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Differentiation of fluorescent pseudomonads by their effect on milk agar
Abstract:
Eighty-six clinical isolates of fluorescent pseudomonads that did not produce pyocyanin on Diagnostic Sensitivity Test Agar or Cetrimide Agar were identified on the basis of their antibiotic sensitivity, production of pigment on King's "A" medium, growth at 42 degrees C, production of lecithinase and hydrolysis of gelatin. The identity of the strains was confirmed in tests with the ammonium salt sugars ethanol, glucose and mannitol. These tests were adequate for distinguishing between the three important fluorescent pseudomonads. The detection of casein hydrolysis on milk agar was assessed as a rapid method of distinguishing P. aeruginosa from the other species of fluorescent pseudomonads but proved unhelpful when compared with, or included in, a small set of tests. Most strains of P. aeruginosa and P. fluorescens hydrolysed casein.
Insights
This study identifies fluorescent pseudomonads using antibiotic sensitivity and biochemical tests. These methods effectively differentiate key species like Pseudomonas aeruginosa and Pseudomonas fluorescens.
Area of Science:
- Clinical microbiology
- Bacterial identification
- Pseudomonas species
Background:
- Fluorescent pseudomonads are clinically significant bacteria.
- Accurate identification is crucial for patient management.
- Distinguishing between species like P. aeruginosa and P. fluorescens can be challenging.
Purpose of the Study:
- To evaluate methods for identifying clinical isolates of fluorescent pseudomonads.
- To assess the utility of various biochemical and antibiotic sensitivity tests.
- To determine the effectiveness of casein hydrolysis for differentiating Pseudomonas species.
Main Methods:
- Identification of 86 clinical fluorescent pseudomonad isolates.
- Utilized antibiotic sensitivity, pigment production (King's "A" medium), growth at 42°C, lecithinase, and gelatin hydrolysis.
- Confirmed identities using ethanol, glucose, and mannitol fermentation tests.
- Assessed casein hydrolysis on milk agar for species differentiation.
Main Results:
- Antibiotic sensitivity and biochemical tests adequately distinguished between important fluorescent pseudomonads.
- Tests confirmed the identity of strains, including Pseudomonas aeruginosa and Pseudomonas fluorescens.
- Casein hydrolysis on milk agar was found to be unhelpful in differentiating P. aeruginosa from other species.
- Most P. aeruginosa and P. fluorescens strains hydrolyzed casein.
Conclusions:
- A combination of antibiotic sensitivity and key biochemical tests is sufficient for identifying important fluorescent pseudomonads.
- Casein hydrolysis is not a reliable differentiator for P. aeruginosa in this context.
- Accurate identification of fluorescent pseudomonads relies on a panel of established microbiological tests.