Biphasic pattern of bacterial infection in multiple myeloma.

Since the 1960s, gram-negative bacilli have become commoner pathogens than Streptococcus pneumoniae in multiple myeloma. To investigate this trend, we analyzed 75 bacterial infections in 57 patients with myeloma. Episodes of infection with Streptococcus pneumoniae and Haemophilus influenzae occurred at presentation, early in the disease, and in patients responding to chemotherapy. Gram-negative bacilli and Staphylococcus aureus caused 80% of infections seen after diagnosis and 92% of deaths from infection. Episodes of infection with gram-negative bacteria occurred in patients with active and advancing disease and in those responding to chemotherapy when neutropenia. Impaired antibody production may be the major immune defect leading to S. pneumoniae and H. influenzae infections whereas some additional factor or factors related to disease activity appear to predispose to gram-negative infection in myeloma.