Daptomycin for the treatment of Staphylococcus aureus infections complicated by septic pulmonary emboli

Staphylococcus aureus Modulates Carotenoid and Phospholipid Content in Response to Oxygen-Restricted Growth Conditions, Triggering Changes in Membrane Biophysical Properties

Staphylococcus aureus membranes contain carotenoids formed during the biosynthesis of staphyloxanthin. These carotenoids are considered virulence factors due to their activity as scavengers of reactive oxygen species and as inhibitors of antimicrobial peptides. Here, we show that the growth of S. aureus under oxygen-restricting conditions downregulates carotenoid biosynthesis and modifies phospholipid content in biofilms and planktonic cells analyzed using LC-MS. At oxygen-restrictive levels, the staphyloxanthin precursor 4,4-diapophytofluene accumulates, indicating that the dehydrogenation reaction catalyzed by 4,4'-diapophytoene desaturases (CrtN) is inhibited. An increase in lysyl-phosphatidylglycerol is observed under oxygen-restrictive conditions in planktonic cells, and high levels of cardiolipin are detected in biofilms compared to planktonic cells. Under oxygen-restriction conditions, the biophysical parameters of S. aureus membranes show an increase in lipid headgroup spacing, as measured with Laurdan GP, and decreased bilayer core order, as measured with DPH anisotropy. An increase in the liquid-crystalline to gel phase melting temperature, as measured with FTIR, is also observed. S. aureus membranes are therefore less condensed under oxygen-restriction conditions at 37 °C. However, the lack of carotenoids leads to a highly ordered gel phase at low temperatures, around 15 °C. Carotenoids are therefore likely to be low in S. aureus found in tissues with low oxygen levels, such as abscesses, leading to altered membrane biophysical properties.

Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Staphylococcus aureus Carotenoids Modulate the Thermotropic Phase Behavior of Model Systems That Mimic Its Membrane Composition

Staphylococcus aureus (S. aureus) is a pathogenic gram-positive bacterium that normally resides in the skin and nose of the human body. It is subject to fluctuations in environmental conditions that may affect the integrity of the membrane. S. aureus produces carotenoids, which act as antioxidants. However, these carotenoids have also been implicated in modulating the biophysical properties of the membrane. Here, we investigate how carotenoids modulate the thermotropic phase behavior of model systems that mimic the phospholipid composition of S. aureus. We found that carotenoids depress the main phase transition of DMPG and CL, indicating that they strongly affect cooperativity of membrane lipids in their gel phase. In addition, carotenoids modulate the phase behavior of mixtures of DMPG and CL, indicating that they may play a role in modulation of lipid domain formation in S. aureus membranes.

Beta Lactams Plus Daptomycin Combination Therapy for Infective Endocarditis: An Italian National Survey (BADAS)

BACKGROUND

infective endocarditis (IE) remains a severe disease frequently encountered in clinical practice and often requiring interdisciplinary medical and surgical management. This national survey aims to describe the clinical prescribing habits of the use of daptomycin in the setting of IE and the possible role for combination therapy with beta-lactams.

METHODS

The study was a cross-sectional internet-based questionnaire survey on therapy with daptomycin. The questionnaire was designed with closed-ended questions and distributed using the SurveyMonkey^® platform between October 2019 to December 2020.

RESULTS

55 clinicians from twelve Italians regions joined the questionnaire. The survey reported use of daptomycin as first-line choice in 31.48% of cases and as the first-line anti-MRSA agent in 44.44%. The empiric use of daptomycin was stated in the high suspicion of MRSA rather than MSSA, enterococcal or streptococcal IE. The rationale of daptomycin for the empirical treatment of native and prosthetic valve IE was mostly the possibility of administering an aminoglycoside-sparing combination regimen, high bacterial killing rate and high clinical efficacy.

CONCLUSIONS

In conclusion, in selected patients, daptomycin could be a feasible option for the treatment of infective endocarditis in line with data from the European registry of daptomycin.

Carotenogenesis of Staphylococcus aureus: New insights and impact on membrane biophysical properties

Staphyloxanthin (STX) is a saccharolipid derived from a carotenoid in Staphylococcus aureus involved in oxidative-stress tolerance and antimicrobial peptide resistance. STX influences the biophysical properties of the bacterial membrane and has been associated to the formation of lipid domains in the regulation of methicillin-resistance. In this work, a targeted metabolomics and biophysical characterization study was carried out to investigate the biosynthetic pathways of carotenoids, and their impact on the membrane biophysical properties. Five different S. aureus strains were investigated, including three wild-type strains containing the crtM gene related to STX biosynthesis, a crtM-deletion mutant, and a crtMN plasmid-complemented variant. LC-DAD-MS/MS analysis of extracts allowed the identification of 34 metabolites related to carotenogenesis in S. aureus at different growth phases (8, 24 and 48 h), showing the progression of these metabolites as the bacteria advances into the stationary phase. For the first time, 22 members of a large family of carotenoids were identified, including STX and STX-homologues, as well as Dehydro-STX and Dehydro-STX-homologues. Moreover, thermotropic behavior of the CH2 stretch of lipid acyl chains in live cells by FTIR, show that the presence of STX increases acyl chain order at the bacterial growth temperature. Indeed, the cooperative melting event of the bacterial membrane, which occurs around 15 °C in the native strains, shifts with increased carotenoid content. These results show the diversity biosynthetic of carotenoids in S. aureus, and their influence on membrane biophysical properties.

Emerging resistance mechanisms for 4 types of common anti-MRSA antibiotics in Staphylococcus aureus: A comprehensive review

Staphylococcus aureus is one of the leading hospital-associated and community-associated pathogens, which has caused a global public health concern. The emergence of methicillin-resistant S. aureus (MRSA) along with the widespread use of different classes of antibiotics has become a significant therapeutic challenge. Antibiotic resistance is a disturbing problem that poses a threat to humans. Treatment options for S. aureus resistant to β-lactam antibiotics include glycopeptide antibiotic, cyclic lipopeptide antibiotic, cephalosporins and oxazolidinone antibiotic. The most representative types of these antibiotics are vancomycin, daptomycin, ceftaroline and linezolid. The frequent use of the first-line drug vancomycin for MRSA treatment has increased the number of resistant strains, namely vancomycin intermediate resistant S. aureus (VISA) and vancomycin resistant S. aureus (VRSA). A systematic literature review of relevant published studies in PubMed before 2020 was conducted. In recent years, there have been some reports on the relevant resistant mechanisms of vancomycin, daptomycin, ceftaroline and linezolid. In this review, we have summarized the antibiotic molecular modes of action and different gene mutants at the whole-genome level, which will aid in further development on new drugs for effective MRSA treatment based on describing different resistance mechanisms of classic antibiotics.

A comparison of daptomycin alone and in combination with ceftaroline fosamil for methicillin-resistant Staphylococcus aureus bacteremia complicated by septic pulmonary emboli

The use of daptomycin (DAP) in septic pulmonary emboli (SPE) remains controversial. We analyzed 29 cases of MRSA bacteremia complicated by SPE treated with DAP (n = 14) or DAP-ceftaroline fosamil (CPT; n = 15). Initial treatment with DAP monotherapy was found to have a success rate comparable with DAP-CPT (71% vs. 80%; p = 0.68).