Combination Therapy of Daptomycin and Fosfomycin for Vancomycin Tolerant Methicillin-Resistant Staphylococcus aureus Endocarditis Complicating Metastatic Osteomyelitis

Fosfomycin as salvage therapy for persistent methicillin-resistant Staphylococcus aureus bacteremia: A case series and review of the literature

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia can be persistent and refractory; however, the optimal approach for its treatment has not been determined. Although fosfomycin (FOM) has been shown to have synergistic effects with anti-MRSA agents in vitro, clinical experience with FOM combination therapy is limited. Thus, we present cases of persistent MRSA bacteremia that improved with the addition of FOM. In case 1, a 48-year-old man with prosthetic vascular graft infection developed persistent MRSA bacteremia despite vancomycin (VCM) and daptomycin (DAP) administration. On day 46, after the first positive blood culture, we added FOM to DAP. The blood culture became negative on day 53. In case 2, an 85-year-old woman presented with pacemaker-related MRSA bacteremia. She was treated with VCM, followed by DAP and DAP plus rifampicin. However, the bacteremia persisted for 32 days because of difficulties in immediate pacemaker removal. After adding FOM to DAP, the blood culture became negative on day 38. In case 3, a 57-year-old woman developed persistent MRSA bacteremia due to pulmonary valve endocarditis and pulmonary artery thrombosis after total esophagectomy for esophageal cancer. The bacteremia continued for 50 days despite treatment with DAP, followed by VCM, VCM plus minocycline, DAP plus linezolid (LZD), and VCM plus LZD. She was managed conservatively because of surgical complications. After adding FOM to VCM on day 51, the blood culture became negative on day 58. FOM combination therapy may be effective in eliminating bacteria and can serve as salvage therapy for refractory MRSA bacteremia.

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.

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.