EXAM 1 Lower Respiratory Tract Infections Flashcards
what is the triad of infectious diseases?
host
pathogen
environment
describe the host portion of the triad of infectious disease
- anatomic defenses
- innate immunity
- acquired immunity
- humoral
- cell-mediated
describe the pathogen portion of the triad of infectious disease
- bacteria
- mycobacteria
- fungi
- viruses
- protozoa
- metazoans
describe the environment portion of the triad of infectious disease
- humans
- animals
- inanimate
- occupational
- travel
- setting (CAP, HCAP)
- inoculum
what is required to make a pneumonia diagnosis?
an x-ray of the chest showing parenchymal infiltrates
describe typical acute pneumonia
- community-acquired (CAP) usually
- measured in hours to days
- onset with chills, fever, and wet cough
- lobar consolidation or segmental or sub-segmental bronchopneumonia
- pleura often invovled giving chest pain with inspiraiton (pleuritis)
- micro-aspiration of upper respiratory tract colonizing bacteria
describe pathogenesis of typical acute pneumonia
- micro-aspiration of upper respiratory tract colonizing bacteria
- most often due to streptococcus pneumoniae
describe the etiology of community-acquired pneumonia
- pneumococcus most common pathogen
- haemophilus has largely disappeared
- gram-negative pneumonia is uncommon but consider klebsiella pneumoniae
- viral pneumonia is often seen in children (respiratory viruses) and during influenza epidemics
name the most common bacteria responsible for community acquired pneumonia
- streptococcus pneumoniae
- hemophilius influenzae
- staphylococcus aureus
what are 3 gram negative bacilli responsible for community acquired pneumonia?
- moraxella catarrhalis
- streptococcus pyogenes
- neeisseria meningitidis
what are 3 atypical agents responsible for community acquired pneumonia?
- legionella species
- mycoplasma pneumoniae
- chalmydia pneumoniae
describe the histology of lobar pneumonia aka lung hepatization
alveolar spaces are infiltrated with neutrophils in an attempt to control the infection
what are 2 types of acute, atypical pneumonias?
- walking pneumonia
- environmentally acquired acute pneumonias
- potentially fatal and require non-beta-lactam antibiotics
- macrolides, fluroquinolones, tetracyclines
what bacteria are responsible for walking pneumonia?
mycoplasma pneumoniae and chlamydophila pneumoniae
what bacteria are responsible for environmentally acquired acute pneumonias?
- legionella pneumophilia (legionnaire’s disease)
- coxiella burnetii (Q fever)
- chlamydophila psittaci
describe aspiration pneumonia
- setting: stupor, coma, or seizures
- focal infiltrates
- dependent portions of lung
- oropharyngeal flora
- community vs hospital environments
- may be complicated by chronic pneumonia with lung abscess formation
describe microbiology of community-acquired aspriation pneumonia
gram positive
anaerobes (up to 20%)
describe the microbiology of hospital-acquired aspiration pneumonia
gram negative
s. aureus
what is the trans-tracheal aspiration method?
- placing a needle with a catheter through the cricothyroid cartilage
- syringe with saline solution is pumped into trachea, causing the patient to aspirate
- sample is taken to determine microbial etiology
name some cultural oral anaerobic bacteria
- gram positive cocci
- peptostreptococcus
- gram positive bacilli
- actinomyces, eubacterium, leptotrichia
- gram negative cocci
- veillonella
- gram negative bacilli
- fusobacterium, prevotella, porphyromonas
what are some examples of viral pneumonia contributors?
- human respiratory virus
- common in children, rare in adults
- hantavirus (Sin Nombre V.)
- coronavirus (SARS, MERS)
- bacterial pneumonia with or in the wake of influenza
name some human respiratory viruses that contribute to viral pneumonia
- influenza
- parainfluenza
- RSV
- adenovirus
- metapneumovirus
- enterovirus
- paraechovirus
describe complications of acute bacterial pneumonia
- necrotizing pneumonitis - death of lung parenchyma
- lung abscess - excavation of lung parenchyma
- empyema - spread of infection into potential space between parietal and visceral pleura - requires drainage as part of management
what is empyema?
- pleural space infection
- invasion from lung parenchyma
- diagnostic thoracentesis
- drainage via chest tube hooked to water seal
- management critical to prevent lung “entrapment”
describe management of acute pneumonia with an empiric Rx
- in most cases, microbiological diagnosis is not possible
- new tests for antigens and nucleic acids may offer etiological diagnosis
- possible pathogens of acute pneumonia are well established from previous studies going way back in medical history
- the development of broad-spectrum antibiotics to cover most possible pathogens makes empiric therapy possible in most cases
- exceptions have arisen due to antibiotic resistance including the pneumococcus, the leading pathogen for lobar and bronchopneumonia
describe chronic pneumonia
- weeks to months - not days
- differential diagnosis
- many non-infectious diseases
- no empiric treatment
- requires diagnosis by bronchoscopy or lung biopsy
describe tuberculosis
- slow-growing acid-fast human pathogen
- cough generates droplet nuclei
- inhaled into alveolar space
- replicates relentlessly and spreads to lymph nodes and then systemic circulation
- becomes dorman as host cell-mediated immunity develops
- host at jeopardy for primary and post-primary (reactivation) disease
- public health issues (human -> human spread)
describe pneumonia in the immunocompromised host
- host factors predominate
- panoply of potential pathogens spanning viruses -> metazoa
- complete history required to investigate possible environmental factors for exposure
- may be acute or chronic
- chest x-ray appearance: myriad of presentations
- search for etiological diagnosis imperative for successful management
