Aspiration of stomach contents in unconscious patients:

The acute aspiration of stomach content in patients unable to protect their airway due to unconsciousness causes chemical pneumonitis and does not respond to antimicrobial treatment.

Aspiration pneumonia due to unsafe swallow:

Treat as community acquired pneumonia or hospital acquired pneumonia (if hospital admission in last 6 weeks or current inpatient for >48 hours) with the addition of metronidazole to cover oral anaerobic organisms.

Add metronidazole oral 400mg 8 hourly or IV 500mg 8 hourly for anaerobic cover to the following:

• amoxicillin
• clarithromycin
• doxycycline
• co-trimoxazole
• levofloxacin
• amoxicillin and temocillin.

True aspiration pneumonia arises from continuous microaspiration of upper respiratory tract secretions in patients with swallowing difficulties. 

If the patient is already receiving co-amoxiclav, piperacillin-tazobactam or meropenem due to known resistant organisms or on Infection Specialist advice, the addition of metronidazole is not required, as these agents provide anaerobic cover.