Question 18

College Answer

a) Clinical features indicating poor prognosis

1. • 1. Common organisms
     • Streptococcus pneumonia
     • Legionella spp
     • Haemophilus influenza
     • Klebsiella pneumonia
     • Staphylococcus aureus
     • Respiratory viruses
     • Mycoplasma
   1. • Reasons for non-response
      1. • Wrong diagnosis
         • Cardiac failure
         • PE
         • Pulmonary haemorrhage
         • Wrong antibiotics
         • Resistant organism e.g.: MRSA
         • Wrong organism: e.g.: viral pneumonitis
         • Wrong dose
         • Under dosing (gentamicin, vancomycin)
         • Wrong interval (vancomycin, cephalosporins)
   • 1. Complication of the disease
        • Empyema
        • Lung abscess

1. 1. Complication of treatment
      1. • Antibiotic reaction
         • Superinfection
   2. Underlying disease
      1. • Cancer
         • Airway obstruction
         • Severe emphysema with bullae
2. Stopping antibiotics

1. • Evidence in area is complicated, but in resolving CAP- 7-10 days most common in studies
   • 5 days seems the minimum
   • More than 8 days may be associated with super infection with resistant organisms.
   • Pseudomonas- may need 15 days Legionella 3 weeks
   • Biomarkers e.g. procalcitonin in some RCTS

Discussion

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a) Clinical features indicating poor prognosis

Now, one might cynically presume that the table presented in the college answer was crudely cut-and-pasted from some paper.

One might be absolutely correct. 

It was the 2007 version of the IDSA guidelines. This is probably a table we candidates were expected to memorise.  Since this paper has come out, in fact an updated form of guidelines has become available (Metlay, 2019), and in case you want to see what the difference between the documents is, they helpfully summarised it for you. Fortunately, they did not change the content of their "Criteria for Defining Severe Community-acquired Pneumonia", which is what that table actually is. 

List 5 common organisms causing severe community acquired pneumonia in immunocompetent adults.

Again, this is a direct transcription of Table 6 from the same paper.

• Streptococcus pneumoniae
• Mycoplasma pneumoniae
• Haemophilus influenzae
• Chlamidophyla pneumonia
• Respiratory viruses

What are the possible reasons for non-response to empiric treatment for patients treated for severe community acquired pneumonia?

The college answer is sub-optimal, as it revolves around the inaccuracy of diagnosis and inadequacy of treatment. Question 7 from the second paper of 2012 looks indepth at the causes of treatment failure for community acquired pneumonia, and the investigations for treatment-refractory pneumonia; the college answer and discussion offered there are far superior.

In brief:

• Wrong disease
  • PE
  • Cardiac failure
  • Autoimmune pneumonitis
• Wrong antimicrobial agents
  • Resistant organism
  • Viral pneumonia
  • Atypical pneumonia
• Wrong use of antimicrobial agents
  • Underdosing
  • Inappropriate dose interval
  • Poor penetration into lung tissue
• Patient and disease factors which predict poor response to antibiotics:
  • Elderly patient
  • Multiple comorbidities
  • Alcoholism
  • Smoking (and COPD)
  • Multilobar pneumonia
  • Bacteraemia
  • Empyema and lung abscess
  • Legionella pneumonia
  • Polymicrobial pneumonia
• Organisms which are known to respond poorly to antibiotics
  • Mycobacterium tuberculosis
  • Nocardia
  • Actinomyces israelii
  • Aspergillus
  • Coxiella burnetii (Q fever)
  • Chlamydia psittaci (psittacosis)
  • Leptospira interrogans (leptospirosis)
  • Pseudomonas pseudomallei (melioidosis)

Briefly outline your approach to stopping antibiotics given for CAP responding to empiric treatment in ICU?

Where, do you ask, did the college get those time intervals? Who said 5 days is minimum?
Well.
It was in the same paper.

The guidelines are:

• Minimum of 5 days
• Stop after 72 hrs of haemodynamic stability without fevers
• Pseudomonas typically needs 15 days

The procalcitonin RCT mentioned is a famous study where antibiotic therapy was deescalated according to a procalcitonin level (anything less than 0.25mic/L was grounds for deescalation).

Bartlett, John G., et al. "Practice guidelines for the management of community-acquired pneumonia in adults." Clinical infectious diseases 31.2 (2000): 347-382.

Mandell, Lionel A., et al. "Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults." Clinical infectious diseases 44.Supplement 2 (2007): S27-S72.

Christ-Crain, Mirjam, et al. "Procalcitonin guidance of antibiotic therapy in community-acquired pneumonia: a randomized trial." American journal of respiratory and critical care medicine 174.1 (2006): 84-93.

Metlay, Joshua P., et al. "Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America." American journal of respiratory and critical care medicine 200.7 (2019): e45-e67.