Lower Respiratory Tract Infections (LRTI)

Pathogens, signs, symptoms, treatment, clinical parameters for monitoring of Acute Bronchitis, AECB, CAP, HCAP, and Bronchiolitis

  • Acute bronchitis = inflammation of the tracheobronchial tree
    • Cough < 2-3 weeks in duration
    • Usually caused by virus
    • Trxt:  apap/ibu + cough suppressant at night to help w/ sleep + antibiotic if signs of fever, HR> 100, RR > 24 or symptoms lasting longer than 2 weeks
    • Bacterial pathogens of complicated acute bronchitis & AECB:   H. Influenzae, S. Pneumoniae, M. Catarrhalis
      • Antibiotic choices:  macrolide, doxycycline, augmentin, 2nd/3rd generation cephalosporin, fluoroquinalone
  • Bronchiolitis = viral infection of newborns
    • Usually occurs seasonally & is self-limiting but it puts the pt at an increased risk of developing asthma later in life
    • Pathogens:  rhinovirus, parainfluenza virus, RSV
    • Clinical manifestations (often confused w/ acute asthma):  URTI symptoms, tachypnea, wheezing, respiratory distress
    • Diagnosis:  nasal secretions w/ positive viral agents, negative CXR, absence of leukocytosis, H&P
    • Treatment:  antivirals, isolation, oxygen, beta agonists, hospitalization if severe, younger than 6 months old or other underlying conditions
      • Ribavirin:
        • expensive (admin’d via a small particle generator), inhibits both DNA & RNA replication
        • Indications:  PaO2 < 65 or rising PCO2, < 6 weeks old, significant comorbities
      • Palivzumab:
        • Expensive & short shelf life after reconstitution
        • Admin 15mg/kg IM monthly from Nov-April

Lab data useful for diagnosis and monitoring of pneumonia.

  • 2nd most common cause of death next to infectious diseases
  • Lab findings:  increased WBC count with left shift, decreased oxygen saturation, rising PCO2
    • Diagnosis:  radiographic evidence, gram stain or positive blood culture (sputum w/ < 10 epithelial cells/lpf & many PMNs)
    • Need to correctly assess the likelihood of infection  (use the CURB score for CAP–higher the number the higher the risk of infection; CURB-65 doesn’t involve BUN)
  • CURB-65 score (helps to determine the severity of community acquired pneumonia (CAP
    • The higher the CURB score, the higher the risk of infection
    • The modified CURB-65 (CRB-65) score eliminates BUN from consideration
Clinical Factor




BUN > 19


RR ≥ 30


Systolic BP < 90 or diastolic BP ≤ 60


Age ≥ 65


Total Points


CURB-65 Score

Percent Mortality




Low risk; may be treated at home






Short inpatient hospitalization or closely supervised as an outpatient



Severe pneumonia; hospitalize and consider ICU admission

4 or 5



  • The modified CURB-65 score classifies severe CAP as a score 3-4
  • Signs/symptoms:
    • Typical symptoms:  cough w/ sputum production, fever/chills, SOB, pleuritic chest pain
    • Atypical symptoms:  HA, dryness, low grade or no fever
    • Physical findings:  rhales, crackles, dullness to percussion, tachypnea, tachycardia, distant breath sounds
      • If a person has any of the following they are considered to have severe pneumonia:
        • respiratory rate > 30/minute
        • respiratory failure by ABG’s
        • mechanical ventilation
        • multilobular involvement  (bilateral pneumonia)
        • Increased radiograph opacity by 50% within 48 hours of admission
        • > 4 hours of vasopressors needed
        • Urine output < 20 ml/min pr < 80 mls over 4 hrs or ARF requiring dialysis


Associated Risk Factors

Community Acquired

Streptococcus pneumon.

Mycoplasma pneumon.

Haemophilus influenzae

Legionella pneumophilia

Klebsiella pneumon.

Splenectomy, DM, URI, young adult, close prox.

Pediatric, elderly

ETOH , diabetic, seizure, Alzheimers

Hospital Acquired/HCAP

Klebsiella pneumon.

Pseudomonas aerugen.

E. Coli

Staph. aureus

Staph. aureus (MRSA)

Mechanical vent., comatose, acid suppressive therapy, NH

Trxt of pneumonia:  antibiotics, hydrate, oxygenate, analgesics/antipyretics

  • In healthy pts:
    • Azithromycin 500mg PO QD x 7-10 days    or     Clarithromycin 500mg PO BID x 10-14 days    or     Doxycycline 100mg PO BID x 10-14 days
      • Alternative trxt:  2nd gen cephalosporin (ex. Cefuroxime) +/- macrolide    or    quinalone
  • In pts w/ cardiopulmonary disease  (COPD/asthma + pneumonia):
    • Cefpodoxime/cefuroxime/augmentin/ceftriaxone + azithromycin/clarithromycin/doxycycline
    • Alternative trxt:  fluoroquinalones (Levofloxacin, ciprofloxacin)
  • Inpatient trxt (not severe disease):  IV azithromycin/doxycycline + IV beta lactam   or  a respiratory fluroquinalone (moxifloxacin, gemifloxacin, levofloxacin)
  • Inpatient w/o risk factors for Pseudomonas & severe disease:  cefotaxime/ceftriaxone + IV azithromycin/a fluoroquinolone
  • Inpatient w/ risk factors for pseudomonas & severe infection:  cefipime/imipenem/monopenem/piperacillin-tazobactam  +  (cipro or aminoglycoside-azithromycin/levaquin) + vanco if MRSA is suspected  (HCAP)
  • Doxycycline, ofloxacin, cipro, levofloxacin, metronidazole, clindamycin all have relatively the same bioavailability IV & PO
    • Generally though, consider switching from IV to PO when:
      • GI tract is functioning well, WBC decrease, there’s an improvement in cough & dyspnea, pts temp < 100 F on at least 2 occasions 8 hrs apart
  • People at risk for drug resistance:  alcoholics, ppl over 65, ppl on immunosuppressive therapy, multiple medical co-morbidities, daycare for kids, ppl on beta-lactam therapy w/in the last 3 months
  • Risk factors for various gram negative bacteria:  nursing homes, recent antibiotic therapy, multiple medical comorbidities, cardiopulmonary disease
    • Very old are more likely to get infected by gram negative & anaerobic pathogens
    • Very young (< 1 mo) are more likely to get infected by Listeria mono or Chlamydia
    • Ppl in their late teens-middle age:  mycoplasma pneumoniae
    • AIDS – Pneumocystis jiroveci (formerly carinii)
    • Alcoholism – Gram negative bacilli &     anerobes
    • COPD – H. influenzae
    • Cystic fibrosis – Pseudomonas aerugenosa
    • Sickle cell anemia – Streptococcus pneum.
    • Viral influenza – Staphylococcus aureus

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