Failure to improve should trigger suspicion of An unusual organism Resistance to the antimicrobial used for treatment Empyema Coinfection or superinfection with a 2nd infectious agent An obstructive endobronchial lesion Immunosuppression Metastatic focus of infection with reseeding (in the case of pneumococcal infection) Nonadherence to treatment (in the case of outpatients) Wrong diagnosis (ie, a noninfectious cause of the illness such as acute hypersensitivity pneumonitis) When usual therapy has failed, consultation with a pulmonary and / or infectious disease specialist is indicated.