In vitro efficacy of β-lactam/β-lactamase inhibitor combinations against bacteria involved in mixed infections

Abstract

Mixed infections are usually caused by a relatively limited range of bacteria, with the anaerobes and opportunistic pathogens contributing to their severity. In order to make the best therapeutic choice for a patient with a life-threatening infection, which is probably of mixed etiology, clinicians must be aware of the organisms that are likely to be involved, and the fact that most of them will produce β-lactamase. Of the options available for empiric therapy, the β-lactam/β-lactamase inhibitor combinations represent a good choice. Their antibacterial spectra include both aerobic and anaerobic pathogens. Five combinations are available in clinical practice: ampicillin–sulbactam, piperacillin–tazobactam, ticarcillin–clavulanic acid, amoxicillin–clavulanic acid, and cefoperazone–sulbactam. More strains of clinically important anaerobic bacteria are susceptible to ampicillin–sulbactam than to either piperacillin–tazobactam or ticarcillin–clavulanic acid, which are also available widely and suitable for more life-threatening infections. In addition, sulbactam itself has the highest intrinsic activity of the β-lactamase inhibitors against the opportunistic pathogen, Acinetobacter baumannii. Thus, ampicillin–sulbactam could be considered a drug of choice for the empirical treatment of mixed infections where there is a reasonable possibility of the presence of A. baumannii.