Activity of dalbavancin against staphylococci and streptococci, assessed by BSAC and NCCLS agar dilution methods

Physico-Chemical Investigation and Antimicrobial Efficacy of Ozonated Oils: The Case Study of Commercial Ozonated Olive and Sunflower Seed Refined Oils

Drug resistance represents one of the great plagues of our time worldwide. This largely limits the treatment of common infections and requires the development of new antibiotics or other alternative approaches. Noteworthy, the indiscriminate use of antibiotics is mostly responsible for the selection of mutations that confer drug resistance to microbes. In this regard, recently, ozone has been raising interest for its unique biological properties when dissolved in natural oils. Ozonated oils have been reported to act in a non-specific way on microorganisms hindering the acquisition of advantageous mutations that result in resistance. Here, we focused on the antimicrobial effect of two commercial olive (OOO) and sunflower seeds (OSO) oils. Nuclear magnetic resonance spectroscopy and thermal analysis showed the change in the chemical composition of the oils after ozonation treatment. Different ozonated oil concentrations were then used to evaluate their antimicrobial profile against Candida albicans, Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli by agar diffusion and broth dilution methods. Cytotoxicity was also evaluated in keratinocytes and epithelial cells. Overall, our results revealed that both OOO and OSO showed a potent microbicidal effect, especially against C. albicans (IC50 = OOO: 0.3 mg/mL and OSO: 0.2 mg/mL) and E. faecalis (IC50 = OOO: 0.4 mg/mL and OSO: 2.8 mg/mL) albeit exerting a certain effect also against S. aureus and E. coli. Moreover, both OOO and OSO do not yield any relevant cytotoxic effect at the active concentrations in both cell lines. This indicates that the ozonated oils studied are not toxic for mammalian cells despite exerting a potent antimicrobial effect on specific microorganisms. Therefore, OOO and OSO may be considered to integrate standard therapies in the treatment of common infections, likely overcoming drug resistance issues.

Efficacy and mechanism of actions of natural antimicrobial drugs

Microbial infections have significantly increased over the last decades, and the mortality rates remain unacceptably high. The emergence of new resistance patterns and the spread of new viruses challenge the eradication of infectious diseases. The declining efficacy of antimicrobial drugs has become a global public health problem. Natural products derived from natural sources, such as plants, animals, and microorganisms, have significant efficacy for the treatment of infectious diseases accompanied by less adverse effects, synergy, and ability to overcome drug resistance. As the Chinese female scientist Youyou Tu received the Nobel Prize for the antimalarial drug artemisinin, antimicrobial drugs developed from Traditional Chinese Medicine are expected to receive increasing attention again. This review summarizes the antimicrobial agents derived from natural products approved for nearly 20 years and describes their efficacy and mode of action. The aim of this unit is to review the current status of antimicrobial drugs from natural products in order to increase the value of natural products as a source of novel drug candidates for infectious diseases.

Subinhibitory Dalbavancin Attenuates Exotoxin Production from Methicillin-Sensitive and Methicillin-Resistant Staphylococcus aureus In Vitro

This study investigated the effects of subinhibitory doses of the lipoglycopeptide antibiotic dalbavancin on Staphylococcus aureus toxin production in vitroS. aureus toxin production levels were compared to those seen with the natural glycopeptide antibiotic vancomycin and with representative beta-lactam and oxazolidinone antibiotics. While neither dalbavancin nor vancomycin adversely affected toxin production, of these glycopeptide antibiotics, only dalbavancin significantly attenuated toxin production at subinhibitory concentrations. These findings support the recent success of dalbavancin for treatment of staphylococcal infections.

The Selective Interaction of Pistacia lentiscus Oil vs. Human Streptococci, an Old Functional Food Revisited with New Tools

Pistacia lentiscus berry oil (LBO) represents a typical vegetal product of the Mediterranean basin that has been formally used in traditional cuisine for 100s of years. In addition to its interesting alimentary properties, this product could represent an interesting candidate in the field of research on the study of new anti-infective agents. In fact, in Mediterranean countries, lentisk oil still continues to be widely used in folk medicine for oral and skin affections, in particular, acute gingivitis, pediatric skin infections such as impetigo and foot plaques, and biofilm related infections often associated with Streptococcus spp. Following these observations, we have hypothesized a “lentisk oil-bacteria” interaction, placing particular emphasis on the different Streptococcal species involved in these oral and skin diseases. In accordance with this hypothesis, the use of standard antimicrobial-antibiofilm methods (MIC, MBC, MBIC) allowed the interesting behavior of these bacteria to be observed and, in this context, the response to lentisk oil appears to be correlated with the pathogenic profile of the considered microorganism. Two probiotic strains of S. salivarius K12/M18 appeared to be non-sensitive to this product, while a set of five different pathogenic strains (S. agalactiae, S. intermedius, S. mitis, S. mutans, S. pyogenes) showed a response that was correlated to the fatty acid metabolic pathway of the considered species. In fact, at different times of bacteria development, selective High Performance Liquid Chromatography analysis of the growth medium containing LBO detected a significant increase in free unsaturated fatty acids (UFAs) in particular oleic, palmitic and linoleic acids, which are already known for their antibacterial activity. In this context, we have hypothesized that LBO could be able to modulate the pathogen/probiotic rate in a Streptococcal population using the fatty acid metabolic pathway to help the probiotic strain. This hypothesis was strengthened by performing antibacterial testing with oleic acid and an in silico evaluation of the Streptococcal MCRA protein, an enzyme involved in the production of saturated fatty acids from UFA. These results show that LBO may have been used in ancient times as a “natural microbial modulating extract” in the prevention of biofilm- associated diseases.

A Reference Broth Microdilution Method for Dalbavancin In Vitro Susceptibility Testing of Bacteria that Grow Aerobically

Antimicrobial susceptibility testing (AST) is performed to assess the in vitro activity of antimicrobial agents against various bacteria. The AST results, which are expressed as minimum inhibitory concentrations (MICs) are used in research for antimicrobial development and monitoring of resistance development and in the clinical setting for antimicrobial therapy guidance. Dalbavancin is a semi-synthetic lipoglycopeptide antimicrobial agent that was approved in May 2014 by the Food and Drug Administration (FDA) for the treatment of acute bacterial skin and skin structure infections caused by Gram-positive organisms. The advantage of dalbavancin over current anti-staphylococcal therapies is its long half-life, which allows for once-weekly dosing. Dalbavancin has activity against Staphylococcus aureus (including both methicillin-susceptible S. aureus [MSSA] and methicillin-resistant S. aureus [MRSA]), coagulase-negative staphylococci, Streptococcus pneumoniae, Streptococcus anginosus group, β-hemolytic streptococci and vancomycin susceptible enterococci. Similar to other recent lipoglycopeptide agents, optimization of CLSI and ISO broth susceptibility test methods includes the use of dimethyl sulfoxide (DMSO) as a solvent when preparing stock solutions and polysorbate 80 (P80) to alleviate adherence of the agent to plastic. Prior to the clinical studies and during the initial development of dalbavancin, susceptibility studies were not performed with the use of P-80 and MIC results tended to be 2-4 fold higher and similarly higher MIC results were obtained with the agar dilution susceptibility method. Dalbavancin was first included in CLSI broth microdilution methodology tables in 2005 and amended in 2006 to clarify use of DMSO and P-80. The broth microdilution (BMD) procedure shown here is specific to dalbavancin and is in accordance with the CLSI and ISO methods, with step-by-step detail and focus on the critical steps added for clarity.

Dalbavancin, a long-acting lipoglycopeptide for the treatment of multidrug-resistant Gram-positive bacteria

Dalbavancin is a new lipoglycopeptide antibiotic in late-stage clinical development as a once-weekly treatment for serious infections including skin and skin structure infections. Its in vitro potency is greater than that of vancomycin, with a MIC(90) of 0.06 mg/l for Staphylococcus aureus and coagulase-negative staphylococci (irrespective of oxacillin susceptibility), 0.06-0.12 mg/l for vancomycin-susceptible Enterococcus spp. and 0.003 mg/l or less for Streptococcus pneumoniae or beta-hemolytic streptococci. Dalbavancin has dual routes of elimination. The results of Phase II/III studies show clinical efficiency in complicated skin and skin structure infection. During clinical trials, dalbavancin was as effective as linezolid or vancomycin in the treatment of patients with complicated skin and skin structure infection, including those with methicillin-resistant S. aureus. An additional Phase II study demonstrated efficacy in catheter-related bacteremia. Other preliminary in vitro and in vivo data have identified putative interest of dalbavancin in endocarditis, osteitis, diabetic foot, respiratory tract or joint infection.

Antimicrobial Spectrum and Potency of Dalbavancin Tested Against Clinical Isolates from Europe and North America (2003): Initial Results from an International Surveillance Protocol

Dalbavancin is a bactericidal dimethylaminopropyl amide glycopeptide derivative possessing an extended serum elimination half-life in humans that allows once-weekly dosing for the therapy of Gram-positive infections. Strains from this baseline surveillance protocol in North America (NA; USA and Canada) and Europe (EU, 14 countries) were sampled in 2003. A total of 7,765 Gram-positive isolates (3,695 from NA and 4,070 from EU) were tested by reference broth microdilution methods against dalbavancin and 10 comparator agents. Species were analyzed separately by resistance phenotypes such as methicillin- (oxacillin-) resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and penicillin-resistant Streptococcus pneumoniae. Dalbavancin and other glycopeptides were very active against staphylococci (n=4648) with dalbavancin being 16- to 32-fold more potent than vancomycin (MIC90, 0.06 versus 2 mg/L). MRSA rates were greater (31.6%) in NA than in EU (26.1%). Quinupristin/dalfopristin resistance (MIC, > or = 2 mg/L; 0.1-0.5%) was documented more often in EU compared to NA. Dalbavancin (MIC50, 0.03-0.06 mg/L) was active against enterococci, except VanA resistance phenotypes. VRE rates were lower in EU (8.3%) then in NA (35.9%) from this resistance-enhanced enterococcal collection. Streptococci (dalbavancin MIC90, 0.016-0.03 mg/L) were generally most susceptible to glycopeptides (100.0%), quinupristin/dalfopristin (98.6-100.0%) and linezolid (100.0%); but dalbavancin was 16-fold more active than comparators. All vancomycin-susceptible enterococci and > 90% of vanB VRE had dalbavancin MIC values at < or = 1 mg/L,but vanA VRE strains had dalbavancin MIC results ranging from 0.06 to > 8 mg/L (median MIC, > or = 8 mg/L). Dalbavancin MIC values were not adversely influenced by geographic region or resistance phenotype (except vanA VRE). Infrequently isolated Gram-positive organisms such as Bacillus spp. (MIC90, 0.12 mg/L), Corynebacterium spp. (MIC90, 0.12 mg/L), Listeria monocytogenes (MIC90, 0.25 mg/L) and Micrococcus spp. (MIC90, 0.03 mg/L) were very susceptible to dalbavancin. In conclusion, these 2003 baseline resistance surveillance findings confirm the potent dalbavancin activity compared to several comparator agents against important Gram-positive pathogens. This high volume international survey indicates potential therapeutic roles for dalbavancin against many troublesome resistant Gram-positive phenotypes.

Dalbavancin: a novel antimicrobial

The increasing incidence of serious infections because of Gram-positive pathogens and the rising cost in parenteral administration of antimicrobials has inspired the development of a novel antibiotic. Dalbavancin is the first once a week antibiotic with activity against a broad range of Gram-positive pathogens. A large multicentre, pivotal, Phase III clinical trial, which included 854 patients with complicated skin and skin structure infections, compared 1-2 doses of dalbavancin vs. linezolid. The results demonstrated non-inferiority and a comparable safety profile. With its unique pharmacokinetic profile, ease of use and excellent safety profile, dalbavancin should provide a valuable addition to the armamentarium used to treat infections because of Gram-positive cocci.

Emerging Options for Treatment of Invasive, Multidrug-ResistantStaphylococcus aureusInfections

Limited established treatment options exist for the treatment of serious, invasive infections caused by multidrug-resistant Staphylococcus aureus, most notably nosocomially acquired methicillin-resistant S. aureus (MRSA). Although vancomycin represents the gold standard for therapy of such invasive infections, reports of increasing in vitro resistance to vancomycin, combined with reports of clinical failures (with this and other antistaphylococcal agents), underscore the need for alternative therapies. Older agents with favorable in vitro activity available in both oral and intravenous dose forms include trimethoprim-sulfamethoxazole and clindamycin. Limited clinical data exist to support their routine use as initial therapy in the treatment of invasive disease. However, these and other options (e.g., tetracyclines) are being reexplored in the setting of increasing concern over MRSA acquired in the community setting. Newer treatment options for MRSA include linezolid, quinupristin-dalfopristin, daptomycin, and tigecycline. With the exception of linezolid, these newer agents require intravenous administration. Combination therapy may be considered in select invasive diseases refractory to standard monotherapies. These diseases include infections such as endocarditis, meningitis, and prosthetic device infections. Additional alternatives to vancomycin are under clinical investigation. Those in later stages of development include oritavancin, dalbavancin, telavancin, and ceftobiprole.

Comparison of dalbavancin MIC values determined by Etest (AB BIODISK) and reference dilution methods using gram-positive organisms

While standardized microdilution testing methodologies and quality control ranges exist for the novel glycolipopeptide dalbavancin, no testing methods have been described that are immediately available for routine use in clinical laboratories. In this study, we found that the dalbavancin Etest (AB BIODISK, Solna, Sweden) procedure demonstrated a high degree of agreement (100% within +/-2 log(2) dilution steps) with the standardized broth microdilution method, validating the use of the Etest as an alternative test for investigational or clinical purposes following regulatory approval.

Viridans group streptococci in blood culture isolates in a Swedish university hospital: antibiotic susceptibility and identification of erythromycin resistance genes

One hundred and twenty-nine isolates of viridans group streptococci in blood cultures from patients with septicaemia or endocarditis isolated between 1998 and 2003 were tested for antibiotic susceptibility to penicillin, ciprofloxacin, clindamycin, dalbavancin, daptomycin, erythromycin, linezolid, tigecycline, trimethoprim/sulphamethoxazole and vancomycin. Reduced susceptibility to penicillin (minimum inhibitory concentration (MIC) > or =0.25 microg/mL) was found in 18% of the isolates, and 4% of the strains were resistant to penicillin (MIC> or =4.0 microg/mL). Nineteen percent of the isolates had reduced susceptibility to erythromycin (MIC> or =0.5 microg/mL), among which ermB and mefA were found in 40% and 80%, respectively. Strains sequenced as Streptococcus mitis by rnpB had a high degree of non-susceptibility to erythromycin (32%) and penicillin (21%). The level of penicillin resistance in this Swedish study was lower compared with studies from other countries where the antibiotic pressure might be higher than in Sweden. Susceptibility to newer antibiotics was high; all strains were susceptible to dalbavancin, daptomycin, linezolid and vancomycin.

Dalbavancin: A Novel Lipoglycopeptide Antibacterial

Dalbavancin is a new lipoglycopeptide antibacterial possessing in vitro activity against a variety of gram-positive pathogens. Against methicillin-susceptible and methicillin-resistant Staphylococcus aureus, it has demonstrated favorable minimum inhibitory concentration ranges compared with those of currently available agents. Dalbavancin is highly protein bound (> 90%), which may contribute to its prolonged half-life of 149-300 hours. Because of this long half-life, once-weekly dosing strategies have been used in clinical trials. Efficacy and tolerability have been demonstrated in a wide variety of animal infection models. Clinical success and safety have been shown in phase II and III trials for skin and soft-tissue infections and a phase II trial for catheter-related bloodstream infections. In these trials with vancomycin, linezolid, and various beta-lactams as comparators, comparable results have been reported. The results of further phase III trials are anxiously awaited and will more clearly define the clinical role of this novel agent.

Spectrum and potency of dalbavancin tested against 3322 Gram-positive cocci isolated in the United States Surveillance Program (2004)

Dalbavancin is an injectable, next generation lipoglycopeptide with an extended serum elimination half-life. Once-weekly dosing has been successful for treatment of skin and skin structure (SSSI) and catheter-related bloodstream infections (CR-BSI). Concurrent with clinical trails, dalbavancin resistance surveillance was initiated in 2003, and results are reported here for the 2004 United States (USA) component. A total of 3322 Gram-positive cocci were tested by reference broth microdilution methods. Organism species tested included: Staphylococcus aureus (2102; 49% oxacillin-resistant), coagulase-negative staphylococci (CoNS; 255, 82% oxacillin-resistant), beta-hemolytic streptococci (241), viridans group streptococci (46), and Streptococcus pneumoniae (678). Dalbavancin (MIC90,0.06-0.12 microg/mL) was comparable in spectrum, but superior in potency to vancomycin (MIC90,1-2 microg/mL) against staphylococci. Dalbavancin MIC90 values against the tested streptococci was 0.03 microg/mL. Dalbavancin was more active against tested SSTI pathogens than comparator agents having complete susceptibility rates (100.0%) similar to vancomycin. Vancomycin, (16- to 32-fold), linezolid (8- to 32-fold), daptomycin (4- to 32-fold), and quinupristin/dalfopristin (4- to 32-fold) were less active than dalbavancin. In conclusion, dalbavancin exhibited greater potency than comparison glycopeptides or lipopeptides, streptogramin combinations, and oxazolidinones against Gram-positive pathogens associated with SSSI or CR-BSI. Dalbavancin wild-type MIC distributions remain unchanged compared with prior sampled years (2002-2003) in the USA.

Glycopeptides: Update on an old successful antibiotic class

The natural product glycopeptides vancomycin and teicoplanin have come to play a significant role in the therapy for Gram-positive bacterial infections. In particular vancomycin is the choice for empiric therapy of these infections primarily due to its activity against and the significance of methicillin-resistant Staphylococcus aureus. While high-level problematic glycopeptide resistance among enterococci was observed initially and continues to increase, the slow creep of vancomycin intermediate susceptibility and the fear of frank resistance among the staphylococci have precipitated increasing work leading to creation of new semisynthetic analogs. These new agents, including dalbavancin and telavancin, are within 1-2 years availability in the clinic. Interestingly, chemical modifications resulting in these second-generation analogs and additional characterization have revealed new mechanisms of antibacterial action, and plasticity regarding additional properties including pharmacokinetics for the drug candidates. The unique beneficial properties of the near term vancomycin replacements, semisynthesis of additional important analogs, and advances in metabolic engineering resulting in novel scaffolds signal a new era for the glycopeptide antibiotics.