Hospital acquired pneumonia (Antimicrobial)
TAM (Treatments and Medicines) NHS Highland
What's new / Latest updates
10/10/25 (V2.2): Added line - For suspected or known Legionnaires Disease, refer to specific guidance here.
For pneumonia presenting more than 3 days into hospital admission, it is important to give broad-spectrum antibiotics which are active against Gram-negative organisms in the first instance. In more severe infection, consider cover for Legionella, Staph aureus, both MSSA and MRSA. Use SIRS criteria for severity assessment.
For suspected or known Legionnaires Disease, refer to specific guidance here.
For glossary of terms see Glossary.
Drug details
Non severe
Co-trimoxazole (oral) 960mg twice daily (reduce dose to 480mg twice daily in renal impairment CrCl 30ml/min or less)
OR Doxycycline (oral) 100mg twice daily
Total IV/oral up to 8 days for clinical responders
Severe - infection with an atypical pathogen is uncommon. If suspected, discuss with Microbiology.
IV aztreonam 1 gram every 8 hours in level 1 and 2 care, 2 gram every 8 hours in level 3 care (ICU) PLUS IV vancomycin refer to NHS Highland vancomycin dosing guidelines
Total IV/oral up to 8 days for clinical responders