[7] In 1981, Hickman et al conducted experiments on 20 indole-negative strains previously grouped with P.vulgaris and demonstrated the existence of three P. vulgaris biogroups.

[9] Similar to other Proteus species, P. penneri has a cell-bound hemolytic factor, which has been shown to facilitate penetration of the organism into cultured Vero cells without any cytotoxic effects.

[11] These differences have been used to cluster P. penneri strains into serogroups based on their agglutinating activity when mixed with antibodies directed against specific species of LPS molecules.

[12] Presently, 15 O-serogroups have been proposed for P. penneri based on the chemical structure of the O-specific polysaccharide chain (O-antigen) of the lipopolysaccharide.

[12] The occurrence of P. penneri organisms in the normal intestine accounts for their higher frequency in urinary tract infections and for their role as opportunistic invaders after surgery.

Certain strains of P. penneri can differentiate into elongated hyperflagelled cells during development on solid media, resulting in the surface translocation event identified as “swarming”.

[9] Since P. penneri was only recently recognized as a new species, many bacteriologists are either generally unaware of it, or have made limited attempts to discover its clinical significance.

Documented human clinical infections caused by P. penneri have been limited to the urinary tract and to wounds of the abdomen, groin, neck, and ankle.

[8] This species is isolated from individuals in long-term care facilities and hospitals and from patients who are immunocompromised or suffering from underlying disease.

[19] Furthermore, in an experiment conducted in India, P. penneri strains were isolated as the sole pathogen in all patients having underlying disease postoperatively.

[2] These include adherence due to the presence of fimbriae or afimbrial adhesins, invasiveness, swarming phenomenon, hemolytic activity, urea hydrolysis, proteolysis, and endotoxicity.

[21] Swarming motility is the coordinated translocation of a bacterial population driven by flagellar rotation in film or on fluid surfaces.

In vitro studies of ceftizoxime, ceftazidime, moxalactam, and cefoxitin suggest these agents also may prove to be clinically useful in treating infections caused by P.