Bacterial infection and antibiotic treatment in chronic rhinosinusitis.

Incomplete resolution of acute rhinosinusitis leading to CRS is associated with a corresponding change in the microbiology of the disease. The shift in microbiology from acute to CRS favors infection with S. aureus, S. epidermidis, anaerobic bacteria (including beta-lactamase-producing strains), and gram-negative bacteria. With the exception of S. epidermidis, there is substantial evidence supporting the role of these organisms in the pathogenesis of CRS. It is worth noting that not all CRS patients are chronically infected. In fact, other inflammatory factors in the disease may predominate in the clinical presentation. This creates a clinical conundrum in which it is difficult to ascertain whether bacteria are involved. In general, a chronic bacterial infection is more likely if there is: underlying immune deficiency, one or more opacified sinuses on sinus CT in the absence of polyps, the presence of frank purulence draining from one or more sinus cavities, or the presence of gram-negative or antibiotic-resistant organisms (e.g., MRSA) on sinus culture. For patients seen for the first time, the approach to antibiotic treatment is usually empiric, following the guidelines outlined in this chapter and directing treatment at both aerobic and anaerobic bacteria. Whenever possible, the choice of antibiotics should be guided by properly obtained sinus cultures. In cases where empiric antibiotics have failed, the need for bacterial cultures is even more critical to assure proper treatment and to minimize antibiotic side effects.