CAMLPR Microbiology Practice Test 2026 - Free Microbiology Practice Questions and Study Guide

Spore placement in endospores is a key clue for identifying Clostridium species in anaerobic cultures. Clostridium tetani forms terminal endospores, giving a distinctive “drumstick” or tennis-racket appearance at the end of the Gram-positive rod. When you see those terminal spores in an anaerobic specimen, along with swarming growth on a rich anaerobic blood agar plate, it strongly points to the tetanus-causing organism. The other species typically show spores in subterminal or central positions and have different associated conditions, so they don’t fit this specific combination as well. Therefore, the organism most likely suspected is Clostridium tetani.