Case Presentation: A healthy 22-year-old woman presented to the ED with five days of fevers, dry cough, dyspnea and right-sided pleuritic chest pain. Lab work and a CXR were unremarkable. A nasal swab diagnosed Influenza B and she was discharged with Oseltamivir, which she did not take. Two days later, the patient returned with progressive symptoms and blood tinged sputum. She was ill-appearing with T 101F, RR 30, BP 103/67, RA sat 93% and diminished breath sounds at the right lower lung field. A CXR now revealed a right lower lobe consolidation with a moderate sized pleural effusion. Empiric treatment for community acquired pneumonia (CAP) with Ceftriaxone, Azithromycin and Oseltamivir was initiated. When worsening hypoxic respiratory failure and severe sepsis developed, Vancomycin was added. Blood and sputum cultures subsequently grew Methicillin sensitive S. Aureus (MSSA). A chest CT showed the previously seen right lower lobe consolidation and a new right middle lobe consolidation with an associated loculated effusion. The patient underwent a video-assisted-thoracoscopic surgery (VATS) with decortication of empyema and tissue cultures grew the previously isolated MSSA. On post-operative day 6, she was discharged home to complete a prolonged antibiotic course for MSSA empyema and pneumonia.

Discussion: infection can increase host susceptibility to bacterial infections by inducing cytokines and altering neutrophil and alveolar macrophage function. Bacterial infections can in turn potentiate influenza viral replication. Due to these synergistic effects, a heightened morbidity and mortality is often seen in influenza-associated bacterial infections compared with bacterial pneumonia without influenza. Bacterial infections can be subsequent or coincident to influenza infection, and the nasopharyngeal colonizers (S. Aureus, S. Pneumoniae, and S. Pyogenes) are typically the implicated pathogens. While Influenza A is predominantly associated with co- and secondary bacterial infections, Influenza B can also cause severe bacterial infections, especially in younger age groups as in our case. In those with sepsis or signs of pneumonia, empiric coverage that includes MRSA is indicated. Adding Oseltamivir may lower ICU admission and deaths. Compliance with seasonal influenza vaccination can be associated a 45% reduction in pneumonia hospitalizations and a 60% mortality reduction. Unfortunately, our patient did not receive pre-morbid influenza vaccination.

Conclusions: Severe pneumonia during periods of high influenza activity should prompt providers to empirically include coverage against MRSA, even among those without recognized risk factors. Maintaining a high index of suspicion for S. Aureus coinfection in this setting can be life-saving. Routine influenza vaccination remains the best preventive strategy.