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PubMedDate not supplied

Penicillin resistance and aminoglycoside-penicillin synergy in enterococci.

Susceptibility to penicillin, vancomycin, imipenem, streptomycin, kanamycin and gentamicin was tested in 130 clinical isolates of Enterococcus spp. by an agar dilution method. Penicillin resistance (MIC > 8 mg/l) was only observed among strains of Enterococcus faecium and Enterococcus raffinosus. Thirty-nine percent of the penicillin-resistant enterococci showed low-level resistance to at least one of the three aminoglycosides tested (gentamicin, kanamycin and streptomycin). Six Enterococcus strains (5 E. faecium and 1 E. raffinosus) with low-level resistance to gentamicin and different MICs for penicillin were tested for antibiotic synergy using time-killing curves. When penicillin concentrations equal to or higher than the MICs were used, synergism was established, even when highly penicillin-resistant strains (MIC > 200 mg/l) were tested. No synergy was observed when penicillin concentrations were below the MICs.

Aminoglycosides↗
PubMed1981

Antibiotic-induced lysis of enterococci.

Enterococci are resistant to penicillin killing in vivo and in vitro. Because some bacteria resistant to penicillin killing have reduced autolytic activity, we examined the lysis of clinical enterococcal isolates suspended in buffer (spontaneous lysis), and compared it with their susceptibility to antibiotic-induced lysis and killing. We found significant correlations between spontaneous and antibiotic-induced lysis, using five antibiotics that inhibit cell wall synthesis (penicillin, cephalothin, bacitracin, cycloserine, and vancomycin). Among isolates, strains more rapidly lysed by one antibiotic were more rapidly lysed by the other antibiotics, and more susceptible to spontaneous lysis. In studies involving a single strain grown in different media, spontaneous lysis also correlated closely with antibiotic-induced lysis. These results are consistent with a common mechanism for spontaneous and antibiotic-induced lysis, such as the autolytic enzyme system. Human serum was one of the least permissive media tested for enterococcal growth and antibiotic-induced lysis and killing. We suggest that the inhibitory effect of human serum on growth and the activation of the enterococcal autolytic enzyme system may be a critical factor in the resistance of enterococcal endocarditis to treatment with penicillin alone.

Anti-Bacterial Agents↗
PubMed2005

Evaluation of in vitro interaction of daptomycin with gentamicin or beta-lactam antibiotics against Staphylococcus aureus and Enterococci by FIC index and timed-kill curves.

The interactions of daptomycin with gentamicin and 5 beta-lactam agents were determined by checkerboard and timed-kill studies. Eighty isolates were tested by checkerboard: 20 each of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible Staphylococcus aureus (MSSA), vancomycin-susceptible Enterococcus faecalis (VSEF) and vancomycin-resistant enterococci (VRE). Time kill curves were performed on 8 selected isolates: 2 each of MRSA, MSSA, VSEF and VRE. Checkerboard results showed highest frequency of synergistic effects against VSEF (35-75%) with daptomycin combined with ceftriaxone, cefepime or imipenem; a modest effect with most combinations against VRE and MRSA (5-20%); and indifference with daptomycin and most agents against MSSA (0-5%); except with daptomycin with oxacillin where 10-20% synergy was observed. Synergistic interaction was confirmed by time kill studies in seven of ten isolates where checkerboard suggested synergy. A bactericidal effect was exerted in 5/7 synergistic combinations. The in vitro data suggest that daptomycin combined with other antibiotics may be microbiologically beneficial and not antagonistic.

Anti-Bacterial Agents↗
PubMed2006

Antibiotic resistance and mechanisms implicated in clinical enterococci in a Tunisian hospital.

Susceptibility testing for 15 antibiotics was performed in a series of 191 clinical enterococci recovered in a Tunisian Hospital during 2000-2003. Species detected were the following ones (number of isolates): E. faecalis (139), E. faecium (41), E. casseliflavus (5), E. gallinarum (3), E. avium (2) and E. hirae (1). The percentages of antibiotic resistance detected were as follows (E. faecalis/ E. faecium/ other species) : penicillin (0/ 73/ 9%), tetracycline (78/ 44/ 54%), chloramphenicol (52/ 29/ 27%), erythromycin (66/ 100/ 82%), spiramycin (84/ 83/ 64%), pristinamycin (100/ 0/ 73%), trimethoprim-sulfamethoxazole (88/ 78/ 91%), rifampicin (72/ 41/ 0%), vancomycin (0/ 0/ 36%), teicoplanin (0/ 0/ 0%), high-level-resistance for gentamicin (24/ 29/ 45%), streptomycin (34/ 56/ 55%) and kanamycin (41/ 68/ 55%). Increased vancomycin minimum inhibitory concentrations (MICs) were only detected in E. casseliflavus and E. gallinarum isolates (MIC range 8-24 microg/ml). The erm(B), catA, tet(M), aac(6')-aph(2''), aph(3')-IIIa, and ant(6)-Ia genes were detected in 91%, 32%, 86%, 98%, 100%, and 72% of the E. faecium and E. faecalis isolates resistant to erythromycin, chloramphenicol, tetracycline and high-level-resistant to gentamicin, kanamycin and streptomycin, respectively. A total of 20 unrelated pulsed-field-gel-electrophoresis patterns were found in the series of 46 high-level gentamicin-resistant E. faecalis and E. faecium isolates of this study.

Anti-Bacterial Agents↗
PubMed2006

A randomized controlled trial assessing infectious disease risks from bathing in fresh recreational waters in relation to the concentration of Escherichia coli, intestinal enterococci, Clostridium perfringens, and somatic coliphages.

We performed epidemiologic studies at public freshwater bathing sites in Germany to provide a better scientific basis for the definition of recreational water quality standards. A total of 2,196 participants were recruited from the local population and randomized into bathers and nonbathers. Bathers were exposed for 10 min and had to immerse their head at least three times. Water samples for microbiological analysis were collected at 20-min intervals. Unbiased concentration-response effects with no-observed-adverse-effect levels (NOAELs) were demonstrated for three different definitions of gastroenteritis and four fecal indicator organisms. Relative risks for bathing in waters with levels above NOAELs compared with nonbathing ranged from 1.8 (95% CI, 1.2-2.6) to 4.6 (95% CI, 2.1-10.1), depending on the definition of gastroenteritis. The effect of swallowing water provided additional evidence for true dose-response relationships. Based on the NOAELs, the following guide values for water quality are suggested: 100 Escherichia coli, 25 intestinal enterococci, 10 somatic coliphages, or 10 Clostridium perfringens per 100 mL. Recreational water quality standards are intended to protect the health of those consumers who are not already immune or resistant to pathogens that may be associated with indicator organisms. In contrast to current World Health Organization recommendations, we concluded that standards should be based on rates of compliance with NOAELs rather than on attributable risks determined above NOAELs, because these risks depend mainly on the unpredictable susceptibility of the cohorts. Although in theory there is no threshold in real concentration-response relationships, we demonstrated that a NOAEL approach would be a more robust and practical solution to the complex problem of setting standards.

Clostridium perfringens↗
PubMedDate not supplied

[Problems with gram-positive bacteria: resistance in staphylococci, enterococci, and pneumococci to antimicrobial drugs].

The resistance in staphylococci, enterococci, and pneumococci is reviewed. The author also recalls the first cases, and presents an overview of the distribution of cases in the world, the genetic and molecular mechanisms of resistance, the importance in Brazil and therapeutic alternatives. The factors that contribute to the dissemination of these problem bacteria and the measures for their control are emphasized.

Drug Resistance, Microbial↗
PubMedDate not supplied

Vancomycin-resistant enterococci in intensive care hospital settings.

Vancomycin-resistant enterococci (VRE) have recently emerged as a nosocomial pathogen and present an increasing threat to the treatment of severely ill patients in intensive-care hospital settings. We outline results of a study of the epidemiology of VRE transmission in ICUs and define a reproductive number R0; the number of secondary colonization cases induced by a single VRE-colonized patient in a VRE-free ICU, for VRE transmission. For VRE to become endemic requires R0 > 1. We estimate that in the absence of infection control measures R0 lies in the range 3-4 in defined ICU settings. Once infection control measures are included R0 = 0.6, suggesting that admission of VRE-colonized patients can stabilize endemic VRE.

Anti-Bacterial Agents↗
PubMed2004

Molecular epidemiology and antimicrobial susceptibility of Enterococci recovered from Brazilian intensive care units.

We studied the antimicrobial resistance and the molecular epidemiology of 99 enterococcal surveillance isolates from two hospitals of Brasilia, Brazil. Conventional biochemical tests were used to identify the enterococcal species and the disk diffusion method was used to determine their resistance profiles. Enterococcus faecalis (76%) and E. faecium (9%) were the most prevalent species. No enterococci showed the vanA or vanB vancomycin resistance phenotypes or genotypes. Only the intrinsically resistant species E. gallinarum (n=2) and E. casseliflavus (n=3) harbored the vancomycin-resistance genes vanC1 and vanC2/3, respectively. We found E. faecalis isolates with high-level resistance to gentamicin (22%) and streptomycin (8%) and both E. faecalis and E. faecium isolates with resistance to more than two antimicrobials (84% and 67%, respectively). Nine E. faecalis isolates (12%) were resistant to ampicillin; the minimal inhibitory concentration (MIC) values were 16 microg/mL (n=6) and 32 microg/mL (n=3). Among these ampicillin-resistant E. faecalis, seven were also resistant to gentamicin, ciprofloxacin, rifampin, penicillin, chloramphenicol, tetracycline and erythromycin. Pulsed-field gel electrophoresis classified those isolates in three different genotypes, suggesting dissemination of genetically related ampicillin-resistant E. faecalis strains among different patients.

Anti-Bacterial Agents↗
PubMed2005

Prevalence and factors associated with rectal vancomycin-resistant enterococci colonization in two intensive care units in São Paulo, Brazil.

Vancomycin-resistant enterococci (VRE) are important pathogens causing nosocomial infections, and there is reason for concern about their resistance and great ability to spread in hospital environments, especially intensive-care units (ICU). To determine the prevalence of rectal colonization by VRE, and the risk factors associated with their presence, rectal surveillance swabs were taken from patients under treatment in two intensive-care units (one medical and another both medical and surgical) at São Paulo Hospital, over a two-year period. Thirty-three percent of the 147 patients evaluated had VRE. The only significant variable in the logistic regression was the length of stay in the ICU.

Adolescent↗
PubMed2006

Impact of a piperacillin-tazobactam shortage on antimicrobial prescribing and the rate of vancomycin-resistant enterococci and Clostridium difficile infections.

UNLABELLED: States in 2002 on antimicrobial prescribing and associated rates of vancomycin-resistant enterococci (VRE) and Clostridium difficile infections.Design. Retrospective chart review.Setting. University-affiliated medical center. Measurements and Main Results. Microbiologic reports, patient demographics, and antimicrobial utilization were evaluated for patients admitted 6 months before the shortage (March 1-August 31, 2001) and for 6 months during the shortage (March 1-August 31, 2002). Significant increases in usage of alternative mu-lactamase inhibitor combinations, cefepime, levofloxacin, vancomycin, clindamycin, and metronidazole were observed during the shortage; in contrast, a significant decrease in the use of ceftriaxone took place. No change in the rate of VRE infection was observed from before to during the piperacillin-tazobactam shortage. However, a paradoxical 47% decrease in the rate of C. difficile colitis was documented during the shortage. Subsequent multivariate analyses suggested the reduced use of ceftriaxone and increased use of levofloxacin, but not the reduced use of piperacillin-tazobactam, correlated with the decreased rate of C. difficile infections. CONCLUSION: The piperacillin-tazobactam shortage was associated with significant changes in antimicrobial prescribing, which resulted in a significant reduction in the rate of C. difficile but not VRE infections.

Anti-Bacterial Agents↗
PubMed1998

Long PCRs of transposons in the structural analysis of genes encoding acquired glycopeptide resistance in enterococci.

Glycopeptide-resistant enterococci (GRE) associated with multiple antibiotic resistance present a major challenge to clinical practice and infection control due to limited or nonexistent antimicrobial treatment options. The genes encoding VanA- and VanB-type glycopeptide resistance have been shown to reside on transposons Tn1546 and Tn1547, respectively. These transferable genetic elements may carry the resistance determinants between and within different ecological niches. Molecular epidemiological studies of nosocomial outbreaks of VanA- and VanB-type GRE indicate horizontal transfer of glycopeptide resistance genes as an important mechanism for the spread of GRE. To target infection control and better understand the epidemiology of GRE, outbreak investigations and molecular epidemiological studies should therefore apply at least two different approaches, i.e., molecular-typing methods to analyze bacterial genomic heterogeneity and structural analysis of mobile resistance determinants. Here we describe the development and use of long PCRs in the structural analysis of vanA and vanB gene clusters in GRE.

DNA Transposable Elements↗
PubMed2002

Isolation and characterization of Streptomyces sp KH-614 producing anti-VRE (vancomycin-resistant enterococci) antibiotics.

The actinomycete strain KH-614 was antagonistic to vancomycin-resistant enterococci (VRE). Based on the diaminopimelic acid (DAP) type, morphological and physiological characteristics examined by scanning electron microscopy (SEM), KH-614 was confirmed as belonging to the genus Streptomyces. Based on the 16S rDNA nucleotide sequences, Streptomyces sp. KH-614 was found to have a relationship with Streptomyces lydicus. The production of antibiotic from this strain was most favorable when cultured in glucose, polypeptone, yeast extract (PY) medium for 6 days at 27 degrees C. The antibiotic was identified as a cyclo(L-leucyl-L-prolyl) by comparing it with the reported spectral data including MS and NMR. Cyclo(leu-pro) was found to be active against twelve VRE strains, including E. faecium (vanA, vanB), and E. faecalis (vanA, vanB), that had been isolated over a period three years (1998-2000). Cyclo(leu-pro) was especially effective against VRE strains such as E. faecalis (K-99-34), E. faecalis (K-00-184), E. faecalis (K-00-221), and the MIC values were 12.5 microg/ml. Moreover, cyclo(leu-pro) was effective against three leukemic cell lines at concentrations below 100 microg/ml. At 100 mg/ml cyclo(leu-pro), K562, HL60, and U937 leukemic cell lines showed growth inhibition of 95, 91, and 93%, respectively. In a normal cell line, MDBK, cyclo(leu-pro) exerted 24% growth inhibition at a concentration of 100 microg/ml, and showed no inhibitory activity at concentrations below 10 microg/ml. These results indicate that cyclo(leu-pro) is a potential anti-leukemic and anti-VRE agent.

Animals↗
PubMed1989

Antibiotic resistance in enterococci at a teaching hospital.

Antibiotic resistance in enterococci is becoming increasingly common throughout the world. Of particular therapeutic concern are strains which produce beta-lactamase, display high-level aminoglycoside resistance or show plasmid-mediated resistance to vancomycin. A prospective survey of 112 enterococcal isolates has been carried out to determine the extent of these resistance mechanisms in a Sydney teaching hospital. No beta-lactamase production was found. Eleven (9.8%) strains displayed high-level streptomycin resistance (MIC greater than 2048 mg/l), and 2 (1.8%) strains high-level gentamicin resistance (MIC greater than 2048 mg/l). No vancomycin resistance was observed. Enterococcal resistance is not as common at this hospital as in many centres in other countries. High-level aminoglycoside resistance may be missed on routine sensitivity testing. All enterococcal isolates from patients with serious infections should be screened for high-level aminoglycoside resistance.

Drug Resistance, Microbial↗
PubMed1994

Antilisterial activity by enterococci in a model predicting the temperature evolution of Taleggio, an Italian soft cheese.

Enterococcus ssp. produced broad-spectrum bacteriocins, which were active against Listeria innocua and Listeria monocytogenes. Inhibition of L. innocua in milk by different starter cultures was evaluated. Milk was inoculated with a conventional starter (Streptococcus salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus mixed cultures) as a sole starter or in combination with inhibitory starter cultures (Enterococcus ssp., bacteriocin-producing strains). Tests were performed under a temperature gradient that reproduced the first 55 h of Taleggio cheese manufacturing and in the presence of rennet. Results indicated that satisfactory inhibition of L. innocua was linked to the combined synergistic antimicrobial effect of pH decrease and bacteriocin production. Overall, data suggested that a potential existed for use of the antagonistic activity from enterococci for protection of Taleggio cheese during ripening, when L. monocytogenes may often reach dangerous concentrations.

Bacteriocins↗
PubMedDate not supplied

Vancomycin-resistant enterococci outside the health-care setting: prevalence, sources, and public health implications.

Although nosocomial acquisition and subsequent colonization of vancomycin-resistant enterococci (VRE), an emerging international threat to public health, has been emphasized in the United States, colonization among nonhospitalized persons has been infrequently documented. In contrast, in Europe, colonization appears to occur frequently in persons outside the health-care setting. An important factor associated with VRE in the community in Europe has been avoparcin, a glycopeptide antimicrobial drug used for years in many European nations at subtherapeutic doses as a growth promoter in food-producing animals. In Europe, evidence suggests that foodborne VRE may cause human colonization. Although avoparcin has never been approved for use in the United States, undetected community VRE transmission may be occurring at low levels. Further studies of community transmission of VRE in the United States are urgently needed. If transmission with VRE from unrecognized community sources can be identified and controlled, increased incidence of colonization and infection among hospitalized patients may be prevented.

Animal Feed↗
PubMedDate not supplied

Proficiency of clinical laboratories in and near Monterrey, Mexico, to detect vancomycin-resistant enterococci.

Early detection of vancomycin-resistant enterococci is important for preventing its spread among hospitalized patients. We surveyed the ability of eight hospital laboratories in and near Monterrey, Mexico, to detect vancomycin resistance in Enterococcus spp. and found that although laboratories can reliably detect high-level vancomycin resistance, many have difficulty detecting low-level resistance.

Anti-Bacterial Agents↗
PubMedDate not supplied

Fecal colonization with vancomycin-resistant enterococci in Australia.

To assess the rate of fecal vancomycin-resistant enterococci (VRE) colon ization in Austalia, we examined specimens from 1,085 healthy volunteers. VRE was cultured from 2(0.2%) of 1,085 specimens; both were vanB Enter ococcus faecium, identical by pulsed-field gel electrophoresis, but with a pattern rare in Melbourne hospitals.

Adult↗