Community acquired pneumonia (CAP)

Mild CAP (CRB65/CURB65 = 0-1):

Amoxicillin* oral 1g 8 hourly

or

Doxycycline^† oral 200mg on day 1 then 100mg daily

Duration: 5 days.

Moderately severe CAP (CRB65/CURB65 = 2):

Amoxicillin IV 1g 8 hourly

If true penicillin / beta-lactam allergy:

Doxycycline^† oral 200mg on day 1 then 100mg daily

Duration: review total (IV plus oral) duration after 5 days.

If risk factors^‡ for L.pneumophila: send Legionella urinary antigen. SWITCH to Clarithromycin if Legionella urinary antigen POSITIVE.

Severe CAP (CRB65/CURB65 = 3-5):

Amoxicillin IV 1g 6 hourly

and

Clarithromycin*^# oral/IV 500mg 12 hourly

If true penicillin / beta-lactam allergy:

Levofloxacin* oral/IV 500mg 12 hourly

Send Legionella urinary antigen and if NEGATIVE discontinue Clarithromycin unless risk factors^‡ for L.longbeachae.

N.B. In pregnant patients, levofloxacin is contraindicated - discuss appropriate empirical choices with an infection specialist.

Duration: review total (IV plus oral) duration after 5 days.

*Use IV route if oral route compromised.

^#Clarithromycin should not be prescribed concurrently with ciclosporin, sirolimus or tacrolimus.

^†In pregnant patients, doxycycline is contraindicated.

^‡Risk factors for infection with Legionella include:

• Male sex
• Age >50 years old
• Smoking
• Immunosuppression, diabetes mellitus, ischaemic heart disease, chronic lung disease
• Travel
• Recent domestic plumbing work
• Exposure to compost and potting mixes is a risk factor for Legionella longbeachae which is not detected by the urinary antigen test, and requires Legionella PCR on sputum or BAL to prove (or exclude).

Use CRB65 (primary care) or CURB65 (hospitalised) score to assess severity. Give one point each for any of the following:

• Confusion (new onset)
• Urea >7mmol/L
• Respiratory rate ≥30 breaths per minute
• BP <90mmHg systolic or ≤60mmHg diastolic
• Age ≥65 years

Primary care, including nursing homes and long-term care facilities: Patients with CRB65 score 0 are suitable for home treatment; scores 1-2 should be referred to hospital for assessment; scores 3 and 4 require urgent hospital admission. 

British Thoracic Society pneumonia severity score:

• Mild = CURB65 0-1
• Moderate = CURB65 2
• Severe = CURB65 3-5

Abnormal vital signs (fever >38°C, tachycardia >100 beats per minute and tachypnoea >20 breaths per minute) or an abnormal physical examination of the chest (crackles, decreased breath sounds, dullness to percussion) can predict radiographic changes of CAP (sensitivity of 95%, negative predictive value 92%). In elderly patients classic symptoms and signs of pneumonia are less likely, but non-specific features, especially confusion, are more likely.

Streptococcus pneumoniae is the most common cause of severe CAP, and respiratory tract infections can be treated with amoxicillin even if intermediate susceptibility to penicillin is found on testing. Use of co-amoxiclav or piperacillin-tazobactam for pneumococcal CAP offers no additional benefit.

Doxycycline resistance rates in Haemophilus influenzae are lower than those to co-amoxiclav.

Levofloxacin provides cover for atypical pneumonia and should not be administered with clarithromycin as both drugs prolong the QTc. Quinolones like levofloxacin should not be used for treatment of mild or moderate infections – MHRA warning (2019).