Is Enterococcus Gram positive or negative?
Enterococci are Gram positive, catalase- and oxidase negative, non-spore forming, ovoid cocci occurring in single, pairs or short chains. Except Enterococcus ( Ent .) gallinarum and Ent. casseliflavus, enterococci are non-motile.
Is genera Enterobacteriaceae oxidase positive or negative?
Genera of the Enterobacteriaceae family are characterized as oxidase negative. Name of Oxidase positive bacteria are: Mneomoics for Oxidase Positive Organisms- PVNCH (It’s just an acronym inspired by the famous mneomonic for Urease Positive organisms-PUNCH) P: Pseudomonas spp. V: Vibrio cholerae. N: Neisseria spp.
What does oxidase negative mean in microbiology?
Bacteria that are oxidase-negative may be anaerobic, aerobic, or facultative; the oxidase negative result just means that these organisms do not have the cytochrome c oxidase that oxidizes the test reagent. They may respire using other oxidases in electron transport. Test requirements for Oxidase test
What are the characteristics of Enterococcus faecalis?
Biochemical Test and Identification of Enterococcus faecalis Characteristics Enterococcus faecalis Gram Staining Positive Shape (Cocci/Diplococci/Rods) Cocci Motility (Motile / Non-Motile) Non-Motile Capsule (Capsulated/Non-Capsulated) – 60 more rows ...
How many biochemical tests are needed to identify enterococcus?
How many tests are needed for Enterococcusspp?
How many isolates were identified in the biochemical key?
What color is the l-arabinose test?
What is the percentage of positive strains?
Can enterococci grow on a selective medium?
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Is Enterococcus oxidase negative?
Most enterococci are oxidase and catalase negative, salt tolerant (as high as 6.5%), resistant to 40% bile, esculin hydrolytic, and able to grow in the presence of sodium azide (up to 0.4%).
Are enterococci oxidase positive?
Enterococci are Gram positive, catalase- and oxidase negative, non-spore forming, ovoid cocci occurring in single, pairs or short chains.
Does Enterococcus faecalis produce oxidase?
Several enzymes present in E. faecalis are known to produce hydrogen peroxide, e.g., hydrogen peroxide-forming NADH oxidase, superoxide dismutase, and pyruvate oxidase.
Is Enterococcus positive or negative?
It is generally agreed that the genus Enterococcus comprises gram-positive cocci that are catalase negative, usually facultative, anaerobic bacteria that grow in 6.5% NaCl, 40% bile salts, and 0.1% methylene blue milk and at pH 9.6.
Which bacteria is oxidase negative?
Bacteria that are oxidase-negative may be anaerobic, aerobic, or facultative; the oxidase negative result just means that these organisms do not have the cytochrome c oxidase that oxidizes the test reagent. They may respire using other oxidases in electron transport.)
Which organisms are oxidase positive?
Oxidase Positive Organisms: Pseudomonas, Neisseria, Alcaligens, Aeromonas, Campylobacter, Vibrio, Brucella, Pasteurella, Moraxella, Helicobacter pylori, Legionella pneumophila, etc.
Can E coli be oxidase positive?
E. coli bacteria are among the few species of lactose (LAC)-positive, oxidase-negative, gram-negative rods that are indole positive.
Is Streptococcus faecalis oxidase positive or negative?
Biochemical Test and Identification of Enterococcus faecalisCharacteristicsEnterococcus faecalisSpore (Sporing/Non-Sporing)Non-SporingFlagella (Flagellated/Non-Flagellated)–CatalaseNegative (-ve)OxidaseNegative (-ve)60 more rows•Aug 10, 2022
Which Enterococcus is catalase positive?
Enterococcus faecalis is one of the few species of lactic acid bacteria that exhibit catalase activity, but only when grown in the presence of heme [2]. E. faecalis catalase (KatA) belongs to the group of heme-containing mono-functional catalases (EC 1.11.
How do you differentiate Streptococcus and Enterococcus?
Main Difference – Enterococcus vs Streptococcus Both types of bacteria are arranged in pairs or chains. Enterococcus tends to form short chains whereas Streptococcus mainly form clusters but, may be single, in pairs or short chains. Both Enterococcus and Streptococcus can be found in the mucous membrane of animals.
How do you identify Enterococcus?
Presumptive identification: Growth on bile esculin agar and in 6.5% salt broth are two characteristics that have commonly been used to identify Enterococcus species to the genus level. A positive esculin in combination with a positive PYR reaction is another approach to presumptive identification.
Is E coli and Enterococcus same?
Results indicated that enterococci might be a more stable indicator than E. coli and fecal coliform and, consequently, a more conservative indicator under brackish water conditions.
Is shigella an oxidase?
Shigella species are oxidase negative. Oxidase positive samples are non-shigella species. Shigella species are urease negative. Urease positive samples are non-shigella species.
How can you differentiate between streptococcus and enterococci?
Main Difference – Enterococcus vs Streptococcus Both types of bacteria are arranged in pairs or chains. Enterococcus tends to form short chains whereas Streptococcus mainly form clusters but, may be single, in pairs or short chains. Both Enterococcus and Streptococcus can be found in the mucous membrane of animals.
Can E coli be oxidase positive?
E. coli bacteria are among the few species of lactose (LAC)-positive, oxidase-negative, gram-negative rods that are indole positive.
Which bacteria is oxidase negative and catalase positive?
Staphylococcus epidermidis is a gram-positive, catalase-positive, coagulase-negative cocci in clusters and is novobiocin sensitive.
What does it mean when a bacteria is oxidase positive?
All bacteria that are oxidase-positive are aerobic and can use oxygen as a terminal electron acceptor in respiration. This does NOT mean that they are strict aerobes. Bacteria that are oxidase-negative may be anaerobic, aerobic, or facultative; the oxidase negative result just means that these organisms do not have the cytochrome c oxidase that oxidizes the test reagent. They may respire using other oxidases in electron transport.
What is the color of the end product of cytochrome C oxidase?
When present, the cytochrome c oxidase oxidizes the reagent (tetramethyl-p-phenylenediamine dihydrochloride) to indophenols, a purple or dark blue color end product. When the enzyme is not present, the reagent remains reduced and is colorless. Mechanism of the Cytochrome Oxidase Reaction. All bacteria that are oxidase-positive are aerobic ...
How much Kovács oxidase to use on organism smear?
Place 1 or 2 drops of 1% Kovács oxidase reagent on the organism smear.
How long can Kovács oxidase be stored in water?
Kovács oxidase reagent (1% tetra-methyl-p-phenylenediamine dihydrochloride, in water). Store refrigerated in a dark bottle for no longer than 1 week.
How to grow bacteria on nutrient agar?
Direct Plate Method. Grow a fresh culture (18 to 24 hours) of bacteria on nutrient agar or trypticase soy agar using the streak plate method so that well-isolated colonies are present. Place 1 or 2 drops of 1% Kovács oxidase reagent on the organisms. Do not invert or flood plate.
What is the oxydase test?
Oxidase test is used as a major characteristic for the identification of Gram-negative rods that are not in the Enterobacteriaceae family. Colonies suspected of belonging to other genera Aeromonas, Pseudomonas, Neisseria, Campylobacter, and Pasteurella are oxidase positive.
How long does it take for a oxidase positive to change to a purple?
Oxidase positive: color changes to dark purple within 5 to 10 seconds. Delayed oxidase-positive: color changes to purple within 60 to 90 seconds. Oxidase negative: color does not change or it takes longer than 2 minutes.
What is the Difference Between Positive and Negative Oxidase Test?
The key difference between positive and negative oxidase test is that positive oxidase test indicates the presence of cytochrome C oxidase in bacterium, whereas negative oxidase test indicates the absence of cytochrome C oxidase.
What is Negative Oxidase Test?
Negative oxidase test is an analytical technique in which we can determine the absence of cytochrome c oxidase enzyme in a given bacteria sample. We can denote this term as OX-. This type of bacteria cannot use oxygen for energy production through an electron transfer chain. If not, these bacteria employ a different cytochrome form for the transfer of electrons to oxygen. Typically, Enterobacteriaceae are oxidase negative.
What is an Oxidase Test?
Oxidase test is useful in determining whether a bacterium can produce cytochrome C oxidases or not. This analytical technique uses disks that are impregnated with reagents such as TMPD or DMPD. When oxidized, the reagent becomes blue to maroon colour. When it is in the reduced state, the reagent is colourless.
What is the function of cytochrome C oxidase?
The bacterium containing cytochrome C oxidases can catalyze the transport of electrons from donor compounds such as NADH to electron acceptors such as oxygen. TMPD or the test reagent in oxidase test acts as the artificial electron donor; thus, the oxidized reagent gives a colour (by forming the coloured compound indophenol blue). Usually, oxidase-positive bacteria species include aerobic organisms (these organisms are capable of using oxygen as the terminal electron acceptor).
What color is oxidase?
In positive oxidase test, the colour change is from blue to maroon, while in negative oxidase test, a colour change does not occur.
Do bacteria use oxygen?
This type of bacteria cannot use oxygen for energy production through an electron transfer chain. If not, these bacteria employ a different cytochrome form for the transfer of electrons to oxygen. Typically, Enterobacteriaceae are oxidase negative.
Does oxidase change color?
Moreover, in positive oxidase test, the colour change is from blue to maroon, while in negative oxidase test, a colour change does not occur. Many Gram-negative bacteria and spiral-curved, rod-shaped bacteria such as Vibrio cholerae are oxidase-positive while bacteria from Enterobacteriaceae species are oxidase-negative.
What is the genus of Enterococcus?
Bacteria of the genus Enterococcus (‘enterococci’) have been recognized since Thiercelin (1899) described them as the ‘entérocoque’ to emphasize their intestinal origin. However, the taxonomy of this group of bacteria has always been vague. Development of genotypic methods for studying phylogenetic relationships of food-associated lactic acid bacteria has resulted in considerable changes in their taxonomy. On the basis of 16S rRNA cataloguing, the genus Streptococcus was separated during the 1980s into the three genera Enterococcus, Lactococcus and Streptococcus. Consequently, bacteria previously named as Streptococcus faecalis, Streptococcus faecium, Streptococcus avium and Streptococcus gallinarum were transferred to the revived genus Enterococcus as Enterococcus faecalis, Enterococcus faecium, Enterococcus avium and Enterococcus gallinarum, respectively.
Where are enterococci found?
The intestinal tract is generally considered the major natural habitat for human-associated enterococci, but it is clear that they are commonly present at low numbers in niches such as the oral cavity, where they can become more prominent in the context of endodontic infections ( Ferrari, Cai, & Bombana, 2005; Sedgley, Lennan, & Clewell, 2004) or oral tumors ( Boonanantanasarn et al., 2012 ). The human intestinal tract is likely to harbor additional enterococcal species (e.g., Enterococcus durans, Enterococcus hirae, Enterococcus mundtii, Enterococcus casseliflavus, Enterococcus gallinarum, or Enterococcus avium) at very low numbers, as evidenced by their regular isolation from vancomycin-resistant hospital infections.
How to identify a strain of vagococcus?
Confirmation that a strain is a Vagococcus requires complete identification to the species level. It generally is accomplished by using a series of additional conventional physiological tests. As already pointed out, even using extensive testing, the differentiation of some vagococcal strains from the enterococci is sometimes problematic. Tests for production of acid from l -arabinose and raffinose may be useful, since V. fluvialis strains are negative and the motile Enterococcus species, Enterococcus gallinarum and Enterococcus casseliflavus, are positive. The arginine test may be a clue for such differentiation as most strains belonging to these enterococcal species are positive. Uncommon arginine-negative variants of the physiological group II enterococcal species and Enterococcus columbae have biochemical characteristics that are similar to those of the vagococci, especially V. fluvialis. Table 2 lists some of the tests that can be used to differentiate among them.
What enterococci are found in farm animals?
faecalis, E. faecium, and several other species are commonly identified as members of the normal intestinal flora of numerous animal species. Certain species and age groups exhibit trends, but not absolute specificity, for presence in a particular host or a particular subpopulation of a given host. Among farm animals, the predominant enterococci in pigs are most similar to those of humans ( Devriese, Hommez, Pot, & Haesebrouck, 1994 ). It is also interesting to note that age-related succession in the predominant enterococcal species has been well documented. For example, newly hatched chicks are colonized by E. faecalis, which tend to be replaced quickly by E. faecium -like strains, and are subsequently succeeded by Enterococcus cecorum in adults ( Devriese, Hommez, Wijfels, & Haesebrouck, 1991; Devriese, Laurier, De Herdt, & Haesebrouck, 1992 ). Likewise, in cattle, E. faecium and E. faecalis predominate in young calves. These strains, along with a few additional species, persist at reduced numbers as the animals age, but in mature adults Streptococcus bovis appears to succeed the enterococci as the predominant species in the intestine. While there is not extensive evidence for strong host-specific enterococci, it has been reported that ducks preferentially harbor E. faecalis and pigeons are specifically colonized by Enterococcus columbae. Relatively little is known about the genetic and phenotypic basis for preferential association of enterococcal species with any of these animal hosts. Although not shown in Table 4.1, it should also be noted that enterococci of diverse species can be isolated from the guts of insects and nematodes ( Martin & Mundt, 1972 ), and the close interactions of these organisms with other microbes derived from the soil may serve as a conduit for transmission of antibiotic resistance genes into the enterococci.
How many species of enterococci are there?
Since the transfer of S. faecalis and S. faecium to the revived genus Enterococcus in 1984, the total number of species presently included here is 20. Several of these species have been transferred from the genus Streptococcus and 11 were newly added ( Table 1 ). This situation continues to fluctuate from time to time as individual species are moved into other genera or new taxa are discovered. In addition to providing a more definitive delineation of the genus Enterococcus, comparative 16S rRNA sequence analysis has also revealed the presence of several ‘species groups’ within the genus ( Table 2 ). The faecium ‘species group’ contains E. durans, E. faecium, E. hirae and E. mundtii. The avium group contains E. avium, E. raffinosus, E. malodoratus and E. pseudoavium. The gallinarum group consists of the species E. casseliflavus, E. gallinarum and E. flavescens. Some species, however, do not cluster with these groups and form individual lines of descent, such as E. faecalis, the type species of the genus, E. sulfureus, E. saccharolyticus and E. dispar. From sequence homology determination of 16S rRNA, E. cecorum and E. columbae are also allocated to two phylogenetic distinct lineages but the high relatedness between the two species led to them being clustered into a common group, i.e. the cecorum group ( Table 2 ).
When were enterococci classified as streptococci?
Based on DNA-DNA hybridization experiments, enterococci were classified separately in 1984 after being described as streptococci. Since then, the taxonomy of the genus Enterococcus has constantly evolved and undergone revision due to the frequent description of new species and the finding that the differences between the taxa are not such as to allow a separate speciation. For example, Ent. thailandicus, Ent. ureasiticus, Ent. pallens, Ent. caccae, Ent. cammelliae, and Ent. lactis have recently been described. Ent. porcinus was shown to be a synonym of Ent. villorum. Similarly, Ent. flavescens and Ent. saccharominimus were reclassified as synonymous species of Ent. casseliflavus and Ent. italicus respectively, whereas Ent. solitarius was reclassified to the genus Tetragenococcus ( Tet) as Tet. solitarius. At the time of writing, Enterococcus represents the third largest LAB genus after Lactobacillus and Streptococcus with 53 species with validly published names based on polyphasic taxonomy, which generally includes DNA-DNA hybridization, 16S rRNA, rpoA and pheS gene sequencing, and phenotypic and biochemical data ( Table 1 ). Enterococcus faecium and Ent. faecalis (the type species of the genus) remain the most important and frequently isolated enterococcal species. Despite close relationships and similarities, the species are well separated by DNA–DNA similarity. Based on comparative 16S rRNA gene sequence analysis, different species groups, such as Ent. faecium, Ent. avium, Ent. gallinarum, Ent. italicus, Ent. faecalis, Ent. dispar, and Ent. cecorum, can be delineated within the genus Enterococcus. The “faecalis” group is the largest and includes Ent. caccae, Ent. faecalis, Ent. haemoperoxidus, Ent. moraviensis, Ent. plantarum, Ent. quebecensis, Ent. rivorum, Ent. rotai, Ent. silesiacus, Ent. termitis, Ent. ureasiticus, and Ent. ureilyticus. However, not all the described species meet the physiological and biochemical traits of the typical enterococci. For example, the species of the “cecorum” group ( Ent. cecorum and Ent. columbae) show unique phenotypic traits in the genus (e.g., the inability to grow at 10 °C and react with the antiserum of group D), which make them phylogenetically distant from other species.
Which chromosomes have vancomycin resistance?
The vanC resistance determinants are present on the chromosome in Enterococcus casseliflavus and Enterococcus gallinarum and are intrinsic characteristics of these species. VanC-harboring enterococci have low-level resistance to vancomycin and remain susceptible to teicoplanin. The pentapeptide that results from the action of the VanC ligase terminates in d -Ala- d -Ser. 47 This substitution probably reduces vancomycin binding, albeit not to the same degree as the depsipeptide found in VanA and VanB enterococci. VanC-harboring strains with high-level resistance to glycopeptides as a result of the acquisition of the vanA gene cluster have also been isolated.
How many biochemical tests are needed to identify enterococcus?
This study provides a scheme for the rapid identification of clinical and environmental species of Enterococcus. The key is based on 12 biochemical tests. The threshold of identification is over 99%, with some exceptions (87, 91.5, and 97% for E. avium, E. hirae, and E. durans, respectively). The use of sucrose fermentation for the discernment of E. aviumfrom E. raffinosusdecreased the threshold of identification in the key. Although other authors (12, 25, 34) claim that these two species can be differentiated on the basis of their ability to ferment raffinose, our results do not support this claim. The selection of sucrose fermentation for the differentiation of these species avoids the discrepancies detected for the raffinose fermentation, though the threshold of identification decreased. Consequently, the key provides for the differentiation of all 19 recognized species of the genus Enterococcuswith few tests. The atypical asaccharolytic variant strains of E. faecalis(24) were not considered in this study. Therefore, they might be misidentified when this key is used. Previous tables, keys, and schemes proposed by other authors do not include all the species described to date and are based on greater numbers of tests (21, 24, 34, 53). However, it is necessary to check that an isolate belongs to the genus Enterococcusbefore this key is used. As previously explained, there is a certain amount of agreement on the phenotypic characters of this genus. Any isolate suspected of being an Enterococcusspp. is a gram-positive coccus, anaerobically facultative and catalase negative. It grows in 6.5% NaCl, 40% bile salts, and 0.1% methylene blue milk and at pH 9.6. It grows at 10 and 45°C and resists 30 min at 60°C (20, 52–54). These criteria were described in order to differentiate the Enterococcusspp. from Streptococcusspp. Both genera have been clearly distinguished by DNA-DNA and DNA-rRNA hybridization (30, 33, 52) and 16S RNA sequencing (36). The genus named Enterococcusby Thiercelin and Jouhaud in 1903 (56) was reviewed by Schleifer and Kilpper-Bälz in 1984 with bacteria previously described as S. faecalisand S. faecium(52). Later, other streptococci having the characteristics of the enterococcus group were transferred to the genus Enterococcus. In addition, new species of this genus have been described (E. cecorum, E. columbae, E. dispar, E. flavescens, E. pseudoavium, E. raffinosus, E. sulfureus, E. solitarius, and E. asini), mainly on the basis of 16S rRNA comparative sequence analysis and DNA-DNA hybridization (12, 13, 17, 19, 38, 46). However, some of these species do not have all the phenotypic characteristics of the genus Enterococcusdefined above. Therefore, there is no final phenotypic determination that provides a differentiation of the genus Enterococcusfrom other gram-positive, catalase-negative cocci (21). This key cannot avoid misidentification at the genus level because it has been developed for species identification. However, the easy use of this key avoids the difficult consultation of several taxonomic reviews of Enterococcusthat do not always lead to unanimous species identification. Some of the tests could be performed with commercial kits (for instance, API 20 Strep or API 50CH), which are widely used (7, 9, 28, 34, 50). It has been observed by other authors that certain tests do not present comparable results when performed according to classical standard methods (28, 34). However, the arginine dihydrolase test gave similar results when performed by standard methods and with a commercial kit. On the other hand, no commercial kit includes the whole set of tests selected in this study for Enterococcussp. identification. It would be ideal if a commercial kit that included all the tests selected in this study was available. It should be applicable to a wide range of studies, such as clinical and environmental analyses. The key provided a consistent identification of the type strains and the clinical and environmental isolates used in this study. The proposed key is a practical, reliable, and very easy system for rapid biochemical identification in routine applications where a high number of isolates are normally involved.
How many tests are needed for Enterococcusspp?
A six-step biochemical key is presented for the identification of all recognized Enterococcusspp. 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.
How many isolates were identified in the biochemical key?
All of the clinical and environmental isolates were identified at the species level with the biochemical key. Only four environmental isolates (one from pig feed, two from hospital sewage and one from sewage from water treatment plants) showed unexpected results for some of the 12 tests included on the key. However, these results were not necessary for their species identification.
What color is the l-arabinose test?
However, the l-arabinose test for E. malodoratus, E. pseudoavium, E. saccharolyticus, and E. sulfureuspresented a weak reaction, giving an orange-yellow color. The microaerophilic species E. solitariusneeded long incubation times (24 to 72 h) for the mannitol test. No difference in results was obtained for the arginine dihydrolase test when performed with commercial kits or by standard methods.
What is the percentage of positive strains?
a+, 90% or more of the strains of isolates are positive; (+), 75 to 89% are positive; V, 26 to 74% are positive; (−), 11 to 25% are positive; −, 10 or less are positive; ND, no data; d, discrepancies among reference studies.
Can enterococci grow on a selective medium?
The ability of enterococci to grow under particular conditions is widely used in their selective isolation. This characteristic allows the detection and enumeration of enterococci with a selective medium (M-enterococcus agar or KF streptococcus agar, for instance) and by using bile-esculin-azide agar as a further test for confirmation (2a, 35). Although this approach can distinguish Enterococcusspp. from other bacterial species, some isolates may be misidentified. The use of these media is a compromise between selectivity and productivity (35). Though the aim of this approach was to isolate enterococcal species, it is unsuitable for the detection of certain enterococcal species because they do not grow on these media (35). In addition, other bacterial species such as Streptococcus bovisare able to grow on the media, presenting results similar to those of Enterococcusspp. In recent years, several authors have described molecular methods for the detection of Enterococcusspp., based mainly on the use of labeled oligonucleotide probes (4, 5, 40). However, the conventional methods for routine species identification are still based on physiological characteristics (3, 34, 57).
