Haemophilus aegyptius

Biochemical Test of Haemophilus aegyptius

Haemophilus aegyptius, commonly referred to as Koch-Weeks bacillus, is a pleomorphic, non-motile, Gram-negative coccobacillus that is mainly linked to acute conjunctivitis, or pink eye. In the lab, identifying this bacteria entails a battery of biochemical assays that take use of its distinct enzymatic and metabolic characteristics.

I will go into great depth about these tests here so that you may have a thorough grasp of the techniques utilized to identify Haemophilus aegyptius.

Haemophilus-influenzae

Gram Stain

Gram-negative Haemophilus aegyptius bacteria have pleomorphic rod-like or coccobacilli-like appearances. The Gram stain, which offers vital details about the morphology and staining properties of the bacteria, is frequently the initial step in identification.

Growth Requirements

Because Haemophilus aegyptius is a fussy eater, it needs enriched media for optimum growth. On chocolate agar, which provides vital growth nutrients, it develops effectively.

Haemophilus aegyptius
Haemophilus influenzae
  • X Factor (hemin): For growth, Haemophilus aegyptius needs X factor, a heme derivative. Because of the presence of X factor, colonies will form around the red blood cells on blood agar plates.
  • V Factor (NAD): V factor, a product of nicotinamide adenine dinucleotide (NAD), is also necessary for H. aegyptius. Colonies may grow slowly and be small if the V factor is not supplied.

Usually, after 24-48 hours of incubation at 35–37°C in an environment enhanced with CO2, growth on these media is seen.

Catalase Test

Haemophilus aegyptius had a positive catalase test. Hydrogen peroxide is added to a bacterium culture in this assay. Hydrogen peroxide will be broken down into water and oxygen by the catalase enzyme, resulting in the formation of visible bubbles.

Oxidase Test

Oxidase positive is Haemophilus aegyptius. The oxidase test determines whether cytochrome c oxidase is present. The existence of this enzyme is confirmed by a positive result, which is shown by a color change to dark purple or blue within 10 to 30 seconds after the oxidase reagent is applied.

Satellite Test

The test takes use of Haemophilus aegyptius’s need for V factor (NAD) and its incapacity to proliferate on blood agar unless it is in close proximity to an organism that produces V factor, such Staphylococcus aureus. H. aegyptius will grow as satellite colonies around the staphylococcal streak when cultured on blood agar alongside S. aureus.

Carbohydrate Utilization

The capacity of H. aegyptius to ferment different carbohydrates and produce acid but not gas allows for differentiation. Important tests consist of:

  • Glucose: Fermented with acid production.
  • Sucrose: Fermented with acid production.
  • Lactose: Not typically fermented.
  • Maltose: Fermented with acid production.

Nitrate Reduction Test

Nitrate is converted to nitrite by H. aegyptius. In order to detect nitrite, this technique entails inoculating a nitrate broth and then adding reagents. A positive outcome is shown by the color red. Zinc powder can be added to determine whether nitrate is present (no reduction) or absent (further reduction to nitrogen gas) if there is no color change.

Urease Test

Urease-negative is H. aegyptius. This test looks for a change in medium color, which indicates that the urease enzyme has hydrolyzed urea to produce ammonia and carbon dioxide.

Indole Production Test

Indole is not present in H. aegyptius. The indole test determines if the bacteria can convert tryptophan into indole. There is no red ring in a negative result when Kovac’s reagent is added.

Porphyrin Test

Based on their capacity to synthesis heme, Haemophilus species are distinguished using this test. Since H. aegyptius needs heme to grow, a negative result will indicate that it is unable to manufacture heme on its own. In the test, a medium containing delta-aminolevulinic acid is inoculated, and fluorescence is detected under UV light.

Motility Test

Homo aegyptius does not move. A semi-solid medium that restricts non-motile bacteria’s growth to the inoculation line can be used to verify this.

Conclusion

The identification of Haemophilus aegyptius involves a combination of Gram staining, growth requirements, and various biochemical tests. The organism’s fastidious nature necessitates enriched media for growth, and its biochemical profile—including catalase and oxidase positivity, specific carbohydrate fermentation patterns, and nitrate reduction—helps distinguish it from other bacteria. Accurate identification is crucial for diagnosing infections caused by H. aegyptius, particularly conjunctivitis, and for guiding appropriate treatment strategies.

Frequently Asked Question(FAQ)

What is the biochemistry of Haemophilus influenzae?

The hitA gene encodes a periplasmic iron-binding protein that is expressed by H. influenzae. Known to encode a traditional high affinity iron acquisition system consisting of hitA, hitB, and hitC (a nucleotide binding protein), this gene is arranged as the first of a three-gene operon.

Where are Haemophilus aegyptius bacteria found?

The Gram-negative bacterium Haemophilus influenzae biogroup aegyptius has the shape of an elongated rod [2]. Human epithelial cell linings are typically home to H. aegyptius [1], which may be seen adhering to and colonizing epithelial cells in huge clusters of elongated chains of cells [2]. In terms of biogroups, H.

Is Haemophilus influenzae catalase and oxidase positive?

A Gram-stained specimen of H. influenzae will reveal Gram-negative coccobacillus under a microscope. Catalase and oxidase testing, both of which should yield good results, can be used to further define the cultivated organism.

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