PROTEUS BACTERIUMBy. Dominic Edward Z. Tomas

Proteus is a genus of Gram-negative Proteobacteria, family of Enterobacteriaceae.

Proteus species do not usually ferment lactose, but have shown to be capable lactose fermenters depending on the species in a triple sugar iron (TSI) test.

General characters: It is oxidase-negative, but catalase- and nitrase-positive. Specific tests include positive urease and phenylalanine deaminase tests.

On the species level, indole is considered reliable, as it is positive for Proteus vulgaris but negative for Proteus mirabilis.

  Some species are motile.

It has a characteristic "swarming" pattern.

What is Proteus?

Scientific classification Kingdom: Bacteria Phylum: Proteobacteria Class: Gamma Proteobacteria Order: Enterobacteriales Family: Enterobacteriaceae Genus: Proteus Species: P. vulgaris

Proteus vulgaris

Swarming motility is a rapid (2-10 μm/s.) and coordinated translocation of a bacterial population across solid or semi-solid surfaces.

Figure 1. Proteus vulgaris

Non-lactose fermenters with slight swarming.

Figure 2. Proteus vulgaris

EMB agar plate inoculated with Proteus vulgaris (a gram-negative coliform bacterium) showing growth of pink colonies indicating non-lactose fermentation and some acid production.

Figure 3. Proteus vulgaris

First, the cells are highly motile and often swarm across the surface of agar plates (Figure A). Swarming gives rise to a very thin film of bacteria on the agar surface, but swarming periods are interspersed with periods when the cells stop and undergo a cycle of growth and division so that the colony has a distinct zonation.

The other notable feature of both Proteus and Providentia is the ability to degrade urea to ammonia, by production of the enzyme urease (Figure B). Bacteria isolated from urine samples are inoculated onto a nutrient agar containing urea and the indicator phenol red. After overnight incubation, the ammonia produced by Proteus or Providentia raises the pH and changes the colour of the medium from yellow to red.

Scientific classification Kingdom: Bacteria Phylum: Proteobacteria Class: Gamma Proteobacteria Order: Enterobacteriales Family: Enterobacteriaceae Genus: Proteus Species: P. mirabilis

Proteus mirabilis

P. mirabilis on an XLD agar plate.

Figure 4. Proteus mirabilis

Bacteria of the species Proteus mirabilis are widely distributed in soil and water in the natural environment.

In humans, Proteus is found as part of the normal flora of the gut. Its main pathological role is in infections of the urinary tract, but it can also cause wound infections and septicaemia.

About a quarter of the human population will have Pr. mirabilis in their faeces. Infection is often by the strains resident in the patient’s faeces.

Proteus mirabilis

Proteus can exist in two distinct morphological and physiological forms, known as swimmer cells and swarmer cells.

In aqueous suspension Pr. mirabilis is found in the swimmer state, small rod-like cells1 to 2 μm in length motile by 8 to 10 flagella.

On contact with a surface, Proteus has the ability to convert to the swarmer state. The bacterial cells elongate dramatically to form highly flagellated filaments 20 to 80 μm in length. These cells line up in parallel to form rafts that are able to move rapidly over surfaces en masse.

Physiologically, there is a significant increase in protein synthesis and urease is produced in amounts 30 to 80 times higher than in the swimmer state.

Proteus mirabilis

Electron micrograph of Proteus mirabilis swarmer cells moving across a surface.

Figure 5. Proteus mirabilis

P. vulgaris, P. mirabilis, and P. penneri—are opportunistic human pathogens.

Proteus includes pathogens responsible for many human urinary tract infections.

Proteus mirabilis causes of wound and urinary tract infections. Most strains of Proteus mirabilis are sensitive to ampicillin and cephalosporins. Once attached to urinary tract, infects the kidney more commonly than E. coli. Proteus mirabilis are often found as free-living organisms in soil and water.

Proteus vulgaris is not sensitive to these antibiotics. However, this organism is isolated less often in the laboratory and usually only targets immunosuppressed individuals. Proteus vulgaris occurs naturally in the intestines of humans and a wide variety of animals; also manure, soil and polluted waters.

Clinical significance

Nosocomial infections

Proteus mirabilis causes 90% of Proteus infections.

Proteus vulgaris and Proteus penneri are easily isolated from individuals in long-term care facilities and hospitals and from patients with underlying diseases or compromised immune systems.

Patients with recurrent infections, those with structural abnormalities of the urinary tract, those who have had urethral instrumentation, and those whose infections were acquired in the hospital have an increased frequency of infection caused by Proteus and other organisms (e.g. Klebsiella, Enterobacter, Pseudomonas, enterococci, staphylococci)

Proteus Infections

Known antibiotics that P. vulgaris is sensitive to:

Ciprofloxacin Ceftazidime Netilmicin Sulbactam or Cefoperazo Meropenem Piperacil or Tazobactam Unasyn

  Antibiotics should be introduced in much higher doses than "normal"

when P. vulgaris has infected the sinus or respiratory tissues. I.E.

Ciprofloxacin should be introduced at a level of at least 2000 mg per day orally in such a situation, rather than the "standard" 1000 mg per day.

Treatment – Proteus vulgaris

P. mirabilis is generally susceptible to most antibiotics apart from tetracycline, however 10%–20% of P. mirabilis strains are also resistant to first generation cephalosporins and ampicillins.

Treatment – Proteus mirabilis

Indole negative and Nitrate reductase positive (no gas bubbles produced)

Methyl Red negative and Voges-Proskauer positive

Catalase positive and CytochromeOxidase negative

Phenylalanine

Deaminase positive Trytophan test-

negative Urea test- positive Casein test-negative Starch test- negative Hydrogen sufide test-

positive Citrate agar test-

positive

Micro-organism Tests

A. Salmonella sp.B. Escherichia coli

C. UnknownD. Proteus mirabilis

Figure 6. Appearace of Enteric Organisms on Triple Sugar Iron Medium