Usefulness of trehalose fermentation and L-glutamic acid decarboxylation for identification of biochemically aberrant Providencia stuartii strains

Abstract

Providencia isolates were collected during a 4-year period when an increased incidence of nosocomial Providencia stuartii infection was noted in urologic wards. Of these isolates, 630 were identified as P. stuartii, 206 were identified as Providencia rettgeri, and 1 was identified as Providencia alcalifaciens. Twelve inositol-positive isolates from 10 patients (10 strains) resembled P. stuartii in fermenting trehalose but resembled P. rettgeri in fermenting D-arabitol or meso-erythritol or both. The latter traits, however, were not stable in all cases. These aberrant strains were identified as P. stuartii on the basis of their O antigens and DNA hybridization experiments. Ail isolates were tested for L-glutamic acid decarboxylase activity by a qualitative thin-layer chromatography method. All P. stuartii isolates, including the aberrant ones, were trehalose positive and L-glutamic acid decarboxylase negative. None of the P. retfgeri isolates fermented trehalose, while 99.0% of them and the single P. alcalifaciens strain were L-glutamic acid decarboxylase positive. Thus, trehalose fermentation and L-glutamic acid decarboxylation are more useful for separating P. stuartii from P. rettgeri than are D-arabitol and meso-erythritol fermentation.

Classification, Identification, and Clinical Significance ofProteus,Providencia, andMorganella

“…Fischer et al successfully employed L-glutamic acid decarboxylase to differentiate between P. rettgeri and P. stuartii (33), but the method is very cumbersome, making it unappealing to clinical laboratories. The production of acid from trehalose or D-arabitol will generally separate the two species.…”

A modified MacConkey medium which allows the recognition of Enterobacteriaceae from other Gram-negative bacteria on primary culture plates

“…In order to determine whether novel formulation could influence growth of gram-negative bacteria, serial dilutions from 10-2 to 10-6 in sterile saline of overnight broth cultures of 41 gram-negative strains (i.e., 3 Escherichia coli, 2 Citrobacter diversus, 3 Citrobacter freundii, 4 Klebsiella pneumoniae, 4 Proteus mirabilis, 4 P. stuartii, 3 Salmonella choleraesuis subsp. choleraesuis, 2 Shigella flexneri, 4 Yersinia enterocolitica, 4 Serratia liquefaciens, 4 Pseudomonas aeruginosa, and 4 Xanthomonas maltophilia species) were inoculated on both MCP and MacConkey media. After 24 h of incubation at 37°C, the plates were examined for number and size of grown colonies.…”

Modified MacConkey medium which allows simple and reliable identification of Providencia stuartii

“…In order to determine whether novel formulation could influence growth of gram-negative bacteria, serial dilutions from 10-2 to 10-6 in sterile saline of overnight broth cultures of 41 gram-negative strains (i.e., 3 Escherichia coli, 2 Citrobacter diversus, 3 Citrobacter freundii, 4 Klebsiella pneumoniae, 4 Proteus mirabilis, 4 P. stuartii, 3 Salmonella choleraesuis subsp. choleraesuis, 2 Shigella flexneri, 4 Yersinia enterocolitica, 4 Serratia liquefaciens, 4 Pseudomonas aeruginosa, and 4 Xanthomonas maltophilia species) were inoculated on both MCP and MacConkey media. After 24 h of incubation at 37°C, the plates were examined for number and size of grown colonies.…”