Effect of nisin on two cultures of rumen ciliates

The effect of nisin (in the form of Nisaplin) was determined using two species of rumen ciliate protozoa in vitro, on their co-culture bacterial population, and volatile fatty acid concentration. Nisaplin did not affect the in vitro growth of Entodinium caudatum at concentrations of 50-400 mg/L during short-term treatment (5 d). Long-term application (30 d) of Nisaplin (100 mg/L) significantly decreased growth of the Epidinium ecaudatum forma caudatum et ecaudatum but not growth of E. caudatum. Nisaplin moderately supported the growth of E. caudatum after omission of wheat gluten (source of amino acids for protozoan growth). An inhibition of Gram-positive facultative anaerobic bacterial population in the protozoan cultures (lactobacilli, enterococci, staphylococci and amylolytic streptococci) was observed during long-term Nisaplin treatment. The concentration of volatile fatty acids significantly increased during the long-term Nisaplin treatment of both cultures. The propionate concentration in the mixture of volatile fatty acids was nearly twice higher on the account of the decreased concentration (from 74 to 63%) of acetate.

Vaccine Development for Potential Bioterrorism Agents

Vaccines are considered to be one of the most effective ways of combating disease caused by bioterrorism agents. Such vaccines must be able to provide protection against pathogens which might enter the body by a number of routes, including the respiratory tract. They should also be able to induce protective immunity rapidly and would ideally be given non-invasively. There are few vaccines which currently meet these requirements. In part, this reflects the low level of research on many bioterrorism agents over the past few decades. Little is known about basic mechanisms of pathogenicity of many of these agents. However, by their very nature these agents cause serious disease, and must be handled in high containment laboratories. This requirement also limits the speed and ease with which research on these pathogens can now take place. Against this background, research on vaccines against potential bioterrorism agents is likely to proceed along two lines. Firstly because the genome sequences of most of the principal bioterrorism agents have either been completed or are close to completion, there is likely to be reliance on the exploitation of this information to devise improved vaccines. A number of groups are working on methodologies to identify vaccine antigens directly from genome sequences. Secondly, there will be a need to formulate such vaccines appropriately for the rapid induction of protective immunity after non-invasive delivery. The prospects for the development of a new generation of bioterrorism vaccines which exploit these technologies are reviewed in this manuscript.

Therapeutic and preventative options for the management of vancomycin-resistant enterococcal infections

Enterococci are naturally resistant to a wide range of antimicrobial agents. In addition, some enterococci, known as vancomycin-resistant enterococci (VRE) have become resistant to glycopeptide antibiotics. The therapeutic options for VRE infections are therefore very limited. New antimicrobials have been developed that are active against VRE, such as linezolid and quinupristin/dalfopristin. Others, e.g. tigecycline, daptomycin and oritavancin, are in the later stages of development. However, resistance has already been detected to some of these agents. Some success has been enjoyed through the application of older antibiotics against VRE. The lack of therapeutic options has led to the consideration of measures to prevent infection with VRE. In addition to standard infection control procedures such as isolation and hand washing, decolonization of the gastrointestinal tract has been investigated as a method for the prevention of VRE infection in vulnerable patient groups. Several decolonization regimens have been investigated. These include the use of ramoplanin, a new glycolipodepsipeptide antibiotic that has features that particularly suit it for decolonization. Ramoplanin is not absorbed from the gastrointestinal tract, has potent bactericidal activity against Gram-positive organisms and limited side effects. These features and current clinical evidence suggest that ramoplanin may have a role in future gastrointestinal decolonization regimens.

Clinical impact of vancomycin-resistant enterococci

In humans, vancomycin-resistant enterococci (VRE) most commonly result in intestinal colonization, which does not result in symptoms, may persist for a long time and serves as a reservoir for transmission of VRE to other patients. Certain VRE-colonized patients are at risk of infection, including haematology and oncology patients, patients in intensive care units and recipients of solid (especially abdominal) organ transplants. Controlling the spread of VRE colonization and preventing colonized patients from becoming infected are important aims. Ramoplanin is a member of a new class of antimicrobial agents; it may have a role in preventing infection in patients colonized with VRE.

Ramoplanin: a novel antimicrobial agent with the potential to prevent vancomycin-resistant enterococcal infection in high-risk patients

The prevention of vancomycin-resistant Enterococcus (VRE) colonization and infection continues to be a high priority for clinicians. An oral antimicrobial agent that reduces or eliminates VRE gastrointestinal colonization could be useful for preventing VRE infection in selected patients. Ramoplanin, a glycolipodepsipeptide, is the first in a new class of antimicrobials. It has excellent in vitro activity against vancomycin-resistant Enterococcus faecium and Enterococcus faecalis. It is orally administered, and not absorbed systemically. In clinical trials, VRE gastrointestinal colonization was reduced to undetectable levels in 80-90% of patients during receipt of ramoplanin. A randomized, double-blinded, placebo-controlled multicentre study is currently being conducted to determine whether ramoplanin will prevent VRE bloodstream infection in oncology patients who are neutropenic due to treatment for a haematological malignancy or a bone marrow/stem cell transplant.

SHEA guideline for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus aureus and enterococcus

BACKGROUND

Infection control programs were created three decades ago to control antibiotic-resistant healthcare-associated infections, but there has been little evidence of control in most facilities. After long, steady increases of MRSA and VRE infections in NNIS System hospitals, the Society for Healthcare Epidemiology of America (SHEA) Board of Directors made reducing antibiotic-resistant infections a strategic SHEA goal in January 2000. After 2 more years without improvement, a SHEA task force was appointed to draft this evidence-based guideline on preventing nosocomial transmission of such pathogens, focusing on the two considered most out of control: MRSA and VRE.

METHODS

Medline searches were conducted spanning 1966 to 2002. Pertinent abstracts of unpublished studies providing sufficient data were included.

RESULTS

Frequent antibiotic therapy in healthcare settings provides a selective advantage for resistant flora, but patients with MRSA or VRE usually acquire it via spread. The CDC has long-recommended contact precautions for patients colonized or infected with such pathogens. Most facilities have required this as policy, but have not actively identified colonized patients with surveillance cultures, leaving most colonized patients undetected and unisolated. Many studies have shown control of endemic and/or epidemic MRSA and VRE infections using surveillance cultures and contact precautions, demonstrating consistency of evidence, high strength of association, reversibility, a dose gradient, and specificity for control with this approach. Adjunctive control measures are also discussed.

CONCLUSION

Active surveillance cultures are essential to identify the reservoir for spread of MRSA and VRE infections and make control possible using the CDC's long-recommended contact precautions.

Vancomycin-resistant enterococci: a road map on how to prevent the emergence and transmission of antimicrobial resistance

Nosocomial acquisition of microorganisms resistant to multiple antibiotics represents a threat to patient safety. Here we review the mechanisms that have allowed highly resistant strains belonging to the Enterococcus genus to proliferate within our health-care institutions. These mechanisms indicate that decreasing the prevalence of resistant organisms requires active surveillance, adherence to vigorous isolation, hand hygiene and environmental decontamination measures, and effective antibiotic stewardship. We suggest how to tailor such a complex, multidisciplinary program to the needs of a particular health-care setting so as to maximize cost-effectiveness.

Vancomycin-resistant enterococci: 15 years and counting

We review the history of vancomycin-resistant enterococci (VRE) and propose a causal model illustrating the roles of exposure to VRE reservoirs, patient characteristics, antimicrobial exposure, and prevalence of VRE in the progression from potential VRE reservoirs to active disease in hospitalized patients. Differences in VRE colonization and VRE infection are discussed with respect to hospital surveillance methodology and implications for interventions. We further document clonal transmission of VRE in a large, urban, teaching hospital and demonstrate VRE susceptibility to a wide array of antimicrobial agents. This model can guide the identification of mutable factors that are focal points for intervention.

Clostridium difficile infection and concurrent vancomycin-resistant Enterococcus stool colonization in a health care worker: case report and review of the literature

Clostridium Difficile diarrhea was noted in a previously healthy health care worker from the study institution after receiving oral clindamycin therapy; the worker also had vancomycin-resistant Enterococcus stool colonization. Health care workers should be aware that antibiotic therapy may place them at increased risk for colonization and infection with nosocomial pathogens such as Clostridium difficile and vancomycin-resistant Enterococcus.

Mechanism of action of oritavancin and related glycopeptide antibiotics

Oritavancin (LY333328) is a semisynthetic glycopeptide antibiotic having excellent bactericidal activity against glycopeptide-susceptible and -resistant Gram-positive bacteria. Oritavancin is the N-alkyl-p-chlorophenylbenzyl derivative of chloroeremomycin (LY264826) and is currently in phase III clinical trials for use in Gram-positive infections. Studies show that oritavancin and related alkyl glycopeptides inhibit bacterial cell wall formation by blocking the transglycosylation step in peptidoglycan biosynthesis in a substrate-dependent manner. As with other glycopeptide antibiotics, including vancomycin, the effects of oritavancin on cell wall synthesis are attributable to interactions with dipeptidyl residues of peptidoglycan precursors. Unlike vancomycin, however, oritavancin is strongly dimerized and can anchor to the cytoplasmic membrane, the latter facilitated by its alkyl side chain. Cooperative interactions derived from dimerization and membrane anchoring in situ can be of sufficient strength to enable binding to either dipeptidyl or didepsipeptidyl peptidoglycan residues of vancomycin-susceptible and -resistant enterococci, respectively. This review describes the antibacterial activity of oritavancin, and examines the evidence supporting the proposed mechanism of action for this agent and related analogs.

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.

Emergence of vancomycin-resistant Enterococcus faecium at a tertiary care hospital in Karachi, Pakistan

Vancomycin-resistant enterococcus (VRE) has not been reported previously in Pakistan. This is the first report where in vancomycin-resistant Enterococcus faecium was isolated from the clinical specimens of six patients admitted to the intensive care unit (ICU) and neonatal intensive care unit (NICU) of the Aga Khan University Hospital, Karachi. To identify the extent of the outbreak, rectal swabs were obtained from all the patients admitted to the ICU and NICU at that time. A total of 10 strains of vancomycin-resistant Enterococcus faecium were isolated. All the strains showed high-level resistance to both glycopeptides (vancomycin and teicoplanin) with a vancomycin minimum inhibitory concentration greater than 256 mg/L. All isolates had the vanA gene detected by polymerase chain reaction. The contour-clamped homogeneous electric field (CHEF) pattern demonstrated that all but one of the isolates were of a single clone, suggesting that they were derived from common source. Use of vancomycin and prolonged hospitalization were common features in all cases investigated.

Effectiveness of pharmacy policies designed to limit inappropriate vancomycin use: a population-based assessment

OBJECTIVE

In Oregon in 1994, a population-based study of 66 nonpsychiatric hospitals indicated that 40% of vancomycin orders were inappropriate according to Centers for Disease Control and Prevention guidelines. We repeated the study to determine whether vancomycin use had been affected by pharmacy policies implemented following the 1994 study.

METHODS

We surveyed pharmacists in nonpsychiatric hospitals in Oregon regarding vancomycin use policies in their hospitals. Using pharmacy records, we identified and abstracted the charts of all patients in Oregon hospitals receiving vancomycin during a 3-week period to determine appropriate use of vancomycin.

RESULTS

Thirteen (20%) of 64 hospitals had implemented a vancomycin restriction policy since 1994; none ofthe remaining hospitals in the study had a policy. In 1999, hospitals with vancomycin restriction policies had substantially decreased rates of inappropriate vancomycin use compared with hospitals without such policies (1.0 vs 1.8 orders per 1,000 patient-days; P = .01). Compared with 1994 baseline rates of inappropriate use, hospitals that adopted policies experienced a decrease (from 1.5 orders per 1,000 patient-days in 1994 to 1.0 in 1999; P= .13), whereas hospitals without policies experienced a statistically significant increase (from 0.9 orders per 1,000 patient-days in 1994 to 1.8 in 1999; P= .001). Restriction policies were most effective at reducing rates of inappropriate use for treatment of confirmed gram-positive infections and prophylaxis.

CONCLUSION

Vancomycin restriction policies were associated with a decrease in inappropriate therapeutic and prophylactic vancomycin use, but had no effect on inappropriate empiric use. Hospitals considering limits regarding inappropriate use should consider implementation of institution-based vancomycin restriction policies as part of an overall strategy.

Preventing bacterial infections and antimicrobial resistance in dialysis patients

Antimicrobial use, in concert with patient-to-patient transmission of resistant strains, has caused a rapid increase in the prevalence of antimicrobial resistance in recent years. This increase is a particular threat to dialysis patients, who often have been in the forefront of the epidemic of resistance. In this report, which was written in collaboration between the American Society of Nephrology and the Centers for Disease Control and Prevention and has been endorsed by the Executive Council of the Infectious Diseases Society of America, we review and summarize existing clinical practice guidelines and recommendations concerning the prevention, diagnosis, and treatment of certain bacterial infections in dialysis patients and present four strategies to limit the spread of antimicrobial resistance in dialysis patients. First, preventing infection eliminates the need for antimicrobials, thereby reducing selection pressure for resistant strains. Efforts to prevent infection include avoidance of hemodialysis catheters, when possible, and meticulous care of hemodialysis and peritoneal catheters and other hemodialysis vascular access sites. Second, diagnosing and treating infections appropriately can facilitate the use of narrower spectrum agents, rapidly decrease the number of infecting organisms, and reduce the probability of resistance emerging. This entails the collection of indicated specimens for culture and avoidance of contamination of cultures with common skin microorganisms. Third, optimizing antimicrobial use helps protect the efficacy of such critical agents as vancomycin. Published guidelines for the use of vancomycin should be followed, and alternate agents should be used when infections with beta-lactam-resistant bacteria are unlikely or not documented. Fourth, preventing transmission in health care settings is important to limit the spread of resistant organisms. In this regard, such basic measures as glove use and hand hygiene are most important.

[Hospital infection control measures for methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci]

Methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci are major hospital pathogens in hospital settings. These organisms are mainly transmitted by direct skin contact with infected/colonized patients. Air borne transmission may rarely occur in MRSA positive cases with upper respiratory infections. Contamination in immediate environment requires proper disinfection after contact. Screening patients for MRSA and VRE can be restricted against those in/from the high risk areas. The clinical pictures, methods for screening and the precautions were also discussed based on the nature of communicability in both pathogens.

Nucleotide substitutions in vanC-2 gene of Enterococcus casseliflavus isolates obtained from chickens

DNA sequencing of the vanC-2 gene was partially carried out on 10 isolates of Enterococcus casseliflavus obtained from 8 samples of imported chickens in Japan between July 1999 and June 2001 to evaluate the variation in the gene. Forty nucleotide substitutions in 36 codons were identified within 345 base pairs when compared with the vanC-2 sequence of the reference strain E. casseliflavus ATCC25788. Identical nucleotide substitutions were commonly found in the isolates recovered from chickens imported from both Brazil and China. Pulsed-field gel electrophoresis (PFGE) patterns of NotI-digested chromosomal DNA of these strains were distinguished by two, or more than six, band differences. These observations suggest that sequencing of the vanC-2 gene may be helpful for epidemiological investigation in combination with the PFGE analyses of the isolates, although particular genotypes are unlikely to be restricted to each of the countries that exported chickens.

Determination of bone and tissue concentrations of teicoplanin mixed with hydroxyapatite cement to repair cortical defects

A highly specific and sensitive isocratic reversed-phase high performance liquid chromatography (HPLC) method for the determination of the major component of teicoplanin in tissue is reported. Comparing fluorescamine and o-phthalaldehyde (OPA) as derivatizing agents, the derivative formed with the latter exhibits superior fluorescence intensity allowing detection of femtomole quantities. Pretreatment for tissue samples is by solid-phase extraction which uses Bakerbond PolarP C(18) cartridges and gives effective clean up from endogenous by-products. Linearity was given from 0.6 to 100 ng per injection. The coefficient of variation did not exceed 5.8% for both interday and intraday assays. It was found that when bone defects are repaired with a hydroxyapatite-teicoplanin mixture, the antibiotic does not degrade, even when it is in the cement for several months. The stability of teicoplanin in bone cement was determined fluorodensitometrically.