Vancomycin: a history

Natural Cyclic Peptides as an Attractive Modality for Therapeutics: A Mini Review

Peptides are important biomolecules which facilitate the understanding of complex biological processes, which in turn could be serendipitous biological targets for future drugs. They are classified as a unique therapeutic niche and will play an important role as fascinating agents in the pharmaceutical landscape. Until now, more than 40 cyclic peptide drugs are currently in the market, and approximately one new cyclopeptide drug enters the market annually on average. Interestingly, the majority of clinically approved cyclic peptides are derived from natural sources, such as peptide antibiotics and human peptide hormones. In this report, the importance of cyclic peptides is discussed, and their role in drug discovery as interesting therapeutic biomolecules will be highlighted. Recently isolated naturally occurring cyclic peptides from microorganisms, sponges, and other sources with a wide range of pharmacological properties are reviewed herein.

The impact of vancomycin trough concentrations on outcomes in non-deep seated infections: a retrospective cohort study

Background

Guidelines recommending vancomycin trough concentrations > 10 mg/L in non-deep seated infections are based on expert opinion. The objective of this study was to evaluate patients with non-deep seated infections treated with short-course vancomycin to determine whether there were differences in outcomes with trough concentrations of ≤10 mg/L (low) versus > 10 mg/L (high).

Methods

A retrospective cohort study of patients hospitalized between March 10, 2010 and December 31, 2015 who received ≤14 days of vancomycin to treat a non-deep seated infection and had at least one steady state trough concentration was completed. Patient data for the low versus high trough cohorts were compared using appropriate statistical tests and binary logistic regression was used to identify factors associated with clinical outcome.

Results

Of 2098 patients screened, 103 (5%) met inclusion criteria. Baseline characteristics between cohorts were not different. Clinical cure was not different between the low (42/48 [88%]) and high trough (48/55 [87%]) cohorts (p > 0.99) and vancomycin trough concentration was not associated with clinical outcome (p = 0.973). More patients in the high trough group had dosing changes (7/48 [15%] vs. 22/55 [40%], p = 0.0046), with approximately three times more dose adjustments per patient (0.17 vs. 0.55, p = 0.0193). No signal for increased vancomycin resistance associated with vancomycin troughs was identified.

Conclusions:

No difference in clinical or microbiological outcomes based on vancomycin trough concentrations were observed in patients with non-deep seated infections treated with vancomycin for ≤14 days. Targeting higher vancomycin trough concentrations of > 10 mg/L may be associated with increased workload with no corresponding benefit in clinical or microbiological outcomes in these patients.

Different formulations of vancomycin: In vitro antimicrobial activity against clinical isolates of methicillin-resistant Staphylococcus aureus

We compared in vitro antimicrobial activity of four vancomycin formulations used clinically against clinical isolates of Staphylococcus aureus, including methicillin-resistant and -susceptible (MRSA and MSSA, respectively), using different susceptibility assays. The minimal inhibitory concentrations (MICs) against MRSA clinical isolates were significantly different for some vancomycin formulations by the broth microdilution and agar dilution methods. However, these variations would not compromise their clinical use, since the MICs were within the range recommended by the Clinical and Laboratory Standards Institute. Furthermore, 26.9% of MRSA clinical isolates showed a vancomycin MIC ≥1.5 μg/mL according to the Etest® method but none by broth microdilution. Regarding quality, all formulations were in accordance with United States Pharmacopeia criteria. Our results showed that all vancomycin formulations tested showed similar in vitro antimicrobial activity, making them suitable for clinical use, and that the evaluation method chosen to determine sensitivity to this antimicrobial should be carefully performed, particularly for MRSA.

Nephrotoxicity With Vancomycin in the Pediatric Population: A Systematic Review and Meta-Analysis

BACKGROUND

Vancomycin is frequently used to treat methicillin-resistant Staphylococcus aureus infections in pediatric patients. Vancomycin exposure may lead to an increase in frequency of nephrotoxicity. Our aim was to conduct a systematic review to describe predictors of nephrotoxicity associated with vancomycin, including documented trough concentrations ≥15 mg/L. We also aimed to use a meta-analysis to assess the impact of a vancomycin trough ≥15 mg/L on nephrotoxicity.

METHODS

A literature search was performed using PubMed, Cochrane Library, Embase and Web of Sciences database. We included randomized clinical trials and observational studies evaluating the relationship between vancomycin troughs and nephrotoxicity in pediatric-age patients. Studies not measuring troughs or defining a different cut-off point than 15 mg/L were excluded. Data on age, exclusion criteria, nephrotoxicity definition, risk factors for nephrotoxicity and vancomycin trough levels were extracted from selected papers.

RESULTS

Ten studies were identified for meta-analysis. All subjects had comparatively normal baseline serum creatinine values. Common risk factors identified included elevated (≥15 mg/L) trough levels, renal impairment, hypovolemia and concurrent use of nephrotoxic medications. Troughs ≥15 mg/L increased nephrotoxicity by 2.7-fold (odds ratio (OR), 2.71; 95% confidence interval: 1.82-4.05; I(2) = 40%; Q = 0.09). These odds were further increased among patients in the pediatric intensive care unit (OR, 3.61; 95% confidence interval: 1.21-10.74; I(2) = 45%; Q = 0.18).

CONCLUSIONS

Though the rate of vancomycin-induced nephrotoxicity is increased in pediatric patients with higher vancomycin troughs, other factors such as intensive care unit admission, hypovolemia and concurrent nephrotoxic drug use appear to contribute to the development of nephrotoxicity.

Penetration of Vancomycin into the Cerebrospinal Fluid: A Systematic Review

INTRODUCTION

Infectious disease and pharmacokinetic textbooks indicate that vancomycin has poor penetration into the central nervous system due to its hydrophilic nature and high molecular weight. Recent literature suggests that penetration of vancomycin into cerebrospinal fluid (CSF) is higher than previously reported; therefore, we conducted a systematic review to assess the penetration of vancomycin into CSF.

METHODS

We searched the MEDLINE, EMBASE, and CENTRAL electronic databases for English-language human studies evaluating serum and CSF concentrations of intravenous vancomycin.

RESULTS

In 13 identified studies, the CSF-to-serum ratio of vancomycin varied from 0.00 to 0.81. CSF penetration ranged 0.06-0.81 in patients with meningitis, 0.05-0.17 in ventriculitis, 0.00-0.36 in other infections, and 0-0.13 in patients without infection. Despite variable CSF penetration, 83% of patients with meningitis and 100% of patients with ventriculitis achieved clinical cure. No factor predicted vancomycin CSF penetration.

CONCLUSION

Contrary to prior belief, studies included in our review did not show universally low penetration of vancomycin into CSF. CSF vancomycin levels were variable and did not predict clinical cure.

Antimicrobial Resistance and Respiratory Infections

Since their introduction into health care and clinical practice in the early 20th century, antibiotics have revolutionized medicine. Alarmingly, these drugs are increasingly threatened by bacteria that have developed a broad diversity of resistance mechanisms. Antibiotic resistance can be transferred between bacteria, often on mobile genetic elements; be acquired from the environment; or arise through mutation because of selective pressures of the drugs themselves. There are various strategies to resistance, including active efflux of the drug from the bacterial cell, reduced permeability of the cell envelope, alteration of the drug's target within the bacterial cell, and modification or destruction of the antibiotic. Streptococcus pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, and Mycobacterium tuberculosis frequently are implicated in respiratory infections, often manifesting with reduced susceptibility to multiple classes of antibiotics. Some mechanisms of resistance, such as the β-lactamases that confer resistance to penicillins and related drugs, have been well characterized and are widespread in clinical isolates. Other newly identified determinants, including the colistin resistance gene mcr-1, are spreading rapidly worldwide and threaten last-resort treatments of multidrug-resistant organisms. Various approaches to detecting antibiotic resistance provide surveys of the determinants that are available for transfer into pathogenic bacteria. Together with molecular characterization of newly identified mechanisms, this surveillance can target drug discovery efforts and increase antibiotic stewardship. A greater understanding of the mechanisms of antibiotic resistance in respiratory pathogens combined with rapid diagnostics ultimately will reduce treatment failure due to inappropriate antibiotic use and prevent further spread of resistance.

Risk factors for recurrence in patients with Clostridium difficile infection due to 027 and non-027 ribotypes

OBJECTIVES

Our objective was to evaluate factors associated with recurrence in patients with 027+ and 027- Clostridium difficile infection (CDI).

METHODS

Patients with CDI observed between January and December 2014 in six hospitals were consecutively included in the study. The 027 ribotype was deduced by the presence of tcdB, tcdB, cdt genes and the deletion Δ117 in tcdC (Xpert® C. difficile/Epi). Recurrence was defined as a positive laboratory test result for C. difficile more than 14 days but within 8 weeks after the initial diagnosis date with reappearance of symptoms. To identify factors associated with recurrence in 027+ and 027- CDI, a multivariate analysis was performed in each patient group. Subdistributional hazard ratios (sHRs) and 95% confidence intervals (95%CIs) were calculated.

RESULTS

Overall, 238 patients with 027+ CDI and 267 with 027- CDI were analysed. On multivariate analysis metronidazole monotherapy (sHR 2.380, 95%CI 1.549-3.60, p <0.001) and immunosuppressive treatment (sHR 3.116, 95%CI 1.906-5.090, p <0.001) were factors associated with recurrence in patients with 027+ CDI. In this patient group, metronidazole monotherapy was independently associated with recurrence in both mild/moderate (sHR 1.894, 95%CI 1.051-3.410, p 0.033) and severe CDI (sHR 2.476, 95%CI 1.281-4.790, p 0.007). Conversely, non-severe disease (sHR 3.704, 95%CI 1.437-9.524, p 0.007) and absence of chronic renal failure (sHR 16.129, 95%CI 2.155-125.000, p 0.007) were associated with recurrence in 027- CDI.

CONCLUSIONS

Compared to vancomycin, metronidazole monotherapy appears less effective in curing CDI without relapse in the 027+ patient group, independently of disease severity.

Assessing Vancomycin Dosing Per Pharmacy in Elderly Patients Over the Age of 74 Years

Vancomycin has a complex pharmacokinetic profile and carries potential risks for nephrotoxicity and ototoxicity. The pharmacokinetic profile in elderly patients significantly differs from that of younger patients. It is common practice in many institutions for pharmacists to intentionally round serum creatinine levels to 1 mg/dl in elderly patients with levels <1 mg/dl to avoid overestimating clearance and toxicities. This can potentially lead to underestimation of creatinine clearance, and subsequently lead to vancomycin under dosing. The aim of this study was to evaluate vancomycin target trough attainment and the time to trough attainment with vancomycin dosing per pharmacy in elderly patients. Methods In this retrospective study, patients 75 years and older who received vancomycin at our institution were evaluated. Subjects were included in the study if they were at least 75 years of age, received intravenous vancomycin therapy, and had a vancomycin trough drawn after the third dose. The study patients were divided into three serum creatinine groups; <0.8 mg/dl (LSCr), 0.8–0.9 mg/dl (MSCr), and ≥1 mg/dl (HSCr). Patients were excluded from the study if they did not meet inclusion criteria, had no trough levels drawn, or were <75 years of age. Results Two hundred and four patients 75 years or older were included in the study. The target trough attainment was highest in the HSCr group (n = 37, 80%), which was significantly higher than the LSCr (n=21, 31%; p<0.0001) and MSCr (n=42, 46%; p<0.0001) groups. The time to target trough goals (days, mean ± SD) differed between the three groups, with the LSCr group taking the longest duration: LSCr: 5.14 ± 2.5; MSCr: 3.74 ± 1.1; HSCr: 3.78 ± 1.6, p=0.005. Conclusion Adjustments need to be done to improve vancomycin dosing per pharmacy in patients 75 years of age and older. This study shows that LSCr patients (<0.8 mg/dl) had the lowest rates of target trough level attainment. Intentionally rounding serum creatinine to 1 mg/dl if values are less when estimating renal function in this older patient population may not be predictive of true renal function and can decrease the likelihood of target attainment or increase time to target attainment.

Developments in Glycopeptide Antibiotics

Glycopeptide antibiotics (GPAs) are a key weapon in the fight against drug resistant bacteria, with vancomycin still a mainstream therapy against serious Gram-positive infections more than 50 years after it was first introduced. New, more potent semisynthetic derivatives that have entered the clinic, such as dalbavancin and oritavancin, have superior pharmacokinetic and target engagement profiles that enable successful treatment of vancomycin-resistant infections. In the face of resistance development, with multidrug resistant (MDR) S. pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) together causing 20-fold more infections than all MDR Gram-negative infections combined, further improvements are desirable to ensure the Gram-positive armamentarium is adequately maintained for future generations. A range of modified glycopeptides has been generated in the past decade via total syntheses, semisynthetic modifications of natural products, or biological engineering. Several of these have undergone extensive characterization with demonstrated in vivo efficacy, good PK/PD profiles, and no reported preclinical toxicity; some may be suitable for formal preclinical development. The natural product monobactam, cephalosporin, and β-lactam antibiotics all spawned multiple generations of commercially and clinically successful semisynthetic derivatives. Similarly, next-generation glycopeptides are now technically well positioned to advance to the clinic, if sufficient funding and market support returns to antibiotic development.

Actinobacteria-Derived peptide antibiotics since 2000

Members of the Actinobacteria, including Streptomyces spp., Kutzneria sp. Actinoplanes spp., Actinomycete sp., Nocardia sp., Brevibacteriumsp.,Actinomadura spp., Micromonospora sp., Amycolatopsis spp., Nonomuraea spp., Nocardiopsis spp., Marinactinospora sp., Rhodococcus sp., Lentzea sp., Actinokineospora sp., Planomonospora sp., Streptomonospora sp., and Microbacterium sp., are an important source of structurally diverse classes of short peptides of ∼30 residues or fewer that will likely play an important role in new antibiotic development and discovery. Additionally, many have unique structures that make them recalcitrant to traditional modes of drug resistance via novel mechanisms, and these are ideal therapeutic tools and potential alternatives to current antibiotics. The need for novel antibiotic is urgent, and this review summarizes 199 Actinobacteria compounds published since 2000, including 35 cyclic lipopeptides containing piperazic or pipecolic acids, eight aromatic peptides, five glycopeptides, 21 bicyclic peptides, 44 other cyclic lipopeptides, five linear lipopeptides, six 2,5-diketopiperazines, one dimeric peptide, four nucleosidyl peptides, two thioamide-containing peptides, 25 thiopeptides, nine lasso peptides, and 34 typical cyclic peptides. The current and potential therapeutic applications of these peptides, including their structure, antituberculotic, antibacterial, antifungal, antiviral, anti-brugia, anti-plasmodial, and anti-trypanosomal activities, are discussed.

Ceftaroline fosamil laden allograft: A new modality in reducing infection?

PURPOSE

Allograft infection remains the greatest challenge in orthopaedic reconstructive surgery especially methicillin-resistant Staphylococcus aureus (MRSA). This risk can be minimized with the use of antibiotic laden allograft (ALA) via iontophoresis. Ceftaroline fosamil (CF) is an advanced-generation cephalosporin, an alternative treatment for MRSA infections. Its antibacterial activity and safety profile are better than vancomycin. CF iontophoresed bone has not been used before. This study was conducted to establish the feasibility of creating a CF ALA and establish the prime conditions for its expenditure.

METHOD

We created an iontophoresis cell; 3% CF was inserted within medullary segment of goat bone and sealed from external saline solution. The cell operated at the following voltages 30, 60 and 90 V and at the following durations 5, 10, 15, 20, 25 and 30 min. Information regarding optimal conditions for its application was then obtained. After which, correlation between voltages and time with CF concentration in the bone was analysed. A bioavailability test was also conducted to observe the optimal rate of CF elution from the graft.

RESULT

The optimal condition for the impregnation process is 3% CF at 90 V for 10 min. Bone graft impregnated with CF at optimal conditions can elute above minimum inhibitory concentration of the CF against MRSA for 21 days.

CONCLUSION

CF iontophoresis was found feasible for allograft impregnation. The technique is simple, inexpensive and reproducible clinically. Iontophoresis offers a novel solution to reduce the rate of perioperative infection in reconstructive surgery involving use of bone graft.

Population Pharmacokinetic Model for Vancomycin Used in Open Heart Surgery: Model-Based Evaluation of Standard Dosing Regimens

The purpose of this study was to investigate the population pharmacokinetics of vancomycin in patients undergoing open heart surgery. In this observational pharmacokinetic study, multiple blood samples were drawn over a 48-h period of intravenous vancomycin in patients who were undergoing open heart surgery. Blood samples were analyzed using an Architect i4000SR immunoassay analyzer. Population pharmacokinetic models were developed using Monolix 4.4 software. Pharmacokinetic-pharmacodynamic (PK-PD) simulations were performed to explore the ability of different dosage regimens to achieve the pharmacodynamic targets. A total of 168 blood samples were analyzed from 28 patients. The pharmacokinetics of vancomycin are best described by a two-compartment model with between-subject variability in clearance (CL), the volume of distribution of the central compartment (V₁), and volume of distribution of the peripheral compartment (V₂). The CL and the V₁ of vancomycin were related to creatinine CL (CL_CR), body weight, and albumin concentration. Dosing simulations showed that standard dosing regimens of 1 and 1.5 g failed to achieve the PK-PD target of AUC_0-24/MIC > 400 for an MIC of 1 mg/liter, while high weight-based dosing regimens were able to achieve the PK-PD target. In summary, the administration of standard doses of 1 and 1.5 g of vancomycin two times daily provided inadequate antibiotic prophylaxis in patients undergoing open heart surgery. The same findings were obtained when 15- and 20-mg/kg doses of vancomycin were administered. Achieving the PK-PD target required higher doses (25 and 30 mg/kg) of vancomycin.

A Rapid and Simple HPLC Method for Therapeutic Monitoring of Vancomycin

Therapeutic monitoring of the antibiotic vancomycin is important to achieve specific plasma concentration and prevent toxic effects. Several assays have been described for vancomycin determination in clinical practice, but high-performance liquid chromatography is still considered the gold standard for the quantification of vancomycin. In this study, we developed a new and rapid high-performance liquid chromatography method requiring 50 μL of plasma for the quantification of vancomycin. Acetonitrile was used for processing plasma by protein precipitation (1:2.5). Isocratic chromatographic analysis was carried out on a C18 silica-based (2.7 μm) column with the mobile phase containing 20 mM ammonium acetate/formic acid buffer (pH 4.0):methanol 88:12 (v/v). A diode array detector was used for UV detection at 240 nm. This method was validated according to the Brazilian Health Surveillance Agency legislation and International Conference on Harmonization guidelines. The measurement range was 1-100 μg/mL, analysis time was 8 min, and intermediate precision was <12%, supporting the present method as a fast, simple, and effective alternative for therapeutic monitoring of vancomycin.

The Relationship Between Vancomycin Trough Concentrations and AUC/MIC Ratios in Pediatric Patients: A Qualitative Systematic Review

BACKGROUND

In adults, the area under the concentration-time curve (AUC) divided by the minimum inhibitory concentration (MIC) is associated with better clinical and bacteriological response to vancomycin in patients with methicillin-resistant Staphylococcus aureus who achieve target AUC/MIC ≥ 400. This target is often extrapolated to pediatric patients despite the lack of similar evidence. The impracticalities of calculating the AUC in practice means vancomycin trough concentrations are used to predict the AUC/MIC.

OBJECTIVE

This review aimed to determine the relationship between vancomycin trough concentrations and AUC/MIC in pediatric patients.

METHODS

We searched the MEDLINE and Embase databases, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials using the medical subject heading (MeSH) terms vancomycin and AUC and pediatric* or paediatric*. Articles were included if they were published in English and reported a relationship between vancomycin trough concentrations and AUC/MIC.

RESULTS

Of 122 articles retrieved, 11 met the inclusion criteria. One trial reported a relationship between vancomycin trough concentrations, AUC/MIC, and clinical outcomes but was likely underpowered. Five studies found troughs 6-10 mg/l were sufficient to attain an AUC/MIC > 400 in most general hospitalized pediatric patients. One study in patients undergoing cardiothoracic surgery found a trough of 18.4 mg/l achieved an AUC/MIC > 400. Two oncology studies reported troughs ≥ 15 mg/l likely attained an AUC/MIC ≥ 400. In critical care patients: one study found a trough of 9 mg/l did not attain the AUC/MIC target; another found 7 mg/l corresponded to an AUC/MIC of 400.

CONCLUSIONS

Potential vancomycin targets varied based on the population studied but, for general hospitalized pediatric patients, troughs of 6-10 mg/l are likely sufficient to achieve AUC/MIC ≥ 400. For MIC ≥ 2 mg/l, higher troughs are likely necessary to achieve an AUC/MIC ≥ 400. More research is needed to determine the relationships between vancomycin trough concentrations, AUC/MIC, and clinical outcomes.

Antimicrobial resistance (AMR) nanomachines-mechanisms for fluoroquinolone and glycopeptide recognition, efflux and/or deactivation

In this review, we discuss mechanisms of resistance identified in bacterial agents Staphylococcus aureus and the enterococci towards two priority classes of antibiotics-the fluoroquinolones and the glycopeptides. Members of both classes interact with a number of components in the cells of these bacteria, so the cellular targets are also considered. Fluoroquinolone resistance mechanisms include efflux pumps (MepA, NorA, NorB, NorC, MdeA, LmrS or SdrM in S. aureus and EfmA or EfrAB in the enterococci) for removal of fluoroquinolone from the intracellular environment of bacterial cells and/or protection of the gyrase and topoisomerase IV target sites in Enterococcus faecalis by Qnr-like proteins. Expression of efflux systems is regulated by GntR-like (S. aureus NorG), MarR-like (MgrA, MepR) regulators or a two-component signal transduction system (TCS) (S. aureus ArlSR). Resistance to the glycopeptide antibiotic teicoplanin occurs via efflux regulated by the TcaR regulator in S. aureus. Resistance to vancomycin occurs through modification of the D-Ala-D-Ala target in the cell wall peptidoglycan and removal of high affinity precursors, or by target protection via cell wall thickening. Of the six Van resistance types (VanA-E, VanG), the VanA resistance type is considered in this review, including its regulation by the VanSR TCS. We describe the recent application of biophysical approaches such as the hydrodynamic technique of analytical ultracentrifugation and circular dichroism spectroscopy to identify the possible molecular effector of the VanS receptor that activates expression of the Van resistance genes; both approaches demonstrated that vancomycin interacts with VanS, suggesting that vancomycin itself (or vancomycin with an accessory factor) may be an effector of vancomycin resistance. With 16 and 19 proteins or protein complexes involved in fluoroquinolone and glycopeptide resistances, respectively, and the complexities of bacterial sensing mechanisms that trigger and regulate a wide variety of possible resistance mechanisms, we propose that these antimicrobial resistance mechanisms might be considered complex 'nanomachines' that drive survival of bacterial cells in antibiotic environments.

Biopsy-proven vancomycin-induced acute kidney injury: a case report and literature review

Background

Vancomycin is the first-line antibiotic for methicillin-resistant Staphylococcus aureus and coagulase-negative strains. The risk of vancomycin-induced acute kidney injury increases with plasma vancomycin levels. Vancomycin-induced acute kidney injury is histologically characterized by acute interstitial nephritis and/or acute tubular necrosis. However, only 12 biopsy-proven cases of vancomycin-induced acute kidney injury have been reported so far, as renal biopsy is rarely performed for such cases. Current recommendations for the prevention or treatment of vancomycin-induced acute kidney injury are drug monitoring of plasma vancomycin levels using trough level and drug withdrawal. Oral prednisone and high-flux haemodialysis have led to the successful recovery of renal function in some biopsy-proven cases.

Case presentation

We present the case of a 41-year-old man with type 1 diabetes mellitus, who developed vancomycin-induced acute kidney injury during treatment for Fournier gangrene. His serum creatinine level increased to 1020.1 μmol/L from a baseline of 79.6 μmol/L, and his plasma trough level of vancomycin peaked at 80.48 μg/mL. Vancomycin discontinuation and frequent haemodialysis with high-flux membrane were immediately performed following diagnosis. Renal biopsy showed acute tubular necrosis and focal acute interstitial nephritis, mainly in the medullary rays (medullary ray injury). There was no sign of glomerulonephritis, but mild diabetic changes were detected. He was discharged without continuing haemodialysis (serum creatinine level, 145.0 μmol/L) 49 days after initial vancomycin administration.

Conclusions

This case suggests that frequent haemodialysis and renal biopsy could be useful for the treatment and assessment of vancomycin-induced acute kidney injury, particularly in high-risk cases or patients with other renal disorders.

The Utility of Vancomycin Powder in Reducing Surgical Site Infections in Deep Brain Stimulation Surgery

BACKGROUND

The impact of vancomycin powder on reducing postoperative surgical site infections (SSIs) in spine surgery has been studied extensively and is considered standard of care at many institutions. More recently, vancomycin powder has been shown to reduce SSI in cranial neurosurgery; however, limited studies have been performed assessing its impact in reducing SSIs in deep brain stimulation (DBS) surgery.

OBJECTIVE

To investigate the use of vancomycin powder as an adjunct to the current antibiotic prophylaxis regimen in DBS surgery in a large cohort of patients.

METHODS

All patients undergoing DBS-lead implantation surgery and chest generator placement or exchange were analyzed prior to and after the implementation of intrawound vancomycin powder, and the impact on infection rate and any complications were subsequently examined.

RESULTS

From 2015 to 2017, a total of 419 consecutive patients (159 in the pretreatment group, 260 in the post-treatment group) were included in the study. The rate of SSI prior to implementation of intrawound vancomycin was 3.1% (n = 5), which was reduced to 0.38% (n = 1) in the post-treatment group. No complications were noted as a direct result of using vancomycin powder.

CONCLUSION

Given its relatively low cost and side effect profile, the use of vancomycin powder may be an effective adjunct in reducing the rate of SSI in DBS surgery.

Time-of-flight secondary ion mass spectrometry analyses of vancomycin

As an antibiotic that prevents and treats infections caused by Gram-positive bacteria such as Staphylococcus aureus, vancomycin incorporated in a biodegradable polymer poly(lactide-co-glycolide) provides opportunities to construct controlled-release drug delivery systems. Developments associated with this promising system have been largely concentrated on areas of drug delivery kinetics and biodegradability. In order to provide surface analytical approaches to this important system, the authors demonstrate applicability of time-of-flight secondary ion mass spectrometry (TOF-SIMS) in three-dimensional molecular imaging for a model system consisting of alternating layers of ploy(lactide-co-glycolide) and vancomycin. TOF-SIMS imaging clarified that the two chemicals can undergo phase separation when dimethyl sulfoxide is used as the solvent. The authors identified two diagnostic ions that are abundant and structural moieties of vancomycin. The results on TOF-SIMS imaging and depth profiling vancomycin provide useful information for further applications of TOF-SIMS in the development of antibiotic drug delivery systems involving the use of vancomycin.

Analogues ofPseudomonas aeruginosasignalling molecules to tackle infections

The emergence of antibiotic resistance coupled with the lack of investment by pharmaceutical companies necessitates a new look at how we tackle bacterial infections.

Topical Vancomycin Reduces Surgical-Site Infections After Craniotomy: A Prospective, Controlled Study

BACKGROUND

Surgical-site infections (SSIs) are an important cause of morbidity and mortality in neurosurgical patients. Topical antibiotics are one potential method to reduce the incidence of these infections.

OBJECTIVE

To examine the efficacy of topical vancomycin applied within the wound during craniotomy in a large prospective cohort study at a major academic center.

METHODS

Three hundred fifty-five patients were studied prospectively in this cohort study; 205 patients received 1 g of topical vancomycin powder in the subgaleal space while 150 matched control patients did not. Patients otherwise received identical care. The primary outcome variable was SSI rate factored by cohort. Secondary analysis examined cost savings from vancomycin usage estimated from hospital costs associated with SSI in craniotomy patients.

RESULTS

The addition of topical vancomycin was associated with a significantly lower rate of SSI than standard of care alone (0.49% [1/205] vs 6% [9/150], P = .002). Based on the costs of revision surgery for infections, topical vancomycin usage was estimated to save $1367 446 per 1000 craniotomy patients. No adverse reactions occurred.

CONCLUSION

Topical vancomycin is a safe, effective, and cost-saving measure to prevent SSIs following craniotomy. These results have broad implications for standard of care in craniotomy.

A Strategy for Dosing Vancomycin to Therapeutic Targets Using Only Trough Concentrations

Effective treatment of complicated methicillin-resistant Staphylococcus aureus (MRSA) infections with vancomycin requires a 24-h area under the concentration-time curve (AUC₂₄) to minimum inhibitory concentration (MIC) ratio of at least 400. To ensure goal AUC₂₄ has been reached requires either dosing to concentrations strongly associated with nephrotoxicity, measurement of patient-specific pharmacokinetics, or use of Bayesian statistics. In this study, we show a method of determining patient-specific pharmacokinetics and dosing to therapeutic AUC₂₄ while minimizing potentially toxic concentrations, guided by only trough measurements. A Monte-Carlo simulation of 10,000 patients with complicated MRSA infections was prepared from two-compartment pharmacokinetic parameters using patient data extracted from the literature. The proposed method of determining patient-specific pharmacokinetics using consecutive trough concentrations was found to be more accurate than the conventional peak-trough method for peaks measured up to 4 h after infusion. Simulated human error in trough timing was found to reduce accuracy of the consecutive trough method, but an approach to resolve timing errors during a loading sequence or at steady-state using iteration is proposed. Both the simulated minimized concentration strategy and trough-based dosing to 15-20 mg/L had a high probability of achieving AUC₂₄ at least 400 mg·h/L, but conventional trough-based dosing was associated with higher probability of potentially toxic 24-h doses and trough concentrations. The proposed strategy must be validated in real patients, with outcomes assessed before it is used in daily practice, but the theoretical benefits found in the simulation suggest this simple strategy should be considered with other AUC₂₄-based approaches.

Overcoming antibiotic resistance: Is siderophore Trojan horse conjugation an answer to evolving resistance in microbial pathogens?

Comparative study of siderophore biosynthesis pathway in pathogens provides potential targets for antibiotics and host drug delivery as a part of computationally feasible microbial therapy. Iron acquisition using siderophore models is an essential and well established model in all microorganisms and microbial infections a known to cause great havoc to both plant and animal. Rapid development of antibiotic resistance in bacterial as well as fungal pathogens has drawn us at a verge where one has to get rid of the traditional way of obstructing pathogen using single or multiple antibiotic/chemical inhibitors or drugs. 'Trojan horse' strategy is an answer to this imperative call where antibiotic are by far sneaked into the pathogenic cell via the siderophore receptors at cell and outer membrane. This antibiotic once gets inside, generates a 'black hole' scenario within the opportunistic pathogens via iron scarcity. For pathogens whose siderophore are not compatible to smuggle drug due to their complex conformation and stiff valence bonds, there is another approach. By means of the siderophore biosynthesis pathways, potential targets for inhibition of these siderophores in pathogenic bacteria could be achieved and thus control pathogenic virulence. Method to design artificial exogenous siderophores for pathogens that would compete and succeed the battle of intake is also covered with this review. These manipulated siderophore would enter pathogenic cell like any other siderophore but will not disperse iron due to which iron inadequacy and hence pathogens control be accomplished. The aim of this review is to offer strategies to overcome the microbial infections/pathogens using siderophore.

Natural Products as Platforms To Overcome Antibiotic Resistance

Natural products have served as powerful therapeutics against pathogenic bacteria since the golden age of antibiotics of the mid-20th century. However, the increasing frequency of antibiotic-resistant infections clearly demonstrates that new antibiotics are critical for modern medicine. Because combinatorial approaches have not yielded effective drugs, we propose that the development of new antibiotics around proven natural scaffolds is the best short-term solution to the rising crisis of antibiotic resistance. We analyze herein synthetic approaches aiming to reengineer natural products into potent antibiotics. Furthermore, we discuss approaches in modulating quorum sensing and biofilm formation as a nonlethal method, as well as narrow-spectrum pathogen-specific antibiotics, which are of interest given new insights into the implications of disrupting the microbiome.

Full hydrodynamic reversibility of the weak dimerization of vancomycin and elucidation of its interaction with VanS monomers at clinical concentration

The reversibility and strength of the previously established dimerization of the important glycopeptide antibiotic vancomycin in four different aqueous solvents (including a medically-used formulation) have been studied using short-column sedimentation equilibrium in the analytical ultracentrifuge and model-independent SEDFIT-MSTAR analysis across a range of loading concentrations. The change in the weight average molar mass M w with loading concentration was consistent with a monomer-dimer equilibrium. Overlap of data sets of point weight average molar masses M w(r) versus local concentration c(r) for different loading concentrations demonstrated a completely reversible equilibrium process. At the clinical infusion concentration of 5 mg.mL-1 all glycopeptide is dimerized whilst at 19 µg.mL-1 (a clinical target trough serum concentration), vancomycin was mainly monomeric (<20% dimerized). Analysis of the variation of M w with loading concentration revealed dissociation constants in the range 25-75 μM, commensurate with a relatively weak association. The effect of two-fold vancomycin (19 µg.mL-1) appears to have no effect on the monomeric enterococcal VanS kinase involved in glycopeptide resistance regulation. Therefore, the 30% increase in sedimentation coefficient of VanS on adding vancomycin observed previously is more likely to be due to a ligand-induced conformational change of VanS to a more compact form rather than a ligand-induced dimerization.

Illustrative examples of probable transfer of resistance determinants from food animals to humans: Streptothricins, glycopeptides, and colistin

Use, overuse, and misuse of antimicrobials contributes to selection and dissemination of bacterial resistance determinants that may be transferred to humans and constitute a global public health concern. Because of the continued emergence and expansion of antimicrobial resistance, combined with the lack of novel antimicrobial agents, efforts are underway to preserve the efficacy of current available life-saving antimicrobials in humans. As a result, uses of medically important antimicrobials in food animal production have generated debate and led to calls to reduce both antimicrobial use and the need for use. This manuscript, commissioned by the World Health Organization (WHO) to help inform the development of the WHO guidelines on the use of medically important antimicrobials in food animals, includes three illustrations of antimicrobial use in food animal production that has contributed to the selection-and subsequent transfer-of resistance determinants from food animals to humans. Herein, antimicrobial use and the epidemiology of bacterial resistance are described for streptothricins, glycopeptides, and colistin. Taken together, these historical and current narratives reinforce the need for actions that will preserve the efficacy of antimicrobials.

WalK(S221P), a naturally occurring mutation, confers vancomycin resistance in VISA strain XN108

Objectives

Vancomycin-intermediate Staphylococcus aureus (VISA) strains have spread globally. We previously isolated an ST239 VISA (XN108) with a vancomycin MIC of 12 mg/L. The mechanism for XN108 resistance to vancomycin was investigated in this study.

Methods

Genome comparison was performed to characterize mutations that might contribute to the XN108 resistance phenotype. The novel mutation WalK(S221P) was identified and investigated using allelic replacement experiments. Vancomycin susceptibilities, autolytic activities and morphologies of the strains were examined. Autophosphorylation activities of WalK and the WalK(S221P) mutant were determined in vitro with [λ- 32 P]ATP, and binding activity of WalK(S221P)-activated WalR to the promoter region of its target gene lytM was determined by electrophoretic mobility shift assay.

Results

Genome comparison revealed three mutations, GraS(T136I), RpoB(H481N) and WalK(S221P), which might be responsible for vancomycin resistance in XN108. The introduction of WalK(S221P) to the vancomycin-susceptible strain N315 increased its vancomycin MIC from 1.5 to 8 mg/L, whereas the allelic replacement of WalK(S221P) with the native N315 WalK allele in XN108 decreased its vancomycin MIC from 12 to 4 mg/L. The VISA strains have thickened cell walls and decreased autolysis, consistent with observed changes in the expression of genes involved in cell wall metabolism and virulence regulation. WalK(S221P) exhibited reduced autophosphorylation, which may lead to reduced phosphorylation of WalR. WalK(S221P)-phosphorylated WalR also exhibited a reduced capacity to bind to the lytM promoter.

Conclusions

The naturally occurring WalK(S221P) mutation plays a key role in vancomycin resistance in XN108.

Antibacterial Activity of Endophytic Actinomycetes Isolated from the Medicinal Plant Vochysia divergens (Pantanal, Brazil)

Endophytic actinomycetes from medicinal plants produce a wide diversity of secondary metabolites (SM). However, to date, the knowledge about endophytes from Brazil remains scarce. Thus, we analyzed the antimicrobial potential of 10 actinomycetes isolated from the medicinal plant Vochysia divergens located in the Pantanal sul-mato-grossense, an unexplored wetland in Brazil. Strains were classified as belonging to the Aeromicrobium, Actinomadura, Microbacterium, Microbispora, Micrococcus, Sphaerisporangium, Streptomyces, and Williamsia genera, through morphological and 16S rRNA phylogenetic analyzes. A susceptibility analysis demonstrated that the strains were largely resistant to the antibiotics oxacillin and nalidixic acid. Additionally, different culture media (SG and R5A), and temperatures (28 and 36°C) were evaluated to select the best culture conditions to produce the active SM. All conditions were analyzed for active metabolites, and the best antibacterial activity was observed from metabolites produced with SG medium at 36°C. The LGMB491 (close related to Aeromicrobium ponti) extract showed the highest activity against methicillin-resistant Staphylococcus aureus (MRSA), with a MIC of 0.04 mg/mL, and it was selected for SM identification. Strain LGMB491 produced 1-acetyl-β-carboline (1), indole-3-carbaldehyde (2), 3-(hydroxyacetyl)-indole (4), brevianamide F (5), and cyclo-(L-Pro-L-Phe) (6) as major compounds with antibacterial activity. In this study, we add to the knowledge about the endophytic community from the medicinal plant V. divergens and report the isolation of rare actinomycetes that produce highly active metabolites.

Comparative Proteomics of Streptococcus pneumoniae Response to Vancomycin Treatment

Streptococcus pneumoniae is a gram-positive pathogen that causes otitis media, pneumonia, meningitis, and other serious diseases. Vancomycin is one of the most important drugs currently used for the treatment of gram-positive bacterial infections, representing, importantly, the last line of defense against bacteria that have developed resistance to other antibiotics. While primary efforts of most investigations focused on the antibacterial mechanism of vancomycin, few studies have been performed to assess the tolerance mechanism of bacteria to vancomycin. In this work, whole cellular proteins were extracted from S. pneumoniae D39 with or without vancomycin treatment. Subsequently, differentially expressed proteins (DEPs) were identified with two-dimensional gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry (MS)/MS. In total, 27 proteins were upregulated and four proteins were downregulated in vancomycin-treated S. pneumoniae. Gene ontology analysis indicated that these DEPs were mainly involved in the nucleic acid, protein, and carbohydrate biosynthetic processes. Verification experiments with real-time quantitative polymerase chain reaction showed that the gene expression profiles were consistent with proteomic data. These new observations may serve as a valuable resource for future investigations of vancomycin tolerance mechanisms of S. pneumoniae.

An "On-Site Transformation" Strategy for Treatment of Bacterial Infection

To date, numerous nanosystems have been developed as antibiotic replacements for bacterial infection treatment. However, these advanced systems are limited owing to their nontargeting accumulation and the consequent side effects. Herein, transformable polymer-peptide biomaterials have been developed that enable specific accumulation in the infectious site and long-term retention, resulting in enhanced binding capability and killing efficacy toward bacteria. The polymer-peptide conjugates are composed of a chitosan backbone and two functional peptides, i.e., an antimicrobial peptide and a poly(ethylene glycol)-tethered enzyme-cleavable peptide (CPC-1). The CPC-1 initially self-assembles into nanoparticles with pegylated coronas. Upon the peptides are cleaved by the gelatinase secreted by a broad spectrum of bacterial species, the resultant compartments of nanoparticles spontaneously transformed into fibrous nanostructures that are stabilized by enhanced chain-chain interaction, leading to exposure of antimicrobial peptide residues for multivalent cooperative electrostatic interactions with bacterial membranes. Intriguingly, the in situ morphological transformation also critically improves the accumulation and retention of CPC-1 in infectious sites in vivo, which exhibits highly efficient antibacterial activity. This proof-of-concept study demonstrates that pathological environment-driven smart self-assemblies may provide a new idea for design of high-performance biomaterials for disease diagnostics and therapeutics.

A review on comparative mechanistic studies of antimicrobial peptides against archaea

Archaea was until recently considered as a third domain of life in addition to bacteria and eukarya but recent studies support the existence of only two superphyla (bacteria and archaea). The fundamental differences between archaeal, bacterial, and eukaryal cells are probably the main reasons for the comparatively lower susceptibility of archaeal strains to current antimicrobial agents. The possible emerging pathogenicity of archaea and the role of archaeal methanogens in methane emissions, a potent greenhouse gas, has led many researchers to examine the sensitivity patterns of archaea and make attempts to find agents that have significant anti-archaeal activity. Even though antimicrobial peptides (AMPs) are well known with several published reviews concerning their mode of action against bacteria and eukarya, to our knowledge, to date no reviews are available that focus on the action of these peptides against archaea. Herein, we present a review on all the peptides that have been tested against archaea. In addition, in an attempt to shed more light on possible future work that needs to be performed we have included a brief overview of the chemical characteristics, spectrum of activity, and the known mechanism of action of each of these peptides against bacteria and/or fungi. We also discuss the nature of and key physiological differences between Archaea, Bacteria, and Eukarya that are relevant to the development of anti-archaeal peptides. Despite our relatively limited knowledge about archaea, available data suggest that AMPs have an even broader spectrum of activity than currently recognized.

The Whole Price of Vancomycin: Toxicities, Troughs, and Time

Vancomycin is a glycopeptide antibiotic that is active against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus. Nephrotoxicity, which is usually reversible, is the most serious common adverse effect of vancomycin. Vancomycin-associated nephrotoxicity prolongs hospital stays, imposes a need for additional antibiotics and, in rare circumstances, dialysis treatment, and increases medical costs and mortality. Risk factors for nephrotoxicity include the dose and duration of vancomycin treatment, serum trough concentration, patient characteristics, and concomitant receipt of nephrotoxins. Contemporary guidelines recommend targeting vancomycin trough concentrations of ≥10 mg/L to prevent resistance and trough concentrations of 15-20 mg/L to optimize outcomes. There is significant correlation between vancomycin trough serum concentrations and the incidence of vancomycin-associated nephrotoxicity; however, evidence of an association between trough concentrations and efficacy is less convincing. Routine monitoring of serum vancomycin concentrations consumes time and limited healthcare resources and may not be cost effective. The use of alternative antibacterial agents that do not require monitoring would free up pharmacy resources. This time could then be devoted to initiatives such as pharmacist-led antibiotic stewardship programs that are known to reduce antibiotic use and promote improved patient outcomes.

Zn(II) mediates vancomycin polymerization and potentiates its antibiotic activity against resistant bacteria

Vancomycin is known to bind to Zn(II) and can induce a zinc starvation response in bacteria. Here we identify a novel polymerization of vancomycin dimers by structural analysis of vancomycin-Zn(II) crystals and fibre X-ray diffraction. Bioassays indicate that this structure is associated with an increased antibiotic activity against bacterial strains possessing high level vancomycin resistance mediated by the reprogramming of peptidoglycan biosynthesis to use precursors terminating in D-Ala-D-Lac in place of D-Ala-D-Ala. Polymerization occurs via interaction of Zn(II) with the N-terminal methylleucine group of vancomycin, and we show that the activity of other glycopeptide antibiotics with this feature can also be similarly augmented by Zn(II). Construction and analysis of a model strain predominantly using D-Ala-D-Lac precursors for peptidoglycan biosynthesis during normal growth supports the hypothesis that Zn(II) mediated vancomycin polymerization enhances the binding affinity towards these precursors.

Reducing acute kidney injury due to vancomycin in trauma patients

BACKGROUND

Supratherapeutic vancomycin trough levels are common after trauma and associated with both increased acute kidney injury (AKI) and mortality. We sought to limit the adverse effects of vancomycin in trauma patients through more frequent trough monitoring.

METHODS

Beginning in January 2011, trauma patients treated with vancomycin had trough levels (VT) monitored daily until steady state was reached. Trauma patients admitted from January 2011 to May 2015 (POST) were compared with those admitted from January 2006 to December 2010 (PRE). Inclusion criteria required administration of intravenous vancomycin, admission serum creatinine (SCr), and SCr within 72 hours of highest VT. Acute kidney injury was defined as an increase in SCr of at least 0.3 mg/dL or 50% from admission to post-vancomycin administration. Those in the POST group were prospectively followed up until discharge or death.

RESULTS

Two hundred sixty-three patients met inclusion criteria in the PRE-phase and 115 in the POST-phase. The two groups were similar in age, gender, race, body mass index, pre-existing comorbidities, admission systolic blood pressure, Glasgow Coma Scale, and head Abbreviated Injury Scale. Injury Severity Score was higher in the POST cohort (18 PRE vs. 25 POST, p < 0.001). Compared with PRE, the POST cohort had lower rates of supratherapeutic VT (>20 mg/L) (34.6% PRE vs. 22.6% POST, p = 0.02) and AKI (30.4% PRE vs. 19.1% POST, p = 0.026). After adjusting for confounders, the POST group had a significantly lower risk of AKI with an adjusted odds ratio of 0.457 (p = 0.027). There was a trend toward decreased mortality in the POST cohort, but this did not reach significance (10% PRE vs. 5.2% POST, p = 0.162).

CONCLUSIONS

A reduction in AKI was observed in trauma patients with daily vancomycin trough levels monitored until steady state. Increased awareness regarding closer surveillance of VT in trauma patients may limit the incidence of vancomycin-related nephrotoxicity.

LEVEL OF EVIDENCE

Therapeutic study, level IV.

Managing acute bacterial skin and skin structure infections: Focus on new lipoglycopeptides

Acute bacterial skin and skin structure infections (ABSSSI) are some of the most commonly encountered infections worldwide. Hospitalizations as a result of ABSSSI are associated with high mortality. This article discusses the role of oritavancin and dalbavancin, two new lipoglycopeptides, in the context of the other I.V. available standard therapy options.

Total Syntheses of Vancomycin-Related Glycopeptide Antibiotics and Key Analogues

A review of efforts that have provided total syntheses of vancomycin and related glycopeptide antibiotics, their agylcons, and key analogues is provided. It is a tribute to developments in organic chemistry and the field of organic synthesis that not only can molecules of this complexity be prepared today by total synthesis but such efforts can be extended to the preparation of previously inaccessible key analogues that contain deep-seated structural changes. With the increasing prevalence of acquired bacterial resistance to existing classes of antibiotics and with the emergence of vancomycin-resistant pathogens (VRSA and VRE), the studies pave the way for the examination of synthetic analogues rationally designed to not only overcome vancomycin resistance but provide the foundation for the development of even more powerful and durable antibiotics.

Nonomuraea sp. ATCC 55076 harbours the largest actinomycete chromosome to date and the kistamicin biosynthetic gene cluster

Glycopeptide antibiotics (GPAs) have served as potent clinical drugs and as an inspiration to chemists in various disciplines. Among known GPAs, complestatin, chloropeptin, and kistamicin are unique in that they contain an unusual indole-phenol crosslink. The mechanism of formation of this linkage is unknown, and to date, the biosynthetic gene cluster of only one GPA with an indole-phenol crosslink, that of complestatin, has been identified. Here, we report the genome sequence of the kistamicin producer Nonomuraea sp. ATCC 55076. We find that this strain harbours the largest actinobacterial chromosome to date, consisting of a single linear chromosome of ∼13.1 Mbp. AntiSMASH analysis shows that ∼32 biosynthetic gene clusters and ∼10% of the genome are devoted to production of secondary metabolites, which include 1,6-dihydroxyphenazine and nomuricin, a new anthraquinone-type pentacyclic compound that we report herein. The kistamicin gene cluster (kis) was identified bioinformatically. A unique feature of kis is that it contains two cytochrome P450 enzymes, which likely catalyze three crosslinking reactions. These findings set the stage for examining the biosynthesis of kistamicin and its unusual indole-phenol crosslink in the future.