Evaluation of meropenem alone and combined with rifampin in the guinea pig model of pneumococcal meningitis

Carbapenems: past, present, and future

In this review, we summarize the current "state of the art" of carbapenem antibiotics and their role in our antimicrobial armamentarium. Among the β-lactams currently available, carbapenems are unique because they are relatively resistant to hydrolysis by most β-lactamases, in some cases act as "slow substrates" or inhibitors of β-lactamases, and still target penicillin binding proteins. This "value-added feature" of inhibiting β-lactamases serves as a major rationale for expansion of this class of β-lactams. We describe the initial discovery and development of the carbapenem family of β-lactams. Of the early carbapenems evaluated, thienamycin demonstrated the greatest antimicrobial activity and became the parent compound for all subsequent carbapenems. To date, more than 80 compounds with mostly improved antimicrobial properties, compared to those of thienamycin, are described in the literature. We also highlight important features of the carbapenems that are presently in clinical use: imipenem-cilastatin, meropenem, ertapenem, doripenem, panipenem-betamipron, and biapenem. In closing, we emphasize some major challenges and urge the medicinal chemist to continue development of these versatile and potent compounds, as they have served us well for more than 3 decades.

Rifampin combination therapy for nonmycobacterial infections

The increasing emergence of antimicrobial-resistant organisms, especially methicillin-resistant Staphylococcus aureus (MRSA), has resulted in the increased use of rifampin combination therapy. The data supporting rifampin combination therapy in nonmycobacterial infections are limited by a lack of significantly controlled clinical studies. Therefore, its current use is based upon in vitro or in vivo data or retrospective case series, all with major limitations. A prominent observation from this review is that rifampin combination therapy appears to have improved treatment outcomes in cases in which there is a low organism burden, such as biofilm infections, but is less effective when effective surgery to obtain source control is not performed. The clinical data support rifampin combination therapy for the treatment of prosthetic joint infections due to methicillin-sensitive S. aureus (MSSA) after extensive debridement and for the treatment of prosthetic heart valve infections due to coagulase-negative staphylococci. Importantly, rifampin-vancomycin combination therapy has not shown any benefit over vancomycin monotherapy against MRSA infections either clinically or experimentally. Rifampin combination therapy with daptomycin, fusidic acid, and linezolid needs further exploration for these severe MRSA infections. Lastly, an assessment of the risk-benefits is needed before the addition of rifampin to other antimicrobials is considered to avoid drug interactions or other drug toxicities.