Aggregatibacter

Aggregatibacter is a genus of Gram-negative bacteria that are part of the family Pasteurellaceae. This genus includes several species that are known to be pathogenic in humans, most notably Aggregatibacter actinomycetemcomitans, which is associated with periodontal disease.

Taxonomy

The genus Aggregatibacter was established to accommodate species previously classified under the genus Actinobacillus. The reclassification was based on phylogenetic studies that demonstrated distinct genetic differences warranting a separate genus.

Species

The genus Aggregatibacter includes the following species:

• Aggregatibacter actinomycetemcomitans
• Aggregatibacter aphrophilus
• Aggregatibacter segnis

Morphology

Aggregatibacter species are small, non-motile, facultatively anaerobic, and coccobacilli in shape. They are known to form characteristic star-shaped colonies on certain agar media.

Pathogenicity

Aggregatibacter actinomycetemcomitans is a well-known pathogen in humans, primarily associated with periodontitis, a serious gum infection that damages the soft tissue and destroys the bone that supports the teeth. It is also implicated in other systemic infections such as endocarditis and bacteremia.

Periodontal Disease

Aggregatibacter actinomycetemcomitans is a key pathogen in aggressive periodontitis, particularly in adolescents and young adults. It produces several virulence factors, including leukotoxin, which can kill white blood cells, and a cytolethal distending toxin that can disrupt cell division.

Systemic Infections

In addition to periodontal disease, Aggregatibacter species can cause systemic infections. A. actinomycetemcomitans has been isolated from cases of infective endocarditis, a condition where the inner lining of the heart chambers and valves become infected. It can also cause bacteremia, where bacteria enter the bloodstream, potentially leading to serious complications.

Diagnosis

Diagnosis of infections caused by Aggregatibacter species typically involves microbiological culture and identification from clinical specimens. Molecular techniques such as polymerase chain reaction (PCR) can also be used to detect specific bacterial DNA in samples.

Treatment

Treatment of infections caused by Aggregatibacter species often involves the use of antibiotics. Commonly used antibiotics include amoxicillin, metronidazole, and doxycycline. In cases of periodontal disease, mechanical debridement of the affected area is also necessary to remove bacterial biofilms.

Prevention

Preventive measures for infections caused by Aggregatibacter species include maintaining good oral hygiene to prevent periodontal disease. Regular dental check-ups and professional cleanings can help reduce the risk of infection.

Research

Ongoing research is focused on understanding the virulence mechanisms of Aggregatibacter species and developing new therapeutic strategies to combat infections. Studies are also exploring the role of these bacteria in systemic diseases beyond the oral cavity.

See also

• Periodontal disease
• Endocarditis
• Bacteremia