Background: Pasteurella multocida pneumonia mainly occurs in immunodepressed patients. Microbiological proof is difficult to obtain.
Case report: A 36-year-old woman with systemic lupus erythematosus treated with cyclophosphamide and corticosteroids developed pneumonia. She was given amoxicillin-clavulanate. Bronchioalveolar lavage fluid cultures on gelose were negative but Pasteurella multocida grew on blood culture medium.
Discussion: Although the direct examination of bronchioalveolar lavage fluid demonstrated Gram negative coccobacilli, gelose cultures were negative, probably because of prior antibiotic therapy. The causal pathogen was only identified when BAL fluid was seeded on blood culture medium, allowing susceptibility tests and subsequent early adaptation of antibiotic therapy. This technique can be helpful in identifying the casual pathogen in microbial pneumonia.