Choosing optimal antimicrobial therapies.

Life-threatening infectious disease emergencies require immediate, aggressive parenteral administration of antimicrobial agents to ensure high bactericidal concentrations of drug at the site of infection. Usually initial treatment is empiric until culture results and antimicrobial sensitivities are reported. This approach necessitates the use of broad-spectrum bactericidal agents that will eradicate the presumed infecting organism(s), which potentially could be multidrug resistant. For infections potentially attributable to gram-positive bacteria, vancomycin is commonly used because it will be effective for highly resistant strains such as MRSA and multidrug-resistant S pneumoniae. For gram-negative infections, broad-spectrum β-lactams, such as ceftriaxone, piperacillin-tazobactam, and the carbapenems, are commonly chosen. Excellent alternatives include the fluoroquinolone antibiotics. For nosocomial infections whereby P aeruginosa and other highly resistant organisms may be the cause, antipseudomonal β-lactams such as cefepime, ceftazidime, piperacillin-tazobactam, or doripenem may be used as well as the fluoroquinolone, ciprofloxacin. For anaerobic infections, it is usually necessary to add either metronidazole or clindamycin. Once an infection is under control and the culture and sensitivity results are reported, it is important to switch to the most narrow-spectrum agent possible. Taking this action will decrease the potential for adverse drug effects and the risk of development of antibiotic-induced resistance.