Observed antagonistic effect of linezolid on daptomycin or vancomycin activity against biofilm-forming methicillin-resistant Staphylococcus aureus in an in vitro pharmacodynamic model

Pharmacodynamic activity in antibiotic combinations of daptomycin, vancomycin and linezolid was investigated in a 48h in vitro pharmacodynamic model. Using free human-simulated concentrations, activity against clinical biofilm-forming methicillin-resistant Staphylococcus aureus isolates was evaluated. Linezolid antagonized vancomycin activity at 24 and 48h. Linezolid antagonized daptomycin at 24 and 48h depending on dose and strain. Adding daptomycin increased vancomycin activity at 48h (P \u3c 0.03). These results may be strain dependent and require further clinical investigation

Comparison of Telavancin and Vancomycin Antibiotic Lock Solutions in the Eradication of Biofilm-Producing Staphylococci and Enterococci from Central Venous Catheters

Purpose: Results of a study of the activity of antibiotic lock solutions of vancomycin and telavancin against biofilm-forming strains of Staphylococcus epidermidis, Enterococcus faecalis, and Staphylococcus aureus are reported. Methods: An established in vitro central venous catheter model was used to evaluate lock solutions containing vancomycin (5 mg/mL) or telavancin (5 mg/mL), with and without preservative-containing heparin sodium (with 0.45% benzyl alcohol) 2500 units/mL, heparin, and 0.9% sodium chloride solution. Lock solutions were introduced after 24-hour bacterial growth in catheters incubated at 35 °C. After 72 hours of exposure to the lock solutions, catheters were drained, flushed, and cut into segments for quantification of colony-forming units. Results: Against S. epidermidis, vancomycin and telavancin (with or without heparin) had similar activity. Against E. faecalis, vancomycin alone was more active than telavancin alone (p \u3c 0.01). Against S. aureus, vancomycin plus heparin had activity than telavancin (p \u3c 0.02). The addition of heparin was associated with reduced activity of the vancomycin lock solution against S. epidermidis and E. faecalis (p \u3c 0.01). Telavancin activity was not significantly changed with the addition of heparin. Conclusion: In a central venous catheter model, vancomycin and telavancin activity was similar in reducing biofilm-producing S. epidermidis. However, vancomycin was more active than telavancin against E. faecalis and S. aureus. None of the tested agents eradicated biofilm-forming strains. The addition of preservative-containing heparin sodium 2500 units/mL to vancomycin was associated with reduced activity against S. epidermidis and E. faecalis

Activity of Daptomycin or Linezolid in Combination with Rifampin or Gentamicin Against Biofilm-Forming Enterococcus faecalis or E. faecium in an In Vitro Pharmacodynamic Model Using Simulated Endocardial Vegetations and an In Vivo Survival Assay Using Galleria mellonella Larvae

Enterococci are the third most frequent cause of infective endocarditis. A high-inoculum stationary-phase in vitro pharmacodynamic model with simulated endocardial vegetations was used to simulate the human pharmacokinetics of daptomycin at 6 or 10 mg/kg of body weight/day or linezolid at 600 mg every 12 h (q12h), alone or in combination with gentamicin at 1.3 mg/kg q12h or rifampin at 300 mg q8h or 900 mg q24h. Biofilm-forming, vancomycin-susceptible Enterococcus faecalis and vancomycin-resistant Enterococcus faecium (vancomycin-resistant enterococcus [VRE]) strains were tested. At 24, 48, and 72 h, all daptomycin-containing regimens demonstrated significantly more activity (decline in CFU/g) than any linezolid-containing regimen against biofilm-forming E. faecalis. The addition of gentamicin to daptomycin (at 6 or 10 mg/kg) in the first 24 h significantly improved bactericidal activity. In contrast, the addition of rifampin delayed the bactericidal activity of daptomycin against E. faecalis, and the addition of rifampin antagonized the activities of all regimens against VRE at 24 h. Also, against VRE, the addition of gentamicin to linezolid at 72 h improved activity and was bactericidal. Rifampin significantly antagonized the activity of linezolid against VRE at 72 h. In in vivo Galleria mellonella survival assays, linezolid and daptomycin improved survival. Daptomycin at 10 mg/kg improved survival significantly over that with linezolid against E. faecalis. The addition of gentamicin improved the efficacy of daptomycin against E. faecalis and those of linezolid and daptomycin against VRE. We conclude that in enterococcal infection models, daptomycin has more activity than linezolid alone. Against biofilm-forming E. faecalis, the addition of gentamicin in the first 24 h causes the most rapid decline in CFU/g. Of interest, the addition of rifampin decreased the activity of daptomycin against both E. faecalis and VRE

Ethanol and Isopropyl Alcohol Exposure Increases Biofilm Formation in Staphylococcus aureus and Staphylococcus epidermidis

Introduction Alcohols, including ethanol and isopropyl alcohol, are used in clinical practice for disinfection and infection prevention. Recent studies, however, demonstrate that alcohols may enhance biofilm production in Staphylococci. Methods We quantified biofilm formation in the presence of ethanol and isopropyl alcohol in six different, well-characterized strains of Staphylococcus epidermidis and Staphylococcus aureus. After 24 h of biofilm development, each strain was exposed to normal saline (NS), ethanol, or isopropyl alcohol (40%, 60%, 80% and 95%) for additional 24 h incubation. Adherent biofilms were stained and optical density was determined. Viability of strains was also determined after alcohol exposure. Results Ethanol increased biofilm formation in all six strains compared to normal saline (p \u3c 0.05). There was increased biofilm formation with increasing ethanol concentration. Isopropyl alcohol also increased biofilm formation with increasing alcohol concentration in all six strains (p \u3c 0.01 vs NS). The slime-negative, chemical mutant strain of S. epidermidis increased biofilm formation after exposure to both alcohols, likely reverting back its primary phenotype through modulation of the intercellular adhesin repressor. All strains demonstrated viability after exposure to each alcohol concentration, though viability was decreased. Conclusion Ethanol and isopropyl alcohol exposure increases biofilm formation of S. aureus and S. epidermidis at concentrations used in clinical settings. Ethanol and isopropyl alcohol did not eradicate viable Staphylococci from formed biofilm

699. Relationship Between Klebsiella pneumoniae Antimicrobial Resistance and Biofilm Formation

Background: Klebsiella pneumoniae is a frequently multidrug-resistant organism with a high propensity to form biofilm. K. pneumoniae is the most common carbapenem-resistant Enterobacteriaceae (CRE), and labeled an urgent threat by the CDC. The relationship between K. pneumoniae biofilm formation and specific antimicrobial resistance patterns has not been well defined. Methods: K. pneumoniae isolates (n = 139) were evaluated for antimicrobial resistance and biofilm formation (CDC, Providence VA Med. Ctr., Rhode Island Hosp., BEI, and ATCC). Susceptibility was based predominantly on 2017 CLSI (Clinical and Laboratory Standards Institute) breakpoints. Isolates were categorized as multidrug-resistant (MDR: resistant to ≥ 1 antimicrobial in ≥ 3 out of 16 antimicrobial categories) or extensively drug-resistant (XDR: resistant to ≥ 1 antimicrobial in all but ≤ 2 out of 16 antimicrobial categories) based on expert consensus criteria for Enterobacteriaceae (European CDC (ECDC)/CDC, 2012). We collapsed antimicrobial categories described by the ECDC/CDC consensus group into nine categories: penicillins, cephalosporins, monobactam, carbapenems, protein synthesis inhibitors, fluoroquinolones, folate pathway inhibitors, fosfomycin, and colistin. Biofilm formation was assessed using a modified crystal violet method (OD570) and defined by tertile cut-points. Antimicrobial resistance was compared for weak (n = 47) vs. strong (n = 46) biofilm formation by chi-square or Fisher’s exact test. Predictors of strong biofilm formation were identified using logistic regression. Results: MDR isolates were more common among weak (n = 46/47, 97.9%) vs. strong biofilm formers (n = 35/46, 76.1%; P = 0.002), whereas XDR was similar between groups (n = 12/47, 25.5% vs. n = 13/46, 28.3% P = 0.77). Resistance to penicillins, cephalosporins, monobactams, carbapenems, protein synthesis, or fluoroquinolones was more common among weak biofilm formers (P \u3c 0.05). Carbapenem resistance was inversely associated with strong biofilm formation (odds ratio 0.09; 95% confidence interval 0.02–0.33). Conclusion: Carbapenem-resistant K. pneumoniae was 91% less likely to form strong biofilm. Potential trade-off mechanisms between antimicrobial resistance and biofilm formation require further exploratio

Vancomycin plus piperacillin/tazobactam and acute kidney injury in adults: a systematic review and meta-analysis

Objectives: The objective of this systematic review and meta-analysis was to assess acute kidney injury with combination therapy of vancomycin plus piperacillin-tazobactam, in general, adult patients and in critically ill adults. Rates of acute kidney injury, time to acute kidney injury, and odds of acute kidney injury were compared with vancomycin monotherapy, vancomycin plus cefepime or carbapenem, or piperacillin-tazobactam monotherapy. Data Sources: Studies were identified by searching Pubmed, Embase, Web of Science, and Cochrane from inception to April 2017. Abstracts from selected conference proceedings were manually searched. Study Selection: Articles not in English, pediatric studies, and case reports were excluded. Data Extraction: Two authors independently extracted data on study methods, rates of acute kidney injury, and time to acute kidney injury. Effect estimates and 95% CIs were calculated using the random effects model in RevMan 5.3. Data Synthesis: Literature search identified 15 published studies and 17 conference abstracts with at least 24,799 patients. The overall occurrence rate of acute kidney injury was 16.7%, with 22.2% for vancomycin plus piperacillin-tazobactam and 12.9% for comparators. This yielded an overall number needed to harm of 11. Time to acute kidney injury was faster for vancomycin plus piperacillin-tazobactam than vancomycin plus cefepime or carbapenem, but not significantly (mean difference, –1.30; 95% CI, –3.00 to 0.41 d). The odds of acute kidney injury with vancomycin plus piperacillin-tazobactam were increased versus vancomycin monotherapy (odds ratio, 3.40; 95% CI, 2.57–4.50), versus vancomycin plus cefepime or carbapenem (odds ratio, 2.68; 95% CI, 1.83–3.91), and versus piperacillin-tazobactam monotherapy (odds ratio, 2.70; 95% CI, 1.97–3.69). In a small subanalysis of 968 critically ill patients, the odds of acute kidney injury were increased versus vancomycin monotherapy (odds ratio, 9.62; 95% CI, 4.48–20.68), but not significantly different for vancomycin plus cefepime or carbapenem (odds ratio, 1.43; 95% CI, 0.83–2.47) or piperacillin-tazobactam monotherapy (odds ratio, 1.35; 95% CI, 0.86–2.11). Conclusions: The combination of vancomycin plus piperacillin-tazobactam increased the odds of acute kidney injury over vancomycin monotherapy, vancomycin plus cefepime or carbapenem, and piperacillin-tazobactam monotherapy. Limited data in critically ill patients suggest the odds of acute kidney injury are increased versus vancomycin monotherapy, and mitigated versus the other comparators. Further research in the critically ill population is needed

Higher Daptomycin Dose Associated with Improved Survival in Methicillin-Resistant Staphylococcus aureus Bacteremia

Study Objective: Current guidelines recommend higher daptomycin doses than the daptomycin label dose of 6 mg/kg for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia; however, the evidence supporting this recommendation is from in vitro and case series studies. This study evaluated the comparative effectiveness of the daptomycin label dose versus higher daptomycin doses in patients with MRSA bacteremia. Design: Retrospective national cohort study. Setting: Veterans Affairs medical centers. Patients: A total of 371 adults with MRSA bacteremia who were admitted between 2002 and 2015 and treated initially with vancomycin within 24 hours of initial culture collection and then switched to daptomycin therapy within 7 days; 138 patients (37.2%) received daptomycin doses higher than the daptomycin label dose (7 mg/kg or greater), and 233 (62.8%) received the daptomycin label dose (6 mg/kg). Measurements and Main Results: Clinical outcomes were compared among those who received the daptomycin label dose and those who received the higher dose using propensity score–matched Cox proportional hazards regression models. To identify dose partitioning associated with optimal survival, classification and regression tree (CART) analysis was used among patients, controlling for confounding with a 30-day mortality disease risk score. Propensity score–matched 30-day mortality was 8.6% (6/70 patients) among the higher dose group versus 18.6% (13/70 patients) among the label dose group (hazard ratio 0.31, 95% confidence interval 0.10–0.94). No significant differences were observed in inpatient mortality, length of stay, 30-day readmission, or 30-day S. aureus reinfection between groups. CART analysis resulted in doses of 7 mg/kg or greater providing benefit only among patients with higher (more than 51%) predicted probabilities of 30-day mortality (p\u3c0.001). Conclusion: To our knowledge, this is the first comparative effectiveness study of daptomycin doses in patients with MRSA bacteremia. Survival benefits were observed with doses higher than the daptomycin label dose (7 mg/kg or greater) for the treatment of MRSA bacteremia. These data suggest that higher doses than the daptomycin label dose may be preferred over the label dose for improving clinical outcomes in patients with MRSA bacteremia

A Review of Combination Antimicrobial Therapy for Enterococcus Faecalis Bloodstream Infections and Infective Endocarditis

Enterococci, one of the most common causes of hospital-associated infections, are responsible for substantial morbidity and mortality. Enterococcus faecalis, the more common and virulent species, cause serious high-inoculum infections, namely infective endocarditis, that are associated with cardiac surgery and mortality rates that remained unchanged for the last 30 years. The best cure for these infections are observed with combination antibiotic therapy; however, optimal treatment has not been fully elucidated. It is the purpose of this review to highlight treatment options, their limitations, and provide direction for future investigative efforts to aid in the treatment of these severe infections. While ampicillin plus ceftriaxone has emerged as a preferred treatment option, mortality rates continue to be high, and from a safety standpoint, ceftriaxone, unlike other cephalosporins, promotes colonization with vancomycin resistant-enterococci due to high biliary concentrations. More research is needed to improve patient outcomes from this high mortality disease

Towards Precision Medicine: Therapeutic Drug Monitoring–Guided Dosing of Vancomycin and β-lactam Antibiotics to Maximize Effectiveness and Minimize Toxicity

Purpose The goal of this review is to explore the role of antimicrobial therapeutic drug monitoring (TDM), especially in critically ill, obese, and older adults, with a specific focus on β-lactams and vancomycin. Summary The continued rise of antimicrobial resistance prompts the need to optimize antimicrobial dosing. The aim of TDM is to individualize antimicrobial dosing to achieve antibiotic exposures associated with improved patient outcomes. Initially, TDM was developed to minimize adverse effects during use of narrow therapeutic index agents. Today, patient and organism complexity are expanding the need for precision dosing through TDM services. Alterations of pharmacokinetics and pharmacodynamics (PK/PD) in the critically ill, obese, and older adult populations, in conjunction with declining organism susceptibility, complicate attainment of therapeutic targets. Over the last decade, antimicrobial TDM has expanded with the emergence of literature supporting β-lactam TDM and a shift from monitoring vancomycin trough concentrations to monitoring of the ratio of area under the concentration (AUC) curve to minimum inhibitory concentration (MIC). PK/PD experts should be at the forefront of implementing precision dosing practices. Conclusion Precision dosing through TDM is expanding and is especially important in populations with altered PK/PD, including critically ill, obese, and older adults. Due to wide PK/PD variability in these populations, TDM is vital to maximize antimicrobial effectiveness and decrease adverse event rates. However, there is still a need for studies connecting TDM to patient outcomes. Providing patient-specific care through β-lactam TDM and transitioning to vancomycin AUC/MIC monitoring may be challenging, but with experts at the forefront of this initiative, PK-based optimization of antimicrobial therapy can be achieved

Weak biofilm formation among carbapenem-resistant Klebsiella pneumoniae

Biofilm formation of multidrug and extensively drug resistant Klebsiella pneumoniaeisolates is poorly understood. We investigated 139 diverse clinical K. pneumoniaeisolates that possess various resistance patterns to evaluate the relationship between biofilm formation and resistance. Antimicrobial resistance was compared among a diverse collection of weak versus strong biofilm-forming K. pneumoniae, and predictors of strong biofilm formation were identified. Multi-drug resistant isolates were more common among weak (97.9%) versus strong biofilm formers (76%; P = 0.002). Carbapenem-resistant K. pneumoniae were 91% less likely to form strong biofilm (odds ratio 0.09; 95% confidence interval 0.02–0.33). The statistically significant inverse relationship between biofilm formation and antibiotic resistance suggests that virulence may be a trade-off for survival