Proteus vulgaris is a short, non-sporing, non-capsulated rod-shaped (bacillus) bacteria of about 1 – 3 µm × 0.5 µm (micrometer). Proteus vulgaris is arranged singly, in pairs, or in short chains, and sometimes in clusters. Proteus belongs to the Enterobacteriaceae family and occurs as normal intestinal flora of humans. They are one of the common causes of urinary tract infections (UTIs) and infection-associated renal stones.
Bacilli possess thermostable somatic (O) and flagellar (H) antigens. Certain Proteus vulgaris strains (OX-2, OX-19, and OX-K) produce O antigens which are shared by some rickettsiae. These strains are used for detecting serum antibodies produced against rickettsiae of typhus and spotted fever groups (Weil-Felix test).
Table of contents
Colony characteristics of Proteus vulgaris
Biochemical characteristics of Proteus vulgaris
Additional biochemical characteristics
Colony characteristics of Proteus vulgaris
1. Motility
Proteus vulgaris is an actively motile bacterium that displays swarming growth on a medium like nutrient agar medium (NAM). Proteus vulgaris has a peritrichous flagellar arrangement i.e., flagella are present all over the surface.
2. Gram staining
Proteus vulgaris is a gram-negative bacterium.
3. Media for isolation
Proteus vulgaris has no special nutritional requirements for growth and can readily grow in ordinary media like nutrient agar medium (NAM). MacConkey agar and NAM are commonly used for the cultivation of bacteria in the laboratory.
Other media which can also be used for culturing Pr. Vulgaris include;
Sheep blood agar medium
Xylose Lysine Dextrose (XLD) Agar medium
Eosin Methylene Blue Agar (EMB Agar) Medium.
Columbia Horse Blood Agar medium
Nutrient Broth medium, TSB medium, etc
The optimum temperature for the cultivation of most of the strains is 37 oC. However, the temperature for growth ranges from 10 – 43 oC.
Proteus vulgaris can survive a wide range of pH from alkaline to acidic ranging from 4.0 – 11.0. However, the maximum growth of the bacteria is observed at 6.0.
Oxygen requirements: Pr. vulgaris grows best in the presence of oxygen i.e., is an aerobic bacterium. However, it can also grow in a low oxygen environment i.e., is also a facultative anaerobic bacterium.
Medium
Cultural characteristics
Nutrient agar medium
Colonies are 1 – 2 mm in size, effused, glistening surface, greyish white in color, translucent structure and exhibit irregular shape due to swarming.
MacConkey agar medium
Colonies are 2 – 3 mm in size, low convex, smooth surface, colorless or pale colored, transparent structure, and exhibit circular shape.
Blood agar medium
Colonies are 1 – 2 mm in size, effused, glistening surface, greyish white in color, translucent to opaque in structure, and exhibit irregular shape due to swarming. They also exhibit ℽ- hemolysis (Non- hemolytic).
EMB agar medium
Colonies are 2 – 3 mm in size, effused, glistening surface, colorless, transparent structure, and exhibit circular shape.
Biochemical characteristics of Proteus vulgaris
1. Catalase test
Proteus vulgaris gives a positive catalase test. A 50ml beaker containing 10ml of 3% hydrogen peroxide (H2O2) is taken. A positive test is indicated by the rapid evolution of oxygen by bubbling due to the rapid breakdown of hydrogen peroxide into oxygen and water.
2. Lactose fermentation
Proteus vulgaris is non-lactose fermenter.
3. Oxidase test:
Oxidase test checks the ability of the bacteria to produce cytochrome c oxidase enzyme. It plays an important role in the electron transport chain portion of aerobic respiration in bacteria. When a bacterium produces cytochrome c oxidase, it is said to be oxidase positive. When a bacterium cannot produce the enzyme, they are termed oxidase negative.
Usually, the cytochrome system is present in aerobic organisms which utilize oxygen as the final hydrogen receptor with either water or hydrogen peroxide as the end product of this metabolism. Oxidase discs (OX) are absorbent paper discs that are impregnated with N, N, N’, N’-Tetramethyl-p-phenylenediamine dihydrochloride which turns into a colorless compound in presence of cytochrome oxidase. Proteus vulgaris gives a negative oxidase test.
4. Urease test
It identifies organisms that are capable of hydrolyzing urea to produce ammonia and carbon dioxide. Urease activity can be detected by a) Christensen’s agar; b) Stuart’s urea broth. Klebsiella shows positive urea hydrolysis test. The development of an intense magenta to bright pink color in 15 min to 24 h throughout the broth is an indicator of a positive test. Proteus vulgaris gives a positive urease test.
The urease enzyme produced by the proteus species plays a major role in the production of infection-induced urinary calculi. Urea breakdown results in the production of ammonia and struvite (magnesium ammonium phosphate) stone formation. The ammonia/ammonium buffer pair has a pK of 9.0, resulting in the combination of highly alkaline, ammonia-rich urine. A staghorn-calculi is formed in the kidney due to recurrent urinary tract infections with a urease-producing organism.
5. Fermentation of carbohydrates
Acid and gas are formed during the fermentation of glucose.
Carbohydrate
Result
D-glucose
Positive
Maltose
Positive
L-rhamnose
Negative
Sucrose
Positive
L-arabinose
Negative
Cellobiose
Negative
D-mannitol
Negative
Salicin
Variable
Trehalose
Variable
Glycerol
Variable
Raffinose
Negative
D-sorbitol
Negative
6. Decarboxylase test
This test is done for the production of the enzyme decarboxylase, which removes the carboxyl group from an amino acid. The decarboxylase enzyme produced by an organism is specific to the amino acid on which it will act. Lysine, arginine, and ornithine are the three amino acids that are tested in the decarboxylase media. If the bacteria are able to decarboxylate the amino acid present in the medium, alkaline byproducts will be formed.
The byproducts formed are alkaline in nature and raise the pH of the media to turn the color of the broth purple. If there is no color change and the inoculated medium is yellow, the bacteria are decarboxylase-negative for that amino acid.
Amino acid
Result for Proteus vulgaris
Lysine decarboxylase
Negative
Ornithine decarboxylase
Negative
7. Hydrogen sulfide production
This test determines whether the bacterium reduces sulfur-containing compounds to sulfides during the process of metabolism. If sulfide is produced, it will combine with the iron compound to produce a black precipitate of iron sulfide (FeS).Proteus vulgaris gives a positive H2S production.
8. Indole production
Bacteria decompose the amino acid tryptophan into pyruvic acid, ammonia, and indole with the help of the enzyme tryptophanase. The presence of indole in the medium can be detected by an indicator aldehyde p-dimethylaminobenzaldehyde or p-dimethylaminocinamaldehyde, giving a color reaction (cherry red) with indole. This test is used to differentiate bacteria from the family Enterobacteriaceae.
Tryptophanase
Tryptophan ————————-> Indole + pyruvic acid + NH3
H2O
A cherry red color in the top alcohol layer indicates a positive reaction. Tests for indole may be made after 24 hr of incubation. 1 or 2 ml of culture should be removed aseptically for testing. If the test is negative, the remaining portion of the culture should be re-incubated for an additional 24 hr. Proteus vulgaris are indole-positive bacteria.
9. Citrate utilization test
Bacteria that can grow on simple chemically defined media can be readily tested for their ability to use a given compound as the sole source of carbon and energy. This test is used to determine the ability of an organism to use citrate as the sole source of carbon and energy and ammonium salt as the sole source of nitrogen.
This ability depends on the presence of citrate permease that facilitates the transport of citrate in the cell. Citrate is ultimately converted to pyruvic acid and CO2. Carbon dioxide combines with sodium to form sodium carbonate- an alkaline product that changes the color of indicator bromothymol blue from green to deep Prussian blue.
Citrate ——————> Oxaloacetate + Acetate
Oxaloacetate ————–> Pyruvate + CO2
CO2 + Na + H2O ———> Na2CO3
The blue color formation is a positive reaction, whereas the slant remaining green colored is afeature for negative test. Proteus vulgaris can test either positive or negative for citrate.
10. Phenylalanine test
It is used to determine the organism’s ability to oxidatively deaminate phenylalanine to phenylpyruvic acid. Bacteria that produce phenylalanine deaminase removes the amine group (NH2) from phenylalanine which results in the production of ammonia (NH3) and phenylpyruvic acid.
Ferric chloride acts as a chelating agent for phenylpyruvic acid and a green-colored complex is formed indicating a positive test. A negative test is indicated by straw color. Proteus vulgaris is positive for the Phenylalanine test.
11. IMViC test
Bacterium
Indole
Methyl Red
Vogues Proskauer
Citrate
Proteus vulgaris
+
+
–
–
Additional biochemical test
Characteristics
Result
Urease production
Positive
Tryptophan deaminase production
Positive
Sulfur reduction
Positive
Gelatin hydrolysis
Positive
Saccharose fermentation
Positive
Several methods have been used to inhibit swarming in Proteus vulgaris:
a) Cysteine lactose electrolyte deficient (CLED) agar: Proteus vulgaris does not show swarming on CLED agar.
b) Increasing the concentration of agar to 6% instead of 1 – 2%.
c) Incorporation of boric acid (1:1000), sodium azide (1:500) and chloral hydrate (1:500)
References
“Morphological Characteristics of P. vulgaris”. Archived from the original on 2017-07-06. Retrieved 2017-05-07.
vulgaris is tested using the API 20E identification system it produces positive results for sulfur reduction, urease production, tryptophan deaminase production, indole production, sometimes positive gelatinase activity, and saccharose fermentation, and negative results for the remainder of the tests on the testing ...
Proteus vulgaris is a rod-shaped, nitrate-reducing, indole-positive and catalase-positive, hydrogen sulfide-producing, Gram-negative bacterium that inhabits the intestinal tracts of humans and animals.
It is oxidase-negative but catalase- and nitrate-positive. Specific tests include positive urease (which is the fundamental test to differentiate Proteus from Salmonella) and phenylalanine deaminase tests. On the species level, indole is considered reliable, as it is positive for P. vulgaris, but negative for P.
MICROBIOLOGY. Aerobic, Gram-negative, urease-splitting rod. It is a non-lactose fermenter, indole-negative, oxidase-negative but catalase- and nitrate-positive.
P. vulgaris is a rod-shaped, chemoorganotrophic, Gram-negative bacteria between 1 and 3 microns in size (2). It is motile by peritrichous flagella, and does not have capsules or spores (2). A key characteristic of genus Proteus is swarming ability, and a simple Dienes test is used to differentiate between strains (17).
Proteus grows on the Blood agar plate in successive waves to form a thin filmy layer of concentric circles ( swarming). Proteus does not swarm in the MacConkey agar medium and forms smooth, pale or colorless (NLF) colonies.
P. vulgaris have two interesting features. The cells are highly motile and swarm across the surface of the agar plates, forming a very thin film of bacteria. When the cells stop and undergo a cycle of growth and division, the swarming periods are interspersed with periods and the colony has a distinct zonation.
Proteus mirabilis is a Proteus species that frequently causes urinary tract infections, while Proteus vulgaris is a Proteus species that causes urinary tract infections less frequently. This is the key difference between Proteus mirabilis and vulgaris.
Proteus organisms are easily recovered through routine laboratory cultures. Most strains are lactose-negative and demonstrate characteristic swarming motility on agar plates. Any positive culture result from an otherwise sterile area should be considered an acute infection if clinical signs and symptoms are present.
⇒ The Eosin Methylene Blue Agar (EMB Agar) medium can also be used for the cultivation of Proteus Vulgaris in laboratory contains Eosin dye and Methylene Blue dye which inhibits the growth of many gram-positive bacteria, inhibits the growth of Shigella and Salmonella species and supports the growth of Proteus Vulgaris.
The term 'indole-positive Proteus' which is often seen in the literature, may be a misnomer for any lactose-negative indole- and urease-forming member of the Enterobacteriaceae and therefore could represent several different bacteria. The only true 'indole-positive Proteus' is P.vulgaris.
P.vulgaris fermented glucose, sucrose, and maltose readily, while P. mirabilis fermented glucose readily and sucrose slowly and did not ferment maltose.
With the exception of Proteus, they are sometimes collectively referred to as the coliform bacilli because of shared properties, particularly the ability of most species to ferment the sugar lactose.
Proteus mirabilis and Proteus vulgaris are commensals of the normal flora of the human gastrointestinal tract, but they also can be found in water and soil. There are opportunistic pathogens that can infect the lungs, or wounds, and frequently cause urinary tract infections.
Most Proteus strains are susceptible to commonly used antibiotics, except nitrofurantoin and tetracycline. Like other members of Enterobacteriaceae, multidrug-resistant (MDR) strains of Proteus exist and are increasing in frequency; strains of P vulgaris are generally more resistant.
Proteus organisms are easily recovered through routine laboratory cultures. Most strains are lactose-negative and demonstrate characteristic swarming motility on agar plates. Any positive culture result from an otherwise sterile area should be considered an acute infection if clinical signs and symptoms are present.
P. vulgaris have two interesting features. The cells are highly motile and swarm across the surface of the agar plates, forming a very thin film of bacteria. When the cells stop and undergo a cycle of growth and division, the swarming periods are interspersed with periods and the colony has a distinct zonation.
Proteus mirabilis is a Proteus species that frequently causes urinary tract infections, while Proteus vulgaris is a Proteus species that causes urinary tract infections less frequently. This is the key difference between Proteus mirabilis and vulgaris.
⇒ The Eosin Methylene Blue Agar (EMB Agar) medium can also be used for the cultivation of Proteus Vulgaris in laboratory contains Eosin dye and Methylene Blue dye which inhibits the growth of many gram-positive bacteria, inhibits the growth of Shigella and Salmonella species and supports the growth of Proteus Vulgaris.
The term 'indole-positive Proteus' which is often seen in the literature, may be a misnomer for any lactose-negative indole- and urease-forming member of the Enterobacteriaceae and therefore could represent several different bacteria. The only true 'indole-positive Proteus' is P.vulgaris.
With the exception of Proteus, they are sometimes collectively referred to as the coliform bacilli because of shared properties, particularly the ability of most species to ferment the sugar lactose.
Proteus grows on the Blood agar plate in successive waves to form a thin filmy layer of concentric circles ( swarming). Proteus does not swarm in the MacConkey agar medium and forms smooth, pale or colorless (NLF) colonies.
P.vulgaris fermented glucose, sucrose, and maltose readily, while P. mirabilis fermented glucose readily and sucrose slowly and did not ferment maltose.
Proteus mirabilis and Proteus vulgaris are commensals of the normal flora of the human gastrointestinal tract, but they also can be found in water and soil.
Diagnosis. An alkaline urine sample is a possible sign of P. mirabilis. It can be diagnosed in the lab due to characteristic swarming motility, and inability to metabolize lactose (on a MacConkey agar plate, for example).
P. vulgaris, previously considered biogroup 2, has been reported to cause UTIs, wound infections, burn infections, bloodstream infections, and respiratory tract infections (71, 137).
E.coli will produced acid from fermenting lactose in the media and thus will turn the media yellow. P. vulgaris will not and the meda will remain a pinkish red color.
Eosin Methylene Blue (EMB) agar is a selective and differential culture medium. It selectively promotes the growth of Gram-negative bacteria and aids in the differentiation of lactose fermenter and non-lactose fermenting colonies. EMB Agar is used for the isolation of fecal coliforms.
A medium containing heart infusion agar supplemented with bile salts, lithium chloride, sodium thiosulfate, and sodium citrate was developed for the selective growth of Proteus.
Introduction: My name is Saturnina Altenwerth DVM, I am a witty, perfect, combative, beautiful, determined, fancy, determined person who loves writing and wants to share my knowledge and understanding with you.
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