Vancomycin-resistant Gram-positive Bacteria Research Articles

New Antibiotics for the Treatment of Nosocomial Central Nervous System Infections.

Nosocomial central nervous system (CNS) infections with carbapenem- and colistin-resistant Gram-negative and vancomycin-resistant Gram-positive bacteria are an increasing therapeutic challenge. Here, we review pharmacokinetic and pharmacodynamic data and clinical experiences with new antibiotics administered intravenously for the treatment of CNS infections by multi-resistant bacteria. Cefiderocol, a new siderophore extended-spectrum cephalosporin, pharmacokinetically behaves similar to established cephalosporins and at high doses will probably be a valuable addition in our therapeutic armamentarium for CNS infections. The new glycopeptides dalbavancin, telavancin, and oritavancin are highly bound to plasma proteins. Although effective in animal models of meningitis, it is unlikely that they reach effective cerebrospinal fluid (CSF) concentrations after intravenous administration alone. The β-lactam/β-lactamase inhibitor combinations have the principal problem that both compounds must achieve adequate CSF concentrations. In the commercially available combinations, the dose of the β-lactamase inhibitor tends to be too low to achieve adequate CSF concentrations. The oxazolidinone tedizolid has a broader spectrum but a less suitable pharmacokinetic profile than linezolid. The halogenated tetracycline eravacycline does not reach CSF concentrations sufficient to treat colistin-resistant Gram-negative bacteria with usual intravenous dosing. Generally, treatment of CNS infections should be intravenous, whenever possible, to avoid adverse effects of intraventricular therapy (IVT). An additional IVT can overcome the limited penetration of many new antibiotics into CSF. It should be considered for patients in which the CNS infection responds poorly to systemic antimicrobial therapy alone.

First detection of vanA positive Enterococcus faecium clonal complex 17 in hospital wastewater in Algeria: an epidemiological report

Enterococcus spp. are Gram-positive cocci that are recognised as critical opportunistic pathogens, especially in immunocompromised patients. Vancomycin is considered as the drug of last resort for the treatment of infections caused by Enterococcus species, making vancomycin resistance a serious public health concern. In this article, we report the first environmental vanA positive Enterococcus faecium isolates in Algeria. The strains were selectively isolated from hospital wastewater and then identified using matrix-assisted laser desorption and ionisation time-of-flight mass spectrometry. Antibiotic susceptibility testing was performed using the disc diffusion method. Vancomycin resistance genes were searched for by standard PCR and the clonal relatedness of our isolates was investigated by multilocus sequence typing. A total of five highly vancomycin-resistant Gram-positive bacteria were isolated and identified as Enterococcus faecium. The isolates harboured the vanA gene and were assigned to the clonal complex 17. Our findings confirm the great potential of hospital wastewater as a reservoir and dissemination pathway of multidrug resistant organisms, and alert to the need for better regulation of hospital waste management in order to reduce their impact on the environment.

Strategy for Producing the High-Quality Glycopeptide Antibiotic A82846B in Amycolatopsis orientalis Based on the CRISPR-Cas12a System.

Oritavancin is a new-generation semisynthetic lipoglycopeptide antibiotic used to prevent the spread of vancomycin-resistant Gram-positive bacteria. The glycopeptide A82846B is the direct precursor of oritavancin. Considering the structural similarity between A82846B and vancomycin, the vancomycin producer Amycolatopsis orientalis was used as a chassis for the construction of a strain producing high-quality A82846B. To construct the A82846B synthetic pathway, we established a highly efficient CRISPR-Cas12a system by optimizing the conditions of conjugation and by screening the regulatory elements in the A. orientalis, which is difficult to be genetically manipulated. The efficiency of gene knockout was almost 100%. The glycosyltransferases module (gtfDE) and glycosyl synthesis module (vcaAEBD) in the vancomycin gene cluster were replaced with the corresponding glycosyltransferases module (gtfABC) and glycosyl synthesis module (evaAEBD) in the A82846B cluster, respectively. A82846B was successfully produced by the artificially constructed synthetic pathway. Moreover, the titer of A82846B was increased 80% by expressing the pathway-specific regulatory strR. This strategy has excellent potential for remodification of natural products to solve antibiotic resistance.

Characterization of a Linezolid- and Vancomycin-Resistant Streptococcus suis Isolate That Harbors optrA and vanG Operons.

Linezolid and vancomycin are among the last-resort antimicrobial agents in the treatment of multidrug-resistant Gram-positive bacterial infections. Linezolid- and vancomycin-resistant (LVR) Gram-positive bacteria may pose severe threats to public health. In this study, three optrA- and vanG-positive Streptococcus suis strains were isolated from two farms of different cities. There were only 1 and 343 single-nucleotide polymorphisms in coding region (cSNPs) of HCB4 and YSJ7 to YSJ17, respectively. Mobilome analysis revealed the presence of vanG, erm(B), tet(O/W/32/O), and aadE-apt-sat4-aphA3 cluster on an integrative and conjugative element, ICESsuYSJ17, and erm(B), aphA3, aac(6′)-aph(2″), catpC194, and optrA on a prophage, ΦSsuYSJ17-3. ICESsuYSJ17 exhibited a mosaic structure and belongs to a highly prevalent and transferable ICESa2603 family of Streptococcus species. ΦSsuYSJ17-3 shared conserved backbone to a transferable prophage Φm46.1. A novel composite transposon, IS1216E-araC-optrA-hp-catpC194-IS1216E, which can be circulated as translocatable unit (TU) by IS1216E, was integrated on ΦSsuYSJ17-3. Vancomycin resistance phenotype and vanG transcription assays revealed that the vanG operon was inducible. The LVR strain YSJ17 exhibited moderate virulence in a zebrafish infection model. To our knowledge, this is the first report of LVR isolate, which is mediated by acquired resistance genes optrA and vanG operons in Gram-positive bacteria. Since S. suis has been recognized as an antimicrobial resistance reservoir in the spread of resistance genes to major streptococcal pathogens, the potential risks of disseminating of optrA and vanG from S. suis to other Streptococcus spp. are worrisome and routine surveillance should be strengthened.

Emergence of drug resistant bacteria at the Hajj: A systematic review.

Hajj is the annual mass gathering of Muslims, and is a reservoir and potential source of bacterial transmission. The emergence of bacterial transmission, including multi-drug resistance (MDR) bacteria, during Hajj has not been systematically assessed. Articles in Pubmed, Scopus, and Google scholar were identified using controlled words relating to antibiotic resistance (AR) at the Hajj from January 2002 to January 2017. Eligible studies were identified by two researchers. AR patterns of bacteria were obtained for each study. We included 31 publications involving pilgrims, Hajj workers or local patients attending hospitals in Mecca, Mina, and the Medina area. Most of these publications provided antibiotic susceptibility results. Ten of them used the PCR approach to identify AR genes. MRSA carriage was reported in pilgrims and food handlers at a rate of 20%. Low rates of vancomycin-resistant gram-positive bacteria were reported in pilgrims and patients. The prevalence of third-generation cephalosporin-resistant bacteria was common in the Hajj region. Across all studies, carbapenem-resistant bacteria were detected in fewer than 10% of E.coli isolates tested but up to 100% in K.pneumoniae and A.baumannii. Colistin-resistant Salmonella enterica, including mcr-1 colistin-resistant E.coli and K.pneumoniae were only detected in the pilgrim cohorts. This study provides an overview of the prevalence of MDR bacteria at the Hajj. Pilgrims are at high risk of AR bacterial transmission and may carry and transfer these bacteria when returning to their home countries. Thus, pilgrims should be instructed by health care practitioners about hygiene practices aiming at reducing traveler's diarrhea and limited use of antibiotics during travel in order to reduce the risk of MDR bacterial transmission.

Impact of Red Blood Cell and Platelet Transfusions in Acute Myeloid Leukemia (AML) Patients Undergoing Remission Induction Chemotherapy

Background: Induction chemotherapy (IC) in Acute Myeloid Leukemia (AML) leads to significant bone marrow suppression. The standard clinical practice to prevent or manage cytopenia related complications, namely anemia or bleeding, has been red blood cell (RBC) and platelet (PLT) transfusion. Accumulating evidence suggests no advantage to patients (pts) managed with liberal transfusion strategies compared to a restrictive approach. However, prior studies excluded patients with bone marrow failure conditions such as AML; hence it remains unclear whether a similar approach can be extrapolated for AML pts. We undertook this study to evaluate the effects of transfusions on treatment outcomes and complications in AML.Methods: Adult pts diagnosed with AML (excluding acute promyelocytic leukemia) at the Cleveland Clinic from 01/2008 - 12/2012 who underwent IC with 7+3 (full dose of cytarabine and anthracycline) and had complete adverse event data were included. Variables including demographics, preexisting comorbidities, AML disease characteristics, organ dysfunction (neurologic, cardiac, pulmonary, renal, hepatic, bleeding and thromboembolic events), infections (bloodstream infection, pneumonia and clostridium difficile associated diarrhea) and treatment response [complete remission (CR), incomplete remission (CRi), persistent disease (PD) and 30-day mortality] were assessed. The outcome of interest was any correlation between the total number of PLT and/or RBC transfusions and (i) organ impairment, (ii) infections, and (iii) treatment outcomes during the induction period. Culture confirmed bloodstream infections included vancomycin resistant enterococcus (VRE), gram-positive bacteria (except VRE), gram-negative bacilli and fungemia. Univariable and multivariable logistic regression models adjusted for potential confounders were performed for each outcome category. Odds ratio (OR) with 95% confidence intervals (CI) are reported.Results: Of 192 pts, 48% (n=93) were female, 85% (n=163) were Caucasian, 54% (n=103) were <60 years, (yrs, range, 19-82), and 17% (n=33) received 2 cycles of induction chemotherapy. Disease characteristics were - de novo AML 89% (n=170) and secondary AML 12% (n=22). Cytogenetic risk groups per CALGB 8461 criteria were - favorable 21% (n=41), intermediate 46% (n=89), unfavorable 24% (n=46), and unknown cytogenetics 8% (n=16). 67% of patients achieved CR (n=128), 15% (n=29) achieved CRi and 14% (n=27) had PD following IC. The median number of RBC and PLT transfusions received during remission induction chemotherapy was 12 RBCs (range 0-49) and 10 PLTs (range 0-62) (figure 1 and 2).In univariable analysis a higher number of RBC and PLT transfusions was associated with an increased risk of bloodstream infections (OR=1.03; CI,1.01-1.05; p=0.001). In multivariable analysis increased number of transfused RBCs and PLTs was associated with lower CR rates (OR=0.94; CI,0.91-0.97; p<0.001) and slightly increased risk for major adverse cardiac events (OR=1.04; CI,1.02-1.07; p=0.002), pulmonary events (OR=1.04; CI,1.02-14.07; p=0.004), neurologic events (OR 1.14; CI,1.07-1.22; p<0.001) and VRE bacteremia (OR=1.04; CI,1.01-1.08; p=0.005). There was no statistically significant association between transfusion and renal dysfunction (OR 1.02; CI,0.99-1.06, p=0.15), liver injury (OR=1.02; CI,1.00-1.05; p=0.067), thromboembolic events (OR=1.02; CI,0.98-1.05; p=0.28), total number of blood stream infections (OR 1.03; CI,1.00-1.05; p=0.019) and 30-day mortality (OR=0.98; CI,0.93-1.03; p=0.56).Conclusion: In multivariable analysis the number of RBC and PLT transfusions during AML IC is associated with a slightly increased risk for cardiac, pulmonary and some infectious complications. Higher numbers of transfusions also appear to be associated with lower CR rates. These data can inform future prospective studies designed to determine the benefits and risks of a restrictive transfusion policy in the AML population. [Display omitted] [Display omitted] DisclosuresSekeres:TetraLogic: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees.

Development, Optimization, and Validation of a Green and Stability-Indicating HPLC Method for Determination of Daptomycin in Lyophilized Powder.

Daptomycin is an antimicrobial that plays an important role in clinical practice today because it is considered a promising drug to combat resistant strains, such as methicilin and vancomycin-resistant Gram-positive bacteria. Considering the analysis of daptomycin in a pharmaceutical dosage form, the only method found in literature uses potentially toxic organic solvents. Therefore, the objective of this work was to develop a green and stability-indicating HPLC method for determination of daptomycin in lyophilized powder. The mobile phase was ethanol-water (55+45, v/v) at pH 4.5 pumped at a flow rate of 0.6 mL/min. A C18 column was used, and UV detection was performed at 221 nm. Stress degradation studies were conducted in order to demonstrate the specificity and stability-indicating capability of the method. The method was validated according to International Conference on Harmonization guidelines, proving to be linear (r=0.9996), precise, accurate, robust (demonstrated by the Plackett-Burman model), and specific within the range 20-70 μg/mL. The retention time of daptomycin was 5.8 min. It can be concluded that the validated method can be a fast, safe, and environmentally friendly alternative for the analysis of daptomycin.

Polyphasic characterization of an anaerobic hexachlorobenzene-dechlorinating microbial consortium with a wide dechlorination spectrum for chlorobenzenes

An anaerobic consortium that was capable of reductively dechlorinating hexachlorobenzene (HCB) to benzene was enriched from contaminated sediment. The consortium was capable of dechlorinating all chlorobenzene isomers except 1,4-dichlorobenzene. Singly and doubly flanked chlorines, as well as unflanked meta-substituted chlorines, were dechlorinated, although doubly flanked chlorines were preferred. Formate, acetate and lactate (but not ethanol) could be utilized as optimum electron donors for reductive dechlorination. Alternative electron acceptors, including nitrate and sulfate, completely inhibited HCB degradation, whereas amorphous iron oxide (FeOOH) did not suppress dechlorination activity. No degradation was found in chloramphenicol-treated consortium; however, vancomycin, molybdate, and 2-bromoethanesulfonate did not inhibit HCB dechlorination. The results of inhibitory treatments suggested that the dechlorinators were non-sulfate-reducing gram-negative or vancomycin resistant gram-positive bacteria. In addition to physiological characterization, analyses of 16S rRNA gene library of the consortium and quantitative PCR of 16S rRNA genes suggested that Dehalococcoides sp. was involved in the reductive dechlorination of HCB, and Geobacter sp. may serve as a dechlorinating candidate.

Oritavancin for the treatment of acute bacterial skin and skin structure infections: an evidence-based review.

The emergence of resistance to glycopeptide antibiotics such as vancomycin and teicoplanin among Gram-positive bacteria has spurred the search for second-generation drugs of this class. Oritavancin, a promising novel, second-generation, semisynthetic lipoglycopeptide, is distinguished by two mechanisms of action: inhibition of cell wall synthesis and disruption of the cell membrane. This dual mechanism of action has increased the activity of oritavancin against vancomycin-resistant Gram-positive bacteria compared to other glycopeptides. Oritavancin has a concentration-dependent and rapid bactericidal activity against Gram-positive bacteria, particularly enterococci, contrary to vancomycin and teicoplanin, which exhibit bacteriostatic activity. It has a long half-life of about 195.4 hours and is slowly eliminated by the liver and kidneys, allowing once-daily dosing. Oritavancin has demonstrated preliminary safety and efficacy in Phase I and Phase II clinical trials. It was recently shown to be noninferior to vancomycin in a large Phase III randomized, double-blind clinical trial. To date, adverse events have been mild and limited, the most common being administration site complaints, headache, and nausea. Oritavancin appears to be a promising antimicrobial alternative to vancomycin with additional activity against Staphylococcus and Enterococcus isolates resistant to vancomycin and a more convenient way of administration.

Vancomycin-Resistant Gram-Positive Cocci Isolated from the Saliva of Wild Songbirds

We analyzed highly vancomycin-resistant Gram-positive bacteria isolated from the saliva of migratory songbirds captured, sampled, and released from a bird-banding station in western Kansas. Individual bacterial isolates were identified by partial 16S rRNA sequencing. Most of the bacteria in this study were shown to be Staphylococcus succinus with the majority being isolated from the American Robin. Some of these bacteria were shown to carry vanA, vanB, and vanC vancomycin-resistance genes and have the ability to form biofilms. One of the van gene-carrying isolates is also coagulase positive, which is normally considered a virulence factor. Other organisms isolated included Staphylococcus saprophyticus as well as Enterococcus gallinarum. Given the wide range of the American Robin and ease of horizontal gene transfer between Gram-positive cocci, we postulate that these organisms could serve as a reservoir of vancomycin-resistance genes capable of transferring to human pathogens.

Management of Infections Caused by Vancomycin-Resistant Gram-Positive Bacteria

For 3 decades, vancomycin has been a favored therapy for serious penicillinand cephalosporin-resistant Gram-positive bacterial infections. Development of vancomycin resistance may have been restrained by the requirement for intravenous administration, which limited its use and lessened exposure to the gastrointestinal flora. Nevertheless, physicians are increasingly encountering children and adults infected with vancomycin-resistant Gram-positive organisms. Resistance to vancomycin has been encountered in all commonly occurring, clinically significant Gram-positive bacterial species except Streptococcus pyogenes, Streptococcus pneumoniae, and Streptococcus agalactiae. Although therapeutic options are usually guided by the antimicrobial susceptibilities of individual isolates, recommended infection-control measures vary with the specific species and the mechanism of resistance. VANCOMYCIN-RESISTANT STAPHYLOCOCCUS AUREUS Vancomycin-resistant Staphylococcus aureus (VRSA) were first recognized in Japan in 1996; the first case of infection due to VRSA in the United States was reported in 2002. Since then, at least 8 additional cases of VRSA infection have been identified in the United States, with more than half of these cases occurring in Michigan. Isolates often seem to have evolved independently in settings where patients were previously colonized with vancomycin-resistant enterococcus (VRE) and methicillin-resistant S. aureus (MRSA). Environments that promote biofilm formation may facilitate transmission of resistance from VRE to MRSA. VRSA isolates (vancomycin MIC 16 g/mL) are fundamentally different from vancomycin-intermediate S. aureus (VISA) isolates (vancomycin MIC 4 – 8 g/mL). Resistance in VISA isolates is typically mediated via mechanisms that develop in the presence of vancomycin and are not readily transferrable to other strains. The potential for spread of these isolates is low in the absence of vancomycin therapy. In contrast, VRSA isolates uniformly contain the vanA gene derived from enterococcus (discussed below). The VanA phenotype is transferable to other MRSA strains and across microbial species, with a much greater potential for spread, even in the absence of vancomycin therapy. Thus far, VRSA outbreaks have not occurred; however, because of the potential for spread with dire consequences, a case of VRSA infection warrants a more rigorous infection-control response than a case of infection with MRSA, VISA, or VRE. Infection-control measures should be implemented urgently according to a written plan, if VRSA is suspected. The local health department and the Centers for Disease Control and Prevention should be consulted immediately. Management of contacts should occur according to contact categorization. Attempts to decolonize individuals who are found to be colonized should be considered on a case-by-case basis. Infections with S. aureus isolates that have vancomycin MICs 4 g/mL typically do not respond clinically to vancomycin therapy. To date, all VRSA have also been found to be resistant to methicillin. Fortunately, all VRSA and VISA isolates have been susceptible to one or more commercially available antibiotics. Recommended antibiotics for VRSA and VISA, according to susceptibilities and other clinical considerations, are listed in Table 1. Secondary agents include teicoplanin (not available in the United States), trimethoprim-sulfamethoxazole, tetracycline, rifampin (usually in combination therapy), and chloramphenicol.

Hexachlorobenzene dechlorination by indigenous sediment microorganisms

Indigenous microbes from the sediments, whether contaminated with hexachlorobenzene (HCB) or not, could dechlorinate HCB effectively without any acclimation and supplemental nourishment. Temperature seriously affected the HCB-dechlorination: within the measured 15–45 °C span, the optimum range was between 30 and 35 °C. Sulfate-reducing bacteria (SRB), denitrifiers, and acetogens might not be directly involved in the HCB dechlorination. However, the SRB retarded subsequent dechlorination of pentachlorobenzene to tetra- and trichlorobenzenes. Some vancomycin-resistant gram-positive bacteria and methanogens were most likely to be the HCB-dechlorinators. The dechlorination followed the Michaelis–Menten behavior with the k′ m and K HCB between 0.45–0.73 mg L −1 day −1 and 3.2–17.2 mg L −1, respectively. These findings suggest a potential HCB treatment and cleanup for wastewater and contaminated site.

Accuracies of Leuconostocphenotypic identification: a comparison of API systems and conventional phenotypic assays

BackgroundCommercial diagnostics are commonly used to identify gram-positive bacteria. Errors have been reported mostly at the species level. We have found certain phenotypic criteria used in API systems which significantly misidentify Leuconostoc, an emerging human pathogen, at the genus level. We also attempt to find practical, conventional phenotypic assays for accurate identification of this group of bacteria.MethodsClinical isolates of catalase-negative, gram-positive coccoid or coccobacillary bacteria with non-β hemolysis in our institute during 1997–2004 were subject to an identification aid by API 20 STREP, following the instruction manual, as an aid to conventional phenotypic tests. Those identified as Leuconostoc by API 20 STREP were re-examined by the same kit and also by API 50 CHL according to the instruction manuals, by our Leuconostoc conventional phenotypic assays, by Leuconostoc- and Lactobacillus-specific PCR's, and, where possible, by 16S rDNA sequence analysis. In addition, catalase-negative gram-positive isolates during 2005–2006 which were resistant to vancomycin at high levels were also evaluated by the same phenotypic and genotypic assays.ResultsOut of several thousands of clinical gram-positive isolates, 26 catalase negative gram-positive isolates initially identified as Leuconostoc by API 20 STREP and 7 vancomycin-resistant gram-positive catalase-negative bacteria entered the study. 11 out of the 26 isolates and all the 7 isolates were identified as Leuconostoc by API 20 STREP. Only 5 isolates, however, were confirmed by both genotypic and all defined conventional phenotypic criteria. API 50 CHL also failed to reliably provide accurate identification of Leuconostoc. We have identified key problem tests in API 20 STREP leading to misidentification of the bacteria. A simple, conventional set of phenotypic tests for Leuconostoc identification is proposed.ConclusionThe current API systems cannot accurately identify Leuconostoc. Identification of vancomycin-resistant, catalase-negative gram-positive bacteria should be performed by a few practical phenotypic assays, with assistance of genotypic assays where available.

Characterization of biosynthetic gene cluster for the production of virginiamycin M, a streptogramin type A antibiotic, in Streptomyces virginiae

Virginiamycin M (VM) of Streptomyces virginiae is a hybrid polyketide-peptide antibiotic with peptide antibiotic virginiamycin S (VS) as its synergistic counterpart. VM and VS belong to the Streptogramin family, which is characterized by strong synergistic antibacterial activity, and their water-soluble derivatives are a new therapeutic option for combating vancomycin-resistant Gram-positive bacteria. Here, the VM biosynthetic gene cluster was isolated from S. virginiae in the 62-kb region located in the vicinity of the regulatory island for virginiamycin production. Sequence analysis revealed that the region consists of 19 complete open reading frames (ORFs) and one C-terminally truncated ORF, encoding hybrid polyketide synthase (PKS)-nonribosomal peptide synthetase (NRPS), typical PKS, enzymes synthesizing precursors for VM, transporters for resistance, regulatory proteins, and auxiliary enzymes. The involvement of the cloned gene cluster in VM biosynthesis was confirmed by gene disruption of virA encoding a hybrid PKS–NRPS megasynthetase, which resulted in complete loss of VM production without any effect on VS production. To assemble the VM core structure, VirA, VirF, VirG, and VirH consisting, as a whole, of 24 domains in 8 PKS modules and 7 domains in 2 NRPS modules were predicted to act as an acyltransferase (AT)-less hybrid PKS–NRPS, whereas VirB, VirC, VirD, and VirE are likely to be essential for the incorporation of the methyl group into the VM framework by a HMG-CoA synthase-based reaction. Among several uncommon features of gene organization in the VM gene cluster, the lack of AT domain in every PKS module and the presence of a discrete AT encoded by virI are notable. AT-overexpression by an additional copy of virI driven by ermEp ⁎ resulted in 1.5-fold increase of VM production, suggesting that the amount of VirI is partly limiting VM biosynthesis.

A Vancomycin-Heparin Lock Solution for Prevention of Nosocomial Bloodstream Infection in Critically Ill Neonates With Peripherally Inserted Central Venous Catheters: A Prospective, Randomized Trial

Critically ill neonates are at high risk for vascular catheter-related bloodstream infection (CRBSI), most often caused by coagulase-negative staphylococci. Most CRBSIs with long-term devices derive from intraluminal contaminants. The objective of this study was to ascertain the safety and the efficacy of a vancomycin-heparin lock solution for prevention of CRBSI. A prospective, randomized double-blind trial was conducted during 2000-2001 at a community hospital level III NICU. Very low birth weight and other critically ill neonates with a newly placed peripherally inserted central venous catheter were randomized to have the catheter locked 2 or 3 times daily for 20 or 60 minutes with heparinized normal saline (n = 43) or heparinized saline that contained vancomycin 25 microg/mL (n = 42). The origin of each nosocomial bloodstream infection (BSI) was studied by culturing skin, catheter hubs, and implanted catheter segments and blood cultures, demonstrating concordance by restriction-fragment DNA subtyping. Surveillance axillary and rectal cultures were performed to detect colonization by vancomycin-resistant organisms. The main outcome measures were (1) CRBSIs and (2) colonization or infection by vancomycin-resistant Gram-positive bacteria. Two (5%) of 42 infants in the vancomycin-lock group developed a CRBSI as compared with 13 (30%) of 43 in the control group (2.3 vs 17.8 per 1000 catheter days; relative risk: 0.13; 95% confidence interval: 0.01-0.57). No vancomycin-resistant enterococci or staphylococci were recovered from any cultures. Vancomycin could not be detected in the blood of infants who did not receive systemic vancomycin therapy. Twenty-six neonates (8 vancomycin-lock group, 18 control group) had at the end of a catheter-lock period asymptomatic hypoglycemia that resolved promptly when glucose-containing intravenous fluids were restarted. Prophylactic use of a vancomycin-heparin lock solution markedly reduced the incidence of CRBSI in high-risk neonates with long-term central catheters and did not promote vancomycin resistance but was associated with asymptomatic hypoglycemia. The use of an anti-infective lock solution for prevention of CRBSI with long-term intravascular devices has achieved proof of principle and warrants selective application in clinical practice.

Mechanism of action of the mannopeptimycins, a novel class of glycopeptide antibiotics active against vancomycin-resistant gram-positive bacteria.

The naturally occurring mannopeptimycins (formerly AC98-1 through AC98-5) are a novel class of glycopeptide antibiotics that are active against a wide variety of gram-positive bacteria. The structures of the mannopeptimycins suggested that they might act by targeting cell wall biosynthesis, similar to other known glycopeptide antibiotics; but the fact that the mannopeptimycins retain activity against vancomycin-resistant organisms suggested that they might have a unique mode of action. By using a radioactive mannopeptimycin derivative bearing a photoactivation ligand, it was shown that mannopeptimycins interact with the membrane-bound cell wall precursor lipid II [C(55)-MurNAc-(peptide)-GlcNAc] and that this interaction is different from the binding of other lipid II-binding antibiotics such as vancomycin and mersacidin. The antimicrobial activities of several mannopeptimycin derivatives correlated with their affinities toward lipid II, suggesting that the inhibition of cell wall biosynthesis was primarily through lipid II binding. In addition, it was shown that mannopeptimycins bind to lipoteichoic acid in a rather nonspecific interaction, which might facilitate the accumulation of antibiotic on the bacterial cell surface.

Structural Basis for Clinical Longevity of Carbapenem Antibiotics in the Face of Challenge by the Common Class A β-Lactamases from the Antibiotic-Resistant Bacteria

Bacteria resistant to antibiotics are being selected in a relatively short time, and cases of infections resistant to treatment by all known antibiotics are being identified at alarming rates. The primary mechanism for resistance to β-lactam antibiotics is the catalytic function of β-lactamases. However, imipenem (a β-lactam) resists the action of most β-lactamases and is virtually the last effective agent against the vancomycin-resistant Gram-positive bacteria, as well as against multiple antibiotic-resistant Gram-negative organisms. Here, we report the crystal structure, to 1.8 Å resolution, of an acyl−enzyme intermediate for imipenem bound to the TEM-1 β-lactamase from Escherichia coli, the parent enzyme of 67 clinical variants. The structure indicates an unprecedented conformational change for the complex which accounts for the ability of this antibiotic to resist hydrolytic deactivation by β-lactamases. Computational molecular dynamics underscored the importance of the motion of the acyl−enzyme intermediate, which may be a general feature for catalysis by these enzymes.

Patent Evaluation Anti-infectives: Glycopeptide antibiotic derivatives active against Vancomycin-resistant Gram-positive bacteria

Patent Evaluation Anti-infectives: Glycopeptide antibiotic derivatives active against Vancomycin-resistant Gram-positive bacteria

In vitro activity of 43 antimicrobial agents tested against ampicillin-resistant enterococci and Gram-positive species resistant to vancomycin

A total of 57 strains of ampicillin-resistant and -susceptible enterococci representing 10 species and 23 strains of vancomycin-resistant Gram-positive bacteria (Leuconostoc and Pediococcus) were tested to determine their susceptibility to 43 antimicrobial agents by the reference broth microdilution method. The drug MICs for the ampicillin-resistant enterococci were generally similar to those of ampicillin-susceptible strains, that is, highly resistant to cephalosporins, moderately susceptible or resistant to quinolones, and susceptible to “glycopeptides.” Some investigational quinolones (PD127391, sparfloxacin, WIN57273), minocycline, and rifampin were highly active. Vancomycin-resistant strains were usually resistant to other “glycopeptides,” for which correlation coefficients of MICs ranged from 0.881 to 0.978, except ramoplanin (MICs, 0.008–0.5 μg/ml). Most isolates resistant to vancomycin were susceptible to the newer quinolones, penicillins, aminoglycosides, clindamycin, and erythromycin, but highly resistant to cephalosporins. Discrepancies between the MICs and MBCs for glycopeptides were noted (⩾8-fold, MBC 50/MIC 50), but not for ramoplanin. The vancomycin disk test was in 96.1% absolute agreement by identifying resistant strains without contributing false-susceptible, very major error.

Antimicrobial susceptibility of vancomycin-resistant Leuconostoc, Pediococcus, and Lactobacillus species

Eighty-five strains of vancomycin-resistant gram-positive bacteria from three genera, Leuconostoc, Pediococcus, and Lactobacillus, were tested to determine susceptibility to 24 antimicrobial agents by broth microdilution and to 10 agents by disk diffusion. The MICs of vancomycin and teicoplanin ranged from 64 to greater than 512 micrograms/ml; however, the MICs of daptomycin, a new lipopeptide, were all less than or equal to 0.25 micrograms/ml. None of the organisms were resistant to imipenem, minocycline, chloramphenicol, gentamicin, or daptomycin. The MICs of penicillin were in the moderately susceptible range for all but three strains. Susceptibility to the other agents varied by genus and, in some cases, by species. When disk diffusion results were compared with MICs for drugs recommended for streptococci by the National Committee for Clinical Laboratory Standards, Villanova, Pa., few very major or major errors were obtained, but the number of minor errors was 19.3%. Therefore, we recommended that MIC testing be used instead of disk diffusion testing for these organisms.