The Medical Importance of Proteus: Small Bacterium, Big Impact

Introduction Genus Proteus

Proteus, Providencia and Morganella are gram negative rods and they differ from other members of enterobacteriaceae by: Their ability to produce the enzyme urease and phenylalnine deaminase, Certain species are very motile and produce a striking swarming colonies on blood agar plate, and Cell wall O antigens of certain strains of Proteus (such as OX -2, OX-19 and OX-K) cross react with antigens of several species of rickettsia. Proteus species are found in the intestinal tract of humans and animals, soil, sewage and water. They are motile, non-capsulated and pleomorphic rods.

Species of medical importance of genus proteus are:

1. P. mirabilis:

A species of gram-negative, facultatively anaerobic, rod-shaped bacteria that is frequently isolated from clinical specimens. Its most common site of infection is the urinary tract. Pathogenesis and epidemiology: the organisms are present in the human colon as well as in soil and water. Their tendency to cause urinary tract infections is probably due to their presence in the colon and to colonization of the urethra, especially in women. The vigorous motility of proteus organisms may contribute to their ability to invade the urinary tract. Production of the enzyme urease is an important feature of the pathogenesis of urinary tract infections by this group. Urease hydrolysis the urea in urine to form ammonia, which raises the pH, producing an alkaline urine. This encourages the formation of stones called struvite composed of magnesium ammonium phosphate. Struvite stones often manifest as staghorn calculi in the renal pelvis. They obstruct urine flaw, damage urinary epithelium, and serve as a nidus for recurrent infection by trapping bacteria within the stone. Because alkaline urine also favors growth of the organisms and more extensive renal damage, treatment involves keeping the urine at a law Ph. prevention:  there are no specific preventive measures, but many hospital acquired urinary tract infections can be prevented by prompt removal of urinary catheters.

2. P. vulgaris:

A species of gram-negative, facultatively anaerobic, rod-shaped of bacteria that occurs in soil, fecal matter, and sewage. It is an opportunistic pathogen and causes cystitis and pyelonephritis. Important nosocomial pathogen. Isolated from wound infection and urinary tract infection. Proteus mirabilis infections usually respond better to antimicrobial therapy than those caused by P. vulgaris and other related organisms.

Virulence factors of genus proteus

These bacteria are characteristically highly motile and chemotaxis may play a part in pathogenesis, Strains of Proteus species produce proteases such as an IgAase. Proteus species and others urease producing organisms create alkaline conditions in the urine and may provoke the formation of calculi ( stones) in the urinary tract.

1.  Urease

Is a critical virulence determinant for colonization of the urinary tract, stone formation & the development of acute pyelonephritis. Urease –induced formation of ammonia protects the bacterial cell from the effects of complements.  Fimbriae also play a significant role in virulence for the urinary tract also have a role in the colonization of the upper part of the urinary tract. Their presence correlates with the development of acute pyelonephritis.

2. Hemolysins

Also known to be important virulence factor of proteus spp. Both HpmA & HlyA are cytotoxic for a wide variety of cell types, together with urease they play an important role in cell invasion & internalization. Hemolysins and urease are expressed at higher levels in P.  mirabilis than in P.vulgaris => this may be the explanation for the greater virulence of P.mirabilis.

Haw to diagnosis genus proteus

• Specimen: Urine, pus, blood, ear discharge.

• Smear: Gram-negative rods.

• Culture: Produce characteristic swarming colonies over the surface of blood agar.

• Are non-lactose fermenting colonies on MacConkey agar.

• Ether shaking technique to kill Proteus for isolation of other bacteria: when a mixed culture (Proteus and other bacteria) observed on blood agar plate, take a loop-full of mixed culture and mix it in ether solution. Ether specifically kills Proteus species which allows to isolate the other bacteria.

How to treatment proteus

• Aminoglycosides

• Trimethoprim-sulfamethoxazole

• Ampicillin – proteus mirabilis

• Cephalosporin

Conclusion

The genus Proteus consists of Gram-negative, facultatively anaerobic bacteria that are widely distributed in the environment and in the intestinal tract of humans and animals. They are best known for their characteristic swarming motility and ability to produce urease. Clinically, Proteus mirabilis and Proteus vulgaris are the most important species, often associated with urinary tract infections, wound infections, and septicemia, particularly in hospitalized or immunocompromised patients. Their ability to form biofilms, resist antibiotics, and alkalinize urine makes them significant pathogens in healthcare settings. Understanding their pathogenic mechanisms and implementing preventive measures is crucial for controlling Proteus-related infections.