The dimerization interface in VraR is essential for induction of the cell wall stress response in Staphylococcus aureus: a potential druggable target.

BACKGROUND: Staphylococcus aureus remains a medical challenge in the treatment of bacterial infections. It has acquired resistance to commonly used antibiotics, and to those considered to be the last weapons in treating staphylococcal infections, such as vancomycin. Studies have revealed that S. aureus is capable of mounting a rapid response to antibiotics that target cell wall peptidoglycan biosynthesis, such as ß-lactams and vancomycin. The two-component system VraSR has been linked to the coordination of this response. VraS is a histidine kinase that undergoes autophosphorylation in the presence of signals elicited upon cell wall damage and it then transfers its phosphoryl group to VraR. VraR is a response regulator protein that functions as a transcription factor. Phosphorylation of VraR leads to its dimerization, which is required for optimum binding to its target promoters. Two-component systems have been targeted for the development of antibacterial agents. Deletion of the vraS or vraR gene has been shown to re-sensitize S. aureus to ß-lactams and vancomycin. RESULTS: In this study, we explored perturbation of the VraR phosphorylation-induced activation as a means to inhibit the VraSR-mediated signal transduction pathway. We show that dimerization of VraR is essential for the phosphorylation-induced activation of VraR. A single point mutation in the dimerization interface of VraR, in which Met13 was replaced by Ala, led to the inability of VraR to dimerize and to bind optimally to the target promoter. The consequences of these in vitro molecular deficiencies are equally dramatic in vivo. Complementation of a vraR deletion S. aureus strain with the vraRM13Ala mutant gene failed to induce the cell wall stress response. CONCLUSIONS: This study highlights the potential of targeting the phosphorylation-induced dimerization of VraR to disrupt the S. aureus cell wall stress response and in turn to re-sensitize S. aureus to ß-lactams and vancomycin.

Real-time monitoring of D-Ala-D-Ala dipeptidase activity of VanX in living bacteria by isothermal titration calorimetry.

The d,d-dipeptidase enzyme VanX is the main cause of vancomycin resistance in gram-positive bacteria because of hydrolysis of the D-Ala-D-Ala dipeptide used in cell-wall biosynthesis. Continuous assay of VanX has proven challenging due to lack of a chromophoric substrate. Here, we report a direct approach for continuous assay of VanX in vitro and in vivo from hydrolysis of D-Ala-D-Ala, based on the heat-rate changes measured with isothermal titration calorimetry (ITC). With the ITC approach, determination of kinetic parameters of VanX hydrolyzing D-Ala-D-Ala and the inhibition constant of d-cysteine inhibitor yielded KM of 0.10 mM, kcat of 11.5 s-1, and Ki of 18.8 µM, which are consistent with the data from ninhydrin/Cd(II) assays. Cell-based ITC studies demonstrated that the VanX expressed in E. coli and in clinical strain VRE was inhibited by d-cysteine with IC50 values of 29.8 and 28.6 µM, respectively. Also, the total heat from D-Ala-D-Ala (4 mM) hydrolysis decreases strongly (in absolute value) from 1.26 mJ for VRE to 0.031 mJ for E. faecalis, which is consistent with the large MIC value of vancomycin of 512 µg/mL for VRE and the much smaller value of 4 µg/mL for E. faecalis. The ITC approach proposed here could be applied to screen and evaluate small molecule inhibitors of VanX or to identify drug resistant bacteria.

Risk factors for vancomycin-resistant enterococcus acquisition during a large outbreak in patients aged 65 years and older.

BACKGROUND: In the context of an aging population, identifying risk factors for Vancomycin-resistant enterococci (VRE), specific to older people, is important. However, if age is a known risk factor for VRE infection, a limited number of studies have focused on older patients. This study aimed to identify potential risk factors for VRE acquisition in a population aged 65 years and older, during a large VRE outbreak that occurred in a teaching hospital in Lyon, France, from December 2013 to July 2014. METHODS: The present retrospective, multi-center, descriptive, and analytical study used part of a previous cohort, and included only a sub-group of patients aged 65 years and older. The analysis of the factors included in the original study was completed with factors more specific to geriatric patients. Inclusion criteria were patients aged 65 years and older, in contact with a VRE index patient. Patients were screened by rectal swabs. Univariate and multivariate logistic regression analyses were performed. RESULTS: A total of 180 VRE contacts were included and 18 patients became carriers. Multivariate analysis showed that risk factors for VRE acquisition in older people included major contact type (RR: 5.31, 95%CI [1.33; 21.19]), number of antibiotics used (RR: 1.36, 95%CI [1.04; 1.76]), a score of McCabe = 2 (RR: 116.39, 95%CI [5.52; 2455.98]), ethylism (RR: 5.50, 95%CI [1.49; 20.25]), and dementia (RR: 7.50, 95%CI [1.89; 29.80]). CONCLUSIONS: This study was able to demonstrate risk factors for VRE acquisition in older people. These risk factors should be taken into account when in the presence of older people in a VRE infected unit.

Metabolic Mitigation of Staphylococcus aureus Vancomycin Intermediate-Level Susceptibility.

Staphylococcus aureus is a major human pathogen whose infections are increasingly difficult to treat due to increased antibiotic resistance, including resistance to vancomycin. Vancomycin-intermediate S. aureus (VISA) strains develop resistance to vancomycin through adaptive changes that are incompletely understood. Central to this adaptation are metabolic changes that permit growth in the presence of vancomycin. To define the metabolic changes associated with adaptive resistance to vancomycin in S. aureus, the metabolomes of a vancomycin-sensitive and VISA strain pair isolated from the same patient shortly after vancomycin therapy began and following vancomycin treatment failure were analyzed. The metabolic adaptations included increases in acetogenesis, carbon flow through the pentose phosphate pathway, wall teichoic acid and peptidoglycan precursor biosynthesis, purine biosynthesis, and decreased tricarboxylic acid (TCA) cycle activity. The significance of these metabolic pathways for vancomycin-intermediate susceptibility was determined by assessing the synergistic potential of human-use-approved inhibitors of these pathways in combination with vancomycin against VISA strains. Importantly, inhibitors of amino sugar and purine biosynthesis acted synergistically with vancomycin to kill a diverse set of VISA strains, suggesting that combinatorial therapy could augment the efficacy of vancomycin even in patients infected with VISA strains.

Comparative Pharmacodynamics of Single-Dose Oritavancin and Daily High-Dose Daptomycin Regimens against Vancomycin-Resistant Enterococcus faecium Isolates in an In Vitro Pharmacokinetic/Pharmacodynamic Model of Infection.

There are limited therapeutic options to treat infections caused by vancomycin-resistant Enterococcus faecium (VREfm). The lipoglycopeptide oritavancin exhibits in vitro activity against this pathogen, although its utility against infections caused by VREfm has not been clinically established. In this study, the pharmacodynamic activity of free-drug levels associated with 12 mg/kg/day of daptomycin and a single 1,200-mg dose of oritavancin were determined against three VanA VREfm isolates in an in vitro pharmacokinetic/pharmacodynamic model.

Analysis on pathogenic and virulent characteristics of the Cronobacter sakazakii strain BAA-894 by whole genome sequencing and its demonstration in basic biology science.

Cronobacter sakazakii is an opportunistic pathogen responsible for necrotizing enterocolitis, meningitis and septicaemia especially to infant and neonate, with high lethality ranging in 40%-80%. This strain is able to survive in infant milk formula and possesses capability of pathogenicity and virulence, biofilm formation, and high resistance to elevated osmotic, low pH, heat, oxidation, and desiccasion. This study is aims to investigate the molecular characteristics of Cronobacter sakazakii BAA 894, including mechanisms of its invasion and adherence, biofilm formation, unusual resistance to environmental stress employing whole genome sequencing and comparative genomics. Results in this study suggest that numerous genes and pathways, such as LysM, Cyx system, luxS, vancomycin resistance pathway, insulin resistance pathway, and sod encoding superoxide dismutase for the survival of C. sakazakii in macrophages, contribute to pathogenicity and resistance to stressful environment of C. sakazakii BAA 894.

Healthcare-acquired infections: prevention strategies.

Healthcare-acquired infections (HAI) impact on patient care and have cost implications for the Australian healthcare system. The management of HAI is exacerbated by rising rates of antimicrobial resistance (AMR). Health-care workers and a contaminated hospital environment are increasingly implicated in the transmission and persistence of multi-resistant organisms (MRO), as well as other pathogens, such as Clostridium difficile. This has resulted in a timely focus on a range of HAI prevention actions. Core components include antimicrobial stewardship, to reduce overuse and ensure evidence-based antimicrobial use; infection prevention strategies, to control MRO - particularly methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus spp. (VRE) and, more recently, multi-resistant Gram-negative bacteria; enhanced institutional investment in hand hygiene; hospital cleaning and disinfection; and the development of prescribing guidelines and standards of care. AMR surveillance and comparisons of prescribing are useful feedback activities once effectively communicated to end users. Successful implementation of these strategies requires cultural shifts at local hospital level and, to tackle the serious threat posed by AMR, greater co-ordination at a national level. HAI prevention needs to be multi-modal, requires broad healthcare collaboration, and the strong support and accountability of all medical staff.

Assessing outcomes of adult oncology patients treated with linezolid versus daptomycin for bacteremia due to vancomycin-resistant Enterococcus.

BACKGROUND: The incidence and severity of vancomycin-resistant Enterococcus blood stream infections continue to rise and is a significant burden in the healthcare setting. Literature thus far is minimal regarding treatment outcomes in patients with malignancy and vancomycin-resistant Enterococcus bacteremia. Appropriate antibiotic selection is vital to treatment success due to high rates of resistance, limited antimicrobials and mortality in this patient population. We conducted this study to determine whether treatment outcomes differed between cancer patients treated with linezolid and those treated with daptomycin for vancomycin-resistant Enterococcus bacteremia. METHODS: This single-center, retrospective study included adult patients hospitalized on the oncology service with documented vancomycin-resistant Enterococcus faecium or Enterococcus faecalis bacteremia who received at least 48 h of either linezolid or daptomycin as primary treatment. RESULTS: A total of 65 patients were included in the analysis. Thirty-two patients received daptomycin as primary treatment, and 33 patients received linezolid as primary treatment. Twenty-six (76.5%) patients in the linezolid cohort versus 22 (71%) patients in the daptomycin cohort achieved microbiological cure (p = 0.6141). Median length of stay in days (30 vs. 42, p = 0.0714) and mortality (7/32 (20.6%) vs. 8/33 (25.8%), p = 0.6180) were also similar between the linezolid and daptomycin treated patients, respectively. CONCLUSION: No differences in microbiological cure, length of stay or mortality were identified between the groups. This study suggests that linezolid and daptomycin are each reasonable options for treating vancomycin-resistant Enterococcus bacteremia in oncology patients. Further prospective, randomized controlled trials are needed to assess the optimal treatment for vancomycin-resistant Enterococcus bacteremia in this patient population.

Persistence of vancomycin resistance in multiple clones of Enterococcus faecium isolated from Danish broilers 15 years after the ban of avoparcin.

The occurrence and diversity of vancomycin-resistant Enterococcus faecium (VREF) were investigated in 100 Danish broiler flocks 15 years after the avoparcin ban. VREF occurred in 47 flocks at low fecal concentrations detectable only by selective enrichment. Vancomycin resistance was prevalently associated with a transferable nontypeable plasmid lineage occurring in multiple E. faecium clones. Coselection of sequence type 842 by tetracycline use only partly explained the persistence of vancomycin resistance in the absence of detectable plasmid coresistance and toxin-antitoxin systems.

Antibiotic susceptibility survey of blood-borne MRSA isolates in Japan from 2008 through 2011.

We conducted an antibiotic susceptibility survey of 830 blood-borne methicillin resistant Staphylococcus aureus collected from nationwide hospitals in Japan over a three-year period from January 2008 through May 2011. Antibiotic susceptibility was judged according to the criteria recommended by the Clinical Laboratory Standard Institute. Over 99% of the MRSA showed to be susceptible to teicoplanin, linezolid, sulfamethoxazole/trimethoprim and vancomycin, and over 97% of them were susceptible to daptomycin, arbekacin and rifampin. The majority of the MRSA strains showed resistant to minocycline, meropenem, imipenem, clindamycin, ciprofloxacin, cefoxitin, and oxacillin in the rates of 56.6, 72.9, 73.7, 78.7, 89.0, 99.5, and 99.9%, respectively. Among the MRSA strains, 72 showed reduced susceptibility to vancomycin, including 8 strains (0.96%) of vancomycin-intermediate S. aureus (VISA), 54 (6.51%) of heterogeneous vancomycin-intermediate S. aureus (hVISA), and 55 (5.63%) of ß-lactam antibiotics-induced vancomycin resistant S. aureus (BIVR). Unexpectedly, among the 54 hVISA and 55 BIVR, 45 isolates (83.3% and 81.8%, respectively) showed both hVISA and BIVR phenotypes. A new trend of vancomycin resistance found in this study was that VISA strains were still prevalent among the bacteremic specimens. The high rates of the hVISA/BIVR two-phenotypic vancomycin resistance, and the prevalence of VISA in the bloodborne MRSA call attention in the MRSA epidemiology in Japan.

Structures of two new flavonoids and effects of licorice phenolics on vancomycin-resistant Enterococcus species.

Since our previous study revealed that several licorice phenolics have antibacterial effects on methicillin-resistant Staphylococcus aureus (MRSA), and suppressive effects on the oxacillin resistance of MRSA, we further investigated effectiveness of licorice constituents on vancomycin-resistant Enterococcus (VRE) bacteria, and purified 32 phenolic compounds. Two flavonoids among them were characterized structurally, and identified their structures as demethylglycyrol (31) and 5,7-di-O-methylluteone (32), respectively. Examination of antibacterial effects of licorice phenolics showed that 3-arylcoumarins such as licoarylcoumarin (9) and glycycoumarin (26), and 2-arylcoumarones such as gancaonin I (17), have moderate to potent antibacterial effects on the VRE strains used in this study.

Staphylococcus aureus with reduced susceptibility to vancomycin in healthcare settings.

Glycopeptide resistance in Staphylococcus aureus is a source of great concern because, especially in hospitals, this class of antibiotics, particularly vancomycin, is one of the main resources for combating infections caused by methicillin-resistant Staphylococcus aureus strains (MRSA). Reduced susceptibility to vancomycin (VISA) was first described in 1996 in Japan; since then, a phenotype with heterogeneous resistance to vancomycin (h-VISA) has emerged. H-VISA isolates are characterised by the presence of a resistant subpopulation, typically at a rate of 1 in 10(5) organisms, which constitutes the intermediate stage betweenfully vancomycin-susceptible S. aureus (VSSA) and VISA isolates. As VISA phenotypes are almost uniformly cross-resistant to teicoplanin, they are also called Glycopeptides-intermediate Staphylococcus aureus strains (GISA) and, in the case of heterogeneous resistance to glycopeptides, h-GISA. The overall prevalence of h-VISA is low, accounting for approximately 1.3% of all MRSA isolates tested. Mortality due to h-GISA infections is very high (about 70%), especially among patients hospitalised in high-risk departments, such as intensive care units (ICU). Given the great clinical relevance of strains that are heteroresistant to glycopeptides and the possible negative impact on treatment choices, it is important to draw up and implement infection control practices, including surveillance, the appropriate use of isolation precautions, staff training, hand hygiene, environmental cleansing and good antibiotic stewardship.

Activity of oritavancin against methicillin-resistant staphylococci, vancomycin-resistant enterococci and ß-haemolytic streptococci collected from western European countries in 2011.

OBJECTIVES: To determine the activity of oritavancin against methicillin-resistant staphylococci, vancomycin-resistant enterococci (VRE) and ß-haemolytic streptococci recently isolated from acute bacterial skin and skin structure infections or bacteraemia in western Europe. METHODS: Forty-one centres in Spain (8), Italy (9), Germany (8), France (8) and the UK (8) submitted 866 isolates [204 methicillin-resistant Staphylococcus aureus (MRSA), 177 methicillin-resistant coagulase-negative staphylococci (MRCoNS), 101 VRE, 193 Streptococcus agalactiae and 191 Streptococcus pyogenes] that were collected during the first 6 months of 2011. These were re-identified and susceptibilities to oritavancin and comparators were determined. RESULTS: Oritavancin was very active against MRSA (MIC(50)/MIC(90) 0.03/0.06 mg/L), MRCoNS (0.06/0.12 mg/L), VRE (0.03/0.06 mg/L), S. agalactiae (0.03/0.06 mg/L) and S. pyogenes (0.06/0.25 mg/L). The highest oritavancin MIC observed was 0.25 mg/L (species were S. aureus, Staphylococcus epidermidis, Staphylococcus hominis, S. agalactiae, S. pyogenes and Enterococcus faecalis). CONCLUSIONS: These data from recently collected Gram-positive bacteria in western Europe confirm the potent in vitro activity of oritavancin against a wide range of resistant MRSA, MRCoNS and VRE isolates, including ones resistant to newer agents.

Vancomycin therapeutics and monitoring: a contemporary approach.

Vancomycin remains a clinically useful antibiotic despite the advent of several alternative drugs. Optimising vancomycin therapy with therapeutic drug monitoring is widely recommended. The aim of therapeutic drug monitoring is to help the clinician to achieve target pharmacodynamic parameters in the case of vancomycin, an area under the concentration time curve/minimum inhibitory concentration ratio of ≥400. Vancomycin monitoring methods can be categorised into four categories: empiric trough concentrations; linear regression analysis (one-compartment model), population methods and Bayesian estimation procedures. Although the empiric trough concentrations and population methods are easy to use and require minimal resources, there are large differences in the published vancomycin model parameters. This demonstrates that there is great variance in pharmacokinetic parameters between the models and a single vancomycin model cannot be applied to all patient populations. The linear regression and Bayesian methods recommended more accurate dosage regimens; however, they require additional resources such as information technology and healthcare personnel with background training in pharmacokinetics. The Bayesian methods offered additional advantages such as calculation of doses based on a single-serum concentration and optimisation of the patient's previous pharmacokinetic data to determine subsequent dosage regimens. Computerised programs, utilising the Bayesian estimation procedures, are able to achieve target concentrations in a greater percentage of patients earlier in the course of therapy than the empiric trough concentrations and population methods. We recommend the use of these programs providing there is appropriate expertise available to make appropriate recommendations.

Identification of VanN-type vancomycin resistance in an Enterococcus faecium isolate from chicken meat in Japan.

Five VanN-type vancomycin-resistant Enterococcus faecium strains were isolated from a sample of domestic chicken meat in Japan. All isolates showed low-level resistance to vancomycin (MIC, 12 mg/liter) and had the same pulsed-field gel electrophoresis profile. The vancomycin resistance was encoded on a large plasmid (160 kbp) and was expressed constitutively. The VanN-type resistance operon was identical to the first resistance operon to be reported, with the exception of a 1-bp deletion in vanT(N) and a 1-bp substitution in vanS(N).

Methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci, and other Gram-positives in healthcare.

PURPOSE OF REVIEW: Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterocci (VRE) are the two most common healthcare-associated multidrug-resistant organisms. The purpose of this article is to review recent data regarding the epidemiology, control and treatment of these organisms as well as to discuss the emergence of additional antimicrobial resistance determinants. RECENT FINDINGS: Although the prevalence of methicillin resistance continues to increase among healthcare-associated S. aureus isolates, the incidence of invasive MRSA infections appears to be decreasing. Reduced susceptibility to vancomycin among MRSA isolates has been associated with glycopeptide treatment failure. Resistance to newer antimicrobial agents, such as daptomycin and linezolid, has been described among isolates of MRSA and VRE, further complicating treatment of infections caused by these organisms. Recent studies that have attempted to assess the efficacy of a variety of strategies for the prevention of MRSA and/or VRE transmission and infection, including active surveillance testing, have been published and additional studies are currently underway. SUMMARY: MRSA and VRE remain important causes of morbidity and mortality among patients receiving healthcare. The emergence of resistance to additional antimicrobial agents highlights the importance of effective prevention programs. Further study to determine the optimal approaches to treatment and prevention is needed.

Effect of Vancomycin on Cellular Fatty Acid Profiles of Vancomycin-Susceptible and Nonsusceptible Staphylococcus aureus.

Vancomycin is widely used for treatment of infection caused by methicillin-resistant Staphylococcus aureus (MRSA) leading to an increasing appearance of low-level vancomycin-resistant isolates called heterogeneous vancomycin-intermediate S. aureus (hVISA). The mechanism of vancomycin tolerance in hVISA is still unclear. This study aimed to investigate the fatty acid compositions of S. aureus isolates under the stress environment with vancomycin. The different responses of hVISA and vancomycin-susceptible S. aureus (VSSA) may lead to more understanding the mechanism. The bacterial lipid profiles were tested three times from three extractions of each isolate cultured on tryptic soy agar (TSA) and TSA with vancomycin. Of the 30 MRSA isolates studied, 13, 12, and 5 isolates were VSSA, hVISA, and VISA, respectively. The analysis of bacterial lipid profiles showed that under vancomycin stress, there was a reduction of straight chain fatty acids (SCFAs) in VSSA isolates but an increase in branched chain fatty acids (BCFAs). In contrast, the hVISA group exhibited an increase only in the BCFAs but not in SCFAs. Of interest, vancomycin had no effect on either BCFAs or SCFAs of the VISA cells. This study provided information of bacterial adaptation during stress with vancomycin that may be helpful to overcome the resistant bacteria.

Rapid depletion of free vancomycin in medium in the presence of beta-lactam antibiotics and growth restoration in Staphylococcus aureus strains with beta-lactam-induced vancomycin resistance.

A class of methicillin-resistant Staphylococcus aureus strains shows vancomycin resistance in the presence of beta-lactam antibiotics (beta-lactam-induced VAN-resistant methicillin-resistant S. aureus [BIVR]). Two possible explanations may be offered: (i) vancomycin in culture medium is depleted, and (ii) the D-Ala-D-Ala terminal of the peptidoglycan network is replaced with D-Ala-D-lactate. We tested these hypotheses by quantifying free vancomycin in the medium through the course of cell growth and by PCR amplification of the van genes. Growth of the BIVR cells to an absorption level of approximately 0.3 at 578 nm required about 24 h in the presence of vancomycin alone at the MIC (4.0 microg/ml). However, growth was achieved in only about 10 h when 1/1,000 to 1/2,000 the MIC of beta-lactam antibiotic was added 2 h prior to the addition of vancomycin, suggesting that the beta-lactams shortened the time to recovery from vancomycin-mediated growth inhibition. Free vancomycin in the culture medium decreased to 2.3 microg/ml in the first 8 h in the culture containing vancomycin alone, yet cell growth was undetectable. When the vancomycin concentration dropped below approximately 1.5 microg/ml at 24 h, the cells began to grow. In the culture supplemented with the beta-lactam 2 h prior to the addition of vancomycin, the drug concentration continuously dropped from 4 to 0.5 microg/ml in the first 8 h, and the cells began to grow at a vancomycin concentration of approximately 1.7 microg/ml or at 4 h of incubation. The gene encoding the enzyme involved in D-Ala-D-lactate synthesis was undetectable. Based on these results, we concluded that BIVR is attributable mainly to a rapid depletion of vancomycin in the medium triggered or promoted by beta-lactam antibiotics.

VanA-type Staphylococcus aureus strain VRSA-7 is partially dependent on vancomycin for growth.

VanA-type Staphylococcus aureus strain VRSA-7 was partially dependent on glycopeptides for growth. The vanA gene cluster, together with the erm(A) and the ant(9)-Ia resistance genes, was carried by the ca. 35- to 40-kb conjugative plasmid pIP848 present at five copies per cell. The chromosomal ddl gene had a mutation that led to a N308K substitution in the d-Ala:d-Ala ligase that resulted in a 1,000-fold decrease in activity relative to that of strain VRSA-6. Strain VRSA-7 grown in the absence or in the presence of vancomycin mainly synthesized precursors ending in d-Ala-d-Lac, indicating that the strain relied on the vancomycin resistance pathway for peptidoglycan synthesis. Greatly enhanced growth in the presence of glycopeptides and the absence of mutations in the genes for VanR and VanS indicated the inducible expression of resistance. Thus, a combination of loose regulation of the vanA operon by the two-component system and a gene dosage effect accounts for the partial glycopeptide dependence of VRSA-7. Since peptidoglycan precursors ending in D-Ala-D-Lac are not processed by PBP 2', the strain was fully susceptible to oxacillin, despite the production of a wild-type PBP 2'.

Successful use of intraperitoneal daptomycin in the treatment of vancomycin-resistant enterococcus peritonitis.

Peritoneal dialysis-associated peritonitis from such resistant organisms as vancomycin-resistant enterococci increasingly is occurring and is challenging to treat. We describe 2 cases of vancomycin-resistant entercoccus peritonitis successfully treated with intraperitoneal daptomycin. Both patients were on automated peritoneal dialysis therapy with culture-positive vancomycin-resistant Enterococcus faecium peritonitis and were treated with 10 to 14 days of intraperitoneal daptomycin given every 4 hours through manual peritoneal dialysate exchanges. Despite the known degradation in dextrose solutions, intraperitoneal daptomycin was effective in clearing both infections. Neither patient experienced a relapse or repeated peritonitis. Additional studies of dosing and pharmacokinetics of intraperitoneal daptomycin in the treatment of patients with vancomycin-resistant enterococcus peritonitis are needed.