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PubMed1998

Calculation of concentrations of equilibrium components in an in vitro activity test of vancomycin antibiotics and the possible mode of action.

The vancomycin group of antibiotics is considered to act by binding the bacterial cell wall mucopeptide precursor terminating in -L-Lys-D-Ala-D-Ala. The dimerization of these antibiotics is also believed to play a role in the action. In this paper, we analyzed the equilibria in the in vitro antibacterial activity test of the vancomycin antibiotics both with and without the cell wall precursor analogue di-acetyl-L-Lys-D-Ala-D-Ala (DALAA). Based on the equilibria and concentration balance, we obtained 10 equations (seven quadratic equations and three linear equations) containing 10 equilibrium concentrations which relate to the antibiotic, cell wall precursor and DALAA. A computer program was written to solve these equations from known dimerization constant and the binding constants (both monomer and dimer) with DALAA of the antibiotic. The concentrations in the test for vancomycin and eremomycin were obtained. The antibiotic activity of these antibiotics may be quantitatively correlated with their dimerization constants and the binding constants through the calculation. By analyzing the calculated results, we concluded that the cell wall-bound dimer may be the major contributor to the antibiotic activity in the case of eremomycin, while the cell wall-bound monomer is possibly the determinant for the activity of vancomycin.

Anti-Bacterial Agents↗

PubMed2002

[Importance of a cefpirome-vancomycin combination on bactericidal kinetics in severe MRSA infections in intensive care].

UNLABELLED: Vancomycin is always the drug of choice for treatment of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) in spite of his bactericidal kinetic. BACKGROUND: The aim of this study was to evaluate in vivo the improvement of bactericidal kinetic of vancomycin associated with cefpirome against MRSA infection in critically ill patients. METHODS: The prospective cross-over study was carried out in 20 patients with severe pneumonia or bacteremia. There were randomized to receive vancomycin 2 g per day (Group 1, n = 10) or vancomycin with cefpirome 2 g x 2 (Group 2, n = 10). Clinical recovery, bacteriologic parameters (bactericidal kinetic and bactericidal power in vivo at the peak and the valley), duration of ventilation and stay in ICU were comparatively explored in both groups. RESULTS: Clinical outcome did not significantly differ between Group 1 and 2. Bactericidal kinetics were better in the Group 2 (40% vs 60% after 6 hours to the dilution for 1/8e) but the difference was not significant. However, bactericidal power in sera was also better in the Group 2 with more bactericidal dilution at 1/16e (68% vs 88.8%: NS) and overall at 1/32e (10.5% vs 50%: p < 0.05) and CRP, an inflammatory marker, was significantly lower in the Group 2 than in the Group 1 (119.5 +/- 24 mg/l vs 198.6 +/- 78 mg/l: p < 0.05) on the third day.

Adult↗

PubMed2002

Biofilm testing of Staphylococcus epidermidis clinical isolates: low performance of vancomycin in relation to other antibiotics.

The in vitro killing effect of widely used antibiotics (cephalothin, clindamycin, erythromycin, ofloxacin, rifampicin, teicoplanin, tetracycline, phosphomycin and vancomycin) was comparatively analyzed in this study on 24-h biofilms of 64 Staphylococcus epidermidis clinical isolates. This effect was assessed at the expected antibiotic concentration reached in serum, using ATP-bioluminescence. Erythromycin, rifampicin, tetracycline and phosphomycin presented generally a higher killing effect than vancomycin, clindamycin, cephalothin, teicoplanin and ofloxacin in these biofilms. Differences in the resistance profiles obtained in classical assays (broth microdilution and diffusion) did not help to predict differences in the killing effect of the antibiotics in biofilms. Only some antibiotics (vancomycin but not rifampicin or tetracycline) highly decreased their killing effect as the biofilm age increased (from 6 to 24 or 48 h). These studies underline the relevance of biofilm susceptibility testing and the potential danger of the indiscriminate use of vancomycin monotherapy as the ultimate resource against infections involving aged biofilms.

Anti-Bacterial Agents↗

PubMed1997

Vancomycin-resistant Enterococcus raffinosus: molecular epidemiology, species identification error, and frequency of occurrence in a national resistance surveillance program.

Enterococcal blood stream infections are the third most common among all nosocomial blood stream infections in the United States and the occurrence of glycopeptide (vancomycin, teicoplanin) resistance in these isolates has markedly increased. Control of hospital-acquired infections with vancomycin-resistant enterococci requires high quality antimicrobial susceptibility test methods and species identification procedures as a supplement to epidemiologic investigation and appropriate infection control procedures. In this report, bacteremias caused by Enterococcus avium (BioMerieux Vitek, Hazelwood, MO, USA) were observed to be Enterococcus raffinosus infections (six of eight cases; 1.1% of all cases) when reference biochemical identification methods were applied. The vancomycin-susceptible E. raffinosis (two strains) and E. avium (two strains) had unique phenotypic and genotypic molecular profiles. In contrast, four vancomycin-resistant E. raffinosus strains (van A by polymerase chain reaction) from a single institution had the same phenotypic and molecular (PCR, PFGE, ribotyping) pattern, indicating clonal dissemination among four patients over a 66-day period. Clinical laboratories should be aware of the high probability that van A genes may be transferred from Enterococcus faecium or Enterococcus faecalis to other more rarely encountered Enterococcus species. Also contemporary, widely used commercial identification systems may fail to accurately identify those rare species. Errors appear to be most prevalent for E. avium, Enterococcus durans, and E. raffinosus based on the experience of the SCOPE Program.

Anti-Bacterial Agents↗

PubMed1999

Susceptibility testing of Clostridium difficile against metronidazole and vancomycin by disk diffusion and Etest.

A prospective study on the susceptibility of Clostridium difficile to metronidazole and vancomycin using the Etest and disk diffusion test was performed over a 6-month period. One hundred strains were tested; one strain was highly resistant to metronidazole (MIC = 64 micrograms/mL). The zone size of inhibition by the disk diffusion test correlated with the MIC as determined by the Etest (regression coefficient = -0.043 for metronidazole and -0.044 for vancomycin, p < 0.001 for both antibiotics). However, the correlation coefficient was low for both metronidazole (r = 0.574) and vancomycin (r = 0.473); hence the zone of inhibition by disk diffusion test could not predict the MIC satisfactorily. Metronidazole is still the first-line antibiotic for the treatment of C. difficile-associated diarrhea because the incidence of metronidazole resistant strains remains very low. However, the efficacy of metronidazole in the treatment of infections attributable to isolates with high-level metronidazole resistance may be compromised because the fecal concentration of metronidazole is relatively low when compared with the MIC values of the less susceptible strains. Oral vancomycin is the drug of choice under such circumstances, as its fecal concentration is much higher than that of metronidazole.

Anti-Bacterial Agents↗

PubMed1999

Vancomycin-resistant enterococci: the clinical effect of a common nosocomial pathogen.

Enterococcus spp. is now the third most common pathogen among hospitalized patients, accounting for nearly 12% of nosocomial infections. Enterococcus faecalis is the most prevalent enterococcal species (85%-89%), whereas Enterococcus faecium accounts for 10%-15% of enterococcal isolates. Only 5% of E. faecalis isolates are resistant to glycopeptides. E. faecium has also been shown to be resistant to nonglycopeptide compounds, such as penicillins (97%), high-level gentamicin (52.1%), and high-level streptomycin (58.3%). Numerous risk factors for vancomycin-resistant enterococci (VRE) have been identified, including as length of hospital- or ICU-stay, proximity to a hospitalized, colonized VRE, patient severity of illness, renal failure, recent surgery, immunosuppression, and organ recipient status. An important risk factor is prior exposure to antibiotics such as vancomycin, ceftazidime, ciprofloxacin, and metronidazole, as well as the number and duration of recent antibiotics. Interventions to reduce nosocomial VRE cross-transmission have also been studied. Using gowns in addition to gloves diminished the incidence of VRE in one study, but had a negligible effect in a second study. Studies have shown that in many cases (> 60%) vancomycin usage is inappropriate. While controlling the use of vancomycin alone has only variably diminished VRE colonization, other efforts such as narrowing the spectrum of antibiotics, antiseptics, and reducing immunosuppression may be salutary. Attempts to eradicate VRE intestinal carriage with enteral agents (bacitracin, tetracycline + rifampin, novobiocin) have been reported but seem to have only a transient effect. Non-antimicrobial interventions such as removal of intravenous or bladder catheters and/or surgical or percutaneous drainage may be beneficial. In addition, the development of new antimicrobial agents such as streptogramins, glycopeptides, everninomicins, and oxazalididones will hopefully play an important role in reducing morbidity from these pathogens.

Anti-Bacterial Agents↗

PubMed1996

Elution characteristics of vancomycin and tobramycin combined in acrylic bone-cement.

Combining two antibiotics in antibiotic-loaded bone-cement is common in clinical practice. As the effect this has on elution characteristics is unknown, an in vitro quantitative elution study was carried out. Three groups of five antibiotic-loaded cement disks were prepared and placed in individual saline baths for 5 weeks. The elution of tobramycin from the disks in the study group (containing 2.4 g tobramycin and 1.0 g vancomycin per 40-g packet of Palacos-R cement powder [Smith & Nephew Orthopaedics, Memphis, TN]) was increased by 68% over that of the tobramycin control disks (2.4 g tobramycin only) (P = .024). The release of vancomycin from the study group disks was increased by 103% over the vancomycin control disks (1.0 g vancomycin only) (P = .007). Combining two antibiotics in bone-cement improves elution of both antibiotics in vitro and may translate into enhanced elution in vivo.

Anti-Bacterial Agents↗

PubMed2002

Effect of vancomycin on Staphylococcus epidermidis adherence to poly(methyl methacrylate) intraocular lenses.

PURPOSE: To study the adherence of Staphylococcus epidermidis in variable loads (10(8) cfu/mL and 10(3) cfu/mL) to poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) and to evaluate the effect of vancomycin treatment on S epidermidis adherence to the IOL. SETTING: L.V. Prasad Eye Institute, Hyderabad, India. METHODS: The study was designed in 2 parts. Phase I: Twelve PMMA IOLs were soaked in a solution of S epidermidis, randomized to 10(8) cfu/mL or 10(3) cfu/mL. They were rinsed or rinsed and vortexed and cultured. Phase II: Twelve IOLs were treated with vancomycin (10 mg/mL), randomized to before and after treatment with S epidermidis. RESULTS: Staphylococcus epidermidis adhered to all portions of the IOL with 10(8) cfu/mL and 10(3) cfu/mL bacterial loads. Treatment with vancomycin reduced S epidermidis adherence. CONCLUSION: Pretreatment of an IOL with vancomycin or a suitable antibiotic agent appears to reduce bacterial adherence to the IOL. Placement of a sustained-release device that could release an antibiotic agent over a specific period, reducing the incidence of postcataract endophthalmitis, should be studied.

Anti-Bacterial Agents↗

PubMedDate not supplied

Vancomycin prophylaxis and intraocular contamination during cataract surgery.

PURPOSE: To investigate the effect of vancomycin added to the intraocular irrigation solution to prevent anterior chamber contamination during phacoemulsification. SETTING: Centre Hospitalier, Villeneuve-Saint-Georges, France. METHODS: A group of 372 patients having cataract extraction by phacoemulsification was divided into two consecutive, nonrandomized groups. The first group (n = 190) was a control; there was no antibiotic in the irrigation solution. The second group (n = 182) received vancomycin in the irrigation solution. Intraocular fluid was aspirated at the end of surgery and injected into a blood culture bottle to evaluate bacterial contamination of the anterior chamber. RESULTS: There was no between-group difference in bacterial intraocular contamination. Eight samples in the first group were contaminated and nine in the second group. All contaminants were gram-positive vancomycin-sensitive organisms. CONCLUSIONS: Adding vancomycin to the intraocular irrigation solution during cataract surgery had no effect on the occurrence of intraocular contamination as evaluated by anterior chamber taps.

Anterior Chamber↗

PubMed2000

Antibiotics for gram-positive bacterial infections. Vancomycin, teicoplanin, quinupristin/dalfopristin, and linezolid.

Vancomycin is a safe, effective antibiotic for a variety of serious gram-positive infections. Because of emerging resistance in enterococci and staphylococci and the emerging threat of spread of vancomycin-resistant genes to other gram-positive organisms, judicious use of vancomycin should be promoted. Quinupristin/dalfopristin, a streptogramin antibiotic, and linezolid, an oxazolidinone, show promise against some strains of gram-positive bacteria that are resistant to vancomycin.

Acetamides↗

PubMed2002

TDM coupled with Bayesian forecasting should be considered an invaluable tool for optimizing vancomycin daily exposure in unstable critically ill patients.

A randomized two-arm prospective study was planned to assess the role of therapeutic drug monitoring (TDM) coupled with a Bayesian approach in tailoring vancomycin dosages in unstable critically ill patients. Group A (n=16) had their regimen adjusted day-by-day according to TDM and Bayesian forecasting (D(a)); group B (n=16) had their regimen adjusted day-by-day according to Moellering's nomogram (D(M)). Blood samples were collected every 1-2 days to assess the trough and peak plasma concentrations. In group A, the tailored D(a) required for optimizing vancomycin exposure were considerably higher than the D(M) in 7/16 cases, and lower than the D(M) in 1/16 cases. In group B, standard D(M) caused under-treatment in 3/16 cases and over-treatment in 4/16 cases. Most of these patients concomitantly had some conditions that might have altered vancomycin disposition. The TDM-guided Bayesian-based approach should be considered an invaluable tool for clinicians to handle appropriately on real-time vancomycin therapy in critically ill patients.

Adult↗

PubMed2003

Antibacterial activity of 2,4-diacetylphloroglucinol produced by Pseudomonas sp. AMSN isolated from a marine alga, against vancomycin-resistant Staphylococcus aureus.

Antibacterial activity of 2,4-diacetylphloroglucinol (DAPG) was evaluated against 23 vancomycin-resistant Staphylococcus aureus (VRSA) strains isolated from several Asian and European countries, Brazil, South Africa and USA, and against vancomycin-resistant Enterococcus spp (VRE) genotypes A, B and C. DAPG was active against a wide range of VRSA isolates as well as vancomycin hetero-resistant S. aureus (h-VRSA) at MIC 4 mg/l. This substance also had moderate activity against both VRE-A and -B at MIC 8 mg/l, but not against VRE-C at up to 16 mg/l. The activity of DAPG did not directly correlate with levels of vancomycin resistance in VRSA and VRE. These results suggest that DAPG might be useful in developing new antibiotics against VRSA.

Anti-Bacterial Agents↗

PubMed2003

Identification of potent and broad-spectrum antibiotics from SAR studies of a synthetic vancomycin analogue.

Dimeric vancomycin analogues based on a lead compound identified from a library of synthetic analogues of vancomycin have up to 60-fold greater activity than vancomycin against vancomycin-resistant Enterococcus faecium (VRE, VanA phenotype). Simplified analogues have also been prepared and found to maintain activity against VRE and have broad-spectrum antibiotic activity.

Anti-Bacterial Agents↗

PubMed2000

Enzymes of vancomycin resistance: the structure of D-alanine-D-lactate ligase of naturally resistant Leuconostoc mesenteroides.

BACKGROUND: The bacterial cell wall and the enzymes that synthesize it are targets of glycopeptide antibiotics (vancomycins and teicoplanins) and beta-lactams (penicillins and cephalosporins). Biosynthesis of cell wall peptidoglycan requires a crosslinking of peptidyl moieties on adjacent glycan strands. The D-alanine-D-alanine transpeptidase, which catalyzes this crosslinking, is the target of beta-lactam antibiotics. Glycopeptides, in contrast, do not inhibit an enzyme, but bind directly to D-alanine-D-alanine and prevent subsequent crosslinking by the transpeptidase. Clinical resistance to vancomycin in enterococcal pathogens has been traced to altered ligases producing D-alanine-D-lactate rather than D-alanine-D-alanine. RESULTS: The structure of a D-alanine-D-lactate ligase has been determined by multiple anomalous dispersion (MAD) phasing to 2.4 A resolution. Co-crystallization of the Leuconostoc mesenteroides LmDdl2 ligase with ATP and a di-D-methylphosphinate produced ADP and a phosphinophosphate analog of the reaction intermediate of cell wall peptidoglycan biosynthesis. Comparison of this D-alanine-D-lactate ligase with the known structure of DdlB D-alanine-D-alanine ligase, a wild-type enzyme that does not provide vancomycin resistance, reveals alterations in the size and hydrophobicity of the site for D-lactate binding (subsite 2). A decrease was noted in the ability of the ligase to hydrogen bond a substrate molecule entering subsite 2. CONCLUSIONS: Structural differences at subsite 2 of the D-alanine-D-lactate ligase help explain a substrate specificity shift (D-alanine to D-lactate) leading to remodeled cell wall peptidoglycan and vancomycin resistance in Gram-positive pathogens.

Adenosine Diphosphate↗

PubMed2001

Structure of the UDP-glucosyltransferase GtfB that modifies the heptapeptide aglycone in the biosynthesis of vancomycin group antibiotics.

BACKGROUND: Members of the vancomycin group of glycopeptide antibiotics have an oxidatively crosslinked heptapeptide scaffold decorated at the hydroxyl groups of 4-OH-Phegly4 or beta-OH-Tyr6 with mono- (residue 6) or disaccharides (residue 4). The disaccharide in vancomycin itself is L-vancosamine-1,2-glucose, and in chloroeremomycin it is L-4-epi-vancosamine-1,2-glucose. The sugars and their substituents play an important role in efficacy, particularly against vancomycin-resistant pathogenic enterococci. RESULTS: The glucosyltransferase, GtfB, that transfers the glucose residue from UDP-glucose to the 4-OH-Phegly4 residue of the vancomycin aglycone, initiating the glycosylation pathway in chloroeremomycin maturation, has been crystallized, and its structure has been determined by X-ray analysis at 1.8 A resolution. The enzyme has a two-domain structure, with a deep interdomain cleft identified as the likely site of UDP-glucose binding. A hydrophobic patch on the surface of the N-terminal domain is proposed to be the binding site of the aglycone substrate. Mutagenesis has revealed Asp332 as the best candidate for the general base in the glucosyltransfer reaction. CONCLUSIONS: The structure of GtfB places it in a growing group of glycosyltransferases, including Escherichia coli MurG and a beta-glucosyltransferase from T4 phage, which together form a subclass of the glycosyltransferase superfamily and give insights into the recognition of the NDP-sugar and aglycone cosubstrates. A single major interdomain linker between the N- and C- terminal domains suggests that reprogramming of sugar transfer or aglycone recognition in the antibiotic glycosyltransferases, including the glycopeptide and also the macrolide antibiotics, will be facilitated by this structural information.

Amino Acid Sequence↗

PubMed1998

Active-site mutants of the VanC2 D-alanyl-D-serine ligase, characteristic of one vancomycin-resistant bacterial phenotype, revert towards wild-type D-alanyl-D-alanine ligases.

BACKGROUND: The rising number of vancomycin-resistant enterococci (VREs) is a major concern to modern medicine because vancomycin is currently the 'last resort' drug for life-threatening infections. The D-alanyl-D-X ligases (where X is an hydroxy or amino acid) of bacteria catalyze a critical step in bacterial cell-wall peptidoglycan assembly. In bacteria that produce glycopeptide antibiotics and in opportunistic pathogens, including VREs, D-, D-ligases serve as switches that confer antibiotic resistance on the bacteria themselves. Peptidoglycans in vancomycin-sensitive bacteria end in D-alanyl-D-alanine, whereas in vancomycin-resistant bacteria they end in D-alanyl-D-lactate or D-alanyl-D-serine. RESULTS: We demonstrate that the selective utilization of D-serine by the Enterococcus casseliflavus VanC2 ligase can be altered by mutagenesis of one of two residues identified by homology to the X-ray structure of the Escherichia coli D-alanyl-Dalanine ligase (DdlB). The Arg322-->Met (R322M) and Phe250-->Tyr (F250Y) ligase mutants show a 36-44-fold decrease in the use of D-serine, as well as broadened specificity for utilization of other D-amino acids in place of D-serine. The F250Y R322M double mutant is effectively disabled as a D-alanyl-D-serine ligase and retains 10% of the catalytic activity of wild-type D-alanyl-D-alanine ligases, reflecting a 6,000-fold switch to the D-alanyl-D-alanine peptide. Correspondingly, the Leu282-->Arg mutant of the wild-type E. coli DdlB produced a 560-fold switch towards D-alanyl-D-serine formation. CONCLUSIONS: Single-residue changes in the active-site regions of D-, D-ligases can cause substantial changes in recognition and activation of hydroxy or amino acids that have consequences for glycopeptide antibiotic efficacy. The observations reported here should provide an approach for combatting antibiotic-resistant bacteria.

Amino Acid Sequence↗

PubMed2006

Safety and effectiveness of a preoperative allergy clinic in decreasing vancomycin use in patients with a history of penicillin allergy.

BACKGROUND: We developed a clinical pathway to optimize the use of antimicrobials by decreasing vancomycin use in preoperative patients with a history of penicillin allergy. OBJECTIVE: To decrease the use of vancomycin in surgical patients with a self-reported penicillin allergy. METHODS: In June 2002, same-day allergy consultation and penicillin skin testing were made available for preoperative patients with self-reported penicillin allergy at the preoperative evaluation (POE) clinic. We reviewed the penicillin allergy skin test results, recommendations, and beta-lactam antibiotic administration outcomes from July 1, 2002, to September 16, 2003. RESULTS: A total of 1,204 of 11,819 patients were evaluated for beta-lactam allergy at the POE clinic. Of these, 1,120 were approved by the institutional review board for inclusion in the study and 9 were excluded from the study. Of the remaining 1,111 patients, 1,030 (93%) underwent skin testing for penicillin allergy. Forty-three (4%) had a positive skin test result to penicillin. A total of 947 (85%) of the 1,111 patients with a history of beta-lactam allergy were advised to use a beta-lactam antibiotic, and 164 (15%) were advised to avoid beta-lactams. A total of 955 patients (86%) actually received preoperative antibiotics. Of these 955 patients, 716 (75%) received cefazolin, and only 149 (16%) received vancomycin compared with 30% historical controls (P < .01). Among the patients with a negative penicillin skin test result who received a cephalosporin, 5 (0.7%) of 675 experienced an adverse drug reaction to a cephalosporin. CONCLUSIONS: Establishment of a clinical pathway in a preoperative clinic that includes allergy consultation and penicillin skin testing reduced vancomycin use to only 16% in surgical patients with a history of beta-lactam allergy.

Adolescent↗

PubMed1997

In vitro susceptibility studies and detection of vancomycin resistance genes in clinical isolates of enterococci in Nagasaki, Japan.

Glycopeptide resistance in enterococci is now a cause of clinical concern in the United States and Europe. However, details of vancomycin resistance in enterococci in Japan have been unknown. We measured minimum inhibitory concentrations (MICs) of various antimicrobial agents for a total of 218 clinical strains of enterococci isolated in our hospital in 1995-6 in addition to 15 strains with known genotypic markers of resistance. We also screened vancomycin resistance genes using a single step multiplex-PCR. In clinical isolates, only two strains of Enterococcus gallinarum were of intermediate resistance to vancomycin (MIC, 8 micrograms/ml), while the others were all susceptible. Glycopeptides (vancomycin and teicoplanin) and streptogramins (RP 58500 and RPR 106972) showed potent antimicrobial effects for the isolates. In addition, ampicillin was also potent for Enterococcus faecalis, while ampicillin, minocycline and gentamicin were potent for Enterococcus avium. No vanA or vanB genes were detected, while vanC1 and vanC23 genes were detected from two and four strains, respectively. Our results suggest that incidence of VRE in Japan may be estimated as still very low at this time.

Anti-Bacterial Agents↗