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Identification of Proteus morganii and distinction from other Proteus species
Abstract:
The identification of Proteus morganii in the clinical laboratory is complicated by the differences in incidence of hydrogen sulfide (H2S) production recorded by different sources. Since this quality appeared to be a frequent feature of strains of P. morganii at the author's center, all isolates of this species were studied over a six-month period. During this time, 12 of 21 were found to produce scant H2S in Kligler's iron agar (KIA) and triple-sugar iron (TSI) agar butts. The strains were, in every respect, biotypical, and were easily distinguished from other species of Enterobacteriaceae by biochemical study. They also possessed the features of high resistance to cephalothin and ampicillin and relative sensitivity to tetracycline, unlike strains of Proteus mirabilis. It is concluded that weak H2S production in TSI or KIA medium is a frequent normal characteristic of P. morganii, and its presence should not deter microbiologists from correctly identifying isolates manifesting this quality.
Insights
Weak hydrogen sulfide (H2S) production is common in Proteus morganii, a characteristic that should not hinder its identification. This finding clarifies a common diagnostic challenge for clinical laboratories.
Area of Science:
- Clinical Microbiology
- Bacteriology
- Medical Laboratory Science
Background:
- Accurate identification of Proteus morganii is crucial in clinical settings.
- Variability in reported hydrogen sulfide (H2S) production complicates P. morganii identification.
- H2S production is a key biochemical test in bacterial identification.
Purpose of the Study:
- To investigate the incidence of H2S production in clinical isolates of Proteus morganii.
- To determine if weak H2S production is a normal characteristic of P. morganii.
- To clarify diagnostic criteria for P. morganii identification.
Main Methods:
- Studied 21 clinical isolates of Proteus morganii over a six-month period.
- Assessed H2S production using Kligler's iron agar (KIA) and triple-sugar iron (TSI) agar.
- Performed comprehensive biochemical characterization and antimicrobial susceptibility testing.
Main Results:
- 12 out of 21 (approximately 57%) P. morganii isolates produced scant H2S in KIA and TSI.
- All isolates were biotypically consistent with P. morganii and distinguishable from other Enterobacteriaceae.
- Isolates showed high resistance to cephalothin and ampicillin, and sensitivity to tetracycline.
Conclusions:
- Weak H2S production in TSI or KIA is a frequent and normal characteristic of Proteus morganii.
- Microbiologists should not let weak H2S production deter the correct identification of P. morganii.
- Understanding this characteristic improves diagnostic accuracy for P. morganii.