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Evaluation of MicroScan for identification of Enterococcus species.

Emerging drug resistance of the enterococci necessitates differentiation from group D streptococci and accurate species identification. MicroScan (Baxter Healthcare Corp., West Sacramento, Calif.) has recently developed a microdilution system for identification and antibiotic susceptibility testing of gram-positive cocci. To evaluate the ability of this system to identify Enterococcus species, 100 isolate identified as enterococci by MicroScan were tested by conventional media and 60 isolates of streptococci were tested by MicroScan. Incubation times for conventional and MicroScan methods were 96 and 18 to 24 h, respectively. For 94 strains of enterococci (77 Enterococcus faecalis, 14 Enterococcus faecium, and 3 Enterococcus durans), identification by conventional media and MicroScan agreed. Of the remaining six isolates, four were identified as E. faecalis and two were identified as E. durans by MicroScan, whereas by conventional media the four E. faecalis isolates were identified as Enterococcus solitarius and the two E. durans isolates were identified as Enterococcus hirae. None of the 60 streptococci were identified as enterococci. MicroScan is a reliable method for identification of the commonly encountered enterococcal species E. faecalis and E. faecium; however, modifications of the system are necessary for identification of other Enterococcus species.

Autoanalysis

Gut Colonization With Vancomycin-Resistant Enterococcus Shapes the Gut Microbiome in the Intensive Care Unit.

BACKGROUND: Gut pathogen colonization with vancomycin-resistant Enterococcus (VRE) is common in the intensive care unit (ICU) and is associated with worse clinical outcomes; however, the timing of VRE colonization and its collateral effects on the gut microbiome are incompletely understood. METHODS: Medical ICU patients admitted with sepsis and receiving broad-spectrum antibiotics were sampled via deep rectal swabs at ICU admission and on ICU day 3, 7, 14, and 30. Rectal swabs were cultured for VRE on selective media and analyzed via 16S ribosomal RNA gene sequencing. RESULTS: Ninety patients were sampled (340 longitudinal swabs). VRE positivity rose from 20% at ICU admission to a peak of 33% by ICU day 14 and then modestly declined to 31% by ICU day 30. Paralleling this, alpha diversity fell while Enterococcus relative abundance rose through ICU day 14 with both returning to baseline by ICU day 30. The median relative abundance of Enterococcus was 38% (interquartile range [IQR], 7.4%-75%) for VRE-positive samples compared to 0.01% (IQR, 0%-19%) for VRE-negative samples (rank-sum P < .01); 38 samples had &#x2265;90% Enterococcus and 8 samples were 100% Enterococcus by sequencing. VRE was associated with lower alpha diversity (median Shannon index 1.90 [IQR, 0.89-2.66] if VRE positive versus 2.64 [IQR, 1.58-3.22] if VRE negative; P < .01). CONCLUSIONS: VRE gut colonization peaked at ICU day 14 followed by a modest decline and was associated with low alpha diversity. Improved understanding of dynamic changes in the gut microbiome may facilitate successful future ICU interventions. CLINICAL TRIALS REGISTRATION: NCT03865706.

Aged

Diarrhea caused by a slow-growing Enterococcus-like agent in neonatal rats.

An enteropathogenic Enterococcus-like agent was isolated from a spontaneous outbreak of diarrhea that occurred in a colony containing neonatal rats. Diarrhea was experimentally reproduced in virus-antibody-free neonatal rats inoculated with this purified "enterococcus." Gram-positive cocci were adhered to the small intestinal villi of affected animals from which the organism was reisolated. The isolate's classification in the genus Enterococcus was confirmed by genetic probe; however, because of its unique fermentation pattern, it could not be definitively speciated. Indirect immunofluorescence assays indicate that this strain of enterococcus and Enterococcus hirae, another strain pathogenic for neonatal rats, differ antigenically. Enterococci should be considered as potential etiologic agents in outbreaks of diarrhea involving neonatal rats and future efforts directed to increasing our understanding of the pathophysiology of this disease.

Animals

Identification of Enterococcus species isolated from human infections by a conventional test scheme.

Streptococci (206 cultures) previously identified as enterococci were retrieved from storage and reidentified by using tests designed to identify species of the genus Enterococcus. Of these 188, 91% were correctly identified as Enterococcus species. Of the remaining strains, nine (4%) were unidentified and six (3%) and 3 (1.5%) were identified as Leuconostoc sp. and Lactococcus sp., respectively. Two new Enterococcus species were discovered: E. raffinosus and E. solitarius. DNA-DNA hybridizations were performed on selected strains to assure correct identification. Cultures representing 10 of the 12 Enterococcus species were among the 188 strains identified. An identification system based on the grouping of key reactions of 20 phenotypic characteristics of Enterococcus species is described.

Bacteriological Techniques

Antimicrobial Resistance in Nontyphoidal Salmonella and Clinically Relevant Enterococcus From Faecal Samples of Conservation-Priority Captive Ungulates in a United Arab Emirates Urban Zoo: A Cross-Sectional Baseline Study.

Antimicrobial resistance (AMR) is a One Health challenge driven by microbial exchange among humans, animals and the environment. Zoological institutions offer useful settings for environmental AMR surveillance. This single-zoo cross-sectional study examined the occurrence, antimicrobial susceptibility and genomic characteristics of nontyphoidal Salmonella enterica (NTS) and clinically relevant Enterococcus spp. in faecal samples from 101 clinically healthy captive ungulates representing seven conservation-priority species at a major urban zoo in the United Arab Emirates. NTS was detected in 4/101 samples (3.9%), including serovars Schwarzengrund (n&#x2009;=&#x2009;2), Kentucky (n&#x2009;=&#x2009;1) and Chester (n&#x2009;=&#x2009;1). Among the four recovered NTS isolates, all met the study MDR definition within the tested panel, including a Salmonella Kentucky ST198 isolate carrying multiple resistance genes and quinolone-associated mutations. Enterococcus spp. were detected in 77/101 samples (76.2%), dominated by Enterococcus faecium and Enterococcus casseliflavus (each 41.5%). Among 33 E. faecium/Enterococcus faecalis isolates tested phenotypically, resistance was generally low, with erythromycin and ciprofloxacin resistance each observed in 9.1%. One clinically important E. faecium isolate showed glycopeptide resistance and genetic markers associated with reduced daptomycin susceptibility. These single-institution cross-sectional data provide an initial regional baseline for AMR-relevant enteric bacteria in conservation-managed ungulates and identify priorities for broader longitudinal and interface-based surveillance.

Animals

Enterococcus lactic acid bacteria strain SF68 and lactulose in hepatic encephalopathy: a controlled study.

Forty cirrhotic patients with non-advanced hepatic encephalopathy were randomly allocated into groups which were given orally either two capsules three times daily of a preparation of Enterococcus lactic acid bacteria strain SF68 or 30 ml lactulose four times daily. The patients were evaluated over a 10-day course of treatment and for 10 days post-treatment. The Enterococcus SF68 preparation proved to be as effective as lactulose in lowering blood ammonia, and in improving mental state and psychometric performance. Moreover, the effects of Enterococcus SF68, contrary to that of lactulose, persisted longer after treatment withdrawal. Some patients reported diarrhoea and abdominal pain with lactulose. Lactulose is a standard therapy in the treatment of patients with hepatic encephalopathy. In this study, however, the use of the Enterococcus SF68 preparation was shown to offer advantages over lactulose in these patients.

Adult

Double-blind report on the efficacy of lactic acid-producing Enterococcus SF68 in the prevention of antibiotic-associated diarrhoea and in the treatment of acute diarrhoea.

A multicentre double-blind, placebo-controlled clinical trial, involving 123 patients at 10 centres, was carried out to assess the efficacy of a preparation of lactic acid-producing Enterococcus SF 68 in the prevention of antibiotic-associated diarrhoea and in the treatment of acute diarrhoea. In the prevention study, 45 patients being treated with antibiotics were given, concurrently, one capsule twice daily of either Enterococcus SF68 or placebo. Acute diarrhoea was present in 78 patients who were given the same treatment but three times daily. All treatments were continued for 7 days. Enterococcus SF 68 was shown to be effective in reducing the incidence of antibiotic-associated diarrhoea in comparison with placebo (8.7% compared with 27.2%, respectively). Patients with acute enteritis showed a significantly faster resolution of bowel abnormalities during treatment with Enterococcus SF68 compared with placebo.

Adult

In vitro activity of daptomycin-metronidazole combinations against mixed bacterial cultures: reduced activity of metronidazole against Bacteroides species in the presence of Enterococcus faecalis.

The in vitro activity of daptomycin-metronidazole combinations against mixed cultures of gram-positive facultative cocci and strains of the Bacteroides fragilis group was investigated. Metronidazole did not influence the high activity of daptomycin against strains of Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis in the absence or presence of the co-cultured Bacteroides strains. In contrast, the Enterococcus faecalis isolates protected the co-cultured Bacteroides strains against the killing effect of metronidazole, even at a concentration four- or eightfold the MIC of metronidazole. Killing curve experiments confirmed this protective effect of different isolates of Enterococcus faecalis.

Anti-Bacterial Agents

Isolation of three strains of beta-lactamase-producing Enterococcus faecalis in Argentina.

Of the 90 strains of Enterococcus spp. isolated in an Argentine laboratory in the period from January to July 1989, three were identified as beta-lactamase-producing Enterococcus faecalis. According to the literature reviewed, these appear to be the first beta-lactamase-positive strains of Enterococcus isolated outside the USA. They differed from most beta-lactamase-producing strains already described in that they were susceptible to low concentrations of macrolides. All three strains were resistant to high concentrations of aminoglycosides.

Aminoglycosides

Enterococcus species in urinary tract infection.

Significant urinary isolates have been prospectively recorded since 1971. Enterococcus species, a common cause of nosocomial urinary tract infection, have been identified, and susceptibilities to a range of antibiotics have been determined. In addition, isolates in 1988 were tested for breakpoint susceptibility to vancomycin and teicoplanin. Despite changes in the hospitals covered, isolation of Enterococcus species rose steadily from 4% in 1971 to 12.6% in 1990 in hospital patients and from 2% to 5.6% in general-practice patients (P less than .01). All isolates of Enterococcus species were sensitive to ampicillin. Teicoplanin inhibited all 526 strains tested at a concentration of 2 micrograms/mL, but the same concentration of vancomycin inhibited only 370 (70%). The increased prevalence of enterococcal urinary tract infection is probably the result of increasing use of catheterization and broad-spectrum antibiotics. Glycopeptides reach high levels in the urine, and teicoplanin might be an alternative for the treatment of urinary tract infections due to enterococci.

Anti-Bacterial Agents

The phylogenetic position of Streptococcus and Enterococcus.

Streptococcus pyogenes, S. equinus, S. bovis, S. salivarius, S. sanguis, S. mutans, S. rattus, S. cricetus, S. lactis, S. raffinolactis and Enterococcus faecalis have been characterized by oligonucleotide cataloguing of their 16S ribosomal RNA. All the organisms form a loose but coherent group that is phylogenetically equivalent to those of lactobacilli, bacilli, the Brochothrix and Listeria group, and related taxa that constitute one of several sublines within the 'Clostridium' branch of Gram-positive eubacteria. Within the Steptococcus-Enterococcus group, organisms fall into three moderately related clusters defined by Enterococcus, the lactic acid streptococci and streptococci of the pyogenic and oral groups, respectively.

Animals

Vancomycin resistance gene vanC is specific to Enterococcus gallinarum.

Nearly all strains of Enterococcus gallinarum are resistant to low levels of vancomycin. The glycopeptide resistance gene vanC from E. gallinarum BM4174 has recently been cloned and sequenced. A probe specific for vanC hybridized with a 2.7-kb EcoRI and a 4.5-kb HindIII fragment of total DNA from the 42 strains of E. gallinarum studied. No homology was detected with DNA of strains belonging to other species intrinsically resistant to vancomycin, including Enterococcus casseliflavus, a species that expresses a vancomycin resistance phenotype similar to that of E. gallinarum. No hybridization with DNA of enterococcal strains with acquired resistance to high or low levels of vancomycin was observed. The specificity of the vanC probe allowed us to distinguish E. gallinarum from 12 other species of enterococci, indicating that this probe is a useful tool for species identification within the genus Enterococcus.

Culture Media

Ampicillin-resistant Enterococcus raffinosus in an acute-care hospital: case-control study and antimicrobial susceptibilities.

A prospective study identified 9 (32%) of 28 ampicillin-resistant (MIC greater than or equal to 16 micrograms/ml) enterococcus isolates as Enterococcus raffinosus. A case-control study found no significant differences with respect to underlying diseases, catheterization, or surgery between patients with ampicillin-resistant E. raffinosus and those with ampicillin-susceptible Enterococcus spp. Prior treatment with antibiotics and prolonged hospitalization were more frequent among patients with ampicillin-resistant E. raffinosus. Patients with the same strain (determined by plasmid analysis) were frequently hospitalized concurrently.

Aged

The NagY antiterminator in Enterococcus faecalis: a novel regulatory mechanism and its impact on cell metabolism.

The Enterococcus genus is the most controversial group of lactic acid bacteria. While some strains are used as probiotics, other species, including Enterococcus faecalis, are responsible for health-related pathologies. Under conditions of infection, the N-acetylglucosamine metabolism of E. faecalis undergoes significant changes in expression, even more important than those of virulence factors. This metabolism is mediated by the nagY-nagE operon, which is regulated by the transcriptional antiterminator NagY. In this report, we focus on the regulatory mechanism of NagY and its impact on bacterial metabolism. We showed that NagY requires the interaction with the RNase III to achieve optimal induction of its own expression by cleaving the 5' untranslated region of the nagY mRNA. The NagY regulon was identified and the central role of the antiterminator in the E. faecalis metabolism was demonstrated, highlighting its importance in the opportunistic nature of the bacterium. This study provides a valuable advance in the understanding of regulation and the importance of post-transcriptional actors in E. faecalis adaptation.IMPORTANCEAs a commensal, Enterococcus faecalis colonizes the gastrointestinal tract of 31 to 80% of the intestinal microbiota in adults and is considered ubiquitous, due to its strong environmental stress resistance capabilities. However, in immunocompromised patients, the poorly understood transition from commensal to opportunistic pathogen occurs, and many studies suggest that the metabolism plays a central role in this process. In this study, we focus on the regulator NagY, which is involved in the metabolism of N-acetylglucosamine, an important carbon source for bacterial pathogens in the human host. We characterized a novel regulatory mechanism involving the NagY antiterminator and the ribonuclease RNase III. In addition, we identified the target genes of the regulator, through which we were able to demonstrate that NagY has a strong impact on the metabolism of &#x3b2;-glucosides. Overall, this work highlights the importance of regulation of the bacterial metabolic adaptation in the host.

Enterococcus faecalis

Aminoglycoside-resistant Streptococcus and Enterococcus species isolated from bovine mammary secretions.

A total of 117 isolates representing four Streptococcus species and 20 isolates representing two Enterococcus species from bovine mammary secretions were examined for resistance to streptomycin, kanamycin, and gentamicin. Resistance to streptomycin (85.4%) was most prevalent, followed by kanamycin (19%) and gentamicin (2.2%). Minimum inhibitory concentration of streptomycin for most organisms examined ranged from 16 to 250 micrograms/ml. For kanamycin, the minimum inhibitory concentration for most organisms was .5 to 62.5 micrograms/ml. Minimum inhibitory concentration for gentamicin was lower than for kanamycin. Two strains each of Streptococcus uberis and Enterococcus faecalis had minimum inhibitory concentration for streptomycin of greater than 2000 micrograms/ml, and two strains of E. faecalis had similar minimum inhibitory concentration for kanamycin. The minimum bactericidal concentration for all organisms was one to four times higher than minimum inhibitory concentration. None of the organisms evaluated was found to carry plasmids. Transfer of antibiotic resistance in plasmid-free strains was not achieved by mobilization with the aid of plasmid pAD1, indicating the absence of conjugative transposons. These data suggest that expression of aminoglycoside resistance of Streptococcus and Enterococcus species of bovine origin is likely due to factors other than plasmids or conjugative transposons.

Animals

Hospital-acquired infection with vancomycin-resistant Enterococcus faecium transmitted by electronic thermometers.

OBJECTIVES: To describe an epidemic of vancomycin-resistant Enterococcus faecium causing bacteremia and bacteriuria, to identify the source of infection, to delineate risk factors associated with acquisition of the organism, and to determine antibiotic sensitivities for the organism. DESIGN: Investigation of an epidemic, including a case-control study. SETTING: Medical-surgical intensive care unit and ward in a university medical center. PATIENTS: Nine patients infected or colonized with vancomycin-resistant Enterococcus faecium and 20 noninfected controls. MEASUREMENTS: Clinical data, environmental surveillance cultures, and in-vitro microbiologic studies. RESULTS: Colonization or infection by vancomycin-resistant E. faecium was associated with an increased duration of treatment with ceftazidime, 13.2 compared with 4.6 days, and a greater number of nonisolated days of hospitalization in the intensive care unit, 19.9 compared with 6.4 days for infected and noninfected patients, respectively (P less than 0.05). Environmental surveillance cultures recovered the organism repeatedly from the rectal probe handles of three electronic thermometers used exclusively on nonisolated patients in the intensive care unit. Restriction endonuclease analysis of plasmid DNA showed that all clinical and environmental isolates were identical. Infection control measures, including isolation of colonized or infected patients and removal of the rectal thermometer probes suspected to be responsible for transmission, resulted in termination of the outbreak. In-vitro, time-kill studies showed that the combination of ciprofloxacin, rifampin, and gentamicin resulted in bactericidal activity against the organism. CONCLUSIONS: This nosocomial outbreak of infection due to a highly vancomycin-resistant strain of Enterococcus is the first epidemic in which an electronic thermometer has been implicated as the vehicle of transmission for an infectious agent.

Adolescent

[Study of the host factors in the occurrence of the postoperative infections--special reference to the pathogenicity of the Enterococcus and MRSA].

A study of the pathogenicity of the Enterococcus and Methicillin resistant S. aureus (MRSA) was made of 781 cases with gastroenterological surgery. The results obtained were summarized as follows. In this study 215 strains were isolated from clinical specimens. In these strains 13% was isolated from the postoperative mixed infection and only 7% occurred in single infection. Most of the single infections by the Enterococcus occurred in the cases with changes in host resistance, such as terminal cancer, disorder of the glucose tolerance, malnutrition and/or organ failures. Seventy-three strains were isolated from clinical specimens. In these strains 10% were the postoperative mixed infection and 40% were single infection. Incidence of the infection by the MRSA was significantly high compared with that by the Enterococcus. Single infection by the MRSA occurred even in the cases with normal host resistance. Strains producing enterotoxin C (single or plus A) were frequently isolated in MRSA enteritis or pneumonia. However, 60 percent of the patients in whom MRSA were detected in their abdominal drains had no signs of infection. These results suggest that the occurrence and severity of the MRSA infection relate with site of the infection and production of the exotoxin.

Enterococcus

Enterococcus columbae, a species from pigeon intestines.

Gram-positive cocci which dominate in the intestinal flora of domestic pigeons were found to constitute a new species of the genus Enterococcus. The strains were most closely related to Enterococcus cecorum, originally described as Streptococcus cecorum, a carboxyphilic species from chicken intestines, and to Enterococcus avium. The pigeon strains resemble E. cecorum and also many E. avium strains in their lack of group D antigen and in being more sensitive to NaCl than other enterococci. The type strain is strain STR 345 (= NCIMB 13013).

Amino Acid Sequence