Rationale for empirical therapy for low- to moderate-severity HAP

Empirical therapy for low- to moderate-severity HAP is directed against Streptococcus pneumoniae and gram-negative bacteria. Treatment for Legionella species, Chlamydophila (Chlamydia) pneumoniae, and Mycoplasma pneumoniae is not routinely required for patients with HAP. The results of investigations can enable directed therapy or de-escalation of antibiotic treatment.

For intravenous therapy of low- to moderate-severity HAP, ceftriaxone or cefotaxime is preferred to amoxicillin+clavulanate because the anaerobic activity of amoxicillin+clavulanate is not required, unless there are specific concerns about anaerobes (eg lung abscess, empyema).

For children who have had a hypersensitivity reaction to a penicillin in whom a penicillin or cephalosporin is not appropriate, dual therapy with ciprofloxacin and clindamycin is no longer recommended. Trimethoprim+sulfamethoxazole is recommended because, compared to clindamycin plus ciprofloxacin, it:

• has comparable activity against S. pneumoniae
• has better activity against Staphylococcus aureus (both methicillin-sensitive and methicillin-resistant isolates)
• does not have anaerobic activity
• provides some activity against gram-negative bacteria, although resistance in Escherichia coli is not uncommon.

Moxifloxacin is an alternative to trimethoprim+sulfamethoxazole for children who have had a hypersensitivity reaction to a penicillin in whom a penicillin or cephalosporin is not appropriate. However, there are fewer data for moxifloxacin in children, so trimethoprim+sulfamethoxazole is preferred.

For adults who have had a hypersensitivity reaction to a penicillin in whom a penicillin or cephalosporin is not appropriate, trimethoprim+sulfamethoxazole can also be used but moxifloxacin is preferred because of its better activity against gram-negative bacteria.