies?
Weeks-months after bite: rapidly progressive encephalopathy with seizures, delirium, dysphagia, hydrophobia
What seen on histology is the hallmark of rabies?
Negri body (clump of viral nucleocapsides that create cytoplasmic inclusions)
What are investigations that can be done to confirm diagnosis of rabies?
- Animal with unknown vaccination status that bit the patient should be quarantined and observed for signs of rabies - may need to be euthanized with brain intact in order to see virus-specific antigens on brain tissue
- Can take skin biopsy specimens of the patient or isolate the virus from saliva
What is the treatment for rabies?
- what do you use for postexposure prophylaxis?
- when would you give postexposure prophylaxis?
In people who are bitten, should give postexposure prophylaxis with RIG and administer rabies vaccine immediately to decrease chance of developing rabies UNLESS the animal was a dog, cat or ferret who was healthy and can be observed for 10 days, then prophylaxis can wait
- once rabies symptoms have developed, unfortunately no specific treatment available
- all animals other than the healthy dog/cat/ferret who can be observed should be caught and euthanized and have its brain tested for rabies
What is the timing of the rabies vaccine?
Day 0, 3, 7, 14, 28 (total of 5 doses)
How is rabies immunoglobulin adminsitered?
Should be administered immediately after the animal bite and infiltrated directly into the wound if present. The remainder should be given IM.
How is HPV transmitted?
-clinical manifestations?
- Direct contact
- Autoinoculation
- Fomites
- clinical manifestations: common warts (verruca vulgaris), periungual warts, plantar warts, anogenital warts (condylomata acuminata), squamous cell carcinoma
- all caused by different subtypes of HPV
Which HPV subtypes cause cervical cancer?
16, 18