[Case of pneumonia caused by beta-lactamase-producing and amoxicillin/clavulanate resistant strains of H. influenzae].

An 80-year-old woman presenting with fever and cough was given a diagnosis of community-acquired pneumonia. She was hospitalized and treated with ampicillin/sulbactam (ABPC/SBT) and clarithromycin (CAM). Gram stain images and sputum culture results led us to believe that the causative agent was Haemophilus influenzae. Drug sensitivity testing indicated that the H. influenzae was a beta-lactamase-positive, ABPC-resistant (BLPAR) strain. Treatment with ABPC/SBT was not clinically effective. We considered the possibility of beta-lactamase-positive amoxicillin/clavulanate-resistant (BLPACR) strains. Further testing revealed that the MIC of ABPC was 128 microg/ml, that of SBT/ABPC was 8 microg/ml, and that of AMPC/CVA was 4 microg/ml. Furthermore, genetic analysis indicated the H. influenzae to be a BLPACR-I strain. The poor clinical course eventually led to a diagnosis of BLPACR. When beta-lactamase-producing H. influenzae is cultured, the possibility of a BLPACR strain resistant to ABPC/SBT and AMPC/CVA must be considered.