Lower Respiratory Bugs Flashcards
Bronchitis
Presents w/ cough, fever, chest pain. Prior to the onset typical to have common cold. Hacking cough w/ some sputum production.
CXR - no consolidations or infiltrates.
Clinical dx w/ CXR differentiating from pneumonia.
Bacterial if lasts longer than 14 days w/ fever and purulent sputum –> bacterial ID and Rx of erythromycin or azithromycin
Viral causes - Rhinovirus, Paramyxovirus, RSV, Influenza C, Cocksackievirus, Adenovirus (same as common cold)
Bacterial causes - Mycoplasma pneumoniae and Chlymidiae pneumoniae
Bronchiolitis
Inflammation of bronchial tree extending into bronchioles
Only in infants. (75% under 1; 95% under 2)
Clinical dx –> start as URI –> tachypnea, tachycardia, fever, diffuse expiratory wheezing, inspiratory crackles, nasal flaring, vomiting, vyanosis, and hyperinflation of the lungs
CXR to rule out pneumonia –> antigen testing for RSV.
Passive immunization w/ anit-RSV antibodies can be given to high risk patients. (REspiGam or palivuzumab)
Cause - RSV most common, also Parainfluenza and Adenovirus
Pertussis
Causative organism - Bordatella pertussis =
- Gram negative
- Coccobaccilli, pleomorphic
- Growth on Bordet-Gengou medium (or Regan-Lowe medium)
- Resistant to cephalexin/penicillin
Virulence factors- pertussis toxin (damages trachea tissue); Filamentous hemagglutinin (atrachment to ciliated cells)
Incubation period 7-10 days.
Catarrhal stage - bacteria present in the respiratory tract casue cold sx (esp. runny nose). Stage lasts 1-2 weeks (most infectious during this stage!)
Paroxysmal stage - characterized by severe and uncontrollable coughing (a paroxysm can be thought of as a convulsive attack). This intense coughing can cause bursting of blood vessels in eye, vomiting, cyanosis, hernia, hemoptysis, seuizures, or death. Worst cases seizures result from small hemorrhages in brain.
Pathognomonic whooping is found on inspiration after coughing paroxysm.
Convalescent phase - recovery; decreasing bacteria numbers w/o sx. Recovery of epithelial cells and cilia takes weeks-months –> secondary infection susceptibility.
Very high WBC’s!
Rx: erythromycin, supportive care, DTaP at 6 weeks and 6 years.
Influenza
Causative organism - Influenza A or B
- Class V
- Helical Nucleocapsid
- Enveloped
- ss - nonsegemented (class v)
- Orthomyxovirudae
Sx:
- Abrupt onset fever (102-104)
- chills
- rigors
- headache
- congested conjunctiva
- extreme prostration w/ myalgia in back and limbs
- nonproductive cough
- fever usually abates in 3-4 days; cough and tiredness in 2 weeks
Secondary pneumonias caused by - S. aureus (most common), S. pyogenes, H. influenza, S. pneumoniae
Pathogenesis - Viral hemagglutin (HA) envelope protein makes contact w/ sialic acid on cell surfaces –> endocytosis. The viral neuraminidase (NA) envelope protein is important for cleaving the HA bound to sialic acid, this permits viral spread.
Adults are infectious from the day before sx begin through approximately 5 days after onset of illness. (key for epidemiology!)
Rx - Vaccine and Oseltamivir (NA inhibitor aka Tamiflu)
Antigenic drift - minor changes due to gene mutation (vaccine still works)
Antigenic shift - major changes due to gene reassortment (influenza A)
Pneumonia
Inflammatory condition of the lung which fluid fills the alveoli. Can be lobar, broncho, or interstitial (atypical).
MCC = Strep pneumoniae
Young children: RSV, parainfluenza virus
18-40 year olds: Mycoplasma, C. pneumo, S. pneumo
40-65 year olds: S. pneumo, H. influ, Legionella
>65: S. pneumo, Gram - rods, H influenza
Sputum:
Rust colored - strep pneumo
Green - pseudomonas, haemophilus, and pneumoccal
Red currant jelly - Klebsiella (mucoid capsule)
Foul smelling/ bad tasting - anaerobic infxs
TB
Sx: Coughing that lasts more than three weeks, hemoptysis, chest pain/pleurisy, weight loss, fatigue, fever, night sweats, chills, loss of appetite
Mycobacterium TB: Acid fast baccilli, aerobic (upper lobes on secondary infx), Ziehl-Neelson stain, Lowenstein-Jensen medium.
Visible growth on agar takes 3-8 weeks
Sputum smear is not very sensitive
Pulmonary cavities contain huge numbers of organisms.
Mycoplasma pneumoniae
Not Gram + or Gram -
Most common cause of atypical pneumonia
MCC of pneumoniae in adults 18-40
Chlamydia pnumoniae
Not gram + or gram -
Obligate intracellular parasite (repilicate within inclusion bodies
Common cause of atypical pneumonia
Neisseria asteroides
Gram +
Beaded filaments
Weakly acid fast
Obligate aerobe
Cause of pneumonia
Strep agalactiae (GBS)
Gram + Cocci Catalase - Beta hemolytic Bacitracin resistant
Lower respiratory Tract Defenses
- Alveolar Macrophages (Most important)
- Complement components
- Alveolar lining fluid containing surfactant, phospholipids, neutral lipids, IgG, IgE, IgA and Factor B
- B and T cells
Mechanisms used to avoid phagocytosis
- Capsule (S. Pneumo, H. Influenza)
- Toxins (i.e. cytotoxins, leukocidins, and exotoxins)
- Parasites and Fungi are too large
- Replication inside cells (i.e. viruses or chlymidiae)
- Mimicry (either very similar proteins, or bind host proteins to their membrane)
Mechanisms used to survive in the phagocyte
- Inhibition of lysosme fusion w/ phagosome
- Escape from the phagosome (influenza)
- Resistance to killing and digestion in the phagolysosome
- Growth in the phagocytic cell (Legionella)
Modes of transmission
- Inhalation
- Aspiration
- Hematogenous spread (bilateral and uniform)
- Direct extension (i.e. URI –> pneumonia)
- Exogenous penetration and contamination (trauma and surgery)
Inhalation and Aspiration are the most common causes.
MCC pneumonia in neonates (0-6weeks)
Group B Strep (Strep. agalactiae) –> screen for this
E. coli
