Multiple choice Which one of the following does not grow on artificial media? Escherichia coli Rickettsias, chlamydias, Treponema pallidum Neisseria gonorrhoeae Mycobacterium leprae Both (2) and (4) Reveal answer Fill a bubble to check yourself E Correct answer Explanation Correct. Rickettsias, Chlamydias (obligate intracellular pathogens) and Treponema pallidum do not grow on artificial media and Mycobacterium leprae is grown in armadillos because of its low temperature.