Pneumonia due to methicillin-resistant Staphylococcus aureus: clinical features, diagnosis and management

The review highlights the clinical findings and the management of community-acquired, health-care associated and nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA).

Although previously considered as a purely nosocomial event, community-acquired MRSA pneumonia is underestimated and is spreading worldwide. A retrospective study showed that almost half of patients with nonnosocomial MRSA pneumonia admitted to a large teaching hospital did not present established criteria for healthcare-associated infections. Recent data show that MRSA ventilator-associated pneumonia is associated with significantly higher mortality than ventilator-associated pneumonia caused by methicillin-susceptible Staphylococcus aureus. Therefore, prompt and appropriate therapy is essential. The optimal therapy for MRSA pneumonia has not been fully elucidated. Although vancomycin has been considered the gold standard for the treatment of MRSA infections, clinical failures have also been reported in the presence of in-vitro susceptibility. Linezolid may provide improved outcomes compared with vancomycin in patients with MRSA pneumonia, but validation in a prospective trial is currently lacking. Recently licensed tigecycline and dalbavancin, a drug in phase III trial, look promising. Animal models showed that immunization against a cytolytic toxin secreted by most Staphylococcus aureus strains protects against lethal pneumonia.

Rapid recognition of possible staphylococcal infection in patients with severe pneumonia is essential. The treatment of MRSA pneumonia must be prompt and effective in order to allow a fast microbiological clearance and to successfully manage the infection.