Principles and problems of combined antibiotic therapy

A Combination Antibiogram Evaluation for Pseudomonas aeruginosa in Respiratory and Blood Sources from Intensive Care Unit (ICU) and Non-ICU Settings in U.S. Hospitals

Pseudomonas aeruginosa is an important pathogen associated with significant morbidity and mortality. U.S. guidelines for the treatment of hospital-acquired and ventilator-associated pneumonia recommend the use of two antipseudomonal drugs for high-risk patients to ensure that ≥95% of patients receive active empirical therapy. We evaluated the utility of combination antibiograms in identifying optimal anti-P. aeruginosa drug regimens. We conducted a retrospective cross-sectional analysis of the antimicrobial susceptibility of all nonduplicate P. aeruginosa blood and respiratory isolates collected between 1 October 2016 and 30 September 2017 from 304 U.S. hospitals in the BD Insights Research Database. Combination antibiograms were used to determine in vitro rates of susceptibility to potential anti-P. aeruginosa combination regimens consisting of a backbone antibiotic (an extended-spectrum cephalosporin, carbapenem, or piperacillin-tazobactam) plus an aminoglycoside or fluoroquinolone. Single-agent susceptibility rates for the 11,701 nonduplicate P. aeruginosa isolates ranged from 72.7% for fluoroquinolones to 85.0% for piperacillin-tazobactam. Susceptibility rates were higher for blood isolates than for respiratory isolates (P < 0.05). Antibiotic combinations resulted in increased susceptibility rates but did not achieve the goal of 95% antibiotic coverage. Adding an aminoglycoside resulted in higher susceptibility rates than adding a fluoroquinolone; piperacillin-tazobactam plus an aminoglycoside resulted in the highest susceptibility rate (93.3%). Intensive care unit (ICU) isolates generally had lower susceptibility rates than non-ICU isolates. Commonly used antipseudomonal drugs, either alone or in combination, did not achieve 95% coverage against U.S. hospital P. aeruginosa isolates, suggesting that new drugs are needed to attain this goal. Local institutional use of combination antibiograms has the potential to optimize empirical therapy of infections caused by difficult-to-treat pathogens.

Combination therapy in the management of giardiasis: What laboratory and clinical studies tell us, so far

Treatment failures in patients suffering from giardiasis are not uncommon feature. The most frequent approach in these cases is to treat these patients with longer repeated courses and/or higher doses of the primary therapy, or using drugs from a different class to avoid potential cross-resistance. However, a higher rate of adverse events may limit this strategy. In this context, combination therapy (CT) is emerging as a valuable option against refractory giardiasis. In the attempt to evaluate the benefits of CT, a number of experimental studies, clinical series, and randomized clinical trials (RCTs), as well as several veterinary studies have been performed, with varying results. Here, we present a critical analysis of the available information regarding CT for the treatment of Giardia infection, as well as the authors' opinion with respect to its use. RCTs of combination therapy are limited and the optimal combinations and administration strategies need yet to be clarified. Analyses of the cost-effectiveness and RCTs of CTs for Giardia infection are required to assess the role of these drugs for the control of giardiasis, mainly in the case of treatment failures linked to suspected drug tolerance are the case.

Burden of antibiotic resistance in common infectious diseases: role of antibiotic combination therapy

Globally, antimicrobial resistance is alarming concern especially in commonly reported disease entities like respiratory tract infection, enteric fever and infections associated with gram-negative bacilli (GNB). Rational use of antimicrobial drugs reported significant decrease in bacterial burden and may also reduce the risk of disease progression. However, at times in particular indication, certain patient and pathogen factor limits the selection and use of specific antibiotic therapy while in some case, due to presence of additional risk factor, aggressive therapy is required to achieve clinical reemission and prevent complications. Delay in start of suitable antibiotic therapy is another imperative factor for treatment failure and rise of drug resistance. With rapidly increasing antibiotic resistance and decline in new antibiotic drug development, the toughest challenge remains to maintain and preserve the efficacy of currently available antibiotics. Therefore, the best rational approach to fight these infections is to 'hit early and hit hard' and kills drug-susceptible bacteria before they become resistant. The preferred approach is to deploy two antibiotics that produce a stronger effect in combination than if either drug were used alone. Various society guidelines in particular indications also justify and recommend the use of combination of antimicrobial therapy. Combination therapies have distinct advantage over monotherapy in terms of broad coverage, synergistic effect and prevention of emergence of drug resistance.