Micro - Respiratory Flashcards
Upper Respiratory Tract Infections
otitis externa, sinusitis, rhinitis, pharyngitis, epiglottitis, laryngitis
Lower Respiratory Tract Infections
bronchitis, bronchiolitis, pneumonia
Respiratory Defenses
- Mucociliary lining of nasal cavity
- Change of direction of airway (pathogens get trapped in mucous layer)
- Ciliary Elevator
- Normal flora competition
- Alveolar macrophages (innate immune system)
- IgA (acquired immune system)
2 Major obstacles organisms must overcome
- Avoid/survive mucus layers
2. Avoid phagocytosis and survive
Turbinate Bones
“Baffle plates”
covered with mucus –> air swirls as it passes over –> pathogens come into contact with mucus covered passages
Mucociliary Elevator
- mucus-producing goblet cells
- ciliated epithelium
* smoking paralyzes the cilia –> smoking cessation can lead to regrowth of cilia
Normal flora of respiratory tract
Upper - lots
Lower - NONE –> considered sterile
Pathogen initiation of disease
- Must be sufficient dose of microorganisms
- infectious particles must be airborne
- airborne particles must be viable in air
- organisms must be deposited on tissue susceptible to infeciton
Rhinitis
Common cold - generally no fever
Nasal stuffiness, sneezing, headache, tiredness, lacrimation, sore throat
Usually seen in winter, spread person-person
- symptoms peak 2-5 days post infection, resolved by 14 days
- supportive therapy
Rhinovirus
#1 cause of rhinitis RNA virus --> icosahedral --> non-enveloped --> ss(+)non-segmented(IV) --> picornaviridae infects nasal passages following attachment to ICAM-1 --> localized inflammation and lytic infection --> ciliated epithelial cells are destroyed - break in barrier may lead to secondary infection by normal flora
Parainfluenza
RNA virus –> helical capsid –> enveloped –> ss(-)non-segmented(V) –> paramyxoviridae
F-protein –> forms multinucleated cells
Hemagglutinin –> interacts with salic acid –> endocytosis
Neuroaminidase –> envelope protein responsible for cleaving HA bound to salic acid –> viral spread
Coronavirus
RNA virus –> helical capsid –> enveloped –> ss(+)non-segmented (IV) –> coronaviridae
Can cause SARS –> rapidly progressive pneumonia
Mastadenovirus
DNA virus –> icosahedreal nucleocapsid –> non-enveloped –> DS linear DNA (I) –> adenoviridae
most common viral cause of conjunctivitis
Rhinosinusitis
inflammation or infection of mucosa of nasal passages and atleast 1 paranasal sinuses
2 most common causes = S. pneumoniae and H. flu
Sx: sneezing, rhinorrhea, congestion, post-nasal drip, aural fullness, facial pressure, headache
Fungal rhinosinusitis –> RARE, aspergillus fumigatus (immunocompromised)
- antibiotic treatment for bacterial causes
Strep pneumoniae
gram (+) diplococci –> catalase (-) –> alpha hemolytic –> bile-esculin negative –> optochin susceptible
Capsule, IgA proteases
Major cause of community acquired pneumonia
H. influenzae
gram (-) –> coccobacilli, pleomorphic –> X & V factors
IgA protease, capsule –> avoids phagocytosis
Pharyngitis
Majority caused by viruses (conjunctivitis, cough, hoarseness)
Strep pyogenes is most common bacterial cause (severe pain with swallowing)
Sx: fever, sore throat, edema, hyperemia of tonsils
Rapid strep test tells if bacterial –> culture takes 1-2 days
needs to be treated within 9 days to prevent glomerulonephritis or rheumatic fever
Strep pyogenes
gram (+) cocci –> catalse (-) –> beta-hemolytic –> bacitracin sensitive
attaches to mucosal epithelial cells with M-protein, lipoteichoic acid, and protein F
Capsule (hyaluronic acid) –> prevents phagocytosis
Protease and Hyaluronidase –> invasion
Streptokinase –> plasminogen to plasmin (fibrinolytic)
Scarlet Fever
certain strains of s. pyogenes
Streptococcal Pyogenic Exotoxins –> SpeA, SpeB, SpeC, SpeF
encoded by lysogenized bacteriophage
“strawberry tongue”
Corynebacterium diphtheriae
gram (+) bacilli –> non-spore forming –> non-motile
produces AB toxin (B=binding, A=enzymatic activity)
toxin A –> acts against EF-2 (inhibits translation –> cellular death) –> airway blockage
DON’T disrupt the capsule –> pathogen will gain access to blood
Dtap and Tdap
Croup (laryngotracheobronchitis)
Fever, restlessness and shortness of breath
Mild URI and cold-like symptoms (winter time)
“Bark-like” cough with respiratory stridor (at night)
Symptoms peak 3-5 days and resolve 4-7 days
Caused by parainfluenza, influenza, and respiratory syncytial virus
Respiratory Syncytial Virus (RSV)
helical nucleocapsid –> enveloped –> ss(-) nonsegmented –> paramyxoviridae –> pneumovirus
F-protein causes fusion of cells into “syncytium”
Attaches to epithelium via protein G
Most common cause of pneumonia in neonates?
Strep agalactiae (group B strep) E. coli
Adult pneumonia causes?
18-40 yrs (Mycoplasma pneumoniae, chlamydia, strep pneumoniae)
40-65 yrs (S. pneumoniae, H. flu, Legionella, virus)
+65 yrs (S. pneumo, gram (-) rods, H. flu)
Most common cause of meningitis in +60 yrs?
S. pneumo, Gram (-) rods, listeria
Most common cause of meningitis in kids
S. pneumo, N. meningitidis, H. flu type B
Coxsackievirus A/B
RNA –> icosahedral –> non-enveloped –> ss(+) (IV) –> picornaviridae –> enterovirus
fecal-to-oral transmission
Influenza C virus
RNA –> helical –> enveloped –> ss(-) (V) –> orthomyxoviridae
Infects through Hemagglutinin –> salic acid and also neuroaminidase –> cleaves binding for viral spread
Immune response to infection?
IL-1 and IFN-gamma
Moraxella catarrhalis
2nd most common cause of bacterial pneumonia in patients with COPD
Pili, endotoxin, capsule
Bronchitis
LRI - cough (hacking with sputum), fever, chest pain
prior to onset, typically common cold
CXR doesn’t reveal bronchitis
typically self limiting –> if longer than 14 days then antibiotic may be needed
Bacterial causes of bronchitis
Mycoplasma pneumoniae
Chlamydia pneumoniae
Mycoplasma pneumoniae
not gram (+) or (-)
Chlamydia pneumoniae
not gram (+) or (-)
Bronchiolitis
no alveolar involvement –> inflammation of bronchiole wall, typically in kids <1 yr because of tiny airways
RSV is main organism
Pertussis (whooping cough)
2 Phases
1. after 3-21 day incubation period –> Catarrhal stage, lasts 1-2 weeks with cold symptoms (runny nose)
2. Paroxysmal stage –> severe uncontrollable coughing, can result in spasms, bursting blood vessels, vomitting
Recovery phase (convalescent stage) –> bacteria no longer cause ongoing symptoms –> epithelial cells recoverying (takes weeks to months)
Bordatella Pertussis
gram (-) –> coccobacilli (pleomorphic) –> growth on bordet-gengou medium
AB toxin –> B-binding, A-enzymatic activity that increases cAMP –> massive overproduction of mucus –> cough
tracheal cytotoxin
Influenza virus
RNA virus –> helical –> enveloped –> ss(-) segmented (V) –> orthomyxoviridae
8 segments
RNA polymerase –> no self-check –> lots of mutations –> constantly mutating
Hemagglutinin binds sialic acid –> neuraminidase cleaves to assist in invasion
Neuraminidase has HIGH rate of mutation so immune system has trouble gaining immunity
Antigenic Shift
occurs when major changes in antigens occur due to gene reassortment in influenza virus
Antigenic Drift
occurs when minor changes in antigens occur due to gene mutation in influenza virus
reason for the need of flu shot every year
Pneumonia
inflammatory condition in which fluid fills alveoli
most common cause = Strep pneumoniae
Typical - Sudden onset of fever, chills, dyspnea, productive cough, crackles of lungs
Atypical - gradual onset of non-productive cough, headache, sore throat, dyspnea, fever
CXR use?
CXR will show infiltrates for pneumonia.
CXR is also used to exclude pneumonia and therefore diagnose bronchitis/bronchiolitis
Nosocomial pneumonia
gram (-) rods, staph aureus
Pneumonia in immunocompromised
Gram (-) rods Streptococcus pneumoniae Fungi Filamentous bacteria Pneumocystis jiroveci Viruses
