Which of the following is the most common organism found in retreatment cases of periapical abscess?
(A) E. faecalis (B) Trepenoma denticola (C) S. mutans (D) Actinomyces
(A) PERSISTENT APICAL PERIODONTITIS

It is post-treatment apical periodontitis in an endodontically treated tooth (re-treatment case).
Enterococcus faecalis is found the most consistently reported organism in persistent apical periodontitis.