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PubMed2004

Prevalence, phenotype and genotype of oral enterococci.

This study investigated the prevalence, phenotype and genotype of oral enterococci. Enterococci were detected in oral rinse samples from 11% of 100 patients receiving endodontic treatment and 1% of 100 dental students with no history of endodontic treatment (P=0.0027). All enterococcal isolates were identified as Enterococcus faecalis. Viable counts ranged from 1 x 10 to 6 x 103 colony forming units per mL of oral rinse sample. Potential virulence traits expressed by oral E. faecalis strains included production of hemolysin (n=4) and gelatinase (n=4), and response to pheromones in E. faecalis culture filtrate (n=1). Six strains produced bacteriocin. All strains were susceptible to ampicillin, benzylpenicillin, gentamicin and vancomycin. There was no evidence of metal-ion resistance. One isolate produced hemolysin, gelatinase and bacteriocin, was resistant to several antibiotics, and responded to the pheromone cPD1. Pulsed-field gel electrophoresis and plasmid analysis showed that oral E. faecalis exhibited widespread genetic polymorphism, with plasmids detected in seven strains.

Adult↗
PubMed1991

Platelet aggregation by strains of enterococci.

The platelet aggregation capability of whole cells of Enterococcus faecalis, E. faecium and E. avium was tested. The optimum ratios of bacteria to platelets in E. faecalis (strain SMU-37), E. faecium (strain SMU-138) and E. avium (strain SMU-197) were 1.0, 1.2 and 2.0, respectively. During the platelet aggregation induced by the three strains of enterococci, 65-69% of total serotonin was released. The aggregation was totally inhibited by ethylenediaminetetraacetate (10 mM) and apyrase (1 mg/ml), while no effect was shown by aspirin (10 mM), indomethacin (10 mM) and quinacrine (1 mM). By pretreatment of platelet-poor plasma with heat (56 C, 30 min) or zymosan, the reactivities with platelets of each strain of species were markedly diminished. These results suggest that enterococci-induced platelet aggregation was an ion-dependent, cyclooxygenase-insensitive event, and plasma component(s) was (were) required for the reaction.

Animals↗
PubMed1987

The effect of ampicillin and tylosin on the faecal enterococci of healthy young chickens.

Enterococcal isolates from young chickens were differentiated into one of three species, namely Enterococcus faecalis, Ent. faecium and Ent. gallinarum. The proportion of each species among the enterococcal population changed with time in birds not dosed with antibiotics. This pattern of change was modified in birds dosed with either tylosin or ampicillin even though ampicillin did not select for ampicillin resistance among the enterococcal population. A gradual increase in tylosin resistance was recorded with time among the enterococci of the 'undosed' control birds. This was associated with an increase in the proportion of Ent. faecium, a species commonly resistant to tylosin, among the enterococci of the birds as they grew older.

Ampicillin↗
PubMed1991

Enumeration by a miniaturized method of Escherichia coli, Streptococcus bovis and enterococci as indicators of the origin of faecal pollution of waters.

Counts of Escherichia coli, faecal streptococci and enterococci were made on faecal specimens from human and animal origin and urban raw sewage waters, with microtiter plates containing selective substances. Escherichia coli was more numerous than faecal streptococci and enterococci in 80% of the samples regardless of the origin. Consequently the use of the ratio E. coli/faecal streptococci to distinguish human from animal origin of faecal pollution is questionable. Enterococcus faecalis was predominant in human and poultry faeces, Streptococcus bovis was typical of the bovine faeces and to a lesser extent also of pig faeces whereas Enterococcus durans, Ent. hirae and Ent. faecium did not characterize any faecal source. Streptococcus bovis could be distinguished in the microtiter plate by its inability to reduce triphenyl tetrazolium chloride (TTC) in the medium.

Animals↗
PubMed2005

Molecular characterization, technological properties and safety aspects of enterococci from 'Hussuwa', an African fermented sorghum product.

AIMS: To identify enterococci from Hussuwa, a Sudanese fermented sorghum product, and determine their technological properties and safety for possible inclusion in a starter culture preparation. METHODS AND RESULTS: Twenty-two Enterococcus isolates from Hussuwa were identified as Enterococcus faecium by using phenotypic and genotypic tests such as 16S rDNA gene sequencing, RAPD-PCR and restriction fragment length polymorphism of the 16S/23S intergenic spacer region fingerprinting. Genotyping revealed that strains were not clonally related and exhibited a considerable degree of genomic diversity. Some strains possessed useful technological properties such as production of bacteriocins and H2O2 or utilization of raffinose and stachyose. None produced alpha-amylase or tannase. A safety investigation revealed that all strains were susceptible to the antibiotics ampicillin, gentamicin, chloramphenicol, tetracycline and streptomycin, but some were resistant to ciprofloxacin, erythromycin, penicillin and vancomycin. Production of biogenic amines or presence of genes encoding virulence determinants occurred in some strains. CONCLUSIONS: Enterococcus faecium strains are associated with fermentation of Sudanese Hussuwa. Some strains exhibited useful technological properties such as production of antimicrobial agents and fermentation of indigestible sugars, which may aid in stabilizing and improving the digestibility of the product respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Enterococci were shown to play a role in the fermentation of African foods. While beneficial properties of these bacteria are indicated, their presence in this food may also imply a hygienic risk as a result of antimicrobial resistances or presence of virulence determinants.

Biogenic Amines↗
PubMed2006

Comparison of 16S rRNA sequencing with conventional and commercial phenotypic techniques for identification of enterococci from the marine environment.

AIMS: To compare accuracy of genus and species level identification of presumptive enterococci isolates from the marine environment using conventional biochemical testing, four commercial identification systems and 16S rRNA sequence analysis. METHODS AND RESULTS: Ninety-seven environmental bacterial isolates identified as presumptive enterococci on mEI media were tested using conventional and Enterococcus genus screen biochemical tests, four commercial testing systems and 16S rRNA sequencing. Conventional and Enterococcus genus screen biochemical testing, 16S rRNA sequencing and two commercial test systems achieved an accuracy of > or = 94% for Enterococcus genus confirmation. Conventional biochemical testing and 16S rRNA sequencing achieved an accuracy of > or = 90% for species level identification. CONCLUSIONS: For confirmation of Enterococcus genus from mEI media, conventional or genus screen biochemical testing, 16S rRNA sequencing and the four commercial systems were correct 79-100% of the time. For speciation to an accuracy of 90% or better, either conventional biochemical testing or 16S rRNA sequencing is required. SIGNIFICANCE AND IMPACT OF THE STUDY: Accurate identification of presumptive environmental Enterococcus isolates to genus and species level is an integral part of laboratory quality assurance and further characterization of Enterococcus species from pollution incidents. This investigation determines the ability of six different methods to correctly identify environmental isolates.

Bacteriological Techniques↗
PubMed2004

Antimicrobial resistance in Campylobacter spp., Escherichia coli and enterococci associated with pigs in Australia.

The major influences on the amplification and spread of antibiotic-resistant bacteria are the therapeutic use of antibiotics in human medicine and their use in livestock for therapy, prophylaxis and growth promotion. The use of veterinary antibiotics has many benefits to the livestock industries ensuring animal health and welfare, but use at subtherapeutic levels also exerts great selective pressure on emergence of resistant bacteria. The possible effect on human health is a problem of current debate. This study involved sampling pig carcasses, pig meat and assessing the level of resistance in zoonotic enteric bacteria of concern to human health. In South Australian pigs, thermophilic Campylobacter species showed widespread resistance (60-100%) to tylosin, erythromycin, lincomycin, ampicillin and tetracycline. No resistance was seen to ciprofloxacin. The enterococci demonstrated little resistance (0-30%) to vancomycin or virginiamycin, but the overall results from the antibiotic sensitivity testing of the enterococci have demonstrated how widespread their resistance has become. Escherichia coli strains showed widespread resistance to tetracycline and moderately common resistance (30-60%) to ampicillin and sulphadiazine. Resistance to more than one antibiotic was common. Pigs from New South Wales were also sampled and differences in resistance patterns were noted, perhaps reflecting different antibiotic use regimens in that state.

Abattoirs↗
PubMed2006

Vancomycin- and erythromycin-resistant enterococci in a pig farm and its environment.

A high prevalence of vancomycin- and erythromycin-resistant enterococci (VRE and ERE respectively) in a pig farm and its environment was observed. A similar structure and composition of enterococcal populations was detected between urban sewage and those associated with the pig environment. Enterococcus faecium was the most predominant species among VRE isolates from both animal and human origin. The high population similarity index (Sp) obtained comparing VRE and ERE isolates from urban sewage and pig slurry suggests that there are certain strains circulating through the food chain from farms to humans. Erythromycin resistance was present in a wider variety of clones and species of enterococci in both pigs and humans than vancomycin resistance.

Animal Feed↗
PubMed2004

Influence of rifaximin treatment on the susceptibility of intestinal Gram-negative flora and enterococci.

The development of rifaximin- and rifampicin-resistant intestinal coliforms was studied in 27 subjects receiving rifaximin for 3 days by plating stool samples on media containing rifaximin 200 mg/L or rifampicin 64 mg/L before treatment (day 0), after treatment was completed (day 3), and after a further 2 days (day 5). The susceptibility of enterococci grown on day 0 and day 3 was also studied in 71 subjects. Significant increases in antimicrobial-resistant coliform flora were not seen in either the rifaximin-treated or the placebo-treated subjects. Enterococci recovered pre- and post-treatment showed similar susceptibilities. Rifaximin did not select for significant resistance in the Gram-negative and Gram-positive intestinal flora during therapy.

Adult↗
PubMed1995

Inhibition of ruminal staphylococci and enterococci by nisin in vitro.

A collection of 59 ureolytic and lactic acid-producing ruminal staphylococci and enterococci, isolates from domestic and wild ruminants, were tested for sensitivity or resistance to lantibiotic nisin. All strains tested were sensitive with zones of inhibition, around wells containing 250 micrograms nisin, from 6 to 26 mm. 74.6% of isolates had zones of inhibition more than 10 mm and 11.1% more than 20 mm. Nisin was more effective against enterococci than staphylococci. Sensitivity of ruminal isolates to nisin may be used to control bacterial growth during the colonization of the rumen or to study the role of antibacterial activity in microbial interactions. Results obtained can be also used in experiments on gnotobiotic animals.

Animals↗
PubMed2005

Effect of media, temperature and culture conditions on the species population and antibiotic resistance of enterococci from broiler chickens.

AIMS: The effect of media type, incubation temperature and enrichment period on the species population and antibiotic susceptibility of enterococci from poultry carcass rinsates was determined. METHODS AND RESULTS: Aliquots of rinsates, incubated in BBL Enterococcosel broth at 37 degrees C, 42 degrees C, or 45 degrees C for 24 and 48 h, were inoculated onto BBL Enterococcosel and M-enterococcus agar. Presumptive positive colonies were identified to species and tested for antibiotic resistance. Significant differences (P < or = 0.05) were observed for media and temperature. More Enterococcus faecalis were isolated from M-enterococcus media and at 37 degrees C while more E. faecium were isolated from Enterococcosel agar and at 45 degrees C. The number of antibiotic-resistant E. faecalis and E. faecium were also affected by media and temperature. CONCLUSIONS: Culture conditions for enterococci affect the observed species and antibiotic resistance patterns and therefore should be carefully considered. SIGNIFICANCE AND IMPACT OF THE STUDY: This study indicates that media and temperature can influence the recovery and selection of enterococcal species and antibiotic susceptibility.

Animals↗
PubMed1994

Ribosomal RNA gene (rrn) organization in enterococci.

A cloned 1.8-kb probe containing the 3' end of 16S ribosomal RNA and the 5' end of 23S ribosomal RNA from Enterococcus hirae was used to analyze various endonuclease digests of enterococci. In the ATCC strains tested we observed a remarkable conservation of the ApaI sites in the rrn operons, and a partial conservation of EcoRI sites. Using a number of other endonuclease digestions with the ApaI rrn probe, we estimate the number of rrn operons in enterococci to be between five and six.

DNA, Bacterial↗
PubMed2006

Evaluation of clonality in enterococci isolated in Brazil carrying Tn1546-like elements associated with vanA plasmids.

Fifty-one vancomycin-resistant enterococci samples isolated from different geographic regions in Brazil were studied. All the isolates harboured the vanA gene as demonstrated by PCR analysis, and in a majority of strains the gene was associated with a transferable plasmid of 70 kb. A single variant of the prototype Tn1546 associated with common transferable vanA-containing plasmids has spread among the enterococcal strains circulating in Brazil. The VanA element integrity in these enterococci strains and the different pulsed-field gel electrophoresis patterns suggest horizontal transmission of the vancomycin resistance transposon in Brazilian strains.

Bacterial Proteins↗
PubMed1989

In vitro activity of vancomycin against enterococci.

The in vitro activity of vancomycin against 40 clinical isolates of enterococci was determined by a macro-tube dilution method and by quantitative killing curve procedures employing the standard medium of our department, i.e. a filtered ox broth. An attempt to remove the influence of technical factors on the MBC determination was made by using an inoculum in the early logarithmic growth phase and ensuring the exposure of all the organisms to the antibiotic. Vancomycin showed a good inhibitory activity for the enterococci tested (MIC90 of 1.6 micrograms/ml, 3.1 micrograms/ml and 1.6 micrograms/ml for S. faecalis, S. faecium and S. durans, respectively), but no bactericidal effect could be demonstrated as measured by the MBCs (greater than 100 micrograms/ml) and killing curve procedures.

Culture Media↗
PubMed2006

Effect of carbapenem administration on establishment of intestinal colonization by vancomycin-resistant enterococci and Klebsiella pneumoniae in mice.

In a mouse model, ertapenem inhibited the anaerobic intestinal microflora and promoted overgrowth of enterococci, whereas imipenem-cilastatin had no effect on the indigenous microflora. Ertapenem, but not imipenem-cilastatin, promoted modest overgrowth of vancomycin-resistant enterococci when exposure occurred during treatment. Neither agent promoted colonization with extended-spectrum beta-lactamase-producing Klebsiella pneumoniae.

Animals↗
PubMed1979

Effect of protein binding on the activity of penicillins in combination with gentamicin against enterococci.

To assess the effect of protein binding by human serum on the synergistic interaction of penicillins with gentamicin, time-kill curves were determined for four penicillins alone and in combination with gentamicin against 10 blood isolates of enterococci. Killing curves demonstrated synergism with penicillin G plus gentamicin against all 10 strains in either broth or 50% human serum. In broth the combinations of nafcillin plus gentamicin and oxacillin plus gentamicin were synergistic against 10 of 10 strains and 4 of 10 strains, respectively. However, in serum, nafcillin plus gentamicin was synergistically bactericidal against only two strains and oxacillin plus gentamicin against none. Methicillin plus gentamicin was synergistic against none of the enterococci in either medium. Thus, the semisynthetic, penicillinase-resistant penicillins are unlikely to be effective in the therapy of patients with enterococcal endocarditis.

Blood Bactericidal Activity↗
PubMed1980

Defective killing of enterococci: a common property of antimicrobial agents acting on the cell wall.

We tested the ability of antimicrobial agents that act on the cell wall to kill enterococci and found defective killing (a minimal bactericidal concentration/minimal inhibitory concentration ratio of greater than or equal to 32) with both beta-lactams (penicillin G and cephalothin) and non-beta-lactams (vancomycin, cycloserine, and bacitracin). Our results indicate that the resistance of enterococci to antimicrobial killing spans the spectrum of agents known to inhibit cell wall synthesis and suggest that the mechanism responsible for enterococcal resistance to killing by these drugs may be a defective autolytic enzyme system.

Anti-Bacterial Agents↗