Biochemical Test of Providencia stuartii

The biochemical test of Providencia stuartii refers to the group of laboratory tests that are used to identify this bacterium on the basis of its metabolic and enzymatic activities. It is a Gram-negative rod shaped facultative anaerobic organism belonging to the family Morganellaceae. In clinical microbiology these tests is carried out to differentiate Providencia stuartii from other members of Enterobacteriaceae like Proteus, Morganella, Escherichia and Klebsiella. Identification is mainly based on carbohydrate fermentation pattern enzyme production and decarboxylation reactions.

Providencia stuartii shows a characteristic positive reaction for Phenylalanine Deaminase (TDA) test. This is the major biochemical feature of members of tribe Proteeae. In this test phenylalanine is deaminated and after addition of ferric chloride a reddish brown colour is produced. This reaction helps in immediate differentiation from non-Proteeae organisms. The organism is indole positive methyl red positive Voges-Proskauer negative and citrate positive (though citrate reaction may be variable in few strains). Hydrogen sulphide (H₂S) production is absent which helps in separating it from Proteus species.

In carbohydrate fermentation tests Providencia stuartii is a non-lactose fermenter and does not produce acid from lactose. It is negative for mannitol and adonitol fermentation which is useful in differentiating it from Providencia rettgeri. It ferments trehalose and is usually positive for inositol fermentation. The organism is negative for lysine decarboxylase ornithine decarboxylase and arginine dihydrolase tests. Urease activity is generally negative or variable and is weaker when compared to Proteus. It is catalase positive and oxidase negative.

Thus biochemical testing of Providencia stuartii includes a combination of TDA test IMViC reactions carbohydrate fermentation pattern and decarboxylase tests. These reactions together form a distinct biochemical profile which is used for its accurate identification in routine diagnostic laboratories. Accurate identification is important because Providencia stuartii is commonly associated with catheter associated urinary tract infections and shows high level of intrinsic and acquired antibiotic resistance.

Biochemical Tests for Providencia stuartii and Results

The biochemical tests of Providencia stuartii are carried out to identify the organism based on its enzymatic activities and carbohydrate utilization pattern. These tests helps in differentiating it from other members of tribe Proteeae and Enterobacteriaceae.

Core Enzymatic and Physiological Tests

• Phenylalanine Deaminase (TDA / PAD) – Positive
• Oxidase – Negative
• Catalase – Positive
• Hydrogen sulphide (H₂S) production – Negative
• Motility – Positive
• Nitrate reduction – Positive
• Gas from glucose – Negative
• Growth in KCN – Positive
• Gelatin hydrolysis – Negative
• Urease – Variable (usually negative)

IMViC Tests

• Indole test – Positive
• Methyl red test – Positive
• Voges–Proskauer test – Negative
• Citrate utilization – Positive

Amino Acid Decarboxylation Tests

• Arginine dihydrolase (ADH) – Negative
• Lysine decarboxylase (LDC) – Negative
• Ornithine decarboxylase (ODC) – Negative

Carbohydrate Fermentation Tests

• Glucose – Positive (acid only no gas)
• Lactose – Negative
• Mannitol – Negative
• Inositol – Positive
• Trehalose – Positive
• Mannose – Positive
• Galactose – Negative
• Sucrose – Variable
• Adonitol – Negative
• Arabinose – Negative
• Sorbitol – Negative
• Maltose – Negative
• Rhamnose – Negative
• Salicin – Negative

Other Biochemical Tests

• ONPG (β-galactosidase) – Negative
• Malonate utilization – Negative
• Esculin hydrolysis – Negative
• Acetate utilization – Positive
• Tartrate (Jordan’s) – Positive
• DNase test – Negative
• Lipase test – Negative

These biochemical reactions together forms a characteristic profile of Providencia stuartii which is useful in its laboratory identification and differentiation from other closely related organisms.

Summary Table of Biochemical Tests for Providencia stuartii

This table summarizes the important biochemical reactions of Providencia stuartii used for its identification in microbiology laboratory.