Relationship of in vitro synergy and treatment outcome with daptomycin plus rifampin in patients with invasive methicillin-resistant Staphylococcus aureus infections. Antimicrob Agents Chemother. 2013;57:3450-3452. [PMID: 23650174 DOI: 10.1128/aac.00325-12]

Within-species variability of antibiotic interactions in Gram-negative bacteria

Treatments with antibiotic combinations are becoming increasingly important even though the supposed clinical benefits of combinations are, in many cases, unclear. Here, we systematically examined how several clinically used antibiotics interact and affect the antimicrobial efficacy against five especially problematic Gram-negative pathogens. A total of 232 bacterial isolates were tested against different pairwise antibiotic combinations spanning five classes, and the ability of all combinations in inhibiting growth was quantified. Descriptive statistics, principal component analysis (PCA), and Spearman's rank correlation matrix were used to determine the correlations between the different combinations on interaction outcome. Several important conclusions can be drawn from the 696 examined interactions. Firstly, within a species, the interactions are in general conserved but can be isolate-specific for a given antibiotic combination and can range from antagonistic to synergistic. Secondly, additive and antagonistic interactions are the most common observed across species and antibiotics, with 87.1% of isolate-antibiotic combinations being additive, 11.6% antagonistic, and only 0.3% showing synergy. These findings suggest that to achieve the highest precision and efficacy of combination therapy, not only isolate-specific interaction profiling ought to be routinely performed, in particular to avoid using drug combinations that show antagonistic interaction and an expected associated reduction in efficacy, but also discovering rare and potentially valuable synergistic interactions.IMPORTANCEAntibiotic combinations are often used to treat bacterial infections, which aim to increase treatment efficacy and reduce resistance evolution. Typically, it is assumed that one specific antibiotic combination has the same effect on different isolates of the same species, i.e., the interaction is conserved. Here, we tested this idea by examining how several clinically used antibiotics interact and affect the antimicrobial efficacy against several bacterial pathogens. Our results show that, even though within a species the interactions are often conserved, there are also isolate-specific differences for a given antibiotic combination that can range from antagonistic to synergistic. These findings suggest that isolate-specific interaction profiling ought to be performed in clinical microbiology routine to avoid using antagonistic drug combinations that might reduce treatment efficacy.

Biofilm Producing Methicillin-Resistant Staphylococcus aureus (MRSA) Infections in Humans: Clinical Implications and Management

Since its initial description in the 1960s, methicillin-resistant Staphylococcus aureus (MRSA) has developed multiple mechanisms for antimicrobial resistance and evading the immune system, including biofilm production. MRSA is now a widespread pathogen, causing a spectrum of infections ranging from superficial skin issues to severe conditions like osteoarticular infections and endocarditis, leading to high morbidity and mortality. Biofilm production is a key aspect of MRSA's ability to invade, spread, and resist antimicrobial treatments. Environmental factors, such as suboptimal antibiotics, pH, temperature, and tissue oxygen levels, enhance biofilm formation. Biofilms are intricate bacterial structures with dense organisms embedded in polysaccharides, promoting their resilience. The process involves stages of attachment, expansion, maturation, and eventually disassembly or dispersion. MRSA's biofilm formation has a complex molecular foundation, involving genes like icaADBC, fnbA, fnbB, clfA, clfB, atl, agr, sarA, sarZ, sigB, sarX, psm, icaR, and srtA. Recognizing pivotal genes for biofilm formation has led to potential therapeutic strategies targeting elemental and enzymatic properties to combat MRSA biofilms. This review provides a practical approach for healthcare practitioners, addressing biofilm pathogenesis, disease spectrum, and management guidelines, including advances in treatment. Effective management involves appropriate antimicrobial therapy, surgical interventions, foreign body removal, and robust infection control practices to curtail spread within healthcare environments.

Current therapies and challenges for the treatment of Staphylococcus aureus biofilm-related infections

Staphylococcus aureus is a major cause of nosocomial and community-acquired infections and contributes to significant increase in morbidity and mortality especially when associated with medical devices and in biofilm form. Biofilm structure provides a pathway for the enrichment of resistant and persistent phenotypes of S. aureus leading to relapse and recurrence of infection. Minimal diffusion of antibiotics inside biofilm structure leads to heterogeneity and distinct physiological activity. Additionally, horizontal gene transfer between cells in proximity adds to the challenges associated with eradication of biofilms. This narrative review focuses on biofilm-associated infections caused by S. aureus, the impact of environmental conditions on biofilm formation, interactions inside biofilm communities, and the clinical challenges that they present. Conclusively, potential solutions, novel treatment strategies, combination therapies, and reported alternatives are discussed.

Single-cell microfluidics enabled dynamic evaluation of drug combinations on antibiotic resistance bacteria

The rapid spread of antibiotic resistance has become a significant threat to global health, yet the development of new antibiotics is outpaced by emerging new resistance. To treat multidrug-resistant bacteria and prolong the lifetime of existing antibiotics, a productive strategy is to use combinations of antibiotics and/or adjuvants. However, evaluating drug combinations is primarily based on end-point checkerboard measurements, which provide limited information to study the mechanism of action and the discrepancies in the clinical outcomes. Here, single-cell microfluidics is used for rapid evaluation of the efficacy and mode of action of antibiotic combinations within 3 h. Focusing on multidrug-resistant Acinetobacter baumannii, the combination between berberine hydrochloride (BBH, as an adjuvant) and carbapenems (meropenem, MEM) or β-lactam antibiotic is evaluated. Real-time tracking of individual cells to programmable delivered antibiotics reveals multiple phenotypes (i.e., susceptible, resistant, and persistent cells) with fidelity. Our study discovers that BBH facilitates the accumulation of antibiotics within cells, indicating synergistic effects (FICI = 0.5). For example, the combination of 256 mg/L BBH and 16 mg/L MEM has a similar killing effect (i.e., the inhibition rates >90%) as the MIC of MEM (64 mg/L). Importantly, the synergistic effect of a combination can diminish if the bacteria are pre-stressed with any single drug. Such information is vital for understanding the underlying mechanisms of combinational treatments. Overall, our platform provides a promising approach to evaluate the dynamic and heterogenous response of a bacterial population to antibiotics, which will facilitate new drug discovery and reduce emerging antibiotic resistance.

Silver Nanoparticles and Its Mechanistic Insight for Chronic Wound Healing: Review on Recent Progress

Wounds are structural and functional disruptions of skin that occur because of trauma, surgery, acute illness, or chronic disease conditions. Chronic wounds are caused by a breakdown in the finely coordinated cascade of events that occurs during healing. Wound healing is a long process that split into at least three continuous and overlapping processes: an inflammatory response, a proliferative phase, and finally the tissue remodeling. Therefore, these processes are extensively studied to develop novel therapeutics in order to achieve maximum recovery with minimum scarring. Several growth hormones and cytokines secreted at the site of lesions tightly regulates the healing processes. The traditional approach for wound management has been represented by topical treatments. Metal nanoparticles (e.g., silver, gold and zinc) are increasingly being employed in dermatology due to their favorable effects on healing, as well as in treating and preventing secondary bacterial infections. In the current review, a brief introduction on traditional would healing approach is provided, followed by focus on the potential of wound dressing therapeutic techniques functionalized with Ag-NPs.

Interaction Tolerance Detection Test for Understanding the Killing Efficacy of Directional Antibiotic Combinations

Combination treatments are commonly prescribed for enhancing drug efficacy, as well as for preventing the evolution of resistance. The interaction between drugs is typically evaluated near the MIC, using growth rate as a measure of treatment efficacy. However, for infections in which the killing activity of the treatment is important, measurements far above the MIC are needed. In this regime, the killing rate often becomes weakly concentration dependent, and a different metric is needed to characterize drug interactions. We evaluate the interaction metric on killing using an easy visual assay, the interaction tolerance detection test (iTDtest), that estimates the survival of bacteria under antibiotic combinations. We identify antibiotic combinations that enable the eradication of tolerant bacteria. Furthermore, the visualization of the antibiotic interactions reveals directional drug interactions and enables predicting high-order combination outcomes, therefore facilitating the determination of optimal treatments. IMPORTANCE The killing efficacy of antibiotic combinations is rarely measured in the clinical setting. However, in cases where the treatment is required to kill the infecting organism and not merely arrest its growth, the information on the killing efficacy is important, especially when tolerant strains are implicated. Here, we report on an easy method for the determination of the killing efficacy of antibiotic combinations which enabled to reveal combinations effective against tolerant bacteria. The results could be generally used to guide antimicrobial therapy in life-threatening infections.

Potentials of nanotechnology in treatment of methicillin-resistant Staphylococcus aureus

Abuse of antibiotics has led to the emergence of drug-resistant pathogens. Methicillin-resistant Staphylococcus aureus (MRSA) was reported just two years after the clinical use of methicillin, which can cause severe infections with high morbidity and mortality in both community and hospital. The treatment of MRSA infection is greatly challenging since it has developed the resistance to almost all types of antibiotics. As such, it is of great significance and importance to develop novel therapeutic approaches. The fast development of nanotechnology provides a promising solution to this dilemma. Functional nanomaterials and nanoparticles can act either as drug carriers or as antibacterial agents for antibacterial therapy. Herein, we aim to provide a comprehensive understanding of the drug resistance mechanisms of MRSA and discuss the potential applications of some functionalized nanomaterials in anti-MRSA therapy. Also, the concerns and possible solutions for the nanomaterials-based anti-MRSA therapy are discussed.

Verification of a Novel Approach to Predicting Effects of Antibiotic Combinations: In Vitro Dynamic Model Study with Daptomycin and Gentamicin against Staphylococcus aureus

To explore whether susceptibility testing with antibiotic combinations at pharmacokinetically derived concentration ratios is predictive of the antimicrobial effect, a Staphylococcus aureus strain was exposed to daptomycin and gentamicin alone or in combination in multiple dosing experiments. The susceptibility of the S. aureus strain to daptomycin and gentamicin in combination was tested at concentration ratios equal to the ratios of 24 h areas under the concentration–time curve (AUC₂₄s) of antibiotics simulated in an in vitro dynamic model in five-day treatments. The MICs of daptomycin and gentamicin decreased in the presence of each other; this led to an increase in the antibiotic AUC₂₄/MIC ratios and the antibacterial effects. Effects of single and combined treatments were plotted against the AUC₂₄/MIC ratios of daptomycin or gentamicin, and a significant sigmoid relationship was obtained. Similarly, when the effects of single and combined treatments were related to the total exposure of both drugs (the sum of AUC₂₄/MIC ratios (∑AUC₂₄/MIC)), a significant sigmoid relationship was obtained. These findings suggest that (1) the effects of antibiotic combinations can be predicted by AUC₂₄/MICs using MICs of each antibacterial determined at pharmacokinetically derived concentration ratios; (2) ∑AUC₂₄/MIC is a reliable predictor of the antibacterial effects of antibiotic combinations.

Effect of tolerance on the evolution of antibiotic resistance under drug combinations

Drug combinations are widely used in clinical practice to prevent the evolution of resistance. However, little is known about the effect of tolerance, a different mode of survival, on the efficacy of drug combinations for preventing the evolution of resistance. In this work, we monitored Staphylococcus aureus strains evolving in patients under treatment. We detected the rapid emergence of tolerance mutations, followed by the emergence of resistance, despite the combination treatment. Evolution experiments on the clinical strains in vitro revealed a new way by which tolerance promotes the evolution of resistance under combination treatments. Further experiments under different antibiotic classes reveal the generality of the effect. We conclude that tolerance is an important factor to consider in designing combination treatments that prevent the evolution of resistance.

Predicting the antistaphylococcal effects of daptomycin-rifampicin combinations in an in vitro dynamic model

To predict the effects of combined use of antibiotics on their pharmacodynamics, the susceptibility of Staphylococcus aureus to daptomycin-rifampicin combinations was tested at concentration ratios equal to the ratios of daptomycin and rifampicin 24-h areas under the concentration-time curve (AUC₂₄s) simulated in an in vitro dynamic model. In combination with rifampicin, daptomycin MICs decreased 2- to 31-fold, whereas rifampicin MICs were similar with or without daptomycin. The enhanced susceptibility of S. aureus to daptomycin combined with rifampicin resulted in both an increase of the actual AUC₂₄/MIC ratios and also more pronounced antibacterial effects compared with single treatments. The areas between the control growth and time-kill curves (ABBCs) determined in combined and single daptomycin treatments were plotted against AUC₂₄/MIC on the same graph (r² 0.90). These findings suggest that the effects of daptomycin-rifampicin combinations can be predicted by AUC₂₄/MICs of daptomycin using its MIC determined at pharmacokinetically derived daptomycin-to-rifampicin concentration ratios.

Treatments and limitations for methicillin-resistant Staphylococcus aureus: A review of current literature

Methicillin-resistant Staphylococcus aureus (MRSA) has remained a major threat to healthcare; in both hospital and community settings over the past five decades. With the current use of antibiotics for a variety of infections, including MRSA, emerging resistance is a major concern. Currently available treatments have restrictions limiting their use. These issues include, but are not limited to, side effects, cross-resistance, lack of understanding of pharmacokinetics and clinical pharmacodynamics, gradual increment in minimal inhibitory concentration over the period (MIC creep) and ineffectiveness in dealing with bacterial biofilms. Despite availability of various therapeutic options for MRSA, the clinical cure rates remain low with high morbidity and mortality. Given these challenges with existing treatments, there is a need for development of novel agents for MRSA. Along with prompt infection control strategies and strict implementation of antibiotic stewardship, cautious use of newer anti-MRSA agents will be of utmost importance. This article reviews the treatments and limitations of MRSA management and highlights the future path.

A study on combination of daptomycin with selected antimicrobial agents: in vitro synergistic effect of MIC value of 1 mg/L against MRSA strains

Background

Daptomycin is an important drug used in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection. A high dose of daptomycin is indicated for an MRSA infection with a minimum inhibitory concentration (MIC) of 1 mg/L for daptomycin. Combination therapies with daptomycin and other antimicrobial agents, including fosfomycin, display in vitro synergism potentially. This study was conducted to investigate the in vitro synergistic effect of daptomycin-based combination therapy against MRSA strains with high daptomycin MIC.

Method

The synergistic effects of daptomycin in combination with fosfomycin, gentamicin, linezolid, oxacillin, or rifampicin against MRSA with an MIC of 1 mg/L for daptomycin were measured using the microbroth checkerboard assay in vitro.

Result

A total of 100 MRSA isolates was tested. The synergistic interactions of the drugs were evaluated using the fractional inhibitory concentration index. The MIC values revealed that all isolates (100%) were found to be susceptible to linezolid, 85% to fosfomycin, 8% to gentamicin, 69% to rifampicin, and no isolate was susceptible to oxacillin. The in vitro synergism rates of daptomycin in combination with fosfomycin, oxacillin, gentamicin, linezolid, and rifampicin were 37, 11, 5, 3, and 1%, respectively.

Conclusion

The combination of daptomycin plus fosfomycin may be an effective therapeutic option for MRSA infection.

Electronic supplementary material

The online version of this article (10.1186/s40360-019-0305-y) contains supplementary material, which is available to authorized users.

Treatment strategies for persistent methicillin-resistant Staphylococcus aureus bacteraemia

WHAT IS KNOWN AND OBJECTIVE

Treatment of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia is a long-standing challenge to health care, often complicated by metastatic infections, treatment failure and mortality. When MRSA bacteraemia persists despite adequate initial treatment, current Infectious Diseases Society of America guidelines recommend evaluation and removal of possible sources of infection. In addition, a change in therapy may be considered. The objective of this review was to explore the therapeutic options for the treatment of persistent MRSA bacteraemia.

METHODS

A literature search of PubMed, MEDLINE and Google Scholar was performed using the following search terms: [methicillin-resistant Staphylococcus aureus OR MRSA] AND [bacteraemia OR bloodstream infection] AND [persistent OR persistence OR refractory OR treatment failure OR salvage] AND treatment. We evaluated relevant, adult, English-language, peer-reviewed studies published between 1985 and May 2018. In vitro and animal studies were considered as supportive of in vivo data.

RESULTS AND DISCUSSION

Randomized, controlled trials are lacking. However, case series and case reports support multiple treatment options including high-dose daptomycin in combination with an antistaphylococcal β-lactam, ceftaroline, trimethoprim-sulfamethoxazole (TMP-SMX) or fosfomycin; ceftaroline alone or in combination with vancomycin or TMP-SMX; linezolid alone or in combination with a carbapenem, or telavancin.

WHAT IS NEW AND CONCLUSION

Given the heterogeneity of the data, a preferred regimen has not emerged. Prescribers must take into consideration recent exposure, source control, and available synergy and clinical data. Further comparative trials are needed to establish a preferred regimen and the creation of a universal treatment algorithm.

Methicillin-resistant Staphylococcus aureus

Since the 1960s, methicillin-resistant Staphylococcus aureus (MRSA) has emerged, disseminated globally and become a leading cause of bacterial infections in both health-care and community settings. However, there is marked geographical variation in MRSA burden owing to several factors, including differences in local infection control practices and pathogen-specific characteristics of the circulating clones. Different MRSA clones have resulted from the independent acquisition of staphylococcal cassette chromosome mec (SCCmec), which contains genes encoding proteins that render the bacterium resistant to most β-lactam antibiotics (such as methicillin), by several S. aureus clones. The success of MRSA is a consequence of the extensive arsenal of virulence factors produced by S. aureus combined with β-lactam resistance and, for most clones, resistance to other antibiotic classes. Clinical manifestations of MRSA range from asymptomatic colonization of the nasal mucosa to mild skin and soft tissue infections to fulminant invasive disease with high mortality. Although treatment options for MRSA are limited, several new antimicrobials are under development. An understanding of colonization dynamics, routes of transmission, risk factors for progression to infection and conditions that promote the emergence of resistance will enable optimization of strategies to effectively control MRSA. Vaccine candidates are also under development and could become an effective prevention measure.

Role of rifampin for the treatment of bacterial infections other than mycobacteriosis

OBJECTIVES

Rifampin was initially approved for the treatment of tuberculosis. Because of its low toxicity, broad-spectrum activity, and good bioavailability, rifampin is now commonly administered as combination antimicrobial therapy for the treatment of various infections caused by organisms other than mycobacteria. This review summarizes the most recent clinical studies on the use of rifampin combinations for treating four common non-mycobacterial infections: acute bacterial meningitis, infective endocarditis and bacteraemia, pneumonia, and biofilm-related infections.

METHODS

We performed a literature search of clinical studies published in English from January 2005 to June 2016 using the PubMed database with the search terms "rifampin" with "meningitis" or "infective endocarditis and bacteraemia" or "pneumonia" or "prosthetic joint infections.

RESULTS

Current evidence to support a rifampin combination therapy as a treatment for non-mycobacterial infections was largely based on in vitro/in vivo studies and non-comparable retrospective case series. Additionally, controlled clinical trials that directly compared outcomes resulting from rifampin treatment versus treatment without rifampin were limited.

CONCLUSIONS

Rifampin combination therapy appears promising for the treatment of non-mycobacterial infections. However, further definitive clinical trials are necessary to validate its use because the risk of adverse drug-drug interactions and of the emergence of rifampin resistance during treatment may outweigh the potential benefits.

Florfenicol As a Modulator Enhancing Antimicrobial Activity: Example Using Combination with Thiamphenicol against Pasteurella multocida

Synergistic effects between the same class of antibiotics are rarely reported. Our previous study found synergistic-like interaction between florfenicol (FFC) and thiamphenicol (TAP) against Staphylococcus aureus. Here, the enhanced antimicrobial activity was evaluated in 97 clinical isolates of both Gram-negative and Gram-positive bacteria. Susceptible strains were initially identified by checkerboard microdilution assay (fractional inhibitory concentration index [FICI] ≤ 0.625), followed by confirmation of synergism using the time-kill methodology (≥2 log₁₀ CFU/ml reduction). In all, 43% of Pasteurella multocida tested were susceptible to the enhanced bactericidal effect. In chicken fowl cholera models, FFC and TAP combination at much lower dosage that is correspondent to their MIC deduction provided maximum protection in vivo. Furthermore, synergistic combination of FFC with oxytetracycline (OTC) against Pseudomonas aeruginosa in vitro was also demonstrated. Based on the enhanced uptake of TAP and OTC, FFC presumably elicits enhanced antimicrobial activity in an orderly manner through alteration of bacterial membrane permeability or efflux systems and subsequent increase of intracellular concentration of the antibiotics used in combination. Results of ethidium bromide accumulation assay and RNA-seq showed little evidence for the involvement of efflux pumps in the synergy but further investigation is required. This study suggests the potentiality of a novel combination regimen involving FFC as an initiating modulator effective against both Gram-positive and Gram-negative bacteria depending on the antibiotics that are combined. The observed improvement of bacteriostatic effect to bactericidal, and the extended effectiveness against FFC-resistant bacterial strains warrant further studies.

Should daptomycin-rifampin combinations for MSSA/MRSA isolates be avoided because of antagonism?

PURPOSE

There is increasing clinical evidence from observational studies, that combination therapy of daptomycin with rifampin is a valuable treatment option for biofilm-associated difficult to treat Staphylococcus aureus infections such as osteomyelitis, prosthetic joint infection and endocarditis. However, two studies analyzing a limited number of S. aureus isolates reported an antagonism of those two drugs questioning the benefit of this combination.

METHODS

To estimate the frequency of this possible antagonism, we performed in vitro checkerboard assays on 58 consecutive clinical isolates of S. aureus (MSSA n = 9, MRSA n = 49). We determined the fractional inhibitory concentration index (FICI) and the susceptible breakpoint index (SBPI). All isolates were characterized by a microprobe array detecting 336 different genes/alleles to ensure their non-clonal origin.

RESULTS

For all isolates, the FICI was between 1.00 and 1.25 indicating additive effects for the daptomycin/rifampin combination. Neither antagonism nor synergism as defined by the FICI was found for any of the isolates.

CONCLUSION

Based on these data, there is no evidence to advise against the daptomycin/rifampin combination therapy.

Staphylococcus aureus infections: epidemiology, pathophysiology, clinical manifestations, and management

Staphylococcus aureus is a major human pathogen that causes a wide range of clinical infections. It is a leading cause of bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections. This review comprehensively covers the epidemiology, pathophysiology, clinical manifestations, and management of each of these clinical entities. The past 2 decades have witnessed two clear shifts in the epidemiology of S. aureus infections: first, a growing number of health care-associated infections, particularly seen in infective endocarditis and prosthetic device infections, and second, an epidemic of community-associated skin and soft tissue infections driven by strains with certain virulence factors and resistance to β-lactam antibiotics. In reviewing the literature to support management strategies for these clinical manifestations, we also highlight the paucity of high-quality evidence for many key clinical questions.

Clinical pharmacological approach for balancing the use of daptomycin and linezolid in comparison with that of vancomycin in the treatment of MRSA-related infections

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most challenging bacterial pathogens responsible for severe infections among hospitalized patients. In recent years there is increasing evidence that the clinical efficacy of vancomycin is progressively decreasing. Although daptomycin and linezolid are valuable alternatives to vancomycin for the treatment of MRSA-related bloodstream infections and pneumonia, respectively, a great deal of debate exists about their role in daily clinical practice due to cost-effectiveness issues. In this article we put into perspective the importance of pharmacokinetic/pharmacodynamic (PK/PD) considerations based on recent experimental and clinical data to argue whether they could be helpful in identifying clinical conditions in which these agents could be advantageous as compared to vancomycin.

Bacteremia, Sepsis, and Infective Endocarditis Associated with Staphylococcus aureus

Bacteremia and infective endocarditis (IE) are important causes of morbidity and mortality associated with Staphylococcus aureus infections. Increasing exposure to healthcare, invasive procedures, and prosthetic implants has been associated with a rising incidence of S. aureus bacteremia (SAB) and IE since the late twentieth century. S. aureus is now the most common cause of bacteremia and IE in industrialized nations worldwide and is associated with excess mortality when compared to other pathogens. Central tenets of management include identification of complicated bacteremia, eradicating foci of infection, and, for many, prolonged antimicrobial therapy. Evolving multidrug resistance and limited therapeutic options highlight the many unanswered clinical questions and urgent need for further high-quality clinical research.

Daptomycin in combination with other antibiotics for the treatment of complicated methicillin-resistant Staphylococcus aureus bacteremia

PURPOSE

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the most important nosocomial pathogens. Resistance to antibiotic therapy has been known to emerge especially in clinically complex scenarios, resulting in challenges in determining optimal treatment of serious MRSA. Daptomycin, in combination with other antibiotics, has been successfully used in the treatment of these infections, with the aims of resulting in reducing the prevention of antimicrobial resistance and increased killing compared with daptomycin monotherapy.

METHODS

This article reviews all the published studies that used daptomycin combination therapy for the treatment of bacteremia and associated complicated infections caused by gram-positive organisms, including MRSA. We discuss the rationale of combination antibiotics and the mechanisms that enhance the activity of daptomycin, with special focus on the role of β-lactam antibiotics.

FINDINGS

There are limited clinical data on the use of daptomycin in combination with other antibiotics. Most of this use was as successful salvage therapy in the setting of failing primary, secondary, or tertiary therapy and/or relapsing infection. Synergy between β-lactams and daptomycin is associated with several characteristics, including increased daptomycin binding and β-lactam-mediated potentiation of innate immunity, but the precise molecular mechanism is unknown.

IMPLICATIONS

Use of daptomycin in combination with other antibiotics, especially β-lactams, offers a promising treatment option for complicated MRSA bacteremia in which emergence of resistance during treatment may be anticipated. Because it is currently not possible to differentiate complicated from uncomplicated bacteremia at the time of presentation, combination therapy may be considered as first-line therapy, with de-escalation to monotherapy in uncomplicated cases and cases with stable pharmacologic and surgical source control.

Treatment options for methicillin-resistant Staphylococcus aureus (MRSA) infection: Where are we now?

Methicillin-resistant Staphylococcus aureus (MRSA) infection continues to be a substantial global problem with significant associated morbidity and mortality. This review summarises the discussions that took place at the 4th MRSA Consensus Conference in relation to the current treatment options for serious MRSA infections and how to optimise whichever therapy is embarked upon. It highlights the many challenges faced by both the laboratory and clinicians in the diagnosis and treatment of MRSA infections.