Kristi, Lorrae and Ayesha have recently joined as AIMED authors– welcome aboard. Here’s a posting from Kristi that unpacks the approach to community-acquired pneumonia (CAP) in Hunter New England Health, NSW.  

In adults, the most common bacterial cause of community-acquired pneumonia (CAP) is Streptococcus pneumoniae. Other pathogens associated with CAP include Haemophilus influenzae and atypical’ organisms, such as Mycoplasma pneumoniae, Chlamydophilia (Chlamydia) pneumoniae and Legionella species.

The Australian Therapeutic Guidelines (TG) recommends patients with high-severity CAP, receive initial treatment with broad spectrum empirical antibiotic therapy, providing the main option of ceftriaxone+azithromycin.  In fine print comes this statement:

As benzylpenicillin is of proven efficacy for of circulating S. pneumoniae strains,  the HNELHD CAP guideline recommends use of this three-drug regimen for patients with high-severity CAP (in the absence of any contraindications). This combination, at the recommended dosages, provides adequate broad spectrum coverage whilst reducing the significant ecological risks associated with ceftriaxone use, such as induction and spread of antimicrobial resistance (MRSA, VRE, ESBL) and Clostridium difficile infections.  In the right clinical setting, ceftriaxone is a great antibiotic;  the real problem is ensuring that it is reserved for such situations (usually proven Gram negative infections) so that it then retains efficacy.

Common misconceptions:

Ceftriaxone and cefotaxime have superior activity against Haemophilus influenzae and Streptococcus pneumoniae in pneumonia

INCORRECT!

• H. influenze is an uncommon cause of serious CAP in Australia (accounting for less than 5% of cases), especially H. influenzae strains that produce betalactamase (34% in 2017).  (N.B. presence in sputum cultures frequently represents colonisation)
• At the recommended dose, benzylpenicillin remains active and achieves satisfactory lung concentrations to treat the occasional strains of S.  pneumoniae with intermediate susceptibility to penicillin.
• S. pneumoniae strains with high-level penicillin resistance remain uncommon in Australia

Once my patient responds to intravenous therapy, I should switch treatment to oral Augmentin (amoxicillin/clavulanate) as it has a broader spectrum of activity and must be better?

INCORRECT!

• When compared to Augmentin (amoxicillin/clavulanate), amoxicillin alone:
  • Is less selective for resistance
  • Has fewer adverse effects
  • At the recommended dose (1g, 8-hourly), achieves significantly higher plasma concentrations of amoxicillin, which is recommended for cases of pneumonia, especially those caused by S. pneumoniae .

More questions? Please email the AIMED team!

Reference

• Int J Antimicrob Agents. 2018 Jun;51(6):862-866. Is gentamicin safe and effective for severe community-acquired pneumonia? An 8-year retrospective cohort study.  Brereton CJ, Lennon D, Browning S, Dunn E, Ferguson JK, Davis JS.

Picture Credit: https://lunginstitute.com/wp-content/uploads/2017/05/050117_FB-Blog_11-15-C-1.png