Respiratory infections Flashcards
1
Q
generalities of step pneumonia
A
- gram positive “lancet”-shaped diplococci → pairs in chains
- catalase negative
- a-hemolytic
- optochin sensitive, facultative anaerobe
- bile soluble
- neufeld-quellung reaction positive → used for capsular serotyping
2
Q
pathogenicity of strep pneumonia
A
- nasopharynx colonization
- polysaccharide capsule → ⭣phagocytosis
- IgA1 protease → cleaves mucosal IgA
- pili → adherence to cell surfaces, ⭡ inflammation
- drug resistant s. pneumonia (DRSP):
- alteration of PBP
3
Q
clinical features of strep pneumonia
A
- pneumonia → MCC in adults, classically lobar, rusty-color sputum, CXR
- otitis media → MCC in children
- meningitis → MCC in adults
- additional diseases → sinusitis, pharyngitis
4
Q
in asplenic people infection with which bacteria are more common and why
A
haemophilus influenzae
strep pneumo
asplenia = ⭡risk of infection w/encapsulated pathogens (streptococcus pneuminiae) → no opsonization bcs no production of IgG
5
Q
treatment for pneumonia + penicillinase sensitive
A
penicillin (1st line), amoxicillin (if sinusitis), axitromycin (mild variants), levofloxacin
6
Q
treatment for pneumonia + penicillinase resistant
A
vancomycin
7
Q
treatment for acute otitis media caused by strep pneumonia
A
amoxicilin-clavulanate
8
Q
treatment for meningitis caused by strep pneumonia
A
cefriaxone and vancomycin
9
Q
which vaccines exists for strep pneumonia and what reactions do they produce
A
penumococcal conjugate (PCV13,15,20) → infants, elderly (humoral IgG response)
pneumococcal capsule (PPSV23) → humoral IgM response
10
Q
generalities of moraxella catarrhalis
A
- gram negative diplococci
- non-glucose fermenter
- non-maltose fermenter
- obligate aerobe, oxidase positive
11
Q
pathogenicity of moraxella
A
- colonization of nasopharynx
- ⭡ risk in infants and children, COPD
12
Q
clinical features of moraxella
A
- acute otitis media → fever, bulging tympanic membrane, otalgia, loss of light reflex
- additional disease variants:
- acute COPD exacerbation
- rhinosinusitis
13
Q
generalities of haemophilus influenzae
A
- gram negative non-motile coccobacilli
- chocolate agar: growth requieres factor V (NAD+) and X (hamatin)
- satellite growth on blood agar when plated with hemolytic pathogen (s.aurus)
- facultative anaerobe
- catalase positive, oxidase positive
14
Q
pathogenicity of haemophilus influenzae
A
- colonization nasopharynx → aerosol transmission
- IgA protease → cleaves serum and secretory IgA → ⭡mucosal adherence to host
- nontypeable = uncapsulated
- polysaccharide polyribosylribitiol phosphate capsule (type B) → ⭣phagocytosis, ⭣complement-mediated destruction
- LOS endotoxin
15
Q
clinical features of non-typeable h. influenzae
A
- acute otitis media (NT) → fever, bulging tympanic membrane, otalgia, loss of light reflex
- mucosal infections (NT) → sinusitis, bronchitis, conjunctivitis
16
Q
clinical features of type B h. influenza
A
bacterial meningitis (type B):
- acute onset headache, nuchal rigidity, photofobia, nausea, emesis, fever, chills, myalgyas
- brudsinki’s sign and kernig sign
epiglottitis (type B) → dysphagia, sore throat, muffled voice, drooling, INSPIRATORY stridor, tripod position, high fever, “thumbprint” sign, “cherry-red” epiglottis
17
Q
which respiratory bacteria is a HACEK
A
h. influenzae is a culture negative endocarditis bacteria
18
Q
treatment for h. influenzae
A
mucosal infection (non-typeable) → amoxicillin + clavulanate
meningitis (Hib) → cefriaxone, prophylaxis with rifampin
19
Q
generalities of mycoplasma pneumonia
A
- incomplete cell wall, non visible on gram stain
- cholesterol-stabilized membrane
- pleomorphic
- I-antigen → binding site
- Easton agar
20
Q
clinical features of mycoplasma pneumonia
A
atypical pneumonia, tracheobronchitis
autoinmune hemolytic anemia (cold agglutinin)
erythema multiforme
stevens-johnson syndrome
21
Q
how does atypical pneumonia presents itself
A
- aka walking pneumonia
- classically younger patients, close contact
- insidious onset of symptoms
- dry cough or minimal sputum, dyspnea
- myalgias, sore throat, headaches, +/- low grade fever
22
Q
what do you see on a CXR of atypical pneumonia
A
CXR: diffuse patchy infiltrates in interstitial areas (> 1 lobe usually)
23
Q
whats the treatment of atypical pneumonia
A
macrolides or doxycycline or respiratory fluoroquinoles (levofloxacin, moxifloxacin)
24
Q
how does autoinmune hemolytic anemia (cold agglutinin) present itself
A
- general anemia features: fatigue, conjunctival pallor, dyspnea
- painful acrocyanosis of distal extremities, livedo reticularis, Raynaud phenomena
- direct coombs: positive (anti-C3b), ⭣serum C3 and C4, ⭡LDH, ⭣haptoglobin
25
whats the treatment of autoinmune hemolytic anemia
Rx: avoid cold exposure and triggers, maintenance w/ Rituximab
26
how does the erythema multiforme present itself
- **symmetric and centripetally spreading** maculopapular rash → **target lesions** include palms and soles
- **Nikolsky negative**, no mucous membrane involvement unless major form
- Rx: symptomatic treatment in most cases
27
how does steven johnson syndrome present itself
painful erythematous/purpuric macules +/- targetoid appearance → full-thickness epidermal necrosis, sloughing of tissue
Nikolsky positive, mucous membrane involvement
28
whats the treatment for SJS
Rx: fluid resuscitation, wound management +/- antibiotic therapy
29
Characteristics of a good specoration mixture
epithelial cells → few → <10
polymorphonuclear cells → many → >25
bacteria → doesn't matter
30
what are the most common bacterial infections in the resp track
strep pneumonia
moraxella
h. influenzae
mycoplasma pneumonia
31
what are the most common respiratory viral infections
rhinovirus
coronavirus
parainfluenza virus
influenza virus
respiratory syncytial virus
adenovirus
32
what are the generalities/main characteristics of rhinovirus
- picornaviridae family member
- naked ss (+) RNA, icosahedral
- acil labile → no GI transmission
- cannot replicate in > 33ºC → no lower respiratory tract infection
33
whats the mechanism of rhinovirus
- transmission → droplets + fomites
- binds to ICAM-1 receptors (CD54) on respiratory epithelial cells
34
clinical features of rhinovirus
- rhinitis = “common cold”
- upper respiratory tract infection → rhinorrhea, nasal congestion, sneezing, headache, fever, sore throat
- common cause of COPD exacerbations
35
treatment for rhinovirus
- supportive, self-limiting
- handwashing and droplet precautions
36
is there a vaccine for rhinovirus?
no
37
generalities about coronavirus:
- enveloped SS (+) RNA, helical
- global distribution → 3 recent outbreaks: SARS-CoV2 (pandemic), SARS-CoV (epidemic), MERS-CoV (epidemic)
- viral intervals → incubation period (-5 days), period of infectiousness (-3.5 days from symptom onset)
38
whats the pathogenicity of coronavirus
reservoir → bats
transmission → aerosol and respiratory droplets
inhalation into URT → dissemination to LRT → spike protein binds to ACE2 receptors on T2 pneumocytes → viremia → systemic manifestations
there is a systemic ACE2 receptor binding → cardiac myocytes, GI tract, endothelial cells
immune dysregulation/persistent viral replication → post covid syndromes
spike protein antigen drift → pandemic (large mutations), epidemics (small mutations → alpha, delta, omicron variants)
39
risk factors for severe disease in coronavirus
age (#1), underlying comorbidities, unvaccinated, immunocompromised, vitamin D deficiency
40
clinical features of covid-19
range of symptoms from asymptomatic to critical illness
common cold → URT infection → rhinorrhea, nasal congestion, sneezing, headache, fever, sore throat +/- myalgias, anosmia and dysgeusia
interstitial pneumonia → LRT infection → hight fever, chills, dyspnea, chest pain, non-productive cough, hypoxia +/- ARDS and death
systemic manifestations → cardiac (myocarditis), GI (nausea, vomiting, diarrhea), endothelium (thrombosis)
41
what are the post COVID syndromes
post-mild (long covid) → myalgic encephalomyelitis (ME) / chronic fatigue syndrome (CFS)
post-severe → post-ICU syndrome, chronic organizing pneumonia, pulmonary fibrosis (sequela of ARDS) and MIS-C (Multisystem Inflammatory Syndrome in Children)
42
MERS and SARS covid?
similar to COVID-19 respiratory illness but ↑ severity and fatality
43
diagnosis of covid 19
rapid antigen test → low sensitivity
PCR detection of viral RNA → high sensitivity
antibody detection → anti-spike (vaccinated vs resolved); anti-nucleocapsid (resolved)
X-ray/CT → bilateral multi-lobe ground glass opacities and reticular interstitial thickening → peripheral and lower lobe predominance
44
management of coronavirus
antivirals → Nirmatrelvir/ritonavir (protease inhibitors), remdesivir (RNA replication inhibitor)
anti-inflammatories → dexamethasone, tocilizumab/baricitinib (IL-6 pathway modulators)
oxigen, respiratory support
anticoagulation
45
prevention of coronavirus
vaccine indication → >6mo of age
IM vaccine → spike protein mRNA (+ mutations) → anti-spike antibody + cytotoxic T cell production → ⭣risk of transmission and severe disease
severe adverse reactions are rare → benefits of indicated vaccine outweigh risk of adverse events
46
generalities about parainfluenza virus
- enveloped SS (-) RNA
- helical
- paramyxoviridae family member
- worldwide distribution, predominately in fall/early winter
- ages 6mo-3years primarily affected
47
what's the most affected population against parainfluenza virus
ages 6mo-3years primarily affected
48
what are the mechanisms of pathogenicity of parainfluenza virus
transmission → respiratory droplets
initial replication in nasal and oropharynx epithelial cells → spread to larger airways (larynx, trachea, bronchi)
hemagglutinin (HA) → viral surface glycoprotein antigen → attachment to host cell sialic acid (SA) receptors
F protein → fusion protein antigen → viral envelope-host cell membrane fusion following attachment + host cell fusion (multinucleated giant cells)
neuraminidase (NA) → promotes viral progeny budding → cleaves HA-SA connection to facilitate viral detachment
49
clinical features of parainfluenza virus:
laryngotracheobronchitis (croup):
- initial → URT symptoms (fever, rhinitis, pharyngitis)
- subsequent → dyspnea, barking (seal-like) cough, INSPIRATORY stridor (inflamed subglottic tissue → upper airway obstruction)
complications = viral pneumonia in adults
50
how do you diagnose parainfluenza virus
mostly clinical diagnosis
frontal neck x-ray → steeple sign (narrowing of subglottis and upper trachea)
51
what's the therapeutic approach to parainfluenza virus?
corticosteroids +/- nebulized epinephrine (if severe)
52
which respiratory virus is associated to inspiratory stridor
parainfluenza virus
53
generalities of respiratory syncytial virus
- enveloped SS (-) RNA
- helical
- former paramyxoviridae member NOW pneumovirus
- worldwide distribution, predominately in the winter
54
what's the most affected population against respiratory syncytial virus
ages <2 years primarily affected + ≥ 75 years or multiple comorbilities
55
what's the pathogenicity of respiratory syncytial virus?
transmission → respiratory droplets or direct contact with infected secretions
initial replication in nasopharynx → infection of smaller airways (bronchioles) → spread to alveolar cells (severe disease)
glycoprotein G → viral surface glycoprotein antigen (↑ mutation rate) → attachment to to host respiratory epithelial cells
F protein → fusion protein antigen → viral envelope-host cell membrane fusion following attachment + host cell fusion (multinucleated giant cells)
56
clinical features associated with respiratory syncytial virus
bronquiolitis:
- initial → URT symptoms (fever, rhinitis, cough)
- subsequent → tachypnea, nasal flaring and retractions (subcostal, supraesternal), hipoxemia, wheezing, crackles
complications:
- infants <2mo → apnea, respiratory failure or recurrent childhood wheezing
- COPD and asthma exacerbations
57
therapeutic mechanisms against respiratory syncytial virus
supportive → supplemental oxygen and nasal suctioning
Ribavirin → immunocompromised individuals and/or severe disease
58
how does prevention against respiratory syncytial virus work?
high-risk infants (prematurity, bronchopulmonary dysplasia, significant CDH) → prophylaxis with palivizumab (monoclonal antibody against F protein)
vaccination → pregnant mothers and older adults (≥ 60 years)
59
generalities of influenza virus:
- enveloped SS (-) RNA, linear segmented genome (8 segments), helical
- orthomyxovirus family member
- ↑ prevalence in winter months
60
pathogenicity mechanisms of influenza virus
transmission → respiratory droplets
inhalation → initial replication in URT → spread to large airways + viremia → posible extension to small airways/alveoli
hemagglutinin (HA) → viral surface glycoprotein antigen → attachment to host cell sialic acid (SA) receptors in respiratory tract
M2 proton channel on viral envelope → cell entry induces proton influx and viral acidification → viral RNA uncoating
viral RNA release to cytosol → trafficked to nucleus for replication → viral endonuclease “5-capsnatch” for viral mRNA → trafficked to ribosome
neuraminidase (NA) → promotes viral progeny budding → cleaves HA-SA connection to facilitate viral detachment → host cell death follows
** influenza A virus (IAV) **→ infects birds, pigs and humans → named HA and NA
- IAV HA/NA mutations → reassortment (shift → pandemics + species-species transmission); point mutations (drift → seasonal epidemics)
**influenza B virus (IBV) **→ mainly infects humans → named by strain (yamagata, victoria) → significant genetic shifts not evident and drift is minimal
61
clinical features of influenza
influenza = “the flu”
- abrupt onset high fever, malaise, myalgias/myosis, headache +/- mild URT symptoms or acute bronchitis (non-productive cough)
complications = pneumonia (1st viral or 2nd bacterial penumonia from S.aureus and S.pneumoniae), ARDS, COPD exacerbation, myocarditis, GBS, Reye syndrome
62
how does diagnosis of influenza work
mostly clinical (typical flu-like symptoms), may be diagnosed with PCR or antigen detection by nasal swab
63
therapeutic mechanisms against influenza
- supportive care + isolation
- antivirals (≤48 hrs or severe disease) → Oseltamivir and Zanamivir
64
preventive mesures against influenza
alcohol-based hand hygiene → dissolves lipid envelope
vaccination → anti-HA antibody production → most effective neutralizing antibodies
** live attenuated vaccine (rarely used) → nasal-spray containing temperature sensitive mutant variant strain → minimal LRT replication
** inactivated vaccine (most common) → IM injection → administered annually in fall for individuals >6mo
65
generalities of adenovirus
- naked dsDNA, icosahedral capsid
- worldwide distribution
66
what's the most affected population because of adenovirus
- young children/adults most affected → crowded areas (daycares, college campuses, military camps)
67
pathogenicity mechanisms of adenovirus
transmission → respiratory droplets, fecal-oral, or direct contact with contaminated surfaces
inhalation/ingestion/contact → host-cell attachment via viral fiber antigen → initial replication in lymphoid tissues (adenoids, tonsils, peyer patches)
varying tissue tropism → respiratory, gastrointestinal, conjunctival, cardiac, urinary tissues
68
clinical features of adenovirus
pharyngoconjunctival fever:
- initial URT prodrome → fever, sore throat, congestion, cough, cervical lymphadenopathy
- subsequent viral conjunctivitis → bilateral conjunctival injection “pink eye” with watery discharge → +/- keratitis
other adenoviral illnesses:
- gastroenteritis → fever, nausea, vomiting, noninflammatory watery diarrhea
- acute hemorrhagic cystitis (young children) → macrohematuria, cystitis, +/- renal failure
- myocarditis → heart failure presentation, ↑ cardiac biomarkers
- viral interstitial pneumonia
69
how does the diagnostic and therapeutic approach of adenovirus work?
diagnosis = clinical diagnosis
management:
- supportive, self-limiting
- viral conjunctivitis → warm or cool compress to provide symptomatic relief
70
is there a vaccine against adenovirus?
live oral viral vaccine → used for military personnel
