Proteus spp. as Putative Gastrointestinal Pathogens

Abstract

Proteus species, members of the Enterobacteriaceae family, are usually considered commensals in the gut and are most commonly recognized clinically as a cause of urinary tract infections. However, the recent identification of Proteus spp. as potential pathogens in Crohn's disease recurrence after intestinal resection serves as a stimulus to examine their potential role as gut pathogens. Proteus species possess many virulence factors potentially relevant to gastrointestinal pathogenicity, including motility; adherence; the production of urease, hemolysins, and IgA proteases; and the ability to acquire antibiotic resistance. Gastrointestinal conditions that have been linked to Proteus include gastroenteritis (spontaneous and foodborne), nosocomial infections, appendicitis, colonization of devices such as nasogastric tubes, and Crohn's disease. The association of Proteus species with Crohn's disease was particularly strong. Proteus species are low-abundance commensals of the human gut that harbor significant pathogenic potential; further investigation is needed.

Keywords: Crohn's disease; Enterobacteriaceae; Proteus; bacteriology; gastrointestinal disease; infections; inflammatory bowel disease.

FIG 1

Phylogenetic tree showing the species from the Enterobacteriaceae family that colonize the human gastrointestinal tract. GenBank accession numbers of the16S rRNA gene sequences are provided for each species, and the family names are indicated. E. coli is highlighted in green, and the Proteus genus is shown in blue. (Reproduced from reference .)

FIG 2

(Top) Strain of P. mirabilis inoculated twice, 1 h apart, demonstrating the macroscopic characteristic bull's-eye pattern produced by periodic swarming. (Reproduced with permission from reference .) (Bottom left) Interacting P. mirabilis swarmer cells; (bottom right) combination of swimmer and swarmer cells within a biofilm. (Both panels reproduced from reference with permission from Elsevier.)

FIG 3

Potentially important Proteus-related virulence factors in relation to anatomical disease location and disease. *, immune evasion includes the production of the ZapA metalloprotease, O-antigens, and flagellin variation.