The Genera Proteus, Providencia, and Morganella
- PDF / 748,608 Bytes
- 25 Pages / 539 x 751 pts Page_size
- 24 Downloads / 286 Views
CHAPTER 3.3.12 ehT
areneG
, sue torP
a i cned i vorP
dna
a l l enagrM o
The Genera Proteus, Providencia, and Morganella JIM MANOS AND ROBERT BELAS
Introduction The three genera Proteus, Morganella and Providencia presently comprise a total of ten species. All are motile, Gram-negative rods with peritrichous flagella, and are assigned to the Enterobacteriaceae family mainly on the basis of shared biochemical characteristics. Most significantly, they are characterized by their ability to oxidatively deaminate phenylalanine and, in most cases (except for some Providencia spp.), to hydrolyze urea (Farmer et al., 1977; Moltke, 1927; Wenner and Retger, 1919). Unusual features include the ability of Proteus sp. to differentiate into swarmer cells upon colonization of solid surfaces. This topic will be covered in more detail in ensuing sections. Interest in the species comprising these genera has occurred mainly from a clinical perspective, as they include a number of significant human pathogens. In human disease, most infections are associated with prolonged hospitalization and in the case of Proteus and Morganella spp., colonization of indwelling catheters and associated urinary tract infections (UTIs).
Taxonomy and Phylogeny Before the advent of phylogenetically based classification, an array of biochemical tests formed the basis for taxonomic classification of the genera Proteus, Providencia, and after its separation into a new genus, Morganella. Tables 1 and 2 list the major biochemical tests used to compare and differentiate between the genera. As shown in Table 1, the most significant shared characteristics are the (oxidative) deamination of phenylalanine and tryptophan; both are used to distinguish between these three genera and other Enterobacteriaceae that do not produce these deaminases. The tests for production of these deaminases were developed in the 1950s and still are widely used (Henriksen, 1950; Thibault and Le Minor, 1957). Table 2 shows the biochemical tests that are commonly used to distinguish between these genera. The only test that will dis-
tinguish Morganella from Proteus and Providencia is the lysine iron agar test. On the other hand, several tests will distinguish Proteus from Providencia. Providencia is characterized by the production of acid from a variety of sugars, whereas Proteus is distinguished from Providencia by the hydrolysis of gelatin and the production of lipase and hydrogen sulfide. The use of molecular phylogenetic methods of classification has resulted in several species being reassigned to separate genera based on relatedness at the DNA level. These changes include: the new genus Morganella, with transfer of the species Proteus morganii to it (Brenner et al., 1978); the classification of Providencia alcalifaciens biogroup 3 as the separate species (Providencia rustigianii; Higashitani et al., 1995); and the identification of a subgroup within the latter as a distinct species, Providencia heimbachae (Muller et al., 1986b). Isolated in 1906 (Morgan, 1906), Morganella morganii was ori
Data Loading...
