To recover Chlamydia spp. from genital specimens, which procedure is appropriate?

Inoculating cycloheximide-treated McCoy cells is the appropriate procedure for recovering Chlamydia spp. because Chlamydia are obligate intracellular pathogens, meaning they must be grown within a host cell to replicate and survive. McCoy cells are tissue culture cells that provide the necessary environment for the growth of these bacteria. The addition of cycloheximide helps to inhibit the growth of contaminating bacteria, ensuring that any Chlamydia present can thrive in the culture without competition from other microbial flora.

The other options are not suitable for culturing Chlamydia. Blood and chocolate agar are designed for culturing a wide variety of bacteria, but they do not support the growth of obligate intracellular organisms like Chlamydia. Thioglycollate broth is generally used to grow anaerobic and facultatively anaerobic bacteria, and would likewise not support the specific growth requirements of Chlamydia. Modified Thayer-Martin agar is tailored for the growth of Neisseria gonorrhoeae and some other organisms, but it does not accommodate the intracellular lifestyle of Chlamydia. Therefore, using cycloheximide-treated McCoy cells is the established culture method for recovering Chlamydia from genital specimens.