Kegg Pathway: Biosynthesis of vancomycin group antibiotics

Int J Antimicrob Agents. 2009 Nov; 34(5): 482-5
Del Pozo JL, García Cenoz M, Hernáez S, Martínez A, Serrera A, Aguinaga A, Alonso M, Leiva J

The aim of this study was to analyse the effectiveness of teicoplanin versus vancomycin lock therapy in the treatment of coagulase-negative staphylococci (CoNS) venous access port-related bloodstream infection (BSI). The study included 44 consecutive patients during a 36-month prospective case-series study. The primary endpoint was failure to cure. Treatment was successful in 39 patients. At the end of the study, the cumulative port survival rate was 100% in the teicoplanin lock group compared with 77% in the vancomycin lock group (P=0.06). In the Cox regression analysis, fever beyond 48 h of treatment was a significant predictor of treatment failure (P=0.02). Use of vancomycin or teicoplanin locks had an effectiveness of 88.6% in the treatment of CoNS port-related BSI. Teicoplanin locks reduced the failure rate from 18.5% to 0% compared with vancomycin locks. The presence of fever after beginning antimicrobial lock therapy was associated with treatment failure.

Int J Antimicrob Agents. 2009 Nov; 34(5): 477-81
Yanagihara K, Kihara R, Araki N, Morinaga Y, Seki M, Izumikawa K, Kakeya H, Yamamoto Y, Yamada Y, Kohno S, Tsukamoto K, Kamihira S

Many strains of community-acquired meticillin-resistant Staphylococcus aureus (MRSA) have a pore-forming leukotoxin, known as Panton-Valentine leukocidin (PVL), which can cause severe necrotising pneumonia. Linezolid (LZD) is a new antibacterial agent with potent antibacterial activity against MRSA. In this study, a mouse model of haematogenous pulmonary infection was used to compare the efficacies of LZD and vancomycin (VAN) against pulmonary infection caused by PVL-positive S. aureus. Following antibiotic administration for 3 days, the number of viable bacteria (mean+/-standard error of the mean) in the control, VAN and LZD groups was 6.77+/-0.14, 5.29+/-0.27 and 4.25+/-0.33 log colony-forming units/lung, respectively. LZD significantly decreased the number of viable bacteria in the lungs compared with the control and VAN groups (P<0.05). The survival rate at Day 7 post-inoculation was higher in the LZD group (100%) than in the VAN group (50%) or the control group (0%). Histopathological examination and cytokine analysis also showed the beneficial efficacy of LZD compared with VAN. In conclusion, LZD significantly reduced bacterial numbers and inflammation in a mouse model of PVL-positive S. aureus haematogenous infection and improved the survival rate of infected mice compared with VAN. LZD is clinically effective against PVL-positive S. aureus.

Bioorg Med Chem. 2009 Aug 15; 17(16): 5874-86
Leung SS, Tirado-Rives J, Jorgensen WL

In order to seek vancomycin analogs with improved performance against VanA and VanB resistant bacterial strains, extensive computational investigations have been performed to examine the effects of side-chain and backbone modifications. Changes in binding affinities for tripeptide cell-wall precursor mimics, Ac(2)-l-Lys-d-Ala-d-Ala (3) and Ac(2)-l-Lys-d-Ala-d-Lac (4), with vancomycin analogs were computed with Monte Carlo/free energy perturbation (MC/FEP) calculations. Replacements of the 3-hydroxyl group in residue 7 with small alkyl or alkoxy groups, which improve contacts with the methyl side chain of the ligands'd-Ala residue, are predicted to be the most promising to enhance binding for both ligands. The previously reported amine backbone modification as in 5 is shown to complement the hydrophobic modifications for binding monoacetylated tripeptides. In addition, replacement of the hydroxyl groups in residues 5 and 7 by fluorine is computed to have negligible impact on binding the tripeptides, though it may be pharmacologically advantageous.

Anesthesiology. 2009 Aug; 111(2): 356-65
Hutschala D, Kinstner C, Skhirdladze K, Thalhammer F, Müller M, Tschernko E

BACKGROUND: vancomycin is frequently used in clinical practice to treat severe wound and systemic infections caused by Gram-positive bacteria after cardiac surgery. The drug is excreted almost entirely by glomerular filtration and might exhibit nephrotoxic side effects. This study compared the nephrotoxic impact of vancomycin during continuous versus intermittent administration. METHODS: The authors analyzed 149 patients admitted to the intensive care unit during a 5-yr period. All patients were treated at the intensive care unit after elective open heart surgery. Thirty patients received a dosage of 1325 +/- 603 mg/d vancomycin (range 300-3400 mg/d) by intermittent infusion, and 119 patients received a mean dosage of 1935 +/- 688 mg/d (range 352-3411 mg/d) by continuous infusion. RESULTS: Nephrotoxicity occurred in 11 patients (36.7%) in the intermittent treatment group and in 33 patients (27.7%) in the continuous treatment group (P = 0.3; 95% CI = 0.283). Continuous veno-venous hemofiltration after vancomycin administration was required for 9 patients (9 of 30; 30%) in the intermittent treatment group and for 28 (28 of 119; 23.5%) in the continuous treatment group (P = 0.053; 95% CI = 0.256). A change of one unit (1 mg/l) in vancomycin serum concentration (DeltaVancoC) induced an average change of 0.04 mg/dl in creatinine (DeltaCrea) in the intermittent treatment group versus 0.006 mg/dl in the continuous treatment group (P < 0.001). CONCLUSIONS: The data show that both the intermittent and also the continuous application modality of vancomycin are associated with deterioration of renal function in critically ill patients after cardiac surgery. However, continuous infusion showed the tendency to be less nephrotoxic than the intermittent infusion of vancomycin.

Am J Kidney Dis. 2009 Oct; 54(4): 702-10
Szeto CC, Kwan BC, Chow KM, Law MC, Pang WF, Chung KY, Leung CB, Li PK

BACKGROUND: The clinical behavior and optimal treatment of relapsing and recurrent peritonitis episodes in patients undergoing long-term peritoneal dialysis are poorly understood. STUDY DESIGN: Retrospective study over 14 years. SETTING & PARTICIPANTS: University dialysis unit; 157 relapsing episodes (same organism or culture-negative episode occurring within 4 weeks of completion of therapy for a prior episode), 125 recurrent episodes (different organism, occurs within 4 weeks of completion of therapy for a prior episode), and 764 control episodes (first peritonitis episode without relapse or recurrence). PREDICTORS: Exit-site infection, empirical antibiotics. OUTCOME MEASURES: Primary response (resolution of abdominal pain, clearing of dialysate, and peritoneal dialysis effluent neutrophil count < 100 cells/mL after 10 days of antibiotic therapy), complete cure (resolution by using antibiotics without relapse/recurrence), catheter removal (for any cause while on antibiotic therapy), and mortality. RESULTS: Compared with the control group, more relapsing episodes were caused by Pseudomonas species (16.6% versus 9.4%) and were culture negative (29.9% versus 16.4%); recurrent infections commonly were caused by Enterococcus species (3.2% versus 1.2%) or other Gram-negative organisms (27.2% versus 11.1%) or had mixed bacterial growth (17.6% versus 12.7%). There were significant differences in primary response, complete cure, and mortality rates among groups (P < 0.001 for all comparisons). Compared with the control and relapsing groups, post hoc analysis showed that the recurrent group had a significantly lower primary response rate (86.4%, 88.5%, and 71.2%, respectively), lower complete cure rate (72.3%, 62.4%, and 42.4%, respectively), and higher mortality rate (7.7%, 7.0%, and 20.8%, respectively). LIMITATIONS: Retrospective analysis. CONCLUSION: Relapsing and recurrent peritonitis episodes are caused by different spectra of bacteria and probably represent 2 distinct clinical entities. Recurrent peritonitis episodes had a worse prognosis than relapsing ones.

Eur J Clin Microbiol Infect Dis. 2009 Oct; 28(10): 1209-15
Gallon O, Guillet-Caruba C, Lamy B, Laurent F, Doucet-Populaire F, Decousser JW,

Staphylococci are a leading cause of skin and soft tissue infections (SSTIs) and bacteremia in France, a country with a high prevalence of oxacillin resistance. We evaluated the in vitro activity of daptomycin compared with reference compounds against 445 Staphylococcus aureus and 53 coagulase-negative Staphylococci (CNS) collected during two large nationwide studies performed in 2006 and 2007. The percentage of oxacillin resistance among S. aureus was 13.6% (SSTIs) and 30.7% (bacteremia). Daptomycin showed lower MIC(90) levels compared to vancomycin, teicoplanin, and linezolid (0.19 mg/L vs. 2, 1.5, and 1 mg/L, respectively), irrespective of oxacillin susceptibility. Amongst the CNS, 64.2% of the isolates originated from clinical bacteremia were resistant to oxacillin and 24.5% to teicoplanin; all but one Staphylococci were susceptible to daptomycin (MIC = 1.5 mg/l). As with linezolid, daptomycin seems to constitute an alternative option to treat some staphylococcal infections in the French context of high oxacillin resistance prevalence and high glycopeptides MIC.

Food Microbiol. 2009 Aug; 26(5): 527-32
Barbosa J, Ferreira V, Teixeira P

Antibiotic susceptibility was evaluated for 182 Enterococcus spp. isolated from Alheira, Chouriça de Vinhais and Salpicão de Vinhais, fermented meat products produced in the North of Portugal. Previously, a choice was made from a group of 1060 isolates, using phenotypic and genotypic tests. From these, 76 were previously identified as Enterococcus faecalis, 44 as Enterococcus faecium, one as Enterococcus casseliflavus and 61 as Enteroccocus spp. In order to encompass several of the known chemical and functional classes of antibiotics, resistance to ampicillin, penicillin G, ciprofloxacin, chloramphenicol, erythromycin, nitrofurantoin, rifampicin, tetracycline and vancomycin was evaluated. All the isolates were sensitive to antibiotics of clinical importance, such as penicillins and vancomycin. Some differences in Minimal Inhibitory Concentrations (MICs) of antibiotics, could be associated with the enterococcal species.

Curr Clin Pharmacol. 2009 May; 4(2): 95-101
Soni A, Chaudhary M, Dwivedi VK

Drug toxicity is a common cause of liver injury and kidney failure. This study was designed to elucidate whether administration of high doses of Ceftriaxone or vancomycin induce oxidative stress in liver as well as kidney, and to investigate the protective effects of VRP 1020 with fixed dose combination of ceftriaxone-vancomycin (Immunox-V). Twenty four Mus musculus mice (weighing 30 +/- 5 g) were divided into four groups containing six mice in each group. The activities of antioxidant enzymes such as superoxide dismutase, catalase and the level of malonaldialdehyde, as an marker of lipid per oxidation, were measured to evaluate oxidative stress in homogenates of the liver and renal tissue. Ceftriaxone or vancomycin administration significantly increased malonaldialdehyde levels (p < 0.001) but significant decreased in superoxide dismutase (p<0.01) and catalase (p<0.001) activities. Co-administration of VRP 1020 with FDC of Immunox-V injections caused significantly decreased malonaldialdehyde levels (p< 0.001) and increased superoxide dismutase (p<0.01) and catalase (p<0.001) activities in liver and renal tissue when compared with other treated groups. Similarly, the levels of extracellular antioxidant (Creatinine and Uric acid) were found to be significant lowered in Immunox-V treated group when compared to ceftriaxone or vancomycin alone treated group. These results indicate that chemical mediated technology of VRP 1020 with fixed dose combination of Immunox-V can prevent drug induced nephrotoxicity and oxidative stress which protects liver injury as well as renal tissue damage by reducing reactive oxygen species which improve the activities of free radical scavenging enzymes.

Klin Mikrobiol Infekc Lek. 2009 Feb; 15(1): 4-6
Kolár M, Hanulík V, Chromá M

INTRODUCTION: Currently, one of the most serious problems in medicine is the increasing resistance of pathogenic bacteria to antimicrobial drugs. Bacterial resistance may potentially be solved in particular by decreasing the consumption of antibiotics and increasing the quality of their use. Equally important, however, is the development of new antimicrobial drugs and their use in clinical practice. One of the new antibiotic agents is tigecycline of the glycylcycline group. The presented work aimed at assessing its in vitro effect on selected multiresistant bacteria. MATERIAL AND METHODS: Clinical samples were collected from patients hospitalized in the University Hospital Olomouc to isolate ESBL- and AmpC beta-lactamase-producing enterobacteria, methicillin-resistant Staphylococcus aureus (MRSA) strains and vancomycin-resistant enterococci (VRE). In the isolates, susceptibility to tigecycline was determined by the standard microdilution method. RESULTS: A total of 350 isolates were tested (100 MRSA, 10 0 VRE, 100 ESBL-positive and 50 AmpC-positive enterobacteria). In the cases of VRE and MRSA, no resistance to tigecycline was detected and the minimum inhibitory concentrations (MIC) did not exceed 0.25 mg/l and 0.5 mg/l, respectively. In ESBL-positive enterobacteria, 97% susceptibility (MIC range = or <0.06 to 4 mg/l) was detected; in AmpC-positive enterobacteria, the MIC range was = or <0.03-2 mg/l and susceptibility reached 98 %. CONCLUSION: Tigecycline may be considered a suitable alternative in the treatment of infections caused by the above-mentioned multiresistant strains.

Bioorg Med Chem Lett. 2009 May 1; 19(9): 2558-61
Kim SY, Park HB, Cho JH, Yoo KH, Oh CH

The synthesis of a new series of oxazolidinones having spiro[2,4]heptane moieties is described. Their in vitro antibacterial activities against both Gram-positive and Gram-negative bacteria were tested and the effect of substituents on the oxazolidinone ring was investigated. A particular compound Ih having fluoro group showed the most potent antibacterial activity.

J Antimicrob Chemother. 2009 May; 63(5): 1050-7
Thomson AH, Staatz CE, Tobin CM, Gall M, Lovering AM

OBJECTIVES: The aims of this study were to develop a population pharmacokinetic model of vancomycin in adult patients, to use this model to develop dosage guidelines targeting vancomycin trough concentrations of 10-15 mg/L and to evaluate the performance of these new guidelines. METHODS: All data analyses were performed using NONMEM. A population pharmacokinetic model was first developed from vancomycin dosage and concentration data collected during routine therapeutic drug monitoring in 398 patients, then new vancomycin dosage guidelines were devised by using the model to predict vancomycin trough concentrations in a simulated dataset. Individual estimates of CL and V1 were then obtained in an independent group of 100 patients using the population model and the POSTHOC option. These individual estimates were used to predict vancomycin trough concentrations and steady-state AUC(24)/MIC ratios using the current and new dosage guidelines. RESULTS: The population analysis found that the vancomycin data were best described using a bi-exponential elimination model with a typical CL of 3.0 L/h that changed by 15.4% for every 10 mL/min difference from a CL(CR) of 66 mL/min. V(ss) was 1.4 L/kg. The proposed dosage guidelines were predicted to achieve 55% of vancomycin troughs within 10-15 mg/L and 71% within 10-20 mg/L, which is significantly higher than current guidelines (19% and 22%, respectively). The proportion of AUC(24)/MIC ratios above 400 was also higher, 87% compared with 58%. CONCLUSIONS: New vancomycin dosage guidelines have been developed that achieve trough concentrations of 10-15 mg/L earlier and more consistently than current guidelines.

Int J Syst Evol Microbiol. 2009 Mar; 59(Pt 3): 498-503
Domingo MC, Huletsky A, Boissinot M, Hélie MC, Bernal A, Bernard KA, Grayson ML, Picard FJ, Bergeron MG

Two vancomycin-resistant, strictly anaerobic, Gram-positive, rod-shaped, spore-forming organisms (strains CCRI-9842(T) and CCRI-9929) isolated from human faecal specimens in Québec, Canada, and Australia were characterized using phenotypic, biochemical and molecular taxonomic methods. Pairwise analysis of the 16S rRNA gene sequences showed that both strains were closely related to each other genetically (displaying 99.2 % sequence similarity) and represented a previously unknown subline within the Clostridium coccoides rRNA group of organisms (rRNA cluster XIVa of the genus Clostridium). Strains CCRI-9842(T) and CCRI-9929 used carbohydrates as fermentable substrates, producing acetic acid as the major product of glucose metabolism. The novel strains were most closely related to Clostridium asparagiforme, Clostridium bolteae and Clostridium clostridioforme, but morphological, biochemical and phylogenetic studies demonstrated that they represent a previously unidentified species of the genus Clostridium. This was confirmed by the unique cellular fatty acid composition of strains CCRI-9842(T) and CCRI-9929. Therefore, on the basis of data from the polyphasic taxonomic analysis, it is proposed that strains CCRI-9842(T) and CCRI-9929 represent a novel species of the genus Clostridium, for which the name Clostridium lavalense sp. nov. is proposed. The type strain is CCRI-9842(T) (=CCUG 54291(T)=JCM 14986(T)=NML 03-A-015(T)).

Orthopedics. 2008 Nov; 31(11): 1140
Mason LW, Randhawa KS, Carpenter EC

Linezolid is the first in a new group of antibiotics called oxazolidinones. As a potent antimicrobial, it has activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus, penicillin-resistant Streptococcus pneumoniae, and macrolide-resistant streptococci. There are several documented case reports of serotonin toxicity when used with selective serotonin reuptake inhibitors. The symptoms of serotonin syndrome are alteration of mental state, autonomic dysfunction, and neuromuscular disorders. This article presents a case of an interaction of the serotonin reuptake inhibitor venlafaxine and linezolid and the possible diagnostic problems that can occur. A 58-year-old woman presented with signs of systemic infection. Her medical history included bladder resection for transitional cell carcinoma, bilateral total hip arthroplasty (THA), and depression, for which she was on venlafaxine. Serological and imaging investigations revealed MRSA infection of the bilateral THA. The patient was started on vancomycin and rifampicin intravenously. As intravenous access was becoming problematic and long-term antibiotics were needed, treatment was changed to oral linezolid and oral rifampicin. Four days after the commencement of linezolid, the patient was acutely disorientated with generalized cerebellar signs and no autonomic dysfunction. A computed tomography scan of the head and lumbar puncture revealed no abnormal findings. A diagnosis of serotonin toxicity was made. The patient recovered when linezolid and venlafaxine were discontinued and supportive measures were provided. Linezolid is a popular choice of antibiotic, especially for the treatment of orthopedic-related MRSA infections. Patients who commonly require linezolid as an antimicrobial are those with complex infections where other antibiotic treatment has failed. It is therefore important to be vigilant with linezolid use. Physicians should be aware of the nonspecific presentation of serotonin symptoms and the treatment.

Antimicrob Agents Chemother. 2009 May; 53(5): 1863-7
Pea F, Furlanut M, Negri C, Pavan F, Crapis M, Cristini F, Viale P

The efficacy of vancomycin against methicillin-resistant Staphylococcus aureus (MRSA)-related infections has been called into question by recent findings of higher rates of failure of vancomycin treatment of infections caused by strains with high MICs. Continuous infusion may be the best way to maximize the time-dependent activity of vancomycin. The aim of this study was to create dosing nomograms in relation to different creatinine clearance (CL(Cr)) estimates for use in daily clinical practice to target the steady-state concentrations (C(ss)s) of vancomycin during continuous infusion at 15 to 20 mg/liter (after the administration of an initial loading dose of 15 mg/kg of body weight over 2 h). The correlation between vancomycin clearance (CL(v)) and CL(Cr) was retrospectively assessed in a cohort of critically ill patients (group 1, n = 70) to create a formula for dosage calculation to target C(ss) at 15 mg/liter. The performance of this formula was prospectively validated in a similar cohort (group 2, n = 63) by comparison of the observed and the predicted C(ss)s. A significant relationship between CL(v) and CL(Cr) was observed in group 1 (P < 0.001). The application of the calculated formula to vancomycin dosing in group 2 {infusion rate (g/24 h) = [0.029 x CL(Cr) (ml/min) + 0.94] x target C(ss) x (24/1,000)} led to a significant correlation between the observed and the predicted C(ss)s (r = 0.80, P < 0.001). Two dosing nomograms based on CL(Cr) were created to target the vancomycin C(ss) at 15 and 20 mg/liter in critically ill patients. These nomograms could be helpful in improving the vancomycin treatment of MRSA infections, especially in the presence of borderline-susceptible pathogens and/or of pathophysiological conditions which may enhance the clearance of vancomycin, while potentially avoiding the increased risk of nephrotoxicity observed with the use of high intermittent doses of vancomycin.

Nucl Med Rev Cent East Eur. 2008; 11(1): 1-4
Jalilian AR, Hosseini MA, Majdabadi A, Saddadi F

BACKGROUND: Tl-201 has potential in the preparation of radiolabelled compounds similar to its homologues, like In-111 and radiogallium. In this paper, recently prepared [(201)Tl](III) vancomycin complex ([(201)Tl](III)VAN) has been evaluated for its biological properties. MATERIAL AND METHODS: [(201)Tl](III)VAN was prepared according to the optimized conditions followed by biodistribution studies in normal rats for up to 52 h. The Staphylococcus aurous specific binding was checked in vitro. The complex was finally injected to normal rats. Tracer SPECT images were obtained in normal animals and compared to those of (67)Ga-citrate. RESULTS: Freshly-prepared [(201)Tl](III)VAN batches (radiochemical yield > 99%, radiochemical purity > 98%, specific activity approximately 1.2 Ci/mmol) showed a similar biodistribution to that of unlabeled vancomycin. The microorganism binding ratios were 3 and 9 for tracer (201)Tl(3+) and tracer (201)Tl(III)DTPA, respectively, suggesting the preservation of the tracer bioactivity. As a nonspecific cell penetrating tracer, [(201)Tl](III)DTPA was used.

Biol Pharm Bull. 2009 Jan; 32(1): 99-104
Omote S, Yano Y, Hashida T, Masuda S, Yano I, Katsura T, Inui K

The pharmacokinetics of vancomycin was retrospectively examined based on trough concentrations obtained during routine therapeutic drug monitoring to examine possible pharmacokinetic differences between adult Japanese cancer and non-cancer patients with various degrees of renal function. A total of 231 data points from 65 cancer patients and 41 non-cancer patients were collected, and patients' background, vancomycin dose, and vancomycin clearance estimated by an empirical Bayesian method were summarized. Regarding the patients' characteristics and clinical laboratory test data, no clear differences were found between the two groups. The relationship between vancomycin clearance and creatinine clearance were similar between the groups, suggesting little effect of malignancy on vancomycin clearance. After the sub-group comparisons regarding fluid retention and cancer type, no clear differences were found in the vancomycin clearance versus creatinine clearance relationship. We conclude that the initial dose of vancomycin should not necessarily be adjusted for cancer patients. For individualized vancomycin-based therapy, dose adjustment at the appropriate time is important according to information from routine therapeutic drug monitoring and clinical laboratory tests, and to observations of the efficacy, nephrotoxicity, and other conditions in each patient.

Syst Appl Microbiol. 2009 Feb; 32(1): 56-64
Fritz E, Fekete A, Lintelmann J, Schmitt-Kopplin P, Meckenstock RU

Two novel Pseudomonas strains were isolated from groundwater sediment samples. The strains showed resistance against the antibiotics tetracycline, cephalothin, nisin, vancomycin, nalidixic acid, erythromycin, lincomycin, and penicillin and grew at temperatures between 15 and 37 degrees C and pH values from 4 to 10 with a maximum at pH 7 to 10. The 16S ribosomal RNA gene sequences and the substrate spectrum of the isolates revealed that the two strains belonged to the Pseudomonas fluorescens group. The supernatants of both strains had an antibiotic effect against Gram-positive bacteria and one Gram-negative strain. The effective substance was produced under standard cultivation conditions without special inducer molecules or special medium composition. The antibiotically active compound was identified as pseudomonic acid A by off-line high performance liquid chromatography (HPLC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The measurement on ultra performance liquid chromatography (UPLC, UV-vis detection) confirmed the determination of pseudomonic acid A which was produced by both strains at 1.7-3.5mg/l. Our findings indicate that the ability to produce the antibiotic pseudomonic acid A (Mupirocin) is more spread among the pseudomonads then anticipated from the only producer known so far.

J Cataract Refract Surg. 2008 Dec; 34(12): 2139-45
Yoeruek E, Spitzer MS, Saygili O, Tatar O, Biedermann T, Yoeruek E, Bartz-Schmidt KU, Szurman P

PURPOSE: To evaluate and compare the cytotoxic and apoptotic properties of cefuroxime and vancomycin on cultured human corneal endothelial cells (HCECs) to determine their safety for intracameral use. METHODS: Human corneal endothelial cells were harvested from human donor eyes and exposed to various concentrations of cefuroxime and vancomycin (0.15 to 15 mg/mL). For cytotoxicity testing, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test was performed. Annexin V binding combined with propidium iodide (PI) co-staining was used for the distinction of viable, early, and late apoptotic cells. Odds ratios (ORs) and confidence intervals were calculated for the control group (without drug exposure) for 2.75 mg/mL and 15 mg/mL. Cell morphology and immunolocalization of zonula occludens 1 (ZO1) were assessed after 24 hours of drug exposure. RESULTS: Reduction in cell viability was observed in a dose-dependent manner after exposure to both drugs. Cefuroxime concentrations higher than 2.75 mg/mL and vancomycin concentrations higher than 5.0 mg/mL led to significant reduction in cell viability. The mean number of annexin V-positive and PI-positive cells was not significantly increased at 2.75 mg/mL for either antibiotic agent. After exposure to 15.0 mg/mL, however, the late apoptotic/necrotic cells predominated, with higher ORs indicating accelerated cell death. Increasing concentrations of both antibiotic agents resulted in fading immunopositivity for ZO1. CONCLUSIONS: These data suggest a dose-dependent toxicity of cefuroxime and vancomycin on HCECs in vitro with a narrow range of safety. Although the clinically used concentrations seem to be safe, slightly higher concentrations might induce irreversible cell death and thus should be avoided.

Antimicrob Agents Chemother. 2009 Feb; 53(2): 428-34
Bubalo JS, Munar MY, Cherala G, Hayes-Lattin B, Maziarz R

Daptomycin is the first antibacterial agent of the cyclic lipopeptides with in vitro bactericidal activity against gram-positive organisms, including vancomycin-resistant enterococci, methicillin-resistant staphylococci, and glycopeptide-resistant Staphylococcus aureus. The pharmacokinetics of daptomycin were determined in 29 adult oncology patients with neutropenic fever. Serial blood samples were drawn at 0, 0.5, 1, 2, 4, 8, 12, and 24 h after the initial intravenous infusion of 6 mg/kg of body weight daptomycin. Daptomycin total and free plasma concentrations were determined by high-pressure liquid chromatography. Concentration-time data were analyzed by noncompartmental methods. The results (presented as means +/- standard deviations and ranges, unless indicated otherwise) were as follows: the maximum concentration of drug in plasma (C(max)) was 49.04 +/- 12.42 microg/ml (range, 21.54 to 75.20 microg/ml), the 24-h plasma concentration was 6.48 +/- 5.31 microg/ml (range, 1.48 to 29.26 microg/ml), the area under the concentration-time curve (AUC) from time zero to infinity was 521.37 +/- 523.53 microg.h/ml (range, 164.64 to 3155.11 microg.h/ml), the volume of distribution at steady state was 0.18 +/- 0.05 liters/kg (range, 0.13 to 0.36 liters/kg), the clearance was 15.04 +/- 6.09 ml/h/kg (range, 1.90 to 34.76 ml/h/kg), the half-life was 11.34 +/- 14.15 h (range, 5.17 to 83.92 h), the mean residence time was 15.67 +/- 20.66 h (range, 7.00 to 121.73 h), and the median time to C(max) was 0.6 h (range, 0.5 to 2.5 h). The fraction unbound in the plasma was 0.06 +/- 0.02. All patients achieved C(max)/MIC and AUC from time zero to 24 h (AUC(0-24))/MIC ratios for a bacteriostatic effect against Streptococcus pneumoniae. Twenty-seven patients (93%) achieved a C(max)/MIC ratio for a bacteriostatic effect against S. aureus, and 28 patients (97%) achieved an AUC(0-24)/MIC ratio for a bacteriostatic effect against S. aureus. Free plasma daptomycin concentrations were above the MIC for 50 to 100% of the dosing interval in 100% of patients for S. pneumoniae and 90% of patients for S. aureus. The median time to defervescence was 3 days from the start of daptomycin therapy. In summary, a 6-mg/kg intravenous infusion of daptomycin every 24 h was effective and well tolerated in neutropenic cancer patients.

BMC Microbiol. 2008; 8: 186
Sass P, Jansen A, Szekat C, Sass V, Sahl HG, Bierbaum G

BACKGROUND: The lantibiotic mersacidin is an antimicrobial peptide of 20 amino acids that is ribosomally produced by Bacillus sp. strain HIL Y-85,54728. Mersacidin acts by complexing the sugar phosphate head group of the peptidoglycan precursor lipid II, thereby inhibiting the transglycosylation reaction of peptidoglycan Biosynthesis. RESULTS: Here, we studied the growth of Staphylococcus aureus in the presence of subinhibitory concentrations of mersacidin. Transcriptional data revealed an extensive induction of the cell wall stress response, which is partly controlled by the two-component regulatory system VraSR. In contrast to other cell wall-active antibiotics such as vancomycin, very low concentrations of mersacidin (0.15xMIC) were sufficient for induction. Interestingly, the cell wall stress response was equally induced in vancomycin intermediately resistant S. aureus (VISA) and in a highly susceptible strain. Since the transcription of the VraDE ABC transporter genes was induced up to 1700-fold in our experiments, we analyzed the role of VraDE in the response to mersacidin. However, the deletion of the vraE gene did not result in an increased susceptibility to mersacidin compared to the wild type strain. Moreover, the efficacy of mersacidin was not affected by an increased cell wall thickness, which is part of the VISA-type resistance mechanism and functions by trapping the vancomycin molecules in the cell wall before they reach lipid II. Therefore, the relatively higher concentration of mersacidin at the membrane might explain why mersacidin is such a strong inducer of VraSR compared to vancomycin. CONCLUSION: In conclusion, mersacidin appears to be a strong inducer of the cell wall stress response of S. aureus at very low concentrations, which reflects its general mode of action as a cell wall-active peptide as well as its use of a unique target site on lipid II. Additionally, mersacidin does not seem to be a substrate for the resistance transporter VraDE.