General Overview
Proteus organisms are present in the human colon, soil and water. P. mirabilis and P. vulgaris cause infections to humans. Proteus species primarily cause urinary tract infections.
They mainly colonize in female urethra as they are present in colon.
In elderly and young males proteus is the common cause of urinary infections following catheterization or cystoscopy.
They can be both hospital-acquired and community- acquired.
In addition, infections are also associated with the presence of renal stones. Abdominal wound infections are also caused by Proteus species.
Furthermore, Proteus invade ulcers, pressure sores, burns and damaged tissues.
Proteus cause Septicemia and occasionally meningitis and chest infections.
The vigorous motility of Proteus mainly contributes for them to invade urinary tract.
Depending on the site of infection specimens are vary. Urine, pus, sputum is used for the laboratory diagnosis.
Microscopy
Proteus species is actively motile in wet preparations. Motility is easily observed at room temperature (20–28 ºC) than at 35–37 ºC.Â
Gram negative pleomorphic rods can be seen in Gram-stained smears. Presence with a capsule.
Culture
They are aerobic bacteria.
They cultured at 35–37 ºC aerobically on culture media.
Blood agar
Proteus produce a striking swarming effect on blood agar. They are like waves (characterized expanding rings).
Swarming occurs due to organism’s rapid motility on agar medium.
MacConkey agar
Produce non lactose fermenting pale colour colonies.
Proteus do not swarm on MacConkey agar.
XLD agar
On XLD agar Proteus mirabilis and Proteus vulgaris give yellow colour, transparent colonies with clear edges.Â
Specially in P. mirabilis, black centers can be seen.
P. morganii and P. rettgeri produce red transparent colonies on XLD agar.
Swarming is prevented by the bile salts containing in the medium.
CLED agar
Produce non lactose fermenting blue colour colonies on CLED agar.
Swarming is inhibited as the medium is electrolyte deficient.
- Do not ferment lactose
- Urease positive (rapidly positive within 4 hours)
- Phenylalanine deaminase test (PDA), positive
- ONPG test negative (Beta-galactosidase)
- Indole negative but vulgaris indole positive
- In VP test different species give different results ( vulgaris VP negative)
- Do not ferment mannitol
- Ferment glucose
- vulgaris sucrose positive and other strains give different results
- Oxidase negative
- Some strains of mirabilis are citrate positive. But others citrate negative or give different results
- Some species Indole positive ( vulgaris) and some species Indole negative (P. mirabilis)
- LDC (Lysine decarboxylase) test negative
- In KIA medium Proteus produce Yellow butt, pink slant, H2S positive and gas positive or negative. Gas production differ from species to species
Treatment
Most strains Of P. mirabilis which do not produce β-lactamase are sensitive to benzylpenicillin, ampicillin and most other β-lactam antibiotics.
vulgaris species usually resistant to penicillins and many types of cephalosporins.
However, P. vulgaris might be sensitive to β-lactamase-stable derivatives like cefotaxime.
All strains are resistant to tetracyclines and polymyxins.
Proteus are inherently sensitive to aminoglycosides.
However, there may be some enzymic or non-enzymic resistance mechanisms.
Urinary tract infections caused by Proteus cannot be cured by nitrofurantoin.
They may can treated with ampicillin or trimethoprim. Infections associated with renal stones, often cannot be treated successfully.
However, antibiotic sensitivity testing should be done as susceptibility to antibiotics is unpredictable.
Prevention
There is no any vaccine found for the prevention of the disease.
Taking hygienic measures and following of aseptic procedures may reduce the infections caused by Proteus species.
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