Intro to Resp Infx Disease Flashcards
3 mechanisms of disease for bacteria:
- Toxin production
- Host immune response
- Bacterial proliferation and invasion
3 mechanisms of disease for viruses:
- Cytopathic effect–> cell death and disease
- Host immune response
3 . Tumorigenesis
Two main obstacles microorganisms must overcome to infect upper resp tract:
- mucous
2. phagocytosis (avoid it or be able to survive it)
Two basic components of the mucociliary elevator:
- goblet cells–produce mucus
2. ciliated epithelium
Most common pathogen causing common cold?
rhinovirus
Pathogen causing common cold any time of year?
adenovirus
Pathogenesis of rhinovirus; adhesion and sx cause?
ICAM-1 (adhesion)
lytic infx destroying ciliated epithelial cells
If clear discharge from common cold becomes purulent think?
secondary bacterial infx
RNA
Icosahedral capsid
NON-enveloped
SS(+) non-segmented (class IV)
Picoraviridae
Rhinovirus
RNA
Helical capsid
Enveloped
SS(-) non-segmented (class V)
Paramixoviridae
Parainfluenza virus
Paramyxovirus
RNA
Helical
Enveloped
SS(+) non-segmented (class IV)
Coronaviridae
Coronavirus
RNA
Helical
Enveloped
SS(-) Non-segmented (class V)
Orthomyxoviridae
Influenza A, B, C
RNA
Icosahedral
Non-enveloped
SS(+) Non-segmented (class IV)
Picornaviridae
Enterovirus
Coxsackie A and B
DNA
Icosahedral
Non-enveloped
DS linear DNA (group I)
Adenoviridae
Adenovirus (Mastadenovirus)
Most common viral cause of conjunctivitis:
adenovirus
inflammation or infx of nasal mucosa + at least one paranasal sinus lasting
acute rhinosinusitis
Two most common bacterial causes of community acquired acute bacterial rhinosinusitis:
S. pneumo
H. influenzae
Refractory sinusitis may be?
Aspergillus fumigatus
Treatment of fungal sinusitis in immunocompetent:
mechanical removal
Patients at higher risk in fungal sinusitis:
immune compromised
General differentiating factors in viral vs bacterial sinusitis:
duration (> 7 days adult, >10-14 days children)
severity of sx (ie. facial pain, fever > 102)
Evidence based treatment of viral sinusitis sx:
saline wash
Abx for bacterial sinusitis:
First line: amoxicillin
second: azithromycin
Gram +
diplococci
Catalase -
a-hemolytic
Bile-Esculin Negative
Optochin susceptible
+ Quellung
S. pneumoniae
Gram -
Cocobacilli, Pleomorphic
X and V factors required
+ Quellung
H. influenzae
Most common cause of pharyngitis:
viral
most common bacterial cause of pharyngitis:
S. pyogenes
pharyngitis
military or boarding school
adenovirus
viral pharyngitis in adolescents in winter
EBV
Pharyngitis + conjunctivitis strongly suggests:
viral cause
Pharyngitis + fever + severe pain w/swallowing suggests:
S. pyogenes
S. pyogenes attachment VF’s:
M protein
lipoteichoic acid
protein F
S. pyogenes prevents phagocytosis via (VFs):
hyaluronic acid CAPSULE
S. pyogenes invasion VFs:
protease
hyaluronidase
S. pyogenes
(shape?)
catalase (?)
? hemolytic
bacitracin (?)
cocci
catalase -
Beta - hemolytic
bacitracin SENSITIVE
C. diptheriae
Gram (?)
(shape?)
spore forming (?)
motility (?)
Gram +
bacilli
NON-spore forming
NON-motile
Tx for S. pyogenes pharyngitis?
penicillin
erythromycin, 2nd line if penicillin allergy
Scarlet Fever causing exotoxins of S. pyogenes:
speA
speC
ssa
***superantigens
“Strawberry tongue”
Scarlet Fever (S. pyogenes)
What does catalase do?
Does S. pyogenes have it?
converts H2O2 –> H2O + O2 (bubbles formes)
nope
How do aerobes deal with reactive oxygen species?
superoxide dismutase
“bark-like” cough
croup
Causes croup any time of year:
Parainfluenza virus
Cause croup mostly in winter and early spring:
Influenza virus
Respiratory syncytial virus
RNA
Helical capsid
Enveloped
SS(-) non-segmented (class V)
Paramixoviridae
Pneumovirus
Respiratory Syncytial Virus (RSV)
What are the two paramyxoviruses that cause croup?
What is the VF involved?
What does that VF do?
RSV
Parainfluenza virus
F-protein
Fusion of respiratory epithelial cells–> multinucleated cells
Most frequent cause of epiglotitis?
2 H. influenzae (actually the only one mentioned in FA), now less common d/t vaccination
group A strep
beta hemolytic (ie. S. pyogenes)
So hopefully the Q stem includes gram stain
Tx for epiglotitis:
SECURE AIRWAY
2nd or 3rd gen Cephalosporin + penicillinase resistant penicillin: Claxacillin, Oxacillin, Naficillin, Dicloxacillin, Methicillin
Differentiates epiglotitis from croup:
Onset (sudden vs gradual)
Supraglottic vs subglottic
High fever vs low fever
Severe dysphagia vs mild or absent
Drooling vs none
Uncommon cough vs barking cough
Positive thumb sign vs steeple sign on imaging
multinucleated giant cells associated with?
Parainfluenza virus
VF for Parainfluenza virus adhesion to sialic acid?
hemagglutinin (HA)
VF for Parainfluenza virus cleaving hemagglutinin facilitating viral spread:
neurominidase (NA)
vesicles on hands, feet, and mouth
typically young children
Coxackievirus A and B
“hand, foot and mouth disease”
gray fibrinous exudate
C. diphtheriae
“Chinese letters” under microscope
C. diphtheriae
Strep. pneumoiae is ___hemolytic.
alpha
Strep pneumo is Bile-Esculin + or - ?
- negative
Is Strep pneumo optochin susceptable?
yes
S. pneumo:
Quellung + or - ?
+ positive
Essential VF for S. pneumoniae
capsule
**also has IgA protease – this makes sense because it’s going to see a lot of IgA
S. pneumo
Optochin ?
SENSITIVE
S. pneumo
Quellung?
POSITIVE
+++++++++++++++
H. influenzae
Quellung ?
POSITIVE
+++++++++++++++
S. pyogenes
bacitracin ?
sensitive
What does C. diphtheriae look like on gram stain?
purple rod
Gram + bacilli
E. coli
catalase ?
positive
