A prospective crossover randomized trial of novobiocin and rifampin prophylaxis for the prevention of intravascular catheter infections in cancer patients treated with interleukin-2

Revealing the Interaction Mechanism between Mycobacterium tuberculosis GyrB and Novobiocin, SPR719 through Binding Thermodynamics and Dissociation Kinetics Analysis

With the rapid emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb), various levels of resistance against existing anti-tuberculosis (TB) drugs have developed. Consequently, the identification of new anti-TB targets and drugs is critically urgent. DNA gyrase subunit B (GyrB) has been identified as a potential anti-TB target, with novobiocin and SPR719 proposed as inhibitors targeting GyrB. Therefore, elucidating the molecular interactions between GyrB and its inhibitors is crucial for the discovery and design of efficient GyrB inhibitors for combating multidrug-resistant TB. In this study, we revealed the detailed binding mechanisms and dissociation processes of the representative inhibitors, novobiocin and SPR719, with GyrB using classical molecular dynamics (MD) simulations, tau-random acceleration molecular dynamics (τ-RAMD) simulations, and steered molecular dynamics (SMD) simulations. Our simulation results demonstrate that both electrostatic and van der Waals interactions contribute favorably to the inhibitors' binding to GyrB, with Asn52, Asp79, Arg82, Lys108, Tyr114, and Arg141 being key residues for the inhibitors' attachment to GyrB. The τ-RAMD simulations indicate that the inhibitors primarily dissociate from the ATP channel. The SMD simulation results reveal that both inhibitors follow a similar dissociation mechanism, requiring the overcoming of hydrophobic interactions and hydrogen bonding interactions formed with the ATP active site. The binding and dissociation mechanisms of GyrB with inhibitors novobiocin and SPR719 obtained in our work will provide new insights for the development of promising GyrB inhibitors.

Synthesis of novobiocin derivatives and evaluation of their antigonococcal activity and pharmacokinetics

Gonorrhea has become a serious problem because the number of infected people is increasing and the multi-drug resistance of the causative bacteria, Neisseria gonorrhoeae, is progressing. To develop novel drugs against resistant N. gonorrhoeae, we focused on the antibiotic novobiocin (1). This natural product has a different mechanism of action from existing drugs for gonorrhea, which may make it effective against resistant strains. Actually, it was applied to resistant N. gonorrhoeae, and moderate antibacterial activity was confirmed. Based on this result, we investigated the development of an antigonococcal drug with 1 as the lead compound. The pharmacophore is thought to be the noviose sugar moiety, especially around the 3'-position, so we derivatized this part in order to improve antibacterial activity. As a result, we found that 5 with an methylpyrrole ester structure have a very potent antibacterial activity. This derivative also showed excellent antigonococcal activity against resistant strains in vitro, however it has poor water solubility and pharmacokinetics because it is the acidic lipid-soluble compound. Therefore, we considered introduction of a basic substituent into the molecule would result in an amphoteric compound with improved water solubility, and we investigated further derivatization. As a result of synthesizing various derivatives, we found 47 containing imidazole with strong antigonococcal activity and greatly improved water solubility. This derivative has also improved metabolism and blood concentration in vivo, and is expected to be orally absorbed. Based on these results, we believe that 47 is a very promising anti-gonococcal lead compound and has great potential for further development.

Copper-mediated C-O/C-N Bond Formation: A Facile Synthesis of 3-Amidocoumarin, 3-amidoazacoumarin and N-Aeroylindole Derivatives

Three different heterocyclic systems, 3-amidocoumarins 1, 3-amidoazacoumarins 11, and N-benzoylindol-2-carboxamides 12 were synthesized based on the strikingly different selectivity of copper-mediated C-O/C-N bond formation from azlactones under conventional heating conditions. The results demonstrated that the stereochemistry of the double bond dictated the outcome of the products. The microwave irradiation played an important role in the isomerization of the trisubstituted olefin leading to the formation of 3-amidocoumarins 1 and 3-amidoazacoumarins 11. Compounds 1h, 1i, and 1l showed promising to good cytotoxic activity against a panel of cancer cell lines including HepG2 (hepatoblastoma) and MOLT-3 (T-lymphoblast acute lymphoblastic leukemia).

Prophylactic antibiotics for preventing gram-positive infections associated with long-term central venous catheters in adults and children receiving treatment for cancer

BACKGROUND

This is an updated version of a Cochrane Review last published in 2013. Long-term central venous catheters (CVCs), including tunnelled CVCs (TCVCs) and totally implanted devices or ports (TIDs), are increasingly used when treating people with cancer. Despite international guidelines on sterile insertion and appropriate CVC maintenance and use, infections remain a common complication. These infections are mainly caused by gram-positive bacteria. Antimicrobial prevention strategies aimed at these micro-organisms could potentially decrease the majority of CVC-related infections. The aim of this review was to evaluate the efficacy of prophylactic antibiotics for the prevention of gram-positive infections in people with cancer who have long-term CVCs.

OBJECTIVES

To assess the effects of administering antibiotics prior to the insertion of long-term CVCs or as a flush/lock solution, or both during long-term CVC access to prevent gram-positive CVC-related infections in adults and children receiving treatment for cancer.

SEARCH METHODS

The search for this updated review was conducted on 19 November 2020. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE via Ovid and Embase via Ovid. We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform portal for additional articles.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared either the administration of prophylactic antibiotics prior to long-term CVC insertion versus no administration of antibiotics, or the use of an antibiotic versus a non-antibiotic flush/lock solution in long-term CVCs, in adults and children receiving treatment for cancer.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two authors independently selected studies, classified them and extracted data onto a predesigned data collection form. The outcomes of interest were gram-positive catheter-related infection events and total number of CVCs and CVC days. We pooled the data using a random-effects model for meta-analyses. We used the GRADE approach to assess the certainty of the evidence.  MAIN RESULTS: For this update, we identified 310 potentially relevant studies and screened them for eligibility. We included one additional RCT with 404 participants. The original review included 11 RCTs with a total of 840 people with cancer (adults and children). In total this review included 12 RCTs with 1244 participants. Antibiotics prior to insertion of the CVC Six trials compared the use of antibiotics (vancomycin, teicoplanin, ceftazidime or cefazolin) versus no antibiotics given before the insertion of a long-term CVC. One study did not observe any CVC-related infection events in either group was not included in the quantitative analysis as it was not possible to calculate a risk ratio. Administering an antibiotic prior to insertion of the CVC may not reduce gram-positive CVC-related infections (pooled risk ratio 0.67, confidence interval (CI) 95% 0.32 to 1.43; control versus intervention group risk 10.4% versus 7.3% of the participants; 5 studies, 648 participants; moderate-certainty evidence). We sought adverse event data, but these were not described by the authors. The overall risk of bias was deemed low.   Antibiotics as a flushing or locking solution Six trials compared a combined antibiotic (vancomycin, amikacin or taurolidine) and heparin solution with a heparin-only solution for flushing or locking the long-term CVC after use. One study did not observe any CRS events and was not include this study in the quantitative analysis as it was not possible to calculate a risk ratio. Flushing and locking long-term CVCs with a combined antibiotic and heparin solution likely reduced the risk of gram-positive CVC-related infections compared to a heparin-only solution (pooled rate ratio 0.47, CI 95% 0.26 to 0.85; control versus intervention group rate ratio 0.66 versus 0.27 per 1000 CVC-days; 5 studies, 443 participants; moderate-certainty evidence). One trial reported a higher incidence of occlusions and participants in one trial reported an unpleasant taste after flushing associated with a combined antibiotic and heparin solution. The overall risk of bias was deemed low.  AUTHORS' CONCLUSIONS: Since the last version of this review, we included one additional study. There was no observed benefit of administering antibiotics before the insertion of long-term CVCs to prevent gram-positive CVC-related infections. Flushing or locking long-term CVCs with an antibiotic solution likely reduces gram-positive CVC-related infections experienced in people at risk of neutropenia through chemotherapy or disease. However, a limitation of this review is heterogeneity between the studies for both outcomes. Insufficient data were available to evaluate if the conclusions apply equally for different CVC types and for adults versus children. It must be noted that the use of an antibiotic flush/lock solution may increase microbial antibiotic resistance, therefore it should be reserved for high-risk people or if the baseline CVC-related infection rates are high. Further research is needed to identify high-risk groups most likely to benefit from these antibiotic flush/lock solutions.

Effect of Nurse Staffing and Antimicrobial-Impregnated Central Venous Catheters on the Risk for Bloodstream Infections in Intensive Care Units

Background:

Defining risk factors for central venous catheter (CVC)-associated bloodstream infections (BSIs) is critical to establishing prevention measures, especially for factors such as nurse staffing and antimicrobial-impregnated CVCs.

Methods:

We prospectively monitored CVCs, nurse staffing, and patient-related variables for CVC-associated BSIs among adults admitted to eight ICUs during 2 years.

Results:

A total of 240 CVC-associated BSIs (2.8%) were identified among 4,535 patients, representing 8,593 CVCs. Antimicrobial-impregnated CVCs reduced the risk for CVC-associated BSI only among patients whose CVC was used to administer total parenteral nutrition (TPN, 2.6 CVC-associated BSIs per 1,000 CVC-days vs no TPN, 7.5 CVC-associated BSIs per 1,000 CVC-days;P= .006). Among patients not receiving TPN, there was an increase in the risk of CVC-associated BSI in patients cared for by “float” nurses for more than 60% of the duration of the CVC. In multivariable analysis, risk factors for CVC-associated BSIs were the use of TPN in non-antimicrobial-impregnated CVCs (P= .0001), patient cared for by a float nurse for more than 60% of CVC-days (P= .0019), no antibiotics administered to the patient within 48 hours of insertion (P= .0001), and patient unarousable for 70% or more of the duration of the CVC (P= .0001). Peripherally inserted central catheters (PICCs) were associated with a lower risk for CVC-associated BSI (P= .0001).

Conclusions:

Antimicrobial-impregnated CVCs reduced the risk of CVC-associated BSI by 66% in patients receiving TPN. Limiting the use of float nurses for ICU patients with CVCs and the use of PICCs may also reduce the risk of CVC-associated BSI.

Hsp90 inhibitor as a sensitizer of cancer cells to different therapies (review)

Hsp90 is a molecular chaperone that maintains the structural and functional integrity of various client proteins involved in signaling and many other functions of cancer cells. The natural inhibitors, ansamycins influence the Hsp90 chaperone function by preventing its binding to client proteins and resulting in their proteasomal degradation. N- and C-terminal inhibitors of Hsp90 and their analogues are widely tested as potential anticancer agents in vitro, in vivo as well as in clinical trials. It seems that Hsp90 competitive inhibitors target different tumor types at nanomolar concentrations and might have therapeutic benefit. On the contrary, some Hsp90 inhibitors increased toxicity and resistance of cancer cells induced by heat shock response, and through the interaction of survival signals, that occured as side effects of treatments, could be very effectively limited via combination of therapies. The aim of our review was to collect the data from experimental and clinical trials where Hsp90 inhibitor was combined with other therapies in order to prevent resistance as well as to potentiate the cytotoxic and/or antiproliferative effects.

Trifluoroacetic acid-promoted Michael addition-cyclization reactions of vinylogous carbamates

A simple and efficient methodology has been developed for the synthesis of pyrrolobenzoxazine and 3-arylamino coumarin derivatives promoted by trifluoroacetic acid. The initial step in the current protocol involves a Michael addition of the 1,4-benzoxazinone derivatives, a novel class of vinylogous carbamates to the Michael acceptors and subsequent cyclization.

Long-term catheterization: current approaches in the diagnosis and treatment of port-related infections

Since the first description in 1982, totally implanted venous access ports have progressively improved patients' quality of life and medical assistance when a medical condition requires the use of long-term venous access. Currently, they are part of the standard medical care for oncohematologic patients. However, apart from mechanical and thrombotic complications, there are also complications associated with biofilm development inside the catheters. These biofilms increase the cost of medical assistance and extend hospitalization. The most frequently involved micro-organisms in these infections are gram-positive cocci. Many efforts have been made to understand biofilm formation within the lumen catheters, and to resolve catheter-related infection once it has been established. Apart from systemic antibiotic treatment, the use of local catheter treatment (ie, antibiotic lock technique) is widely employed. Many different antimicrobial options have been tested, with different outcomes, in clinical and in in vitro assays. The stability of antibiotic concentration in the lock solution once instilled inside the catheter lumen remains unresolved. To prevent infection, it is mandatory to perform hand hygiene before catheter insertion and manipulation, and to disinfect catheter hubs, connectors, and injection ports before accessing the catheter. At present, there are still unresolved questions regarding the best antimicrobial agent for catheter-related bloodstream infection treatment and the duration of concentration stability of the antibiotic solution within the lumen of the port.

Prophylactic antibiotics for preventing Gram positive infections associated with long-term central venous catheters in oncology patients

BACKGROUND

This is an updated version of the review which was first published in the Cochrane Database of Systematic Reviews in 2006. Long-term central venous catheters (CVCs), including tunnelled CVCs (TCVCs) and totally implanted devices or ports (TIDs), are increasingly used when treating oncology patients. Despite international guidelines on sterile insertion and appropriate CVC maintenance and use, infection remains a common complication. These infections are mainly caused by Gram positive bacteria. Antimicrobial prevention strategies aimed at these micro-organisms could potentially decrease the majority of CVC infections. The aim of this review was to evaluate the efficacy of antibiotics in the prevention of Gram positive infections in long-term CVCs.

OBJECTIVES

To determine the efficacy of administering antibiotics prior to the insertion of long-term CVCs, or flushing or locking long-term CVCs with a combined antibiotic and heparin solution, or both, to prevent Gram positive catheter-related infections in adults and children receiving treatment for cancer.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (to June 2013) and the MEDLINE and EMBASE databases (1966 to 2013).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing prophylactic antibiotics given prior to long-term CVC insertion with no antibiotics, RCTs comparing a combined antibiotic and heparin solution with a heparin-only solution to flush or lock newly inserted long-term CVCs, and RCTs comparing a combination of these interventions in adults and children receiving treatment for cancer.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies, classified them and extracted data on to a pre-designed data collection form. We pooled data using the RevMan software version 5.2 and used random-effects (RE) model methods for meta-analyses.

MAIN RESULTS

We included 11 trials with a total of 828 oncology patients (adults and children). We assessed most included studies to be at a low or unclear risk of bias. Five trials compared the use of antibiotics (vancomycin, teicoplanin or ceftazidime) given before the insertion of the long-term CVC with no antibiotics, and six trials compared antibiotics (vancomycin, amikacin or taurolidine) and heparin with a heparin-only solution for flushing or locking the long-term CVC after use. Administering an antibiotic prior to insertion of the CVC did not significantly reduce Gram positive catheter-related sepsis (CRS) (five trials, 360 adults; risk ratio (RR) 0.72, 95% confidence interval (CI) 0.33 to 1.58; I² = 5 2%; P = 0.41).Flushing and locking long-term CVCs with a combined antibiotic and heparin solution significantly reduced the risk of Gram positive catheter-related sepsis compared with a heparin-only solution (468 participants, mostly children; RR 0.47, 95% CI 0.28 to 0.80; I² = 0%; P = 0.005). For a baseline infection rate of 15%, this reduction translated into a number needed to treat (NNT) of 12 (95% CI 9 to 33) to prevent one catheter-related infection. We considered this evidence to be of a moderate quality.

AUTHORS' CONCLUSIONS

There was no benefit to administering antibiotics before the insertion of long-term CVCs to prevent Gram positive catheter-related infections. Flushing or locking long-term CVCs with a combined antibiotic and heparin solution appeared to reduce Gram positive catheter-related sepsis experienced in people at risk of neutropenia through chemotherapy or disease. Due to insufficient data it was not clear whether this applied equally to TCVCs and totally implanted devices (TIDs), or equally to adults and children. The use of a combined antibiotic and heparin solution may increase microbial antibiotic resistance, therefore it should be reserved for high risk people or where baseline CVC infection rates are high (> 15%). Further research is needed to identify high risk groups most likely to benefit.

Device-Related Infections in Critically Ill Patients. Part I: Prevention of Catheter-Related Bloodstream Infections

Device utilization in critically ill patients is responsible for a high risk of complications such as catheter-related bloodstream infections (CRBSI), ventilator-associated pneumonia (VAP) and urinary tract infections (UTI). In this article we will review the current status of data regarding CRBSI prevention. General recommendations include staff education and use of a surveillance program with a restrictive antibiotic policy. Adequate time must be allowed for hand washing and barrier precautions must always be used during device manipulation. The routine changing of central catheters is not necessary and increases costs; it is necessary to decrease the handling of administration sets, to use a more careful insertion technique and less frequent set replacement. Antiseptic-coated catheters appear to reduce catheter colonization but their ability to prevent catheter-related infections requires further demonstration. More clinical trials are needed to verify the efficacy of measures to prevent CRBSI.

Central venous catheter care for the patient with cancer: American Society of Clinical Oncology clinical practice guideline

PURPOSE

To develop an evidence-based guideline on central venous catheter (CVC) care for patients with cancer that addresses catheter type, insertion site, and placement as well as prophylaxis and management of both catheter-related infection and thrombosis.

METHODS

A systematic search of MEDLINE and the Cochrane Library (1980 to July 2012) identified relevant articles published in English.

RESULTS

The overall quality of the randomized controlled trial evidence was rated as good. There is consistency among meta-analyses and guidelines compiled by other groups as well.

RECOMMENDATIONS

There is insufficient evidence to recommend one CVC type or insertion site; femoral catheterization should be avoided. CVC should be placed by well-trained providers, and the use of a CVC clinical care bundle is recommended. The use of antimicrobial/antiseptic-impregnated and/or heparin-impregnated CVCs is recommended to decrease the risk of catheter-related infections for short-term CVCs, particularly in high-risk groups; more research is needed. The prophylactic use of systemic antibiotics is not recommended before insertion. Data are not sufficient to recommend for or against routine use of antibiotic flush/lock therapy; more research is needed. Before starting antibiotic therapy, cultures should be obtained. Some life-threatening infections require immediate catheter removal, but most can be treated with antimicrobial therapy while the CVC remains in place. Routine flushing with saline is recommended. Prophylactic use of warfarin or low-molecular weight heparin is not recommended, although a tissue plasminogen activator (t-PA) is recommended to restore patency to occluded catheters. CVC removal is recommended when the catheter is no longer needed or if there is a radiologically confirmed thrombosis that worsens despite anticoagulation therapy.

Coumabiocins A-F, aminocoumarins from an organic extract of Streptomyces sp. L-4-4

Bioassay-directed fractionation of the butanol extract of Streptomyces sp. L-4-4, using the hyphae formation inhibition assay of a prokaryotic whole cell, led to the isolation of six new aminocoumarins, coumabiocins A-F (1-6), along with two known compounds, novobiocin (7) and isonovobiocin (8). Coumabiocins A-E (1-5) contain three structural elements, a central 3-amino-7-hydroxycoumarin that is linked at the 3-amino group to a prenylated 4-hydroxybenzoic acid moiety and at the 7-position to an l-noviosyl sugar, while coumabiocin F (6) lacks the sugar moiety. Their structures were elucidated by spectroscopic methods including 1D- and 2D-NMR techniques and mass spectrometric analyses. Coumabiocins A-E (1-5) exhibited significant inhibitory activity against Streptomyces 85E and gave a 10-15 mm clear zone of inhibition at 20 microg/disk and a 10 mm bald and a 10 mm clear zone of inhibition at 5 and 10 microg/disk, respectively, whereas coumabiocin F (6) was inactive.

Synergistic effects between conventional antibiotics and 2-aminoimidazole-derived antibiofilm agents

2-aminoimidazoles are an emerging class of small molecules that possess the ability to inhibit and disperse biofilms across bacterial order, class, and phylum. Herein, we report the synergistic effect between a 2-aminoimidazole/triazole conjugate and antibiotics toward dispersing preestablished biofilms, culminating with a 3-orders-of-magnitude increase of biofilm dispersion toward Staphylococcus aureus biofilms. Furthermore, we document that the 2-aminoimidazole/triazole conjugate will also resensitize multidrug-resistant strains of bacteria to the effects of conventional antibiotics, including methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Acinetobacter baumannii.

The efficacy of catheters coated with minocycline and rifampin in the prevention of catheter-related bacteremia in cancer patients receiving high-dose interleukin-2

High-dose interleukin-2 (HDIL-2) has proven to be an effective treatment for metastatic renal cell carcinoma and melanoma. Previous studies have shown an increase in catheter-related bacteremia (CRB) in patients on HDIL-2. The primary objective of this study was to evaluate the effectiveness of minocycline and rifampin-coated catheters (M/R-C) in reducing CRB in cancer patients on HDIL-2. This was a retrospective study where non-coated catheters (NC-C) and M/R-C were used for the administration of HDIL-2 before and after December 2004, respectively. Data collected included demographics, cancer type, catheter type, antibiotic prophylaxis, and infection rates. A total of 107 episodes of catheter use for HDIL-2 were evaluated in 78 patients (30 episodes in patients with M/R-C vs. 77 with NC-C). A total of nine episodes of CRB were identified, all in patients with NC-C (M/R-C 0% vs. NC-C 12%; p=0.06). The median time to bacteremia was 11 days (range 1-315 days). A log-rank test showed a trend that the M/R-C group had lower probability of getting CRB than the NC-C group (p=0.06). The use of M/R-C in patients on HDIL-2 therapy for advanced melanoma and renal cell carcinoma may have reduced the risk of CRB to nil. CRB still occurred despite antibiotic prophylaxis in patients with NC-C.

Biological activities of novel gyrase inhibitors of the aminocoumarin class

Thirty-one aminocoumarin antibiotics derived from mutasynthesis experiments were investigated for their biological activities. Their inhibitory activities toward Escherichia coli DNA gyrase were determined in two different in vitro assays: an ATPase assay and a DNA supercoiling assay. The assays gave a similar rank order of the activities of the compounds tested, although the absolute 50% inhibitory concentrations (IC(50)s) obtained in each assay were different. To confirm that the compounds also acted as gyrase inhibitors in vivo, reporter gene assays were carried out with E. coli by using gyrA and sulA promoter fusions with the luxCDABE operon. A strong induction of both promoters was observed for those compounds that showed gyrase inhibitory activity in the biochemical assays. Compounds carrying analogs of the prenylated benzoyl moiety (ring A) of clorobiocin that were structurally very different showed high levels of activity both in the biochemical assay and in the reporter gene assay, indicating that the structure of this moiety can be varied considerably without a loss of affinity for bacterial gyrase. The experimentally determined IC(50)s were compared to the binding energies calculated in silico, which indicated that a shift of the pyrrole carboxylic acid moiety from the O-3'' to the O-2'' position of the deoxysugar moiety has a significant impact on the binding mode of the compounds. The aminocoumarin compounds were also investigated for their MICs against different bacterial pathogens. Several compounds showed high levels of activity against staphylococci, including a methicillin-resistant Staphylococcus aureus strain. However, they showed only poor activities against gram-negative strains.

Old antibiotics for infections in critically ill patients

PURPOSE OF REVIEW

The alarming epidemic of multidrug-resistant bacteria and the reluctance of the pharmaceutical industry to invest in the development of new antibiotics have forced clinicians to reintroduce forgotten antibiotics into their practice. This review highlights the effectiveness and safety of older antibiotics when used in the treatment of infections of critically ill patients.

RECENT FINDINGS

Polymyxins emerged as useful antibiotics for the treatment of infections due to multidrug-resistant Gram-negative bacteria, in particular Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae. The nephrotoxicity and neurotoxicity associated with their use are less frequent and serious than previously reported. In addition, aerosolized polymyxins may be a useful weapon in the treatment of hospital-acquired pneumonia. Fosfomycin and chloramphenicol have a wide antimicrobial spectrum, are used extensively in Europe and Africa, respectively, and may have an expanded role in our antimicrobial arsenal. Fusidic acid remains active against various staphylococcal strains, while isepamicin (an aminoglycoside used in some European countries) is slightly more effective than amikacin against some Gram-negative bacteria.

SUMMARY

The declining investment of the pharmaceutical industry in the development of new antibiotics and the increasing antimicrobial resistance create a fertile ground for the study and, probably, revival of older antibiotics for use, especially in critically ill patients.

Central venous access

Central venous access plays an important role in the management of an ever-increasing population of patients ranging from those that are critically ill to patients with difficult clinical access. Interventional radiologists are key in delivering this service and should be familiar with the wide range of techniques and catheters now available to them. A comprehensive description of these catheters with regard to indications, technical aspects of catheterization, success rates, and associated early and late complications, as well as a review of various published guidelines on central venous catheter insertion are given in this article.

Prophylactic antibiotics for preventing early central venous catheter Gram positive infections in oncology patients

BACKGROUND

Long-term tunnelled central venous catheters (TCVCs) are increasingly used when treating oncology patients. Despite international guidelines on sterile insertion, appropriate catheter maintenance and use, infections still a complication of TCVC. These infections are mainly caused by Gram-positive bacteria. Antimicrobial prevention strategies aimed at these micro-organisms could potentially decrease the majority of TCVC infections. The aim of this review was to evaluate the efficacy of antibiotics in the prevention of early TCVC infections.

OBJECTIVES

To determine the efficacy of administering antibiotics prior to insertion of a TCVC with or without vancomycin/heparin flush technique in the first 45 days after insertion of the catheter to prevent Gram-positive catheter-related infections in oncology patients.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) to July 2006. MEDLINE (1966 to 2006) and EMBASE (1966 to 2006). Reference lists from relevant articles were scanned and conference proceedings were hand searched. The authors of eligible studies were contacted to obtain additional information.

SELECTION CRITERIA

We selected RCTs which administered prophylactic antibiotics prior to insertion of the TCVC, and RCTs using the combination of an antibiotic and heparin to flush the CVC in oncology patients (both adults and children).

DATA COLLECTION AND ANALYSIS

The studies identified were assessed and the data extracted independently by the two authors. Authors were contacted for details of randomization, and a quality assessment was carried out. The analysis was carried out using the standard Cochrane software package, RevMan 4.2.

MAIN RESULTS

We included nine trials with a total of 588 patients. Four reported on vancomycin/teicoplanin prior to insertion of the TCVC compared to placebo, and five trials reported on antibiotic flushing combined with heparin, compared to heparin flushing only. The overall effect of administering an antibiotic prior to insertion of the catheter decreases the number of Gram positive TCVC infections (odds ratio [OR] = 0.42, 95% confidence interval (CI) 0.13 to 1.31), this effect is not significant. Flushing the TCVC with antibiotics and heparin proved to be beneficial (OR = 0.43, 95% CI 0.21 to 0.87). For intraluminal colonization the baseline infection rate is 15% which leads to a number needed to treat (NNT) of 13 (95 % CI 5 to 23).

AUTHORS' CONCLUSIONS

Flushing of the catheter with a vanco/heparin lock solution leads to a positive overall effect. Depending on the baseline TCVC infection rate it is justified to flush the catheter with a combination of an antibiotic and heparin, if the catheter related infection-rate is high.

Metabolic Engineering of Aminocoumarins: Inactivation of the Methyltransferase Gene cloP and Generation of New Clorobiocin Derivatives in a Heterologous Host

Aminocoumarin antibiotics are highly potent inhibitors of bacterial gyrase and represent a class of antibiotics that are very suitable for the generation of new compounds by metabolic engineering. In this study, the putative methyltransferase gene cloP in the biosynthetic gene cluster of clorobiocin was inactivated. Expression of the modified gene cluster in the heterologous host Streptomyces coelicolor M512 gave three new aminocoumarin antibiotics. The structures of the new compounds were elucidated by MS and 1H NMR, and their antibacterial activities were determined. All three compounds lacked clorobiocin's methyl group at 4-OH of the deoxysugar moiety, noviose. They differed from each other in the position of the 5-methylpyrrole-2-carbonyl group, which was found to be attached to either 2-OH, 3-OH or 4-OH of noviose. Attachment at 4-OH resulted in the highest antibacterial activity. This is the first time that an aminocoumarin antibiotic acylated at 4-OH in noviose has been detected.

Heterologous expression of novobiocin and clorobiocin biosynthetic gene clusters

A method was developed for the heterologous expression of biosynthetic gene clusters in different Streptomyces strains and for the modification of these clusters by single or multiple gene replacements or gene deletions with unprecedented speed and versatility. Lambda-Red-mediated homologous recombination was used for genetic modification of the gene clusters, and the attachment site and integrase of phage phiC31 were employed for the integration of these clusters into the heterologous hosts. This method was used to express the gene clusters of the aminocoumarin antibiotics novobiocin and clorobiocin in the well-studied strains Streptomyces coelicolor and Streptomyces lividans, which, in contrast to the natural producers, can be easily genetically manipulated. S. coelicolor M512 derivatives produced the respective antibiotic in yields comparable to those of natural producer strains, whereas S. lividans TK24 derivatives were at least five times less productive. This method could also be used to carry out functional investigations. Shortening of the cosmids' inserts showed which genes are essential for antibiotic production.

Prophylactic antibiotics for preventing early Gram-positive central venous catheter infections in oncology patients, a Cochrane systematic review

OBJECTIVE

Long-term tunnelled central venous catheters (TCVC) are increasingly used in oncology patients. Infections are a frequent complication of TCVC, mostly caused by Gram-positive bacteria. The objective of this review is to evaluate the efficacy of antibiotics in the prevention of early Gram-positive TCVC infections, in oncology patients.

DATA SOURCES

We searched MEDLINE, EMBASE, and the Cochrane Controlled Trials Register up to July 2003.

REVIEW METHODS

We selected randomised controlled trials (RCT) evaluating prophylactic antibiotics prior to insertion of the TCVC, and the combination of an antibiotic and heparin to flush the TCVC, in paediatric and adult oncology patients. The primary outcome was documented Gram-positive bacteraemia in patients with a TCVC. All trials identified were assessed and the data extracted independently by two reviewers.

RESULTS

There were nine trials included. Four trials reported on vancomycin/teicoplanin prior to insertion of the TCVC compared to no antibiotics. There was no reduction in the number of Gram-positive TCVC infections with an Odds ratio of 0.42 (95% confidence interval 0.13-1.31). Five trials studied flushing of the TCVC with a vancomycin/heparin solution compared to heparin flushing only. This method decreased the number of TCVC infections significantly with an Odds ratio of 0.43 (95% CI 0.21-0.87).

CONCLUSION

Flushing the TCVC with a vancomycin/heparin solution reduced the incidence of Gram-positive infections.

Catheter-Related Bloodstream Infections in the Intensive Care Unit Population

Catheter-related bloodstream infections (CRBIs) are a cause of significant morbidity and mortality in intensive care unit patients. Development of CRBIs may occur by several mechanisms. The role of fibrin and biofilm development and their impact on therapy are described. Multiple preventative strategies related to the insertion and maintenance of the catheter site have been identified. Topical antisepsis and use of antibiotic-impregnated catheters are also beneficial for reducing the incidence of CRBI. Antibiotic lock solutionsmay be effective in preventing CRBI for select patients with longterm catheter use. Treatment of CRBIs should be based on suspected organisms, whichmost commonly include staphylococci, gram-negatives, including Pseudomonas aeruginosa andCandida species. Duration of treatment and decisions regarding catheter removal are controversial. Evaluation and treatment of potential complications of CRBIs, including endocarditis, infected thrombophlebitis, osteomyelitis, and endophthalmitis, are essential.

In vitro and in vivo production of new aminocoumarins by a combined biochemical, genetic, and synthetic approach

The aminocoumarin antibiotics clorobiocin, novobiocin, and coumermycin A(1) are inhibitors of bacterial gyrase. Their chemical structures contain amide bonds, formed between an aminocoumarin ring and an aromatic acyl component, which is 3-dimethylallyl-4-hydroxybenzoate in the case of novobiocin and clorobiocin. These amide bonds are formed under catalysis of the gene products of cloL, novL, and couL, respectively. We first examined the substrate specificity of the purified amide synthetases CloL, NovL, and CouL for the various analogs of the prenylated benzoate moiety. We then generated new aminocoumarin antibiotics by feeding synthetic analogs of the 3-dimethylallyl-4-hydroxybenzoate moiety to a mutant strain defective in the biosynthesis of the prenylated benzoate moiety. This resulted in the formation of 32 new aminocoumarin compounds. The structures of these compounds were elucidated using FAB-MS and (1)H-NMR spectroscopy.

Reduction of catheter-related infections in neutropenic patients: a prospective controlled randomized trial using a chlorhexidine and silver sulfadiazine-impregnated central venous catheter

Antiseptic coating of intravascular catheters may be an effective means of decreasing catheter-related colonization and subsequent infection. The purpose of this study was to assess the efficacy of chlorhexidine and silver sulfadiazine (CH-SS)-impregnated central venous catheters (CVCs) to prevent catheter-related colonization and infection in patients with hematological malignancies who were subjected to intensive chemotherapy and suffered from severe and sustained neutropenia. Proven CVC-related bloodstream infection (BSI) was defined as the isolation of the same species from peripheral blood culture and CVC tip (Maki technique). This randomized, prospective clinical trial was carried out in 106 patients and compared catheter-related colonization and BSI using a CH-SS-impregnated CVC (n=51) to a control arm using a standard uncoated triple-lumen CVC (n=55). Patients were treated for acute leukemia (n=89), non-Hodgkin's lymphoma (n=10), and multiple myeloma (n=7). Study groups were balanced regarding to age, sex, underlying diseases, insertion site, and duration of neutropenia. The CVCs were in situ a mean of 14.3+/-8.2 days (mean+/-SD) in the study group versus 16.6+/-9.7 days in the control arm. Catheter-related colonization was observed less frequently in the study group (five vs nine patients; p=0.035). CVC-related BSI were significantly less frequent in the study group (one vs eight patients; p=0.02). In summary, in patients with severe neutropenia, CH-SS-impregnated CVCs yield a significant antibacterial effect resulting in a significantly lower rate of catheter-related colonization as well as CVC-related BSI.

Production of 8′-Halogenated and 8′-Unsubstituted Novobiocin Derivatives in Genetically Engineered Streptomyces coelicolor Strains

In the present study, we produced a hybrid antibiotic, carrying a chlorine atom instead of a methyl group at position 8 of the aminocoumarin moiety of novobiocin. This compound was not accessible by conventional gene inactivation/gene expression experiments due to difficulties in the genetic manipulation of the novobiocin producer Streptomyces spheroides. However, the desired compound was obtained after modification of the novobiocin biosynthetic gene cluster by using lambda-Red-mediated recombination in Escherichia coli, followed by integration of the resulting modified cosmid into the phiC31 attachment site of Streptomyces coelicolor and coexpression of the halogenase Clo-hal of clorobiocin biosynthesis. The halogenase BhaA, responsible for chlorination of tyrosyl moieties of the glycopeptide antibiotic balhimycin, was unable to functionally replace the halogenase Clo-hal, suggesting that the two enzymes have different substrate specificities.

Antimicrobial and DNA gyrase-inhibitory activities of novel clorobiocin derivatives produced by mutasynthesis

Twenty-eight novel clorobiocin derivatives obtained from mutasynthesis experiments were investigated for their inhibitory activity towards Escherichia coli DNA gyrase and for their antibacterial activities towards clinically relevant gram-positive and gram-negative bacteria in comparison to novobiocin and clorobiocin. Clorobiocin was the most active compound both against E. coli DNA gyrase in vitro and against bacterial growth. All tested modifications of the 3-dimethylallyl-4-hydroxybenzoyl moiety reduced biological activity. The highest activities were shown by compounds containing a hydrophobic alkyl substituent at position 3 of the 4-hydroxybenzoyl moiety. Polar groups in this side chain, especially amide functions, strongly reduced antibacterial activity. Replacement of the alkyl side chain with a halogen atom or a methoxy group at the same position markedly reduced activity. Transfer of the pyrrole carboxylic acid moiety from O-3" to O-2" of L-noviose moderately reduced activity, whereas the complete absence of the pyrrole carboxylic acid moiety led to a loss of activity. Desclorobiocin derivatives lacking the chlorine atom at C-8 of the 3-amino-4,7-dihydroxycoumarin moiety also showed low activity. Lack of a methyl group at O-4" of L-noviose resulted in an inactive compound. From these findings it appears that clorobiocin represents a "highly evolved" structure optimized for bacterial transport and DNA gyrase inhibition.

Clorobiocin biosynthesis in Streptomyces: identification of the halogenase and generation of structural analogs

Clorobiocin (clo) and novobiocin (nov) are potent inhibitors of bacterial DNA gyrase. The two substances differ in the substitution pattern at C-8' of the aminocoumarin ring, carrying a chlorine atom or a methyl group, respectively. By gene inactivation, clo-hal was identified as the gene of the halogenase responsible for the introduction of the chlorine atom of clorobiocin. Inactivation of cloZ did not affect clorobiocin formation, showing that this ORF is not essential for clorobiocin biosynthesis. Expression of the methyltransferase gene novO in the clo-hal(-) mutant led to the very efficient formation of a hybrid antibiotic containing a methyl group instead of a chlorine atom at C-8'. Comparison of the antibacterial activity of clorobiocin analogs with -Cl, -H, or -CH(3) at C-8' showed that chlorine leads to 8-fold higher activity than hydrogen and to 2-fold higher activity than a methyl group.

Prophylactic antibiotics for preventing early central venous catheter Gram positive infections in oncology patients

BACKGROUND

Long-term tunnelled central venous catheters (TCVC) are increasingly used in oncology patients. Despite guidelines on insertion, maintenance and use, infections remain an important complication. Most infections are caused by Gram-positive bacteria. Therefore antimicrobial prevention strategies aimed at these micro-organisms could potentially decrease the majority of the TCVC infections.

OBJECTIVES

To determine the efficacy of administering antibiotics prior to insertion of a TCVC with or without vancomycin/heparin flush technique in the first 45 days after insertion of the catheter to prevent Gram-positive catheter-related infections in oncology patients.

SEARCH STRATEGY

We searched MEDLINE, EMBASE,and CENTRAL up to July 2001. Reference lists from relevant articles were scanned and conference proceedings were hand searched. The authors of eligible studies were contacted to obtain additional information.

SELECTION CRITERIA

We selected randomized controlled trials giving prophylactic antibiotics prior to insertion of the TCVC, and trials using the combination of an antibiotic and heparin to flush the TCVC in oncology patients.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the studies for inclusion, extracted the data and assessed the quality.

MAIN RESULTS

We included eight trials totalling 527 patients. Four reported on vancomycin/teicoplanin prior to insertion of the TCVC, and four reported on antibiotic flushing combined with heparin. The overall effect of an antibiotic prior to catheter insertion decreases the number of Gram-positive TCVC infections (odds ratio [OR] = 0.55, 95% confidence interval [CI] 0.29 to1.04). Given an expected infection rate of TCVC during the first 45 days of up to 30% this OR implies that the number needed to treat (NNT) will be 10 (95% CI 4 to13), this means vancomycin needs to be given to 10 patients to prevent one TCVC infection. Flushing the TCVC with antibiotics and heparin proved to be beneficial (OR = 0.35, 95% CI 0.16 -to 0.77). For intraluminal colonization the baseline infection-rate is 15% which leads to a NNT of 13 (95% CI 5 to 23).

REVIEWER'S CONCLUSIONS

Both interventions lead to a positive overall effect but should be considered with care due to the small number of studies. Depending on the baseline TCVC infection rate it is justified to administer antibiotics prior to the TCVC insertion or to flush the catheter with a combination of an antibiotic and heparin, if the catheter-related infection rate is high.

Role of antibiotic prophylaxis for the prevention of intravascular catheter-related infection

Intravascular catheters have become essential tools for the management of patients in modern medical practice, but there are complications. In particular, catheter-related infection remains a major cause of nosocomial infection and primary septicemia. The development of preventive strategies to reduce the incidence of catheter-related infection is an important goal for all health providers. Over recent years, significant advances in prophylactic measures for the prevention of catheter-related infection have been made. This paper reviews strategies based on antibiotic prophylaxis such as systemic administration of antibiotics, application of antibiotic ointments to the skin insertion site as well as catheter flushing with antibiotics, the antibiotic-lock technique and the use of antimicrobial impregnated catheters.

Identification of the coumermycin A(1) biosynthetic gene cluster of Streptomyces rishiriensis DSM 40489

The biosynthetic gene cluster of the aminocoumarin antibiotic coumermycin A(1) was cloned by screening of a cosmid library of Streptomyces rishiriensis DSM 40489 with heterologous probes from a dTDP-glucose 4,6-dehydratase gene, involved in deoxysugar biosynthesis, and from the aminocoumarin resistance gyrase gene gyrB(r). Sequence analysis of a 30.8-kb region upstream of gyrB(r) revealed the presence of 28 complete open reading frames (ORFs). Fifteen of the identified ORFs showed, on average, 84% identity to corresponding ORFs in the biosynthetic gene cluster of novobiocin, another aminocoumarin antibiotic. Possible functions of 17 ORFs in the biosynthesis of coumermycin A(1) could be assigned by comparison with sequences in GenBank. Experimental proof for the function of the identified gene cluster was provided by an insertional gene inactivation experiment, which resulted in an abolishment of coumermycin A(1) production.

Cloning, overexpression, and purification of novobiocic acid synthetase from Streptomyces spheroides NCIMB 11891

Novobiocic acid synthetase, a key enzyme in the biosynthesis of the antibiotic novobiocin, was cloned from the novobiocin producer Streptomyces spheroides NCIMB 11891. The enzyme is encoded by the gene novL, which codes for a protein of 527 amino acids with a calculated mass of 56,885 Da. The protein was overexpressed as a His(6) fusion protein in Escherichia coli and purified to apparent homogeneity by affinity chromatography and gel chromatography. The purified enzyme catalyzed the formation of an amide bond between 3-dimethylallyl-4-hydroxybenzoic acid (ring A of novobiocin) and 3-amino-4,7-dihydroxy-8-methyl coumarin (ring B of novobiocin) in an ATP-dependent reaction. NovL shows homology to the superfamily of adenylate-forming enzymes, and indeed the formation of an acyl adenylate from ring A and ATP was demonstrated by an ATP-PP(i) exchange assay. The purified enzyme exhibited both activation and transferase activity, i.e. it catalyzed both the activation of ring A as acyl adenylate and the subsequent transfer of the acyl group to the amino group of ring B. It is active as a monomer as determined by gel filtration chromatography. The reaction was specific for ATP as nucleotide triphosphate and dependent on the presence of Mg(2+) or Mn(2+). Apparent K(m) values for ring A and ring B were determined as 19 and 131 micrometer respectively. Of several analogues of ring A, only 3-geranyl-4-hydroxybenzoate and to a lesser extent 3-methyl-4-aminobenzoate were accepted as substrates.

Uses of rifampin for infections other than tuberculosis

Rifampin has limited use in monotherapy because of the rapid development of resistance. In combination therapy with a variety of antimicrobials, it has many applications for treatment of serious infections.