Dalbavancin reduces biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE)

The pathogenicity and virulence of the opportunistic pathogen Staphylococcus epidermidis

The pervasive presence of Staphylococcus epidermidis and other coagulase-negative staphylococci on the skin and mucous membranes has long underpinned a casual disregard for the infection risk that these organisms pose to vulnerable patients in healthcare settings. Prior to the recognition of biofilm as an important virulence determinant in S. epidermidis, isolation of this microorganism in diagnostic specimens was often overlooked as clinically insignificant with potential delays in diagnosis and onset of appropriate treatment, contributing to the establishment of chronic infection and increased morbidity or mortality. While impressive progress has been made in our understanding of biofilm mechanisms in this important opportunistic pathogen, research into other virulence determinants has lagged S. aureus. In this review, the broader virulence potential of S. epidermidis including biofilm, toxins, proteases, immune evasion strategies and antibiotic resistance mechanisms is surveyed, together with current and future approaches for improved therapeutic interventions.

Reconstructive breast implant-related infections: Prevention, diagnosis, treatment, and pearls of wisdom

Implant-based reconstructions are increasingly utilized following mastectomy in the prevention and treatment of breast cancer. However, these implants are associated with a high rate of infection, which is a major complication that can lead to implant removal, delay in adjuvant radiation and chemotherapy, and increase in health care costs. Early clinical signs and symptoms of infection, such as erythema, warmth, and tenderness, are challenging to discern from expected postsurgical responses. Furthermore, when atypical features are present or the patient's condition does not improve on adequate antimicrobials, the clinician should be prompted to consider an alternative noninfectious etiology. Herein we highlight the key elements of the preventive, diagnostic, and multidisciplinary therapeutic approach to salvaging the infected breast implant; review several infectious disease mimickers; and provide many pearls of wisdom that the practicing clinician must be familiar with and be able to manage in an effective and successful manner.

Antibiotic Efficacy against Methicillin-Susceptible Staphylococcus aureus Biofilms on Synthetic and Biological Vascular Grafts

BACKGROUND

Biofilm formation is one of the greatest challenges encountered in vascular graft infections. Our aim is to compare the efficacy of 5 antibiotics against methicillin-susceptible Staphylococcus aureus (MSSA) biofilms on the surface of 4 vascular grafts.

METHODS

In vitro study of 2 clinical MSSA strains (MSSA2 and MSSA6) and 4 vascular grafts (Dacron, Dacron-silver-triclosan (DST), Omniflow-II, and bovine pericardium). After a 24-hr incubation period, the graft samples were divided into 6 groups: growth control (no treatment), ciprofloxacin 4.5 mg/L, cloxacillin 100 mg/L, dalbavancin 300 mg/L, daptomycin 140 mg/L, and linezolid 20 mg/L. Quantitative cultures were obtained and results expressed as log10 colony-forming units per milliliter (CFU/mL). Analysis of variance was performed to compare biofilm formation between the different groups.

RESULTS

The mean ± standard deviation MSSA2 count on the growth control Dacron graft was 10.05 ± 0.31 CFU/mL. Antibiotic treatment achieved a mean reduction of 45%; ciprofloxacin was the most effective antibiotic (64%). Baseline MSSA2 counts were very low on the DST (0.50 ± 1.03 CFU/mL) and Omniflow-II (0.33 ± 0.78 CFU/mL) grafts. On the bovine pericardium patch, the count was 9.87 ± 0.50 CFU/mL, but this was reduced by a mean of 45% after antibiotic treatment (61% for ciprofloxacin). The mean MSSA6 count on the growth control Dacron graft was 9.63 ± 0.53 CFU/mL. Antibiotics achieved a mean reduction of 48%, with ciprofloxacin performing best (67% reduction). The baseline MSSA6 count on the DST graft was 8.54 ± 0.73 CFU/mL. Antibiotics reduced biofilm formation by 72%; cloxacillin was the most effective treatment (86%). The MSSA6 count on the untreated Omniflow-II graft was 1.17 ± 1.52 CFU/mL. For the bovine pericardium patch, it was 8.98 ± 0.67 CFU/mL. The mean reduction after antibiotic treatment was 46%, with cloxacillin achieving the greatest reduction (68%).

CONCLUSIONS

In this in vitro study, ciprofloxacin and cloxacillin performed best at reducing biofilms formed by clinical MSSA strains on the surface of biological and synthetic vascular grafts.

A Narrative Review on the Role of Dalbavancin in the Treatment of Bone and Joint Infections

Bone and joint infections (BJI) require prolonged antimicrobial treatment, leading to lengthy hospitalizations, high costs, the risk of nosocomial infections, and the development of antimicrobial resistance. Dalbavancin is a novel semisynthetic lipoglycopeptide approved for the treatment of adults and children with acute bacterial skin and skin structure infections. This narrative review aims to summarize the characteristics of dalbavancin and the current scientific evidence regarding its clinical efficacy and safety in the treatment of BJI. A literature search until June 2023 was performed to identify all published research about the role of dalbavancin in the management of BJI. Due to its unique pharmacokinetics characterized by prolonged half-life, high bactericidal activity against most Gram-positive bacteria, a good safety profile, and high tissue penetration, dalbavancin can be a valuable alternative to the treatment of BJI. Clinical studies have shown its non-inferiority compared to conventional therapies in BJI, offering potent activity against key pathogens and an extended dosing interval that may shorten hospitalization. In conclusion, dalbavancin represents a promising treatment option for BJI with a favorable safety profile, but further research in both adults and particularly children, who are ideal candidates for long-acting antibiotics, is necessary to evaluate the role of dalbavancin in BJI.

Pharmacokinetic and pharmacodynamic considerations for optimizing antimicrobial therapy used to treat bone and joint infections: an evidence-based algorithmic approach

INTRODUCTION

Bone and joint infections (BJIs) are a major health concern causing remarkable morbidity and mortality. However, which antimicrobial treatment could be the best according to specific clinical scenarios and/or to the pharmacokinetic/pharmacodynamic (PK/PD) features remains an unmet clinical need. This multidisciplinary opinion article aims to develop evidence-based algorithms for empirical and targeted antibiotic therapy of patients affected by BJIs.

AREAS COVERED

A multidisciplinary team of four experts had several rounds of assessment for developing algorithms devoted to empirical and targeted antimicrobial therapy of BJIs. A literature search was performed on PubMed-MEDLINE (until April 2023) to provide evidence for supporting therapeutic choices. Four different clinical scenarios were structured according to specific infection types (i.e. vertebral osteomyelitis, prosthetic joint infections, infected non-unions and other chronic osteomyelitis, and infectious arthritis), need or not of surgical intervention or revision, isolation or not of clinically relevant bacterial pathogens from blood and/or tissue cultures, and PK/PD features of antibiotics.

EXPERT OPINION

The proposed therapeutic algorithms were based on a multifaceted approach considering the peculiar features of each antibiotic (spectrum of activity, PK/PD properties, bone penetration rate, and anti-biofilm activity), and could be hopefully helpful in improving clinical outcome of BJIs.

Antibacterial and Antibiofilm Effect of Unifloral Honeys against Bacteria Isolated from Chronic Wound Infections

Honey is known as an alternative remedy for the treatment of wounds. To evaluate the potential of five Hungarian honey types against wound-associated bacteria, in vitro microbiological assays were conducted on Pseudomonas aeruginosa, Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus (MRSA). Minimum inhibitory concentration (MIC) was determined with the broth macrodilution method, and biofilm degradation capacity was tested with a crystal violet assay. To understand the underlying mechanisms, the effects of honey treatments were assessed on bacterial membrane integrity and quorum sensing (QS). The highest antibacterial activity, indicated by the lowest MIC values, as well as the highest biofilm inhibition rates and membrane disruption, was displayed by chestnut and linden honeys. The most sensitive bacterium was S. epidermidis. Bacterial membrane degradation took place 40 min after treatment with honey solutions of at least a 40% concentration. Each honey sample exhibited anti-QS activity, which was most pronounced in the case of chestnut honey. It was concluded that the antibacterial, biofilm-inhibiting and anti-QS activities of linden and chestnut honeys were superior to those of acacia, goldenrod and milkweed honeys. In addition to the floral source, the antibacterial effect of honey is influenced by the microbial species treated. The use of honey in wound treatment can be justified by its diverse antibacterial mechanisms.

Novel dalbavancin-PLLA implant coating prevents hematogenous Staphylococcus aureus infection in a minimally invasive mouse tail vein model

Infective/bacterial endocarditis is a rare but life-threatening disease with a hospital mortality rate of 22.7% and a 1-year mortality rate of 40%. Therefore, continued research efforts to develop efficient anti-infective implant materials are of the utmost importance. Equally important is the development of test systems that allow the performance of new materials to be comprehensively evaluated. In this study, a novel antibacterial coating based on dalbavancin was tested in comparison to rifampicin/minocycline, and the suitability of a recently developed mouse tail vein model for testing the implant coatings was validated. Small polymeric stent grafts coated with a poly-L-lactic acid (PLLA) layer and incorporated antibiotics were colonized with Staphylococcus (S.) aureus before implantation into the tail vein of mice. The main assessment criteria were the hematogenous spread of the bacteria and the local tissue reaction to the contaminated implant. For this purpose, colony-forming units (CFU) in the blood, spleen and kidneys were determined. Tail cross sections were prepared for histological analysis, and plasma cytokine levels and expression values of inflammation-associated genes were examined. Both antibiotic coatings performed excellently, preventing the onset of infection. The present study expands the range of available methods for testing the anti-infectivity of cardiovascular implants, and the spectrum of agents for effective surface coating.

A Bombyx mori Infection Model for Screening Antibiotics against Staphylococcus epidermidis

The increasing number of microorganisms that are resistant to antibiotics is prompting the development of new antimicrobial compounds and strategies to fight bacterial infections. The use of insects to screen and test new drugs is increasingly considered a promising tool to accelerate the discovery phase and limit the use of mammalians. In this study, we used for the first time the silkworm, Bombyx mori, as an in vivo infection model to test the efficacy of three glycopeptide antibiotics (GPAs), against the nosocomial pathogen Staphylococcus epidermidis. To reproduce the human physiological temperature, the bacterial infection was performed at 37 °C and it was monitored over time by evaluating the survival rate of the larvae, as well the response of immunological markers (i.e., activity of hemocytes, activation of the prophenoloxidase system, and lysozyme activity). All the three GPAs tested (vancomycin, teicoplanin, and dalbavancin) were effective in curing infected larvae, significantly reducing their mortality and blocking the activation of the immune system. These results corroborate the use of this silkworm infection model for the in vivo studies of antimicrobial molecules active against staphylococci.

Dalbavancin in clinical practice: a particular place for the elderly?

We investigate dalbavancin efficiency and tolerance among elderly in Grenoble-Alpes 32 university hospital. Among the 65 patients who received dalbavancin, 51% (33) were considered as old. Patients presented mainly bones and joint infections (52%), surgical site infection 34 (31%), and infective endocarditis (IE) (8%). Clinical cure was confirmed for 79% of old 35 patients at 1, 3, and 6 months. Six adverse events (9%) were reported after 36 dalbavancin's administration, but each time in combination with other antibiotics. 37 Dalbavancin had a significant effectiveness and safety profile and represents a real 38 therapeutic option in the management of deep and complex infections of elderly patients.

Orthopaedic Implant-Associated Staphylococcal Infections: A Critical Reappraisal of Unmet Clinical Needs Associated with the Implementation of the Best Antibiotic Choice

Infections associated with orthopaedic implants represent a major health concern characterized by a remarkable incidence of morbidity and mortality. The wide variety of clinical scenarios encountered in the heterogeneous world of infections associated with orthopaedic implants makes the implementation of an optimal and standardized antimicrobial treatment challenging. Antibiotic bone penetration, anti-biofilm activity, long-term safety, and drug choice/dosage regimens favouring outpatient management (i.e., long-acting or oral agents) play a major role in regards to the chronic evolution of these infections. The aim of this multidisciplinary opinion article is to summarize evidence supporting the use of the different anti-staphylococcal agents in terms of microbiological and pharmacological optimization according to bone penetration, anti-biofilm activity, long-term safety, and feasibility for outpatient regimens, and to provide a useful guide for clinicians in the management of patients affected by staphylococcal infections associated with orthopaedic implants Novel long-acting lipoglycopeptides, and particularly dalbavancin, alone or in combination with rifampicin, could represent the best antibiotic choice according to real-world evidence and pharmacokinetic/pharmacodynamic properties. The implementation of a multidisciplinary taskforce and close cooperation between microbiologists and clinicians is crucial for providing the best care in this scenario.

Exebacase: A Novel Approach to the Treatment of Staphylococcal Infections

Lysins are bacteriophage-derived enzymes that degrade essential components of bacteria. Exebacase (Lysin CF-301) is an attractive antimicrobial agent because it demonstrates rapid bacteriolytic activity against staphylococcal species, including Staphylococcus aureus, has a low resistance profile, eradicates biofilms, and acts synergistically with other antibiotics. Combinations including exebacase and standard of care antibiotics represent an alternative to antibiotic monotherapies currently used to treat invasive staphylococcal infections. This manuscript reviews what is known about exebacase and explores how this novel agent may be used in the future to treat human bacterial pathogens.

A Dalbavancin Lock Solution Can Reduce Enterococcal Biofilms After Freezing

Introduction

We previously demonstrated the efficacy of a frozen dalbavancin–heparin (DH) lock solution against biofilms of staphylococci. However, as enterococci also commonly cause catheter-related bloodstream infections (C-RBSI), we assessed the bioactivity of frozen dalbavancin (D) and DH against enterococci.

Methods

Over 6 months, we compared the bioactivity of a solution of DH (1 mg/ml) with that of D in terms of cfu counts and metabolic activity against biofilms of Enterococcus faecalis and Enterococcus faecium (four strains each). For each solution, we individually compared results obtained at each time point (months 3 and 6) with baseline (month 0). We also compared the median DH value of each variable at baseline and at months 3 and 6 of freezing with the values obtained for D alone. We used both statistical and clinical criteria when results were within 25% of the reference value.

Results

At the end of the experiment (month 6), neither a statistically nor a clinically significant reduction in the bioactivity of D solution was observed in terms of cfu count and metabolic activity against enterococcal biofilms. Regarding the DH solution, we found both statistical and clinical significance in the median percentage reduction in metabolic activity between months 0 and 6 in E. faecalis strains (51.8% vs. 77.8%, P = 0.007). Moreover, after freezing, the DH solution lost significant bioactivity compared with the D solution, especially in E. faecalis.

Conclusion

A dalbavancin lock solution can be frozen for up to 6 months with no negative effect on its bioactivity against enterococcal biofilms. However, when combined with heparin, its efficacy was reduced. Therefore, we recommend that if lock therapy with frozen dalbavancin is used in the management of enterococcal C-RBSI, heparin should be added simultaneously at the time of catheter lock.

Clinical Pharmacokinetics and Pharmacodynamics of Dalbavancin

Dalbavancin is a synthetic lipoglycopeptide that exerts its antimicrobial activity through two distinct modes of action, inhibition of cell wall synthesis and an anchoring mechanism. Compared with previous glycopeptide antibiotics, dalbavancin demonstrates improved antibacterial potency against Gram-positive organisms and a long half-life of approximately 1 week, which is longer in tissues (e.g., skin, bone) than plasma. These factors facilitated the development of single-dose or once-weekly dosing regimens to treat acute bacterial skin and skin structure infections (ABSSSI). Dalbavancin exhibits dose-proportional pharmacokinetics and is highly protein bound (93%). Despite being highly protein bound, it has a steady-state volume of distribution >10 L and distributes widely into the skin, bone, peritoneal space, and epithelial lining fluid, but not cerebrospinal fluid. Dalbavancin elimination occurs via a combination of renal (approximately 45%) and non-renal clearance, with dose adjustments recommended only in patients with a creatinine clearance <30 mL/min not receiving any form of dialysis. The established pharmacokinetic/pharmacodynamic index associated with bacterial kill is free area under the concentration-time curve over the minimum inhibitory concentration (fAUC/MIC), with a goal 24-h fAUC/MIC of at least 27.1 for Staphylococcus aureus infections. Recent data suggest usefulness in the treatment of infections beyond ABSSSI, with convenient dosing and redosing strategies for complicated infections requiring extended treatment durations. Additional studies are needed to confirm these preliminary findings.

New Perspectives on Old and New Therapies of Staphylococcal Skin Infections: The Role of Biofilm Targeting in Wound Healing

Among the most common complications of both chronic wound and surgical sites are staphylococcal skin infections, which slow down the wound healing process due to various virulence factors, including the ability to produce biofilms. Furthermore, staphylococcal skin infections are often caused by methicillin-resistant Staphylococcus aureus (MRSA) and become a therapeutic challenge. The aim of this narrative review is to collect the latest evidence on old and new anti-staphylococcal therapies, assessing their anti-biofilm properties and their effect on skin wound healing. We considered antibiotics, quorum sensing inhibitors, antimicrobial peptides, topical dressings, and antimicrobial photo-dynamic therapy. According to our review of the literature, targeting of biofilm is an important therapeutic choice in acute and chronic infected skin wounds both to overcome antibiotic resistance and to achieve better wound healing.

Biofilm-Related Infections in Gram-Positive Bacteria and the Potential Role of the Long-Acting Agent Dalbavancin

Infections caused by Gram-positive bacteria are a major public health problem due to their increasing resistance to antibiotics. Staphylococcus and Enterococcus species' resistance and pathogenicity are enhanced by their ability to form biofilm. The biofilm lifestyle represents a significant obstacle to treatment because bacterial cells become highly tolerant to a wide range of antimicrobial compounds normally effective against their planktonic forms. Thus, novel therapeutic strategies targeting biofilms are urgently needed. The lipoglycopeptide dalbavancin is a long-acting agent for treating acute bacterial skin and skin structure infections caused by a broad range of Gram-positive pathogens. Recent studies have shown promising activity of dalbavancin against Gram-positive biofilms, including methicillin-resistant S. aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), and vancomycin-susceptible enterococci. This review outlines the mechanisms regulating biofilm development in Staphylococcus and Enterococcus species and the clinical impact of biofilm-related infections. In addition, it discusses the clinical implications and potential therapeutic perspectives of the long-acting drug dalbavancin against biofilm-forming Gram-positive pathogens.

In vitro activity of dalbavancin and other anti-staphylococcal agents against infecting isolates of methicillin-resistant coagulase-negative staphylococci

Introduction. Dalbavancin was approved in Europe in 2015 for skin and soft tissue infections.Hypothesis/Gap Statement. Data on methicillin-resistant coagulase-negative staphylococci (MR-CNS) dalbavancin susceptibility are scarce.Aim. To assess the susceptibility of MR-CNS to dalbavancin and other anti-staphylococcal agents.Methodology. A total of 443 MR-CNS clinical isolates from patients hospitalized in a Greek university hospital during a 2.5-year period (January 2018 to June 2020) were included. The MICs for vancomycin, teicoplanin, linezolid and daptomycin were investigated by Etest and the MIC for dalbavancin was determined according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines in 196 isolates. The consumption of the aforementioned antimicrobials was calculated.Results. In total, 51 isolates were resistant to teicoplanin (11.5 %) and 211 (47.6 %) to linezolid; all were susceptible to vancomycin and daptomycin. Among 196 isolates tested, 32 (16.3 %) were resistant to dalbavancin. A significant increase of MIC during the study period was found for vancomycin, teicoplanin and daptomycin, while a decrease in linezolid's MIC was observed. Dalbavancin's MIC remained stable. No difference in consumption was observed among the studied anti-staphylococcal agents.Conclusion. An increase of vancomycin, teicoplanin and daptomycin MICs among MR-CNS was observed, whereas 47.6 % of isolates were non-susceptible to linezolid. Dalbavancin retains excellent potency against MR-CNS, even in the presence of non-susceptibility to other anti-staphylococcal antibiotics.

Efficacy of dalbavancin against MRSA biofilms in a rat model of orthopaedic implant-associated infection

OBJECTIVES

The aim of this study was to evaluate the efficacy of dalbavancin against MRSA biofilm-related infection in orthopaedic implants in vivo.

METHODS

One MRSA strain isolated from human osteomyelitis was used to promote biofilm formation on the surface of screws. The implants were inserted in the proximal tibia under general anaesthesia. Thirty-nine Wistar rats were divided into three groups [control group (no treatment), Group 1 (7 days of treatment) and Group 2 (14 days of treatment)]; both treatment groups were administered dalbavancin intraperitoneally and euthanized after treatment. cfu of bacteria present in both the tibia and the implant were quantified. The infection severity was assessed by histopathology and scored from 0 (no infection) to 4 (severe infection).

RESULTS

The high number of cfu/g and cfu/mL present in the control group indicated a well-established infection. There was a significant reduction in cfu in rats treated with dalbavancin both in the tibia (2.8 × 105 cfu/g) and the implant (1.1 × 106 cfu/mL) in Group 1 (1.8 × 103 cfu/g and 2.4 × 105 cfu/mL, respectively) and in Group 2 (8.2 cfu/g and 8.2 × 103 cfu/mL, respectively). Most animals from the control group presented an infection scored as 3 (severe). At the end of the experiment, most rats from Groups 1 and 2 presented an infection scored as 2 (moderate) and 0 (no infection), respectively.

CONCLUSIONS

Although there was a marked decrease in cfu number, signs of biofilm-induced infection prevailed after 14 days of treatment. Further studies should be carried out to evaluate the potential of dalbavancin in the treatment of bone and orthopaedic implant-associated MRSA infections.

Dalbavancin for the Treatment of Prosthetic Joint Infections: A Narrative Review

Dalbavancin (DAL) is a lipoglycopeptide with bactericidal activity against a very wide range of Gram-positive microorganisms. It also has unique pharmacokinetic properties, namely a prolonged half-life (around 181 h), which allows a convenient weekly dosing regimen, and good diffusion in bone tissue. These features have led to off-label use of dalbavancin in the setting of bone and joint infection, including prosthetic joint infections (PJI). In this narrative review, we go over the pharmacokinetic and pharmacodynamic characteristics of DAL, along with published in vitro and in vivo experimental models evaluating its activity against biofilm-embedded bacteria. We also examine published experience of osteoarticular infection with special attention to DAL and PJI.

Dalbavancin treatment for prosthetic joint infections in real-life: a national cohort study and literature review

OBJECTIVES

Dalbavancin is a long-lasting lipoglycopeptide active against Gram-positive bacteria, especially methicillin-resistant staphylococci. Few data are available on dalbavancin use for treatment of prosthetic joint infections (PJIs). We describe a cohort of patients treated for PJI with dalbavancin and review the literature regarding this condition.

METHODS

All adult patients with PJI from the French dalbavancin national cohort from 1 June 2017 to 1 January 2019 were included. We collected clinical and microbiological characteristics and outcome through a standardised questionnaire. Clinical cure was defined as absence of clinical signs of infection at last visit. Failure was a composite criterion defined by persistence or reappearance of signs of infection, and/or switch to suppressive antibiotic treatment and/or death from infection. The literature review was performed using PubMed.

RESULTS

Seventeen patients were included. Bacteria were identified in 16 cases: Staphylococcus aureus (n = 10), including methicillin-resistant S. aureus (n = 1); and coagulase-negative staphylococci (n = 10), including methicillin-resistant Staphylococcus epidermidis (n = 4). Sixteen patients (94.1%) had received antibiotic therapy prior to dalbavancin use (mean of 2.2 ± 1.3 lines). Clinical cure was achieved in 8/17 patients after a median follow-up of 299.0 (IQR 97.0-476.0) days. We reviewed all cases of PJI treated with dalbavancin available in the literature and the overall clinical cure was estimated at 73.1%.

CONCLUSION

Our study and literature data suggest that use of dalbavancin in PJI could be considered, even as salvage therapy. Dalbavancin appears to be a safe and easy treatment for patients with staphylococcal PJIs.

Anti-biofilm activity of dalbavancin against methicillin-resistant Staphylococcus aureus (MRSA) isolated from human bone infection

The presence of methicillin-resistant Staphylococcus aureus (MRSA) in bone infections difficults its treatment and is a sign of concern. The aim of this study was to evaluate in vitro activity of dalbavancin on pre-established adhered cells and 24 h old biofilms of MRSA strains isolated from a human bone infection. Thirty-three MRSA were isolated from osteomyelitis episodes. The antimicrobial susceptibility of these strains was assessed by the Kirby-Bauer disc diffusion method and the presence of resistance genes was screened by PCR. MRSA planktonic minimum inhibitory concentration and minimum bactericidal concentration were assessed. Minimum biofilm eradication concentration (MBEC) was performed by the microtiter biofilm formation assay. All 33 MRSA strains were classified as multidrug-resistant strains and susceptible to dalbavancin. Dalbavancin inhibited the growth of 54.6% and 52% of strains at the concentrations of 0.05 µg/mL and 1 µg/mL, respectively. The MBEC values up to 0.4 µg/mL demonstrated that dalbavancin was active against most strains in pre-established adhered cells and 24 h old biofilms. The current results show that dalbavancin is active against adhered cells and biofilms in vitro, suggesting that this antimicrobial agent may be an option for the treatment of bone infections caused by MRSA.

In Vitro Study To Evaluate the Bioactivity of Freezing a Heparin-Based Dalbavancin Lock Solution

The use of dalbavancin as a catheter lock solution must be addressed in depth before implementation in clinical practice. We assessed whether a heparin-based dalbavancin lock solution could be frozen in single-dose vials for 6 months without affecting its bioactivity against biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). Over 6 months, we tested the bioactivity of a frozen solution of dalbavancin (≈1 mg/ml) plus heparin (60 IU) in terms of CFU counts and metabolic activity against biofilms of Staphylococcus aureus ATCC 43300 (MRSA) and Staphylococcus epidermidis ATCC 35984 (MRSE). The Anti-Xa assay was also performed to assess whether the anticoagulant activity of heparin was reduced under freezing. Every month, we compared the mean value of each variable with that obtained at baseline (before freezing, month 0) using both clinical criteria (values were within 25% of the baseline value) and statistical criteria (linear mixed models). At the end of the experiment (month 6), neither a clinically nor a statistically significant reduction in the bioactivity of dalbavancin-heparin solution was observed in terms of CFU counts and metabolic activity against biofilm of MRSA. Regarding MRSE, considering the clinical criteria, neither CFU counts nor metabolic activity decreased significantly. However, the reduction was statistically significant for all variables. Anti-Xa values (mean [standard deviation] international units per milliliter) for heparin in combination with dalbavancin were within 25% of the heparin-water value. A heparin-based dalbavancin lock solution can be frozen for up to 6 months with no effect on its bioactivity against MRSA and MRSE biofilms.

Therapeutic Strategies To Counteract Antibiotic Resistance in MRSA Biofilm-Associated Infections

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the leading causes of persistent human infections. This pathogen is widespread and is able to colonize asymptomatically about a third of the population, causing moderate to severe infections. It is currently considered the most common cause of nosocomial infections and one of the main causes of death in hospitalized patients. Due to its high morbidity and mortality rate and its ability to resist most antibiotics on the market, it has been termed a "superbug". Its ability to form biofilms on biotic and abiotic surfaces seems to be the primarily means of MRSA antibiotic resistance and pervasiveness. Importantly, more than 80 % of bacterial infections are biofilm-mediated. Biofilm formation on indwelling catheters, prosthetic devices and implants is recognized as the cause of serious chronic infections in hospital environments. In this review we discuss the most relevant literature of the last five years concerning the development of synthetic small molecules able to inhibit biofilm formation or to eradicate or disperse pre-formed biofilms in the fight against MRSA diseases. The aim is to provide guidelines for the development of new anti-virulence strategies based on the knowledge so far acquired, and, to identify the main flaws of this research field, which have hindered the generation of new market-approved anti-MRSA drugs that are able to act against biofilm-associated infections.

Antimicrobial peptide-modified silver nanoparticles for enhancing the antibacterial efficacy

Antibiotic-resistant bacteria are becoming a serious threat to public health worldwide. To address this problem, we have developed multifunctional peptide (MFP)-coated silver nanoparticles (MFP@AgNPs) for antibacterial studies. MFPs, which can physically adsorb to AgNPs via electrostatic interactions are comprised of a matrix metalloproteinase (MMP) cleavable sequence (PVGLIG), an antimicrobial peptide (tachyplesin-1), and a target peptide (PGP-PEG). The resulting MFP@AgNPs were characterized by various technologies, including UV-vis spectrophotometry, zeta potential analyzer, circular dichroism (CD) spectroscopy, attenuated total reflection-Fourier-transform infrared spectroscopy (ATR-FTIR), and transmission electron microscopy (TEM). The MIC and MBC were investigated against both Gram-positive bacteria and Gram-negative bacteria. The antibacterial activity in vivo was evaluated on MDR-AB (multidrug-resistant Acinetobacter baumannii) infected mice. We found that MFP@AgNPs exhibited antibacterial activity against both Gram-positive bacteria and Gram-negative bacteria. Compared to bare AgNPs, MFP@AgNPs-1 killed MDR-AB faster and more efficiently. SEM images showed that MFP@AgNPs-1 induced cell disruption via cell membrane damage. In vivo studies further confirmed the enhanced antibacterial activity against MDR-AB infections. The developed MFP@AgNPs-1 reduced the cytotoxicity of AgNPs and enhanced the antibacterial activity against MDR-AB in vitro and in vivo, providing a possible solution against multidrug-resistant bacterial infections.

Dalbavancin as long-term suppressive therapy for patients with Gram-positive bacteremia due to an intravascular source-a series of four cases

We present four cases with Gram-positive bacteremia (pathogens: MRSA n = 1, Enterococcus spp. n = 3) due to an intravascular source (left ventricular assist device: n = 2, transfemoral aortic valve implantation n = 1, prosthetic aortic valve: n = 1) where no curative treatment was available. These patients received indefinite, chronic suppressive (palliative) therapy with dalbavancin (500 mg weekly or 1000 mg biweekly regimens). Outcomes and clinical characteristics are described; treatment was effective in suppression of bacteremia in all patients over several months (range: 1 to more than 12 months), we observed no relevant side effects.

Efficacy and safety of dalbavancin in the treatment of acute bacterial skin and skin structure infections (ABSSSIs) and other infections in a real-life setting: data from an Italian observational multicentric study (DALBITA study)

OBJECTIVES

We evaluated the efficacy and safety of dalbavancin in ABSSSI and 'other sites' infections' (OTA).

METHODS

Observational study involving 11 Italian hospitals including patients that received ≥1 dose of dalbavancin in 2016-2019. The outcome was end-of-treatment efficacy and safety in ABSSSI and OTA in a real-life setting.

RESULTS

206 patients enrolled (males 50%, median age 62 [IQR 50-76] years), 60.2% ABSSSI, 39.8% OTA. 69.7% ABSSSI vs 90.7% OTA (p = 0.003) and 46.3% ABSSSI vs 37.2% OTA (p = 0.786) received previous and concomitant antibiotics, respectively. 82.5% reached clinical cure . Eleven (5.4%) patients had non-serious adverse events (AE). OTA patients showed longer hospitalization (13.5 days, 5.5-22 vs 3, 0-11.7; p<0.0001) and received longer previous (18 days, 9-30 vs 11, 7-19; p = 0.007)/concomitant antibiotic treatments (21 days, 14-52 vs 11, 8-14; p < 0.0001), compared to ABSSSI. ABSSSI and OTA showed similar efficacy (85.5% vs 75%, p = 0.459) and safety (no AE: 81.5% vs 64.3%, p = 0.258); efficacy was independent of previous/concomitant therapies.

CONCLUSIONS

Dalbavancin demonstrated a success rate of >80%, with similar efficacy/safety in ABSSSI and off-label indications. The preferential use of dalbavancin as second-line or combination therapy would seem to suggest the need for in-depth studies focused on its off-label use.

Treatment of osteoarticular, cardiovascular, intravascular-catheter-related and other complicated infections with dalbavancin and oritavancin: A systematic review

BACKGROUND

There is increasing interest in the use of oritavancin and dalbavancin for complicated Gram-positive infections as an alternative to in-hospital intravenous or outpatient antimicrobial therapy.

OBJECTIVE

To evaluate the efficacy and safety of long-acting lipoglycopeptides (laLGPs) in patients with osteoarticular, cardiovascular, intravascular-catheter-related and other complicated infections.

METHODS

A systematic literature search was performed using 'dalbavancin' and 'oritavancin' as search terms. For inclusion in this review, studies had to include at least one human subject treated for an indication other than acute bacterial skin and skin structure infections. The primary outcome for this review was clinical success as defined by each individual study, and patients were stratified by type of infection.

RESULTS

In total, 38 studies (18 randomized controlled trials/case series and 20 case reports) met the inclusion criteria. The most common off-label indication for oritavancin and dalbavancin was osteoarticular infection, with a median success rate of 73% [interquartile range (IQR) 58-85%] among the 14 studies with more than one patient. The success rate for endocarditis and cardiac-device-related infections was 68% (IQR 56-86%) among nine studies, and the success rate for catheter-related bloodstream infection was 75% (IQR 59-90%) among seven studies. Among the 16 studies of almost 700 patients receiving laLGPs, there were 98 reports of adverse events, resulting in 13% of treated patients reporting an event.

CONCLUSIONS

This review provides evidence that laLGPs are safe and efficacious for osteoarticular, cardiovascular, intravascular-catheter-related and other complicated infections. Further research is needed to confirm these results.

Dalbavancin for the Treatment of Complicated Gram-Positive Skin and Soft Tissue Infections

New antimicrobial agents have been developed to treat infections caused by methicillin-resistant Staphylococcus aureus and other multidrug-resistant pathogens. Dalbavancin is a novel semisynthetic lipoglycopeptide antibiotic, particularly active against methicillin-resistant Staphylococcus aureus. Due to its unique pharmacological characteristics and longer half-life, it can be administered once-weekly or every 15 days and in outpatient setting. Currently, it is indicated for complicated skin and soft tissue infections, but accumulating evidence points to its off-label efficacy in osteomyelitis and endocarditis. Further experience is still needed to increase our knowledge on the role of dalbavancin in a wider range of Gram-positive infections requiring prolonged antimicrobial treatment.

Advantages of Outpatient Treatment with Long-Acting Lipoglycopeptides for Serious Gram-Positive Infections: A Review

Treatment of serious gram-positive infections presents multiple challenges. Treatment often results in prolonged hospitalization for administration of intravenous antimicrobials and presents an inefficient use of hospital resources. Prolonged hospitalization is typically also unfavorable to patient preferences and potentially subjects patients to additional health care-associated complications. Current strategies of transition to outpatient settings-outpatient parenteral antimicrobial therapy and use of oral antibiotics-often do not adequately serve vulnerable populations for whom there is often no alternative to inpatient therapy. Specifically, people who use drugs, those who cannot reliably adhere to unsupervised treatment (poor mental or physical health), people with complicating life circumstances (e.g., homelessness, incarceration, rural location), and those with inadequate health insurance remain hospitalized for weeks longer than persons without such conditions. We suspected that long-acting lipoglycopeptides (laLGP), such as dalbavancin and oritavancin, may be useful in patient transitions to outpatient settings. Thus, we conducted a search of the peer-reviewed literature using the PubMed, Google Scholar, and MEDLINE databases. Based on accumulating literature, it appears that laLGPs offer a reliable alternative therapeutic strategy that addresses many of the personal and systemic barriers to the traditional transitioning approaches. Current evidence also suggests that these agents may be cost-effective from patient, payer, and hospital perspectives. Barriers to broader use of laLGPs include, among others, a relative lack of prospective data regarding efficacy in serious infections, a narrow United States Food and Drug Administration-approved indication restricted to only acute bacterial skin and skin structure infections, and lack of reimbursement infrastructure for inpatient settings.

Effect of Dalbavancin on Staphylococcal Biofilms When Administered Alone or in Combination With Biofilm-Detaching Compounds

Microorganisms grown in biofilms are more resistant to antimicrobial treatment and immune system attacks compared to their planktonic forms. In fact, infections caused by biofilm-forming Staphylococcus aureus and Staphylococcus epidermidis are a large threat for public health, including patients with medical devices. The aim of the current manuscript was to test the effect of dalbavancin, a recently developed lipoglycopeptide antibiotic, alone or in combination with compounds contributing to bacterial cell disaggregation, on staphylococcal biofilm formation and elimination. We used real-time impedance measurements in microtiter plates to study biofilm growth dynamics of S. aureus and S. epidermidis strains, in the absence or presence of dalbavancin, linezolid, vancomycin, cloxacillin, and rifampicin. Further experiments were undertaken to check whether biofilm-detaching compounds such as N-acetylcysteine (NAC) and ficin could enhance dalbavancin efficiency. Real-time dose–response experiments showed that dalbavancin is a highly effective antimicrobial, preventing staphylococcal biofilm formation at low concentrations. Minimum biofilm inhibitory concentrations were up to 22 higher compared to standard E-test values. Dalbavancin was the only antimicrobial that could halt new biofilm formation on established biofilms compared to the other four antibiotics. The addition of NAC decreased dalbavancin efficacy while the combination of dalbavancin with ficin was more efficient than antibiotic alone in preventing growth once the biofilm was established. Results were confirmed by classical biofilm quantification methods such as crystal violet (CV) staining and viable colony counting. Thus, our data support the use of dalbavancin as a promising antimicrobial to treat biofilm-related infections. Our data also highlight that synergistic and antagonistic effects between antibiotics and biofilm-detaching compounds should be carefully tested in order to achieve an efficient treatment that could prevent both biofilm formation and disruption.

The role of dalbavancin in the treatment of acute bacterial skin and skin structure infections (ABSSSIs)

Introduction: Acute bacterial skin and skin-structure infections (ABSSSI) are a subgroup of skin and soft tissue infections and are a common source of morbidity in both the community and the hospital setting. The most common cause of ABSSSI is Staphylococcus aureus, which also includes methicillin-resistant S. aureus (MRSA), together with beta-hemolytic streptococci, enterococci, and Gram-negative bacteria. Since the emergence of MRSA, the management of ABSSSI has become more challenging. Novel therapies alternative to teicoplanin and vancomycin, intravenous agents commonly used against MRSA and employed in hospitalized patients, and to other antibiotics which are used as standard of care for MRSA infection, with a higher efficacy and safer profile are worth evaluating.Areas covered: This review presents and discusses current evidence on the use of dalbavancin in the treatment of ABSSSI.Expert opinion: Dalbavancin represents a promising therapeutic choice in patients with ABSSSI, thanks to its favorable pharmacokinetic profile, valuable antimicrobial spectrum, and good safety profile.

Bioprospecting Staphylococcus Phages with Therapeutic and Bio-Control Potential

Emergence of antibiotic-resistant bacteria is a serious threat to the public health. This is also true for Staphylococcus aureus and other staphylococci. Staphylococcus phages Stab20, Stab21, Stab22, and Stab23, were isolated in Albania. Based on genomic and phylogenetic analysis, they were classified to genus Kayvirus of the subfamily Twortvirinae. In this work, we describe the in-depth characterization of the phages that electron microscopy confirmed to be myoviruses. These phages showed tolerance to pH range of 5.4 to 9.4, to maximum UV radiation energy of 25 µJ/cm2, to temperatures up to 45 °C, and to ethanol concentrations up to 25%, and complete resistance to chloroform. The adsorption rate constants of the phages ranged between 1.0 × 10-9 mL/min and 4.7 × 10-9 mL/min, and the burst size was from 42 to 130 plaque-forming units. The phages Stab20, 21, 22, and 23, originally isolated using Staphylococcusxylosus as a host, demonstrated varied host ranges among different Staphylococcus strains suggesting that they could be included in cocktail formulations for therapeutic or bio-control purpose. Phage particle proteomes, consisting on average of ca 60-70 gene products, revealed, in addition to straight-forward structural proteins, also the presence of enzymes such DNA polymerase, helicases, recombinases, exonucleases, and RNA ligase polymer. They are likely to be injected into the bacteria along with the genomic DNA to take over the host metabolism as soon as possible after infection.

Can dalbavancin be used as a catheter lock solution?

Purpose. The new lipoglycopeptide dalbavancin has only been approved for acute bacterial skin and skin structure infections. However, its alternative use as a catheter lock solution could facilitate the conservative management of catheter-related bloodstream infection. Our objective was to assess the stability and activity of dalbavancin alone and in combination with heparin against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) biofilms. We also compared the results with those obtained with vancomycin alone and in combination with heparin.Methodology. We used a 96-well plate in vitro model based on 24 h biofilms of MRSA and MRSE (ATCC 43300, ATCC 35984 and one clinical strain of each). The biofilms were exposed to dalbavancin (0.128 mg ml^-1) and vancomycin (5 mg ml^-1) alone and in combination with heparin (60 IU). The median percentage reductions in metabolic activity, biomass, bacterial load, and cell viability for each solution were compared.Results. Dalbavancin combined with heparin significantly reduced the median [interquartile range (IQR)] percentage of metabolic activity in MRSA biofilms compared with vancomycin [90.0 % (70.4-92.9 %) versus 35.0 % (14.8-59.6 %), P=0.006]. For the remaining variables studied, the combination was not inferior to vancomycin for MRSA and MRSE.Conclusions. Dalbavancin proved to be active against MRSA and MRSE biofilms. The combination of dalbavancin with heparin is a promising catheter lock solution that has the advantage of locking the catheter at home for 7 days.

Real-world experience with dalbavancin therapy in gram-positive skin and soft tissue infection, bone and joint infection

PURPOSE

Dalbavancin is a novel lipoglycopeptide with potent activity against several gram-positive pathogens, an excellent safety profile and a long elimination half-life.

METHODS

In this case series observed at the University Hospital of Vienna between 2015 and 2017, all adult patients with gram-positive infections who received at least one dosage of dalbavancin were screened (n = 118). A total of 72 patients were included in the final analysis. The number of included patients stratified by the source of infection was: skin and soft tissue infection (SSTI) (n = 26), osteomyelitis (n = 20), spondylodiscitis (n = 14), acute septic arthritis (n = 4) and prosthetic joint infection (n = 8).

RESULTS

In 46 patients (64%), clinical cure was detected at the end of dalbavancin therapy without additional antibiotic therapy. Of the 26 patients who received additional antibiotic therapy other than dalbavancin, 15 patients (21%) showed no clinical improvement under dalbavancin therapy, four patients (5%) had side effects (nausea n = 1, exanthema n = 2, hyperglycemia n = 1), and in seven patients (10%) clinical improvement under dalbavancin therapy was detected but antibiotic therapy was de-escalated to an oral drug.

CONCLUSION

We demonstrated high clinical effectiveness of dalbavancin for acute gram-positive infections primarily acute SSTI, acute septic arthritis, acute osteomyelitis and spondylodiscitis. In patients with biofilm-associated infection (chronic infection or joint prosthesis), source control was absolutely necessary for treatment success.

Chemical Composition of Aspergillus creber Extract and Evaluation of its Antimicrobial and Antioxidant Activities

Among the species belonging to the Aspergillus section Versicolores, Aspergillus creber has been poorly studied and still unexplored for its biological activities. The present study was undertaken to analyze A. creber extract and to evaluate its in vitro antimicrobial and anti-oxidant activities. UHPLC-MS/MS analysis of A. creber extract allowed the characterization of five known fungal metabolites including: asperlactone, emodin, sterigmatocystin, deoxybrevianamide E, and norsolorinic acid. The highest antimicrobial activity was displayed against Candida albicans, with a mean strongest inhibition zone of 20.6 ± 0.8 mm, followed by Gram-positive drug-resistant bacteria. The MIC values of A. creber extract varied from 0.325 mg/ml to 5 mg/ml. A. creber extract was shown a potent antioxidant activity and a high level of phenolic compounds by recording 89.28% scavenging effect for DPPH free radical, 92.93% in ABTS assay, and 85.76 mg gallic acid equivalents/g extract in Folin-Ciocalteu assay. To our knowledge, this is the first study concerning biological and chemical activities of A. creber species. Based on the obtained results, A. creber could be a promising source of natural antimicrobial and antioxidant compounds.

Among the species belonging to the Aspergillus section Versicolores, Aspergillus creber has been poorly studied and still unexplored for its biological activities. The present study was undertaken to analyze A. creber extract and to evaluate its in vitro antimicrobial and anti-oxidant activities. UHPLC-MS/MS analysis of A. creber extract allowed the characterization of five known fungal metabolites including: asperlactone, emodin, sterigmatocystin, deoxybrevianamide E, and norsolorinic acid. The highest antimicrobial activity was displayed against Candida albicans, with a mean strongest inhibition zone of 20.6 ± 0.8 mm, followed by Gram-positive drug-resistant bacteria. The MIC values of A. creber extract varied from 0.325 mg/ml to 5 mg/ml. A. creber extract was shown a potent antioxidant activity and a high level of phenolic compounds by recording 89.28% scavenging effect for DPPH free radical, 92.93% in ABTS assay, and 85.76 mg gallic acid equivalents/g extract in Folin-Ciocalteu assay. To our knowledge, this is the first study concerning biological and chemical activities of A. creber species. Based on the obtained results, A. creber could be a promising source of natural antimicrobial and antioxidant compounds.

Dalbavancin for treating prosthetic joint infections caused by Gram-positive bacteria: A proposal for a low dose strategy. A retrospective cohort study

OBJECTIVE

Gram-positive bacteria are the leading cause of prosthetic joint infection (PJI). Dalbavancin is a lipoglycopeptide with remarkable pharmacokinetic properties and high bactericidal activity against most Gram-positive bacteria. Although clear evidence regarding its effectiveness in bone and joint infections lacks, recent studies suggest a promising role of dalbavancin in PJI.

METHODS

From June 1st 2016 to May 1st 2018, all patients diagnosed of PJI and treated with DAL alone or in combination with other drugs were retrospectively evaluated. Dalbavancin susceptibility of every isolate was studied following CLSI criteria. The primary objective was to assess the clinical efficacy and tolerability of the drug in patients with PJI. A cost-analysis was performed following the DALBUSE study methodology.

RESULTS

Sixteen patients were treated with dalbavancin, eight with total hip arthroplasty infection (THAi) and eight with total knee arthroplasty infection (TKAi). Staphylococcus spp. and Enterococcus spp. were the microorganisms involved. No major side effects were detected. Infection resolved in 12 patients. In 2 patients the treatment failed, and another patient died due to unrelated causes. One patient is currently being treated for hematogenous-spread knee infection secondary to prosthetic aortic arch endocarditis. After discontinuation of dalbavancin, and excluding patients who died or with clinical failure, the median follow up of the cohort was 503 days (interquartile range IQR, 434.5 to 567 days). We calculate that US$ 264,769 were saved.

CONCLUSIONS

This study suggests that dalbavancin treatment for PJI caused by Gram-positive bacteria is a safe and effective option that reduces hospital stay and costs. Future reports are needed to confirm these findings.

In vitro analysis of the minimal inhibitory concentration values of different generations of anti-methicillin-resistant Staphylococcus aureus antibiotics

Methicillin-resistant Staphylococcus aureus (MRSA) resistance to antimicrobials may result in the increased risk of treatment failure. The objective of the study was to analyse in vitro MRSA susceptibility to vancomycin, linezolid, daptomycin, tigecycline, ceftaroline, dalbavancin, clindamycin, ciprofloxacin and trimethoprim/sulfamethoxazole. All MRSA strains isolated from hospitalised patients were analysed according to the current microbiological recommendations. Finally, a total of 124 MRSA strains were analysed; all were susceptible to tested antibiotics. Dalbavancin had the lowest minimum inhibitory concentration (MIC), and vancomycin the highest MIC value. There were 28/124 strains of MRSA susceptible for clindamycin, 36/124 for ciprofloxacin and 121/124 for trimethoprim/sulfamethoxazole. Dalbavancin was the most effective antimicrobial in our study.

Dalbavancin is active in vitro against biofilms formed by dalbavancin-susceptible enterococci

We tested the in vitro activity of dalbavancin, vancomycin and daptomycin against 83 enterococcal isolates in planktonic and biofilm states. The MIC₉₀ for vancomycin-susceptible Enterococcus faecalis was 0.125 and 4μg/mL for dalbavancin and daptomycin, respectively. For vancomycin-resistant Enterococcus faecium, the MIC₉₀ was >16 and 2μg/mL for dalbavancin and daptomycin, respectively. Dalbavancin minimum biofilm inhibitory concentrations (MBICs) for vancomycin-susceptible and -resistant isolates were ≤0.25 and >16μg/mL, respectively. The daptomycin MBIC₉₀ for all isolates was 4μg/mL. For E. faecalis and E. faecium, dalbavancin minimum biofilm bactericidal concentrations (MBBCs) for vancomycin-susceptible and -resistant isolates were ≤4 and >16μg/mL, respectively, whereas vancomycin MBBCs were >128μg/mL for all isolates, and daptomycin MBBC₉₀ values for both species were 128μg/mL. In summary, dalbavancin exhibited in vitro activity against all tested isolates of vancomycin-susceptible, but not against vancomycin-resistant enterococci; activity was observed in both the planktonic and biofilm states.