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Surveillance of antibiotic resistance in ICUs in southeastern Sweden. ICU Study Group of the South East of Sweden.

BACKGROUND: A study was designed to assess a computer-based program for continuous registration of antibiotic resistance, statistics concerning severity of illness, and consumption of antibacterial drugs. METHODS: The frequency of antibiotic resistance among bacteria in eight ICUs in southeastern Sweden was investigated yearly from 1995 through 1997. The antibiotic consumption in the ICUs was registered as defined daily doses (DDD) and compared to severity of illness (APACHE-II scores). RESULTS: There was a statistically significant increase in ampicillin resistance among Enterococcus spp. between 1996 and 1997, which was due to a shift from Enterococcus faecalis to Enterococcus faecium. A high prevalence of resistance among coagulase-negative staphylococci to oxacillin (approximately 70%), ciprofloxacin (approximately 50%), fucidic acid (approximately 50%) and netilmicin (approximately 30%) was seen in all ICUs during the whole study period. There was a statistically significant increase in ciprofloxacin resistance among Escherichia coli and Enterococcus spp. The resistance among Enterobacter spp. to cefotaxime decreased but this change was not statistically significant. Efforts were made to avoid betalactam antibiotics, except carbapenems, for treatment of infections caused by Enterobacter spp. and the consumption of cephalosporins decreased whereas the consumption of carbapenems increased. The total antibiotic consumption decreased by 2.5% during the study period. There was no correlation between APACHE II scores and antibiotic consumption. CONCLUSIONS: Each ICU within a hospital ought to have a program for "on-line" antibiotic resistance surveillance of drugs used in that unit so that changes in empirical treatment can be made when there is an increase in antibiotic-resistant isolates within that unit.

APACHE↗

Glycopeptide resistance mediated by enterococcal transposon Tn1546 requires production of VanX for hydrolysis of D-alanyl-D-alanine.

Cloning and nucleotide sequencing indicated that transposon Tn1546 from Enterococcus faecium BM4147 encodes a 23,365 Da protein, VanX, required for glycopeptide resistance. The vanX gene was located downstream from genes encoding the VanA ligase and the VanH dehydrogenase which synthesize the depsipeptide D-alanyl-D-lactate (D-Ala-D-Lac). In the presence of ramoplanin, an Enterococcus faecalis JH2-2 derivative producing VanH, VanA and VanX accumulated mainly UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Lac (pentadepsipeptide) and small amounts of UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala (pentapeptide) in the ratio 49:1. Insertional inactivation of vanX led to increased synthesis of pentapeptide with a resulting change in the ratio of pentadepsipeptide: pentapeptide to less than 1:1. Expression of vanX in E. faecalis and Escherichia coli resulted in production of a D,D-dipeptidase that hydrolysed D-Ala-D-Ala. Pentadepsipeptide, pentapeptide and D-Ala-D-Lac were not substrates for the enzyme. These results establish that VanX is required for production of a D,D-dipeptidase that hydrolyses D-Ala-D-Ala, thereby preventing pentapeptide synthesis and subsequent binding of glycopeptides to D-Ala-D-Ala-containing peptidoglycan precursors at the cell surface.

Alanine↗

Antibiotic-induced enterococcal expansion in the mouse intestine occurs throughout the small bowel and correlates poorly with suppression of competing flora.

To test the hypothesis that establishing gastrointestinal colonization with multiresistant Enterococcus faecium (VRE) C68 results from expansion of the enterococcal population in the upper small bowel, we compared VRE quantities recovered from the proximal, middle, and distal segments of the small bowel from mice treated with different antimicrobial agents. Antibiotics associated with high-level VRE fecal colonization (cefotetan, ceftriaxone, clindamycin, and ticarcillin-clavulanic acid) increased VRE quantities in all small-bowel segments, whereas cefepime and piperacillin-tazobactam did not. Enterococcal expansion did not correlate with reductions in numbers of native gram-negative or anaerobic flora. Green fluorescence protein-expressing E. faecium bacteria were found adjacent to the small bowel epithelial lining in colonized mice. These data indicate that enterococcal bowel colonization begins within the proximal small bowel and does not correlate with inhibition of other cultivable flora. Host or enterococcal factors induced by exposures to certain antibiotics may play a role in facilitating E. faecium colonization of the mammalian gastrointestinal tract.

Animals↗

In vitro activity of RPR 106972 alone and in combination with vancomycin, ampicillin, and gentamicin against multidrug-resistant enterococci.

This investigation used checkerboard and time-kill assays to evaluate the in vitro activity of RPR 106972 (45% pristinamycin IB and 55% pristinamycin IIB) alone and in combination with vancomycin or ampicillin +/- gentamicin against multidrug-resistant enterococci. The checkerboard procedure resulted in synergistic or additive effects in 91% of the isolates with the combination of RPR 106972 plus vancomycin versus 68% with RPR 106972 plus ampicillin. The addition of gentamicin to either combination resulted in synergistic or additive results in 100% of the isolates. Inhibitory activity was observed with the time-kill assay with mean change in log10 CFU/mL at 24 h of -0.31 for RPR 106972, 3.3 for vancomycin, -0.46 for RPR 106972 plus vancomycin, and -0.35 for RPR 106972 plus vancomycin and gentamicin. No antagonism was noted with any of the combinations. RPR 106972 demonstrates good inhibitory activity against Enterococcus faecium and may prove useful in the treatment of enterococcal infections.

Ampicillin↗

Comparative in vitro activity of levofloxacin and ofloxacin against gram-positive bacteria.

The in vitro activity of levofloxacin against 506 Gram-positive bacteria was compared with those of D(-)-ofloxacin, ofloxacin, ciprofloxacin, and sparfloxacin. Levofloxacin was generally twice as active as ofloxacin against these organisms (range, 0-3 twofold dilutions). Sparfloxacin appeared to have the greatest activity overall, but for several groups of organisms minimum inhibitory concentrations (MIC90s) of this compound were within one twofold dilution of those of levofloxacin. Resistance to levofloxacin (MIC > or = 8 micrograms/ml) was not encountered among streptococcal species, was rare in methicillin-susceptible staphylococci (1.7%), and was infrequent in vancomycin-susceptible Enterococcus faecalis and Enterococcus faecium (8.7%). Resistance was more common among vancomycin-resistant enterococci and methicillin-resistant staphylococci.

Anti-Bacterial Agents↗

Application of DNA probes for rRNA and vanA genes to investigation of a nosocomial cluster of vancomycin-resistant enterococci.

DNA probes specific for genes encoding rRNA and the glycopeptide resistance gene vanA were used to investigate a cluster of vancomycin-resistant (MICs, > 512 mg/liter) Enterococcus faecalis and Enterococcus faecium isolated from separate patients in a renal unit in a London hospital. When digested with BamHI, 12 of 13 vancomycin-resistant E. faecalis isolates exhibited a common restriction fragment length polymorphism pattern of rRNA genes (ribotype). A vanA probe hybridized with chromosomal DNA in these 12 isolates. The other isolate of vancomycin-resistant E. faecalis had a different ribotype and the vanA gene was located on plasmid DNA. These data suggest that cross-infection with a single strain of vancomycin-resistant E. faecalis occurred in most instances. In contrast, 23 vancomycin-resistant E. faecium isolates showed greater heterogeneity, comprising 8 ribotypes, suggesting that multiple strains were present in the unit. Twenty-one of these 23 isolates harbored a 24-MDa plasmid which hybridized with the vanA probe, implying that interstrain dissemination of a vancomycin resistance plasmid may have occurred among E. faecium isolates in the renal unit.

Bacterial Proteins↗

Concomitant high-level vancomycin and penicillin resistance in clinical isolates of enterococci.

Enterococci are important nosocomial pathogens among which resistance to multiple antibiotics is being recognized with increasing frequency. We characterized three clinical isolates from three New York City hospitals that demonstrated concomitant resistance to vancomycin (one VanA, two VanB phenotypes) and high-level resistance to penicillin. Two Enterococcus faecium strains were intrinsically highly resistant to penicillin and showed very low affinity for penicillin of penicillin-binding protein 5. Unlike previously described glycopeptide-resistant enterococci, these strains were not hypersusceptible to beta-lactam agents after vancomycin induction, and combinations of penicillin and vancomycin were not synergistic against them. A third isolate, Enterococcus faecalis, produced beta-lactamase. Two of the three strains were also highly resistant to all aminoglycosides. Emergence of concomitant high-level resistance to multiple antibiotic classes among enterococci considerably narrows the therapeutic options for treatment of infections due to these opportunistic pathogens.

Aged↗

Bloodstream infections in organ transplant recipients receiving alemtuzumab: no evidence of occurrence of organisms typically associated with profound T cell depletion.

BACKGROUND: Alemtuzumab is a humanized monoclonal antibody directed against CD52, a cell surface antigen expressed on B and T lymphocytes, monocytes and NK cells. Its use results in a profound decrease in CD4 positive T lymphocytes. Alemtuzumab is used as induction immunosuppression and therapy for rejection in organ transplant recipients in some centers. We followed a cohort of 449 consecutive transplant recipients who received alemtuzumab to determine the occurrence of bloodstream infections, particularly those previously associated with decrease in CD4 positive T lymphocytes. PATIENTS AND METHODS: Fifteen percent (69/449) patients had at least one episode of bloodstream infection. However, no patient had bacteremia with Streptococcus pneumoniae, Listeria monocytogenes, non-typhoidal Salmonella or Mycobacterium avium complex. Fungaemia was rare, occurring in 1.5% of patients. The most common organisms isolated from the blood were Staphylococcus aureus (21 episodes), coagulase negative Staphylococcus (14 episodes), Klebsiella pneumoniae (12 episodes), Enterococcus faecium (11 episodes), Pseudomonas aeruginosa (10 episodes), Enterococcus faecalis (9 episodes) and Escherichia coli (7 episodes). DISCUSSION: We conclude that although alemtuzumab use is associated with profound CD4 positive T lymphocyte depletion, alemtuzumab does not seem to be associated with an increased risk of bloodstream infection with pathogens typically seen in other disorders of CD4 cell depletion, such as acquired immunodeficiency syndrome.

Adolescent↗

Vancomycin-resistant enterococci (VRE) colonization of high-risk patients in tertiary care Canadian hospitals. Canadian VRE Surveillance Group.

We isolated 1487 Enterococcus species from 1200 stool specimens collected from high-risk patients in 12 Canadian tertiary care hospitals between October 1995 and November 1996. The composition of the 1487 isolates was 601 vancomycin-sensitive Enterococcus faecalis (40.4%), 667 vancomycin-sensitive Enterococcus faecium (44.9%), 18 vancomycin-resistant (nine isolates MIC 8-16 micrograms/mL; nine isolates MIC > or = 32 micrograms/mL) E. faecium (VREF) (1.2%), 95 vancomycin-sensitive Enterococcus gallinarum (6.4%), 29 vancomycin-resistant (all MICs 8-16 micrograms/mL) E. gallinarum (2.0%), and 77 vancomycin-sensitive Enterococcus casseliflavus (5.2%). Nine of the 18 VREF isolates collected possessed the vanA genotype and were from three patients at one hospital. Two other VREF isolates, of the vanB genotype, were from a single patient at a second hospital, and the remaining seven isolates, also all of the vanB genotype, were from five patients at a third hospital. All VREF were ampicillin resistant (MIC > or = 16 micrograms/mL), streptomycin resistant (MIC > 1000 micrograms/mL), and ciprofloxacin resistant (MIC > or = 4 micrograms/mL). Ten of the 18 VREF were also resistant to gentamicin (MIC > 500 micrograms/mL), while all 18 isolates had quinupristin/dalfopristin MICs < or = 0.5 microgram/mL. In conclusion, high-risk patients in tertiary care Canadian hospitals are rarely colonized (9/1200 patients, 0.75%) with VREF in their lower gastrointestinal tract. These findings correlate well with the lack of reported VREF infection in high-risk patients in Canadian hospitals. Quinupristin/dalfopristin demonstrated excellent in vitro activity against VREF and other non-faecalis species of Enterococcus, many of which also possessed high-level ampicillin, and/or high-level aminoglycoside, and/or ciprofloxacin resistance.

Canada↗

Antibacterial activity of enterococci strains against Vibrio cholerae.

Thirty-seven strains of enterococci isolated from milk and milk products from Santa Fe (Argentina) region were tested for antagonistic activity against Vibrio cholerae 01 and non-01. Seven of 17 strains of Enterococcus faecalis, five of 10 strains of Enterococcus faecium and four of 10 strains of Enterococcus durans produced inhibition zones against the indicator species. The activity of the antibacterial compounds was completely destroyed by treatment with trypsin and pronase E in most cases (only the supernatant fluids of a few strains remained weakly active after the treatment), but was resistant to heat treatment at 100 degrees C during 10 and 30 min. When the 10-fold concentrated supernatant fluids were added to a fresh culture of sensitive cells it produced a rapid inactivation. According to these preliminary tests, different strains of enterococci produced compounds with slightly different antivibrio properties, and these compounds were heat-resistant and had a predominantly proteinaceous nature.

Bacteriocins↗

Successful treatment of chronic bone and joint infections with oral linezolid.

Linezolid is an attractive alternative for the treatment of chronic bone and joint infections because it is active against common pathogens including methicillin-resistant staphylococci and vancomycin-resistant enterococci and because its oral formulation is convenient for long-term administration. To evaluate the ability of linezolid to produce long-term remission, we prospectively monitored 11 consecutive adult patients who received linezolid for osteomyelitis (n = 9) or prosthetic joint infection (n = 2). Linezolid 600 mg was administered orally twice daily for a mean of 10 weeks (range, 6 to 19 weeks). Pathogens were methicillin-resistant Staphylococcus aureus (n = 5), methicillin-resistant coagulase-negative staphylococci (n = 4), vancomycin-resistant Enterococcus faecium (n = 1), and vancomycin-sensitive Enterococcus faecalis (n = 1). After a mean followup of 27 months (range, 17 to 41 months), all 11 patients had remission by clinical, laboratory, and radiographic criteria. During week 8 of linezolid treatment, one patient developed a gram-negative superinfection, which resolved with appropriate therapy. During week 6 of linezolid treatment, one patient developed mild thrombocytopenia and another patient developed mild anemia. Both episodes of myelosuppression were reversible within 10 days after completing the planned 6-week courses of linezolid. We recommend weekly complete blood counts to detect hematologic abnormalities. We conclude that oral linezolid seems to be a useful and convenient alternative for the treatment of bone and joint infections.

Acetamides↗

Enterococcus villorum sp. nov., an enteroadherent bacterium associated with diarrhoea in piglets.

The taxonomic positions of five enteroadherent bacterial pig isolates, showing phenotypic characteristics most similar to those of Enterococcus durans and Enterococcus hirae, were investigated in a polyphasic study that included 16S rDNA sequence analysis, DNA-DNA hybridizations, DNA base-ratio determinations, whole-cell protein fingerprinting, D11344-primed PCR typing and an extensive examination of phenotypic properties. The results demonstrated that the organisms represent a new species in the Enterococcus faecium species group, for which the name Enterococcus villorum sp. nov. is proposed. The type strain is LMG 12287T (= CCM 4887T).

Animals↗

Application of tRNA intergenic spacer PCR for identification of Enterococcus species.

tRNA intergenic spacer PCR (tDNA-PCR) was evaluated for its usefulness in the differentiation of enterococcal species of human and animal origin. This technique was carried out for 124 strains belonging to 17 enterococcal species and generated DNA fragments, which were separated by capillary electrophoresis. tDNA-PCR enabled us to discriminate for all species tested. Enterococcus faecium showed minor but reproducible differences with Enterococcus durans, while Enterococcus hirae was easily distinguishable. Enterococcus avium, Enterococcus malodoratus, and Enterococcus raffinosus generated highly similar though distinctive patterns.

Animals↗

Evaluation of the oxolinic acid--esculin--azide medium for the isolation and enumeration of faecal streptococci in a routine monitoring programme for bathing waters.

m-Enterococcus agar (m-Ent) has been generally considered the reference medium for faecal streptococci in bathing waters. However, it shows several shortcomings, and therefore it is important to test newly developed media that can guarantee more precise results. In this sense, the recently described oxolinic acid--esculin--azide agar medium (OAA) and m-enterococcus agar (m-Ent) were comparatively evaluated for the detection of faecal streptococci from seawater and fresh water. The OAA medium showed a significantly higher relative recovery percentage and specificity for both types of water than m-Ent. A similar spectrum of species was recorded from both media, Enterococcus faecium being predominant in fresh water and Enterococcus faecalis, in seawater. The superior performance of the OAA medium in both types of bathing waters, added to the fact that it does not require the use of complementary confirmative tests, makes this medium an excellent candidate to be employed for monitoring programmes.

Azides↗

Successful treatment of vancomycin-resistant enterococcus meningitis with linezolid: case report and review of the literature.

OBJECTIVE: To describe the successful treatment of a case of vancomycin-resistant enterococcus meningitis with linezolid. DESIGN: Case report and review of the literature. PATIENTS: The patient is a 35-yr-old man who suffered a cerebellar hemorrhage after embolization of a cerebellar arteriovenous malformation. The patient underwent ventriculostomy drainage and craniectomy. The patient was on broad-spectrum antibiotics for pneumonia including vancomycin. The patient remained febrile and grew vancomycin-resistant Enterococcus faecium from the cerebrospinal fluid. INTERVENTIONS: The patient was treated with intravenous chloramphenicol without success. On postoperative day 16, the patient was begun on intravenous linezolid. MAIN RESULTS: The patient received 4 wks of intravenous linezolid with complete eradication of the meningitis. CONCLUSIONS: Intravenous linezolid appears to be a safe and effective therapy for vancomycin-resistant enterococcus meningitis.

Acetamides↗

The effect of temperature on the antimicrobial activity of Optisol-GS.

PURPOSE: To determine the survival of different bacteria inoculated in Optisol-GS at refrigerated storage temperature (6 degrees C) and after subsequent warming to room temperature (19-22 degrees C). METHODS: Staphylococcus aureus, Enterococcus faecium, Streptococcus pneumoniae, and Pseudomonas aeruginosa were chosen from stock clinical isolates for inclusion in the study. The first group consisted of 12 Optisol-GS vials. The second group consisted of 12 Optisol-GS vials containing corneas inappropriate for transplantation according to the Eye Bank Association of America (EBAA) protocols. Each group was inoculated with 3 concentrations of approximately 10, 10, and 10 colony-forming units (CFU)/mL of each bacterial species and then refrigerated per EBAA protocol. After 48 hours of refrigeration, all vials were placed at room temperature (RT) and counts were performed at 48, 50 (2 hour RT), 54 (6 hour RT), 60 (12 hour RT), 72 (24 hour RT), and 96 (48 hour RT) hours. At 96 hours, the corneal tissue from 10 and 10 inocula were cultured. All samples underwent serial dilution, spiral plating on blood agar plates, and incubation at 35 degrees C. Viable colony counts were determined at 24 hours. RESULTS: Except for the 10 CFU/mL inocula of P. aeruginosa, all isolates were viable after 48 hours of refrigeration. Rapid bactericidal activity was observed against P. aeruginosa after 2 hours at RT, with complete sterilization by 6 hours. The rate and extent of killing against S. aureus were influenced by the initial inoculum. Bactericidal activity was achieved after 2 hours at RT with 10 CFU/mL of S. aureus versus 24 hours with the 10 inoculum. Of note, bactericidal activity was not observed against S. pneumoniae and E. faecium following 24 hours of storage at RT. The presence of corneal tissue did not affect viable counts, with counts from corneal tissue cultures reflecting the counts seen from Optisol-GS after 48 hours at RT. CONCLUSIONS: The antimicrobial activity of Optisol-GS was reduced at refrigerated temperature and enhanced at RT. Bactericidal activity was not observed against E. faecium at either refrigerated temperature or RT.

Anti-Bacterial Agents↗

Isolation and biochemical characterisation of enterocins produced by enterococci from different sources.

AIMS: Comparison of enterocins produced by six Enterococcus faecium strains and one Ent. faecalis strain isolated from different origin with regard to their microbiological and biochemical characteristics in view of their technological potential and practical use. METHODS AND RESULTS: The seven enterococci were sensitive to the glycopeptide antibiotics vancomycin and teicoplanin and did not show haemolytic activity. The absence of the glycopeptide-resistant genotypes and the genes involved in the production of the lantibiotic cytolysin was confirmed by PCR. The enterocins were active towards Listeria innocua and other lactic acid bacteria. Their temperature stability was dependent on the pH and their activity was higher at acidic pH. A bactericidal and bacteriolytic effect was shown. PCR analyses revealed that the gene of enterocin A was present in the genome of Ent. faecium CCM 4231, Ent. faecium 306 I.2.20 and Ent. faecalis Y; both enterocin A and B genes were present in the genome of Ent. faecium LMG 11423T, Ent. faecium RZS C5 and Ent. faecium RZS C13. Enterocin P was detected in the genome of Ent. faecium RZS C5 and Ent. faecium RZS C13. No signal was found for Ent. faecium SF 68. Enterocins from Ent. faecium RZS C5, Ent. faecium RZS C13 and Ent. faecium SF 68 were purified to homogeneity. CONCLUSIONS: Ent. faecium RZS C5 and Ent. faecium RZS C13 produced an enterocin with a molecular mass of 5460 and 5477 Da, respectively, which was in the range of that of enterocin B. The amino acid sequence analysis of the enterocin from Ent. faecium RZS C13 revealed 24 N-terminal residues, which were identical to those of enterocin B. The enterocin from Ent. faecium SF 68 had a molecular mass of 4488 Da, which did not correspond to any enterocin known so far. SIGNIFICANCE AND IMPACT OF THE STUDY: The number of characterized enterocins is increasing. As this type of work is tedious and time-consuming, it may be interesting to include PCR as a first step to know if the Enterococcus strain in study produces either a known or a new enterocin. Also, it is important to check the absence of cytolysin and resistance to vancomycin for a further application of the Enterococcus strain in food or health applications.

Animals↗

Binding kinetics of triclosan (Irgasan) to alloplastic vascular grafts: an in vitro study.

The aim of this study was to investigate the binding kinetics of triclosan (Irgasan) to alloplastic vascular grafts and to examine its antimicrobial activity against various microbial pathogens in vitro. Vascular grafts made by Intergard (Intervascular), Fluoropassiv (Vascutek), and Gore-tex (Gore) were examined. Grafts were incubated in 10 g/L triclosan (Irgasan), dried, sterilized, and incubated in RPMI medium. One-centimeter segments of the grafts were resected under sterile conditions at intervals of minutes, then hours, followed by days and up to 4 weeks. Samples were stored frozen at -20 degrees C for the measurement of triclosan bound to the vascular graft by high-performance liquid chromatography (HPLC). The binding kinetics under perfusion conditions were determined for Intergard grafts, which were perfused with 50 mL of nutrient medium for 24 hr. Samples were taken at various time intervals for the measurement of triclosan. The antimicrobial activity of triclosan against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans as well as Enterococcus faecium was determined. Triclosan effectively binds to vascular graft without the use of intermediate binding substances. It stayed on the graft for the duration of 4 weeks. Under both static and perfusion conditions, the binding kinetics are similar. Triclosan binds most effectively to Intergard grafts, less so to Fluoropassiv grafts, and not at all to Gore-tex material. Antimicrobial activity of triclosan is very effective against S. aureus and E. faecium but not against P. aeruginosa.

Anti-Infective Agents, Local↗