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The Aggregatibacter actinomycetemcomitans

Background

There is a strong relationship between the presence of A.a. and the occurrence of juvenile and refractory periodontitis. In this situation, the bacteria is often only present in very high numbers, without the other paropathogens being detected. A.a. cannot be removed mechanically (scaling and root planing) because it occurs everywhere in the mouth, not just in the periodontal pocket. A.a. has been shown to be transferable, especially vertically from parent to child.

Risk

Mainly because of the many enzymes that this bacteria can make, this bacterium is able to use many substances as a food source. As a result, he can cause a lot of tissue damage. It also induces very strong immune reactions. The A.a. bacteria produces substances (leukotoxins) that are toxic to leukocytes and monocytes. Other virulence factors include the production of toxins that take over the control system of eukariotic cells (cytolethal distending toxins) and immunosuppression factors that inhibit blastogenesis and antibody production and activate T-supressor cells. Publications indicate that the A.a. bacteria is probably involved in endocarditis and pneumonia.

Colony characteristics

On a special agar plate, you can see colonies with a star-shaped pattern. As a result, the A.a. is easily recognisable when grown. It is a facultative anaerobic bacteria, so it grows in both oxygen-rich and oxygen-poor environments at an increased concentration of CO2. The bacteria is visible under the microscope as a Gram-negative rod.

Antibiotic sensitivity

A.a. is sensitive to amoxicillin, clarithromycin and doxycycline but virtually insensitive to metronidazole.