Targeted Mutagenesis in the Study of the Tight Adherence (tad) Locus of Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans is a Gram-negative, capnophilic (CO2 loving), coccobacillus found only in humans and Old World primates (for reviews, see Henderson et al., 2003, 2010). This bacterium is primarily known as the etiologic agent of Localized Aggressive Periodontitis (LAP), which is predominantly an infection of adolescents (Slots & Ting, 1999; Zambon, 1985). A. actinomycetemcomitans also causes extraoral infections, including infective endocarditis, septicemia, and abscesses (Fine et al., 2006; Fives-Taylor et al., 1999; Rahamat-Langendoen et al., 2011; van Winkelhoff & Slots 1999). A. actinomycetemcomitans is a member of the HACEK group of Gram-negative bacteria, all of which can cause infective endocarditis (Paturel et al., 2004). Most HACEK bacteria-caused cases of infective endocarditis result from A. actinomycetemcomitans. Poor oral health is a risk factor for developing severe extraoral infections by A. actinomycetemcomitans (Paturel et al., 2004; van Winkelhoff & Slots 1999). One study showed that 16% of patients with infective endocarditis from A. actinomycetemcomitans had dental procedures immediately prior to the onset of disease. A staggering 42% of A. actinomycetemcomitans-caused infective endocarditis patients had generalized dental disease  an indication of poor overall oral health.