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Selective medium for primary isolation of members of the tribe Proteeae
1Faculty of Science, Masaryk University, Brno, Czech Republic. urban@sci.muni.cz
Abstract:
A selective Proteeae medium (SPM) for isolation and preliminary detection of species of genera Proteus, Morganella, and Providencia was evaluated. The SPM contains tryptose phosphate agar with phenolphthalein monophosphate (as substrate for phosphatase activity), bile salts and polymyxin B (as inhibitors). The selectivity of the SPM was tested by the ecometric method of quality assurance of culture media. Fourteen reference cultures of enterobacteria and fifty-four strains of Proteeae were tested for their absolute growth index (AGI). Ninety-five percent of tested Proteeae strains display an AGI above 2.5. The detected phosphatase activity proved to be able to discriminate colonies of members of the tribe Proteeae. The ability of SPM for primary isolation of members of Proteeae was tested on food and clinical material and 94 strains were isolated. In addition, the SPM was employed in routine practice of clinical microbiology. From 1016 clinical samples (stool, urine, vaginal and urethral swabs), 57 strains of Proteeae were detected by the SPM in contrast to 35 strains by the routine procedure. The difference amounts to nearly 40%.
Insights
A new selective Proteeae medium (SPM) effectively isolates and detects Proteeae bacteria, including Proteus, Morganella, and Providencia. This method significantly improves detection rates in clinical samples compared to standard procedures.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Bacteriology
Background:
- The accurate isolation and identification of bacteria from the tribe Proteeae (Proteus, Morganella, and Providencia) are crucial in clinical and food microbiology.
- Existing culture media may lack the selectivity or sensitivity required for optimal detection of these opportunistic pathogens.
Purpose of the Study:
- To evaluate a novel selective Proteeae medium (SPM) for the isolation and preliminary detection of Proteeae species.
- To assess the selectivity and efficacy of SPM using reference strains and clinical samples.
Main Methods:
- SPM formulation: Tryptose phosphate agar with phenolphthalein monophosphate, bile salts, and polymyxin B.
- Ecometric method for quality assurance and selectivity testing.
- Testing with 14 enterobacteria reference cultures and 54 Proteeae strains to determine the absolute growth index (AGI).
- Evaluation of SPM on food and clinical materials for primary isolation.
- Comparison with routine methods in clinical microbiology using 1016 clinical samples.
Main Results:
- Ninety-five percent of tested Proteeae strains exhibited an AGI above 2.5, indicating good growth.
- Phosphatase activity detected by SPM effectively discriminated Proteeae colonies.
- SPM enabled the isolation of 94 Proteeae strains from food and clinical materials.
- In routine clinical practice, SPM detected 57 Proteeae strains from 1016 samples, compared to 35 strains by the routine procedure, a nearly 40% increase.
Conclusions:
- The developed selective Proteeae medium (SPM) demonstrates high selectivity and sensitivity for isolating and detecting Proteeae species.
- SPM offers a significant improvement in the detection of Proteeae in clinical microbiology settings.
- The medium's ability to detect phosphatase activity aids in the preliminary identification of these bacteria.