Oral infections - Laboratory Diagnosis

Laboratory diagnosis of oral infections

The laboratory diagnosis of oral infections is as follows:

Sample

• Oral swabs

• pus

Collection and transport

It is important to minimize contamination with oral flora when collecting oral, and dental samples. Contamination can not be completely avoided. For root canal infections, first, the tooth is swabbed with 70% alcohol and then the root canal is exposed.

A sterile paper point is inserted, removed, and placed into a semisolid, non-nutritive, anaerobic transport medium. Needle aspiration can be used as an alternative.

Microscopy

Materials submitted for culture should be smeared, gram-stained, and microscopically examined.

Culture

The anaerobes involved in oral infections are much more delicate and can be cultured. Thus, methods should be used to recover them.

Identification etiological agents

Diagnosis of Actinobacillus actinomycetocomitans

• Gram-negative

• Grows in NA in microaerophilic condition

• star-shaped

• 24-48 hours incubation at 37°C

• motility negative

• growth in MA negative

• Acid from glucose positive

• β- hemolysis negative

• Catalase negative

• Oxidase positive

• Indole negative

Diagnosis of Fusobacterium nucleatum

• slender, spindle-shaped gram-negative rods with tapering ends

• on BA <1mm, circular irregular colonies

• greenish discoloration when exposed to O2

• Non-saccharolytic

Diagnosis of Leptotrichal buccalis

• gram-negative rod, 1.5x1 micrometer

• BA: 2-3mm irregular colony

• sensitive to Metronidazole

Diagnosis of Pervotella melanogenica

• Non-motile, non-sporing, small, gram negative, coccobacilli

• grow well in freshly prepared BA

• opaque, very small colonies on BA

• colonies change from light grey to brown due to pigment production

• saccharolytic

• bile sensitive

Diagnosis of Pervotella intermedia

• isolated in a selective medium which is a BA base containing sulfamethoxazole, Trimethoprim lactate, and defibrinated horse blood.

• The sample is inoculated in the selective agar and incubated in a gas system for 7 days.

• It gives black-pigmented colonies

• gram-negative rods

• Fluorescent under UV light with a wavelength of 366nm and the ability to ferment lactose.