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Differentiation of Enterococcus spp. by cell membrane fatty acid methyl ester profiling, biotyping and ribotyping.

AIMS: Gas chromatographic analysis of cell membrane fatty acid methyl esters (FAME), biochemical profiling (biotyping) and EcoRI restriction endonuclease profiling of DNA containing ribosomal RNA sequences (ribotyping) were compared for differentiation of Enterococcus spp. METHODS AND RESULTS: FAME profiling, biotype profiling and ribotyping of 41 strains from retail Swiss-type cheeses and five strains from culture collections resulted in 17, 25 and 26 groups, respectively, with only two pairs of strains having the same FAME group, biotype profile and ribogroup. CONCLUSION: Substantial overlap occurred in groupings assigned by the three methods. SIGNIFICANCE AND IMPACT OF THE STUDY: Differentiation of Enterococcus spp. strains increases if multiple methods are used.

Bacterial Typing Techniques↗

Vancomycin-resistant Enterococcus spp. isolated from wastewater and chicken feces in the United States.

Vancomycin-resistant Enterococcus spp. (VRE) were isolated from sewage and chicken feces but not from other animal fecal sources (dog, cow, and pig) or from surface waters tested. VRE from hospital wastewater were resistant to > or =20 microg of vancomycin/ml and possessed the vanA gene. VRE from residential wastewater and chicken feces were resistant to 3 to 5 microg of vancomycin/ml and possessed the vanC gene.

Animals↗

Antibiotic resistance of Enterococcus spp. isolated from wastewater and sludge of poultry slaughterhouses.

Antibiotimicrobial resistance was investigated in 537 Enterococcus spp. isolates recovered from 22 samples of crude inflow, treated effluent and sludge collected in wastewater treatment plants of eight poultry slaughterhouses of Portugal. No significant differences (P > 0.05) were found in the resistance to each antimicrobial agent with regards to the origin of the sample (inflow, sludge and effluent). Many of the isolates displayed resistance to tetracycline (85.7%), erythromycin (45.7%), nitrofurantoin (34.0%) and rifampicin (17.8%). Resistance was also observed, but to a lesser extent, to ciprofloxacin (10.2%), ampicillin (8.0%), chloramphenicol (4.6%), vancomycin (0.9%) and gentamicin (0.4%). Resistance to three or more antimicrobial classes was present in 37.1% of the isolates. Wastewater treatment resulted in viable enterococci decrease between less than 1 log and 4 log; nevertheless, more than 4.4 x 10(5) colony forming units (CFU)/100 mL were present in the outflow of the plants and thus resistant enterococci are not prevented from reaching the general environment.

Abattoirs↗

[Comparison of ATB STREP, AMS-Vitek GPS-TA, and disk diffusion for the detection of a high level of aminoglycoside resistance in Enterococcus spp].

BACKGROUND: The absence of the synergic effect between beta-lactam and aminoglucoside versus Enterococcus is predicted by the presence of a high level of resistance to aminoglucoside. There are several commercial systems which include wells for the performance of this determination for streptomycin and gentamicin. METHODS: A comparative study of two commercial systems, Vitek GPS-TA and ATB STREP (Biomérieux) and disk diffusion versus the Mueller-Hinton agar dilution method used as a method of reference. Two hundred ninety strains of Enterococcus spp. from blood, wounds, pus, fluids from paracentesis and urine were studied. RESULTS: By the reference method, 17 presented high level of resistance only to gentamicin, 45 only to streptomycin, 46 to both and 182 were sensitive to the two antibiotics. The sensitivity of ATB STREP, Vitek GPS-TA and disk diffusion was respectively for high level of resistance to gentamicin of 96.8, 100 and 100% and specificity of 99.5, 99.1 and 96.5%. For high level of resistance to streptomycin sensitivity was 78.2, 100 and 100% and specificity 96, 79.4 and 72.4% respectively. CONCLUSIONS: The authors consider the three methods valid for the determination of high level of resistance to gentamicin, presenting excellent correlation between the results of the reference methods. However, for high level of resistance to streptomycin with ATB STREP 1/5 of the resistant strains would not be detected due to low sensitivity. With Vitek GPS-TA and disk diffusion, although excellent sensitivity was presented, a high percentage of false positives were obtained due to low specificity, thus the authors recommend that before a results of resistance be decided the same should be confirmed by another alternative method (agar dilution, macrodilution in tubes or death-time curve).

Diffusion↗

[Antibiotic susceptibility analysis of Enterococcus spp. isolated from urine].

Recently increase of enterococcal infections has been observed. These bacteria, mainly Enterococcus faecalis and Enterococcus faecium are members of the normal flora of gastrointestinal tract but also are typical opportunistic pathogens. Enterococci are characterized by natural resistance to numerous antibiotics (among them cephalosporins), and also by easy acquired resistance to antibiotics. Infections caused by multiresistant strains are difficult in treatment, chronic, recurrent and sometimes fatal are described. Enterococcal infections are caused often by E. faecalis, rarely by E. faecium. In the last years other species of enterococci have been isolated from different clinical materials (E. casseliflavus, E. avium, E. durans, E. gallinarum). The aim of this study was to analyze the antibiotics susceptibility of Enterococcus spp. isolated from urine of children with urinary tract infection (UTI), hospitalized in the Upper Silesian Health Center of Child and Mother or treated ambulatory. Susceptibility of the 130 strains of E. faecalis and 41 E. faecium to: penicillin, tetracycline, high level of aminoglycoside (gentamycin 120 microg and streptomycin 300 microg), glycopeptides (vancomycin and teicoplanin), ciprofloxacin and nitrofurantoin was estimated. All isolated strains of E. faecalis (100%) were sensitive to glycopeptides (vancomycin and teicoplanin) and to nitrofurantoin, 96% strains were sensitive to penicillin, 43% to ciprofloxacin and 28% to tetracycline. All strains of E. faecium were sensitive to glycopeptides (vancomycin and teicoplanin), 32% strains were sensitive to penicillin, 19% to tetracycline 14% to ciprofloxacin and 50% to nitrofurantoin. Twenty two strains of E. faecalis (17%) and twelve strains of E. faecium (29%) were demonstrated high level resistance to aminoglycosides (HLAR). Among HLAR strains of enterococci, were observed strains of high level resistance only to streptomycin, high level resistance only to gentamycin and high level resistance to both aminoglycosides. The HLAR strains of E. faecalis and E. faecium were also resistant to other antibiotics: penicillin, tetracycline and ciprofloxacin. The most frequent cause of child urinary tract infection was E. faecalis, with high sensitivity to penicillins, glycopeptides and nitrofurantoin. The increased role of E. faecium and other strains of enterococci also has been shown. These species demonstrated sensitivity to glycopeptides, but resistance to other antibiotics, routinely used for treatment of UTI as well as to nitrofurantoin.

Anti-Bacterial Agents↗

The control of hyperendemic glycopeptide-resistant Enterococcus spp. on a haematology unit by changing antibiotic usage.

The rectal carriage of glycopeptide-resistant Enterococcus spp. (GRE) had been established at approximately 50% in a series of prevalence studies on a busy haematological malignancy unit. The aim of this study was to reduce the chance of patients acquiring GRE. A prospective three-phase sequential study was performed. In Phase 1, the acquisition rate of GRE detectable by rectal swab was measured without any intervention for a period of 4 months. For the following 8 months (Phase 2), the first-line treatment for febrile neutropenic episodes was changed from monotherapy with ceftazidime to piperacillin/tazobactam. In addition, an intense education programme was introduced to improve hygiene to reduce the risk of case-to-case spread. In the final 4 months (Phase 3), ceftazidime was again used as the first-line antimicrobial, while continuing the same level of training in relation to hygiene. The carriage of GRE was measured from rectal swabs done weekly. During the initial 4 months, at any time, 40-50% of patients in the unit were colonized with GRE, and 43 of 75 (57%) new patients initially negative for GRE acquired it within 6 weeks of their admission. In Phase 2, 25 patients out of 129 (19%) acquired GRE, with the acquisition rate falling progressively so that in the last 3 months, only one new patient acquired GRE (logrank comparison of probabilities for cohort 1 vs cohort 2b: P < 0.0001). A return to ceftazidime in Phase 3 was associated with a return of the risk of acquiring detectable GRE colonization, despite continued hygiene teaching and surveillance, with 21 out of 58 patients (36%) acquiring GRE (cohort 1 vs cohort 3: P = 0.08). Glycopeptide usage was not reduced during the period of the study. Clinical cases were seen only in Phases 1 and 3. Although the reduction in the risk of acquiring GRE may have been due in part to hygiene practices as well as to the change in antimicrobial usage, or may have occurred spontaneously for other reasons, the return of the problem with the reintroduction of ceftazidime strongly suggests that this antibiotic was responsible for encouraging the acquisition of detectable GRE.

Adolescent↗

Identification of Enterococcus spp. with a biochemical key.

A six-step biochemical key is presented for the identification of all recognized Enterococcus spp. The key consists of 12 tests, but no more than 6 are needed for the most complicated identification. The reliability of the key has been evaluated with collection type strains and clinical and environmental isolates. This key has fewer tests than those reported in previous studies. There is no commercial kit that includes the whole set of tests. However, some of the tests are included in enzyme activity-based kits that could be used with the proposed key. The key is designed for use in routine applications, especially in environmental and clinical studies with a high number of isolates.

Enterococcus↗

Molecular characterization of multidrug-resistant Enterococcus spp. from poultry and dairy farms: detection of virulence and vancomycin resistance gene markers by PCR.

Thirty multidrug-resistant Enterococcus spp. strains, including two from the milk of cows with mastitis, nine from chicken litter and 19 from turkey litter, were isolated. Twenty-five were identified by biochemical methods as E. gallinarum and five as E. faecalis. Most of the isolates were resistant to vancomycin, gentamicin, streptomycin, tetracycline, erythromycin, bacitracin, kanamycin and nalidixic acid but sensitive to ciprofloxacin, sulfamethoxazole, chloramphenicol, ampicillin and ofloxacin. Attempts were made by partial amplification of the gene sequences to detect the vancomycin resistance markers vanA (734-bp), vanB (420-bp), vanC1 (531-bp), and vanC2-C3 (673-bp); virulence markers cylA (427-bp) and cylB (225-bp) for enterococcal cytolysin and a biofilm-forming surface protein (Esp). Individual and multiplex-PCR assays for vancomycin resistance markers revealed the vanC1 gene in 22 E. gallinarum strains. None of the remaining isolates including five E. faecalis strains (MIC=2 microg ml(-1)) and three E. gallinarum strains (MIC=8 microg ml(-1)) had any of the van genes tested. Analysis by pulsed-field gel electrophoresis (PFGE) and a comparison of smaI banding profiles showed 11 different patterns. Probing with a DIG-labeled vanC1 PCR product indicated a common 38.0 kb SmaI DNA fragment in all the E. gallinarum strains harboring the vanC1 gene. The genes cylA and cylB were detected only in one clinical E. gallinarum isolate and two quality control clinical strains of E. faecalis (ATCC 51299 and 29212). None of the virulence factors were found in milk or poultry isolates. Intermediate level resistance to vancomycin in enterococci from the US animal farms was predominantly due to the presence of vanC1 gene.

Animals↗

Photobactericidal activity of methylene blue derivatives against vancomycin-resistant Enterococcus spp.

The toxicities and phototoxicities of methylene blue and its two methylated derivatives were measured against one standard and three vancomycin-resistant pathogenic strains of Enterococcus spp. Each of the compounds was bactericidal and the derivatives exhibited photobactericidal activity on illumination at a 'light' dose of 6.3 J/cm(2) against one or more of the strains. Increased bactericidal and photobactericidal activity in the methylated derivatives is thought to be due to their higher hydrophobicities allowing greater interaction with the bacterial cell wall. In addition, the derivatives exhibited higher inherent photosensitizing efficacies.

Enterococcus faecalis↗

Assessment of the marker value of various components of the coli-aerogenes group of Enterobacteriaceae and of a selection of Enterococcus spp. for the official monitoring of drinking water supplies.

The traditional indicators Escherichia coli (in practice currently, though ecologically inaccurately, represented by 'thermotolerant coliforms' at 44 degrees C) and Enterococcus spp. proved to be suitable for the diagnosis of heavy and frequent faecal pollution observed in potentially dangerous waters, especially those originating from karstic aquifers. On the other hand, natural and treated waters, slightly and inconsistently contaminated, occasionally showed a variable Gram-negative flora, difficult to classify by routine tests. In that case, complete identification of isolates may be necessary to ensure a valid decision on the potability of the supply. At any rate some of the Enterobacteriaceae contained in the 'faecal coliform' group and many other 'coliforms', distinct from E. coli, lack sanitary significance although their presence at certain levels may indicate inadequate disinfection, hiatuses in the integrity of the distribution system or both.

Biomarkers↗

Use of rapid, nonradioactive DNA probes in culture confirmation tests to detect Streptococcus agalactiae, Haemophilus influenzae, and Enterococcus spp. from pediatric patients with significant infections.

Acridinium ester-labeled, chemiluminescent DNA probe tests (Accuprobe; Gen-Probe, Inc.) for culture confirmation of Streptococcus agalactiae, Haemophilus influenzae, and Enterococcus spp. were compared with conventional identification techniques. The probe is a DNA oligomer that is a complementary to the RNA of the target. The DNA-RNA hybrids are measured in a luminometer. The 40-min assay requires one reaction tube and the addition of three reagents. When two colonies were used to add a sample of the reaction tube, 325 of 327 isolates were detected by the probe. Isolates of 404 nonprobe target organisms did not hybridize with the probe.

Child, Preschool↗

Galangin expresses bactericidal activity against multiple-resistant bacteria: MRSA, Enterococcus spp. and Pseudomonas aeruginosa.

The antimicrobial activity of three propolis ethanol extracts (EEP) was examined for various Gram-negative and Gram-positive bacterial species, including multiple-resistant Staphylococcus aureus, Enterococcus spp. and Pseudomonas aeruginosa strains. EEP had a good bactericidal activity against Gram-positive species, and all multiple-resistant bacterial strains tested were sensitive to EEP. Minimal inhibitory concentrations (MICs) were lower in samples of higher flavonoid content (from 0.65 to 7.81 mg mL(-1)), indicating the influence of the concentration of some potent bactericidal compound(s) in propolis or synergism among some bactericidal compounds. Antimicrobial-guided separation of flavonoid aglycones (bioassay in situ on thin-layer chromatogram) showed that galangin (3,5,7-trihydroxyflavone) is one compound in EEP with bactericidal activity. Galangin was isolated by preparative chromatography. After determining the quantity present, the MIC against multiple-resistant bacteria was determined. The MIC of galangin against multiple-resistant bacterial strains was significantly lower (from 0.16 to 0.44 mg mL(-1), p < 0.05) than that of EEP. The bactericidal activity of galangin against P. aeruginosa strains was present at 0.17+/-0.05 mg mL(-1).

Anti-Bacterial Agents↗

Suppression of gastric acid production by proton pump inhibitor treatment facilitates colonization of the large intestine by vancomycin-resistant Enterococcus spp. and Klebsiella pneumoniae in clindamycin-treated mice.

Proton pump inhibitor treatment of clindamycin-treated mice elevated the gastric pH and facilitated the establishment of colonization of the large intestine by vancomycin-resistant Enterococcus spp. (75 to 80%, versus 20 to 25% for saline-treated controls) and Klebsiella pneumoniae (90%, versus 30% for saline-treated controls). These findings demonstrate a mechanism by which proton pump inhibitor therapy could contribute to the dissemination of nosocomial pathogens.

Animals↗

Comparative study of bacteremias caused by Enterococcus spp. with and without high-level resistance to gentamicin. The Grupo Andaluz para el estudio de las Enfermedades Infecciosas.

A prospective, multicenter study was carried out over a period of 10 months. All patients with clinically significant bacteremia caused by Enterococcus spp. were included. The epidemiological, microbiological, clinical, and prognostic features and the relationship of these features to the presence of high-level resistance to gentamicin (HLRG) were studied. Ninety-three patients with enterococcal bacteremia were included, and 31 of these cases were caused by HLRG (33%). The multivariate analysis selected chronic renal failure, intensive care unit stay, previous use of antimicrobial agents, and Enterococcus faecalis species as the independent risk factors that influenced the development of HLRG. The strains with HLRG showed lower levels of susceptibility to penicillin and ciprofloxacin. Clinical features (except for chronic renal failure) were similar in both groups of patients. HLRG did not influence the prognosis for patients with enterococcal bacteremia in terms of either the crude mortality rate (29% for patients with bacteremia caused by enterococci with HLRG and 28% for patients not infected with strains with HLRG) or the hospital stay after the acquisition of enterococcal bacteremia. Hemodynamic compromise, inappropriate antimicrobial therapy, and mechanical ventilation were revealed in the multivariate analysis to be the independent risk factors for mortality. Prolonged hospitalization was associated with the nosocomial acquisition of bacteremia and polymicrobial infections.

Adult↗

Effect of a selective decontamination of the digestive tract regimen including parenteral cefepime on establishment of intestinal colonization with vancomycin-resistant Enterococcus spp. and Klebsiella pneumoniae in mice.

In mice, a selective decontamination of the digestive tract regimen consisting of orogastric tobramycin, polymyxin E, and amphotericin B in combination with subcutaneous cefepime inhibited gram-negative bacilli, including Klebsiella pneumoniae, and did not promote vancomycin-resistant Enterococcus spp. (VRE) colonization. However, concurrent administration of subcutaneous ampicillin-sulbactam resulted in promotion of VRE.

Animals↗

Identification of Enterococcus spp. based on specific hybridisation with 16S rDNA probes.

The conventional methods for routine enterococci species identification are usually based on phenotypic characteristics. However, in recent years, some studies have defined specific probes based on both 16S and 23S rRNA genes for the identification of some Enterococcus spp. A set of probes based on the 16S rRNA gene has been developed in order to evaluate the usefulness of a six-step biochemical key for species level identification of enterococci. Probe specificity has been evaluated with type collection and environmental strains by dot blot hybridisation. A high correlation was obtained between biochemical key and hybridisation identifications. This set of probes provides a confirmative method for phenotypic species identification.

Animals↗

Evaluation of Chromocult enterococci agar for the isolation and selective enumeration of Enterococcus spp. in broilers.

AIMS: To investigate the productivity and specificity of a new chromogenic enterococci selective medium (Chromocult enterococci agar) recently developed by Merck. METHODS AND RESULTS: The study was carried out comparing Chromocult enterococci agar with MRS agar (Merck), a basal lactic acid bacteria medium in current use. A total of 216 faecal samples from poultry were collected and enterococci populations were counted. Likewise, 100 randomly selected strains were identified for each medium. The differences found between the two media were analysed and discussed. CONCLUSIONS: A good sensitivity of 98% was obtained for Chromocult agar and all false-positive isolates obtained were identified as Leuconostoc spp. However significant differences (P<0.01) were obtained between the enterococci species isolation rates identified from these two media, suggesting the poor growth of some species in Chromocult enterococci agar. Viable counts of Enterococcus spp. obtained with MRS agar were significantly higher than those obtained with Chromocult enterococci agar. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of chromogenic media for microbiological analysis is increasing. Independent studies are important to evaluate newly developed chromogenic media.

Agar↗

Cloning and preliminary characterization of a GATC-specific beta2-class DNA:m6A methyltransferase encoded by transposon Tn1549 from Enterococcus spp.

A recent study revealed a subfamily of N6-adenine (m6A) methyltransferases that comprises a few functionally studied eukaryotic members acting on mRNA and prokaryotic members acting on DNA as well as numerous uncharacterized open reading frames. Here, we report cloning and functional characterization of a prokaryotic member of this family encoded by transposon Tn1549 from Enterococcus spp.

Amino Acid Sequence↗