Infectious Disorders (Raf with Danielle additions) Flashcards
What is the most common type of pulmonary infection in HIV?
- Bacterial pneumonia
- TB
Echinococcus genus (hydatid organism)–>how is it passed on? What is the treatment?
- Passed to humans by contact with eggs in feces of definitive host (eg. fox, wolf) or close contact with canine or sheep
- Treatment: surgical resection, or percutaneous drainage with treatment with albendazole, which also potentially used after treatment. For Canadian variety, may ok to just use medical treatment and not surgical
Post exposure prophylaxis for varicella?
Red Book algorithm
Immune or not?
Any contraindications to vaccine, which is ideally within 5 days?
If can’t get vaccine, are they within 10 day time frame for VZIG?
What does and duration of prednisone is defined as immunosuppression?
> =2 mg/kg/day x 14 days
What is the evidence for high flow in bronchiolitis?
CPS statement re: evidence in general:
- Extensive neonatal literature that there is decreased need for intubation and ventilation. (They don’t go into details about specific disease conditions)
- Pediatric studies have suggested reduced need for intubation, but studies were inadequately powered to show difference in mortality or length of icu stay. (They don’t specify these pediatric conditions)
Bronchiolitis:
NEJM 2018:
- Largest RCT to date
- Infants <12 months of age requiring oxygen for bronchiolitis were randomized to either receive low flow oxygen therapy or high flow at 2 L/kg/min
- Primary outcome: therapy escalation
- Secondary outcome: various including transfer to ICU, mortality, length of stay, intubation
- Finding: children on high flow were less likely to have an escalation in therapy compared to children on low flow, but there were no differences in any of the secondary outcomes, such as transfer to ICU
- Key critiques:
- The jump from high flow to further escalation is perceived as a bigger jump than from low flow to high flow, so this could explain the differencethey try and account for the difference in RR before escalation of therapy by doing a sensitivity analysis
- The presence of an ICU on site also affected decision for escalation of therapybut they also try and account for this with sensitivity analysis
Radiographic signs for Echinococcus
1) Meniscus sign/crescent sign
2) Cumbo sign/onion peel (double air layer appearance/onion peel/double arch)
3) Water lily
4) serpent sign
5) cavity
6) well defined round opacity (due to uncomplicated cyst, no rupture)
4) U/S: same as CXR + honeycomb appearance, ball of wool sign, cyst wall calcification
3 major forms for Echinococcus
Cystic (predominant form affecting lungs)
Alveolar
Polycystic
(two major organs affected are liver and lung. In children, lung is more commonly affected)
Treatment for Echinococcus
U/S guided aspiration of cysts
Surgery
Drugs: Albendazole or Mebendazole
Mechanisms of Acute Flaccid Paralysis causing lung disease
Atelectasis
Aspiration
Hypoventilation/respiratory muscle weakness
Secondary infection
Guillam Barre = autonomic neuropathy - cardiac failure - pulmonary edema
Causes of Acute Flaccid Paralysis
Enterovirus: polio and non-polio enteroviruses, D68 (anterior horn cell) West Nile (anterior horn cell) Guillain Barre (axon demyelination) Adenovirus (anterior horn cell) Botulism (NM junction) Tetanus (NM junction) Spinal cord compression
What are features of an airborne isolation room?
- negative pressure ventilation
- door closed at all times
- no opening of windows
- bathroom and hygeine area for patient
- handwashing sink for healthcare staff
- exhaust of air goes to outside of the building
- air has to go through HEPA filter before going to general circulation
- healthcare workers must wear N95 and be fit tested
Infectious disorders that cause GBS?
Often prior infection, resulting in molecular mimicry:
- Campylobacter jejuni - most important
- Mycoplasma pneumonia
Viruses- CMV, EBV, HIV, Influenza
- post vaccination, such as influenza
What organisms is a patient with CGD at risk of?
recurrent infections with catalase positive bacteria or fungi
The mnemonic “cats Need PLACESS to Belch their Hairballs” can be used to memorise the catalase-positive bacteria (and Candida and Aspergillus, which are fungi): nocardia, pseudomonas, PJP, listeria, aspergillus, candida, E. coli, staphylococcus, serratia, B. cepacia and H. pylori.[52] (so some common CF bugs like Pseudomonas and Burkholderia can actually be seen in CGD patients)
Where are endemic fungi located in Canada?
BC: cryptococcus
Manitoba: blastomycoses
Ontario: blasto and histo
Quebec: blasto and histo
What sorts of infections are patient with neutropenia at risk for?
Neutropenia:
- Decreased number of neutrophils: chemotherapy induced neutropenia
- Decreased function of neutrophils: CGD, steroids
- At risk for infection with bacteria and fungi
- Chemotherapy induced neutropenia: risk of infection with own bacteria such Strep, Staph. G - like E. coli, Klebsiella, Pseudomonas and Fungi like aspergillus
- CGD: see above
What infections are patients with impaired humoral immunity at risk of?
- Mostly bacteria, in particular encapsulated (Strep pneumo, Neisseria, Haemophilus, GBS, salmonella) and some virus (like enterovirus)
What infections are patients with cell mediated immunity problems at risk of?
Intracellular pathogens:
Viruses: CMV, VZV, EBV, community viruses (eg. RSV)
Fungi: PJP, aspergillus, endemic fungi
Intracellular bacteria like nocardia
Mycobacteria
Parasites: toxoplasma gondii and strongyloides
Conditions needing airborne precautions?
Active pulmonary TB (specify that it is active and pulmonary) VZV Measles SARS - severe acute respriatory syndrome small pox
Why is diphtheria deadly?
- Airway obstruction: diphtheria makes a toxin which destroys tissue and causes membranous pharyngitis–>these membranes can extend to larynx and can cause airway obstruction OR pharyngeal membrane can get dislodged and obstruct airway
- toxin also causes:
- myocarditis/cardiomyopathy
- sepsis
- secondary pneumonia
If suspicious of diptheria, do you wait for laboratory confirmation before giving anti-toxin?
No.
Diphtheria antitoxin to neutralize circulating toxin (administer before lab confirmation).
· Antibiotics (penicillin, erythromycin x 14d) to eradicate the organism, stop toxin production and reduce transmission, but do not replace antitoxin.
Most common cause of croup (D)
Parainfluenza
Infectious causes of upper airway obstruction (D)
Viral croup Epiglottitis Bacterial Tracheitis Diphtheria Retropharyngeal abscess Peritonisllar abscess Infectious mono
Non-infectious causes of upper airway obstruction (D)
FB Trauma Caustic burns Spasmodic Croup Angioneurotic Edema
Common causes of Epiglottitis (D)
Historically - H. influenzae (type B)
Now: Strep (Group A, B, C, G), H. parainfluenzae, Staph aureus, Moraxella catarrhalis,
Pneumococcus, Klebsiella, Psuedomonas, Candida, viruses
Most common cause of Bacterial Tracheitis (D)
S. Aureus
Characteristic of Diphtheria infection (D)
Membrane formation - “Membranous Pharyngitis”
Predominant organisms for Peritonsillar Abscess (D)
Strep pyogenes
Definition of Bronchitis (D)
Inflammation of the bronchus
Dominant symptom = Cough.
Usual resolution time of bronchitis (D)
Acute respiratory illness resolution: w/n 10-days = 50%, w/n 25 days - 90%
What is the most important air pollutant in acute bronchitis? (D)
Tobacco smoke
Most common cause of cough in children (D)
Viral acute respiratory infection
Pointers to the presence of specific cough (D)
Auscultatory findings (crackles, wheezes) Cardiac abnormalities Chest wall abnormalities Digital clubbing Daily moist or productive cough Dyspnea Exertional dyspnea Hemoptysis Immune deficiency Neurodevelopmental abnormality Recurrent pneumonia Respiratory noises (stridor, wheeze) Systemic symptoms
Are OTC cough med recommended for bronchitis? (D)
No
Clinical definition of PBB (D)
1) Isolated chronic (>4 weeks) wet cough
2) Resolution of cough with antimicrobial therapy
3) Absence of pointers suggesting alternate diagnosis
How is PBB differentiated from acute bronchitis? (D)
duration of illness
Common features of PBB (D)
Children usually <5
Lack other systemic symptoms including sinus, ear disease
Parents may report “wheeze” however “rattle” of airway secretions more common
May be misdiagnosed as asthma
Tracheo/bronchomalacia may coexist (common finding)
CXR = peribronchial thickening = most common
Resolution only after prolonged antibiotic course
Most common bacteria for PBB (D)
non-typeable H.flu
S.pneumo
M.catarrhalis
*often preceded by viral respiratory illness
Colonization may be due to impaired cough (nmd), mucous plugging (asthmatics), airway lesions that impair clearance (tracheomalacia = common finding) or mucosal damage (aspiration)
Characteristics of Plastic Bronchitis (D)
Characterized by extensive bronchial cast formation → airway obstruction
2 types of Plastic Bronchitis (D)
Type-1: Inflammatory = fibrin w/ cellular infiltrates; occurs in inflammatory lung d/o
-Assoc w: Sickle cell (ACS), asthma, aspergillosis, pna, CF, pulmonary lymphatic dz, neoplastic infiltrates
Type-2: Acellular = mucin, w/ few cells; occurs in congenital cardiac defect (esp FONTAN) -NOTE: Cast may not totally fit one type
Definition of Bronchiolitis (D)
Wheezing illness assoc w/ URTI in children <2 years
Characterized by inflammation, edema, mucous prod, bronchospasm, necrosis of a/w epithelium
Most common RTI of infancy
Most common cause of bronchiolitis (D)
RSV
HMPV = up to 19% (2nd place)
Mechanism of RSV causing bronchiolitis (D)
binds TLR-4 on aiway epithelium → fuses w/ membrane.
- Causes direct cell & ciliary damage. Indirect inflammation resp tract
- Viral replication → epithelial cell necrosis and ciliary destruction
- Cell destructn → inflam response → infiltration submucosa with PMNS, lymphs
- ↑ mucous productn + desquamated epithelium = mucous plugs → airway obstructn -Bronchiolar obstructn → air trapping / hyper-inflation & lobar collapse → V/Q abn
-Immunopathogenesis poorly understood - T-cells play some (unclear) role
“Typical” radiograph for bronchiolitis (D)
hyperinflation, flattened diaphragm, peribronchial thickening, airway was thickening and occasionally patchy atelectasis
Differential diagnosis of bronchiolitis (D)
-Upper a/w obstructn (adenoid hypertrophy)
-Laryngeal obstructn (croup, FB)
-Asthma
-Pneumonia
-Metabolic d/o (DKA, IEM, salicylate
poisoning)
-Congestive heart failure
-Parenchymal dz (CF, CLD, chILD)
Management principles of bronchiolitis (D)
- Cornerstone = SUPPORTIVE care
- Most managed at home
- Mod-severe resp distress (1-3%) = admission
- Guidelines exist (AAP, SIGN, CPS).
- not much evidence for medication of any sort
Suggested admission criteria for bronchiolitis (D)
- No clear criteria
- Consider admission when RR >60-70, Sats <90%, hx of apnea, lethargy or dehydration
- Factors influencing disposition: prematurity, v. young age, prev cardiopulm dz, immunodef, NMD
- Social situation a factor as well
- Cdn study assoc gestational age, HR, RR, Resp distress score, O2 w/ risk of severe bronchiolitis
RSV prevention strategies (D)
- Hand hygiene reduced nosocomial spread in hosp + at home.
- Virus capable of living on objects in the environment for hours
- No vaccine - difficult due to multiple strains - and infection does not confer long-term immunity -Passive immunity (Synagis/Palivizumab) recommended for high risk infants
- Palivizumab (Synagis) = agent of choice
Palivizumab - What is it and Is there risk of transferring infection? (D)
Palivizumab = a humanized murine monoclonal immunoglobulin G-1 directed against an epitope on the F glycoprotein of RSV
It is produced by recombinant DNA technology and directed against an epitope of the F glycoprotein of RSV.
Palivizumab binds to this glycoprotein and prevents viral invasion of the host cells in the airway. This reduces viral activity and cell-to-cell transmission, and blocks the fusion of infected cells
Standard dosing is 15 mg/kg administered intramuscularly every 30 days during RSV season for a maximum of five doses.
The most common reported adverse effects of palivizumab are local erythema, pain at the injection site, fever, and rash
Palivizumab is a recombinant product and has no potential for transmitting blood-borne infectious diseases. Moreover, it does not interfere with response to vaccines and does not affect the measles-mumps-rubella or other live virus immunization schedules.
National recommendations for those who should have RSV prophylaxis (D)
1) Children with hemodynamically significant CHD or CLD who require ongoing diuretics, bronchodilators, steroids or supplemental oxygen if they are <12 months of age at the start of RSV season.
2) In preterm infants without CLD born before 30 + 0 weeks’ GA who are <6 months of age at the start of RSV season
3) Infants in remote communities who would require air transportation for hospitalization born before 36 + 0 weeks’ GA and <6 months of age at the start of RSV season
Children with immunodeficiencies, Down syndrome, cystic fibrosis, upper airway obstruction or a chronic pulmonary disease other than CLD should not routinely be offered palivizumab. However, prophylaxis may be considered for children <24 months of age who are on home oxygen, have had a prolonged hospitalization for severe pulmonary disease or are severely immunocompromised.
Long term sequelae of bronchiolitis (D)
Bronchiolitis Obliterans
possible development of asthma/wheezing illness later in life
Definition of pneumonia (D)
Inflammation of lung tissue due to an infectious agent, thereby stimulating a response resulting in damage to lung tissue
Common preceding infection for bacterial pneumonias (D)
Bacterial infections are commonly preceded by viral or Mycoplasma infections
Viral pathogens can impair cough, interrupt mucociliary clearance, and enhance bacterial adherence to cell wall
Most common causes of pneumonia birth to 1 mos (D)
GBS, or Gram-negative bacteria, RSV
Most common causes of pneumonia infants to 3 mos (D)
Multiple causes (Chlamydia trachomatis, viruses, Bordetella pertussis, or Ureaplasma urealyticum) Also: S.pneumo, Haemophilus, S. Aureus
Most common causes of pneumonia children <5 (D)
Viruses are most common
Most common bacteria are pneumococcus and atypicals (M. pneumoniae, C. pneumoniae), S. pneumo
Most common causes of pneumonia children older than 5 (D)
S. pneumoniae
M. pneumoniae
C. pneumoniae
Most prevalent bacteria causing CAP (D)
S. pneumoniae
Typical symptoms suggestive of typical bacterial pneumonia (D)
Fever, chills, abdominal and/or chest pain, cough (productive)
Symptoms consistent with atypical organisms (including M pneumonia) include = gradual onset, with headache, malaise, non-productive cough, low grade/absent
fever
Wheezing tends to occur with viral pneumonia, also with Mycoplasma pneumonia or Chlamydia pneumonias
Most sensitive sign and most specific signs associated with alveolar infiltrate on CXR in pneumonia (D)
Fever = most sensitive sign
Grunting and retraction = most specific signs
Features that suggest a viral cause for pneumonia (D)
Bilateral interstitial infiltrates, atelectasis, signs of bronchiolitis (wheeze), generalized hyperinflation
When to do follow-up CXR in pneumonia? (D)
Round pneumonia
Lobar collapse
Clinical deterioration
Most common cause of pneumatoceles associated with pneumonia (D)
Staph aureus
Effusion and empyema are also common (90%)
Risk factors for antibiotic resistance (D)
Prior use of Abx, daycare attendance, travel, infection exposure, coexisting morbidities
Choice of antibiotic for CAP (D)
Penicillins can be used for most (penicillin, amoxicillin, or ampicillin)
Beta-lactams can be used in hospitalized patients
With pneumonia, in what time period would you expect children to get better with empiric antibiotic treatment? (D)
Typically children improve between 48-96 hrs after empiric treatment
- Recommended to not change antibiotics during this time, unless new information available (Ie. Culture results, pneumatocele development)
Consider empyema/abscess with ongoing fevers or pleuritic pain
With slow resolution consider the following:
o Right drug, right dose, resistant organisms, compliance
How does necrotizing pneumonia happen? (D)
Necrosis and liquefaction of consolidated lung disease
Majority confined to a single lobe, can have multilobar involvement
Pneumatoceles are common
Commonly see hemoptysis, high fevers, leucopenia, hypoalbuminemia, empyema
Complication of necrotizing pneumonia (D)
Radiolucent foci (solitary, multiple, multiloculated)
Bronchopleural fistula
Intrapulmonary abscess
Formation of pneumatoceles in necrotizing pneumonia (D)
Consequence of localized bronchiolar and alveolar necrosis = one way passage of air into the peripheral airways and alveoli
Common causes of necrotizing pneumonia (D)
Usually due to pneumococcus, Staphylococcus aureus, or Pseudomonas aeruginosa
How do pleural effusion and empyema in the setting of pneumonia happen? (D)
Occur when inflammatory response creates increase in pleura permeability, with accumulation of fluid into the pleural space
(Consequence of increased capillary permeability that occurs with lung injury = This favours migration of inflammatory cells into the pleural space)
What characterizes an empyema? (D)
When germs enter pleural space = appearance of pus
Stages of infectious pleural effusion (D)
Stage I (Exudative stage) = 3-5 days Stage II (Fibropurulent stage) = 7-10 after first sign of acute disease Stage III (Organizing stage) = Takes place in 2-3 weeks time - Fibroblast infiltration of pleural cavity
Most common causes of infectious pleural effusions (D)
Streptococcus spp (predominantly S. pneumococcus) S. aureus (most common for empyema) H influenza Mycobacterium spp Pseudomonas aeruginosa Anaerobes (more so with aspiration, especially with neurodevelopmental delay) Mycoplasma pneumoniae Fungi
Complications of infectious pleural effusion or empyema (D)
Bronchopleural fistula
Lung abscess
Perforation through chest wall (empyema necessitatis)
Most sensitive diagnostic test for pleural effusion (D)
U/S
What does bubbling in the underwater seal mean for a chest tube?
Bubbling represents pneumothorax
Continuous bubbling represents bronchopleural fistula
Pathogenesis of lung abscess (D)
Inflammation of parenchyma, necrosis, cavitation abscess formation
Common causes of primary lung abscesses (D)
Typically due to Gram positive cocci (Pneumococcus, S. aureus, S. pyogenes) or by Pseudomonas or Klebsiella
Treatment for lung abscess (D)
IV Abx for 2-3 weeks, then 4-8 weeks of PO Abx
▪ Penicillin +/- clindamycin, or metronidazole
Consider interventional drainage/CT aspiration
