Can bacteria cause bronchitis and how is it treated?

Bacteria as a Cause of Bronchitis and Its Treatment

While bacteria can cause bronchitis, they are responsible for only 5-10% of acute bronchitis cases in otherwise healthy adults, with the vast majority (≥90%) being caused by viruses. Routine antibiotic treatment is not recommended for uncomplicated acute bronchitis regardless of cough duration. 1

Etiology of Bronchitis

Viral Causes (Predominant)

• Respiratory viruses account for 90% or more of acute bronchitis cases 1, 2
• Common viral pathogens include:
  • Primary lower respiratory tract viruses: Influenza A and B, Parainfluenza, Respiratory syncytial virus
  • Upper respiratory tract viruses: Coronavirus, Adenovirus, Rhinovirus 2

Bacterial Causes (Less Common)

• Only three bacteria have been established as causes of uncomplicated acute bronchitis in adults without underlying lung disease:
  • Bordetella pertussis
  • Mycoplasma pneumoniae
  • Chlamydia pneumoniae (TWAR) 1, 2
• These bacterial pathogens collectively account for only 5-10% of acute bronchitis cases 1, 2
• They are found more frequently (10-20%) in studies of adults with persistent cough 1

Important Distinction

• Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are not established causes of acute bronchitis in adults without underlying lung disease 1, 2
• When these bacteria appear in sputum cultures of acute bronchitis patients, they represent colonization rather than true infection 1, 2
• These bacteria do play significant roles in acute exacerbations of chronic bronchitis, which is a different clinical entity 2, 3, 4

Treatment Approach

Antibiotic Treatment

• Routine antibiotic treatment of uncomplicated acute bronchitis is not recommended, regardless of cough duration 1
• Multiple randomized, placebo-controlled trials and meta-analyses have shown that antibiotics:
  • Do not have a consistent impact on duration or severity of illness
  • Do not prevent complications such as pneumonia
  • Provide only minimal benefit (reducing cough by about half a day)
  • Have potential adverse effects including allergic reactions, gastrointestinal symptoms, and risk of C. difficile infection 1, 5

Special Circumstances for Antibiotic Use

• Bordetella pertussis infection (whooping cough):
  • Diagnostic tests should be performed and antibiotic treatment initiated
  • Antibiotics primarily reduce pathogen shedding and disease spread
  • Treatment has limited effect on symptoms if started >7-10 days after symptom onset 1
• Bacterial superinfection:
  • Consider if fever persists more than 7 days 1
  • Requires clinical judgment and possibly chest imaging to rule out pneumonia

Symptomatic Treatment

• Focus on symptom management rather than antibiotics
• Provide realistic expectations about cough duration (typically 10-14 days after office visit) 1
• Consider referring to the illness as a "chest cold" rather than bronchitis to reduce antibiotic expectations 5

Common Pitfalls to Avoid

1. Misinterpreting purulent sputum as indicating bacterial infection:

   • Purulent sputum can result from inflammatory cells or sloughed mucosal epithelial cells due to either viral or bacterial infection 1
   • The presence of purulent sputum alone does not justify antibiotic use

2. Confusing acute bronchitis with acute exacerbation of chronic bronchitis:

   • These are distinct clinical entities with different microbiology and treatment approaches
   • Bacterial pathogens play a more significant role in exacerbations of chronic bronchitis 3, 4

3. Prescribing antibiotics to satisfy patient expectations:

   • Patient satisfaction depends more on effective communication than receiving antibiotics 1
   • Educate patients about the viral nature of most bronchitis cases and the limited benefit of antibiotics

4. Failing to consider pertussis in persistent cough:

   • Consider pertussis in patients with cough persisting >2 weeks with paroxysmal cough, whooping, post-tussive emesis, or recent exposure 5
   • Pertussis is one of the few bacterial causes of acute bronchitis that may benefit from antibiotic treatment (primarily to reduce transmission) 1

By understanding the predominantly viral etiology of acute bronchitis and the limited role of bacteria, clinicians can avoid unnecessary antibiotic use while providing appropriate symptomatic care for patients.