Considerations in the choice and administration of agents for empiric antimicrobial therapy

Infections remain a common problem for critically ill patients and often are responsible for early mortality, especially following inadequate antibiotic therapy. The choice of empiric therapy has become increasingly difficult because of the increasing incidence of antibiotic-resistant bacteria.

A retrospective review of the literature over the last two decades was conducted to assess the importance of adequate empiric antibiotic therapy and which factors should be considered in choosing the "best" empiric therapy.

Current diagnostic and treatment guidelines suggest that all seriously ill patients in whom infection is suspected undergo a comprehensive work-up (e.g., blood, urine, sputum cultures) to confirm the etiology prior to initiation of antibiotic therapy. Whereas the selection of the most appropriate antimicrobial agent(s) must consider the likely etiologies and anticipated resistance patterns, the lack of rapid and sensitive culture techniques has made this process difficult. Recent literature has concluded that empiric therapy for many nosocomial infections must be directed at multi-drug-resistant, gram-negative bacilli and methicillin-resistant Staphylococcus aureus (MRSA), especially in patients with a history of prolonged hospitalization and recent antibiotic use. There is also growing evidence that inadequate or prolonged antibiotic administration may encourage the emergence of resistant bacteria. New antibiotics directed against multi-drug-resistant, gram-positive pathogens include daptomycin, linezolid, and tigecycline.

Initial empiric broad-spectrum antibiotic therapy is necessary for treatment of patients with serious infections following a thorough evaluation of possible sources, including culture and susceptibility testing. Clinicians may need to tailor antibiotic therapy based on the patient's initial response after the organism is confirmed, and susceptibility test results are available.