Piperacillin+tazobactam (Tazocin) is an important broad spectrum antibiotic that is still active in most Australian settings against a wide range of Gram negatives (including Pseudomonas) , Gram positives (excluding MRSA and VRE) and nearly all anaerobic bacteria. It comes into great demand for management of a range of healthcare-associated infections, especially in ICU. Its use needs to be targeted effectively to reduce emergence of resistance.
There is a currently a tendency for unnecessary use in patients presenting with community-acquired pneumonia, particularly in our (HNE) tertiary facilities. Situations that lead to this include:
- patients admitted from residential aged care facilities (RACF)
- patients who have previously isolated Pseudomonas aeruginosa from respiratory samples (in the absence of significant bronchiectasis or cystic fibrosis)
- non-Pseudomonas colonised patients with some degree of bronchiectasis or chronic obstructive lung disease- COPD (conditions that have become much more frequently diagnosed owing to high resolution CT scanning)
- patients who have a degree of immune-compromise / diabetes / other condition
In all these situations, it remains most important to provide Gram positive cover – especially for Streptococcus pneumoniae. Benzylpenicillin or amoxycillin remains the best agent for that. Patients with non-severe CAP do not require additional Gram negative cover. For CAP associated with severe sepsis or severe pneumonia, addition of Gram negative cover (empirical once daily gentamicin is used in Hunter New England), atypical organism cover (azithromycin) and potentially cover for MRSA (vancomycin) is indicated- please discuss these patients with the Infectious Diseases service or Pathology North Clinical Microbiologist. Also do not neglect investigation for viral causes (see below)!
Patients in RACF in Australia do not show an increased incidence of Gram negative pneumonia and do not warrant a different approach. In the USA, many long term care facilities look after patients of higher acuity than RACF and are considered to be part of ‘healthcare’ system- their guidelines recommend broader spectrum therapy. This is not an approach recommended by the Australian Therapeutic Guidelines.
Pneumonia due to Pseudomonas aeruginosa is severe and usually straightforward to diagnose. It occurs in a very small minority of patients, even in the setting of COPD, bronchiectasis and requires aggressive treatment.
Conversely respiratory tract colonisation with Pseudomonas aeruginosa (with no evidence of consolidation) only requires consideration for treatment in the setting of acute lower respiratory exacerbation in patients who have a significant degree of bronchiectasis or cystic fibrosis. Even in such patients, viral infection is frequently the trigger for the acute illness and Pseudomonas is not the primary cause.
Patients with other conditions including mild-moderate degrees of immune-compromise, in large part develop pneumonia due to the same range of pathogens that cause CAP in other patients. The empirical antibiotic approach need not differ. However more extensive microbiological investigation may be warranted – seek advice from your local microbiologist.