Bacteroides spp. - Introduction, Classification, Culture, Biochemical Characters

Classification of Bacteroides spp.

Domain: Bacteria

Phylum: Bacteroidota

Class: Bacteroidia

Order: Bacteroidales

Family: Bacteroidaceae

Genus: Bacteroides

Introduction of Bacteroides spp.

Bacteroides spp. is obligate, anaerobic, gram-negative rods, non-sporing, non-motile, and are normal flora of the human GI tract (typically isolated from mucosal surfaces of the oral cavity and GI tract).

In general, an infection caused by Bacteroides spp. group occurs below the diaphragm.

This classification is done on the basis of the microorganism's ability to break down types of sugar as a food source.

Asacchrolytic => Prophyromonas

Eg: Prophyromonas gingivalis (periodontal disease)

Moderately saccharolytic => inhibited by 20% bile => Pervotella

Eg: (Prophyromonas melanogenica, Prophyromonas denticola, Prophyromonas buccalis)

Saccharolytic => grow in 20% bile

Eg: Bacteriodes (Bacteroides fragilis). The commonly isolated spp. In clinical specimen is B. fragilis

Cultural characteristics of Bacteroides spp.

They can be cultured in artificial media- it forms non-hemolytic grey colonies of 1-3mm diameter in anaerobic BA.

In Bacteroides Bile Esculin medium (BBE), it gives glistering convex light to grey-colored colonies surrounded by a grey zone is obtained.

Other culture mediums for Bacteroides spp. are Thioglycolate broth (liquid medium) and Robertson’s cooked meat medium.

Biochemical characteristics of Bacteroides spp.

The biochemical characteristics of Bacteroides spp. includes:

• ferments sucrose

• grows in presence of 20% bile

• Indole: Negative

• Urease: Negative

• Catalase: Positive

• Oxidase: variable

• Esculin hydrolysis: Positive

• Arabinose: Negative

• Glucose: Positive

• Lactose: Positive

• Maltose: Positive

• Rhamnose: Negative

• Trehalose: Negative

• Salicin: Negative