Which specimen type is collected directly from a sterile site?

The collection of a urine sample via catheter is the specimen type that is obtained directly from a sterile site, specifically the bladder. In this procedure, a catheter is inserted into the urethra and advanced into the bladder, allowing for the collection of urine that is free from contamination by surrounding tissues or external bacteria. This method is particularly useful in clinical scenarios where a clean voided sample might not be reliable, such as in patients with urinary tract infections.

In contrast, other specimen types like a throat swab, sputum sample, and ear swab are collected from areas that are not sterile. For instance, a throat swab involves collecting material from the oropharynx, which is populated with various bacteria and flora. Similarly, sputum samples are taken from the respiratory tract and can be contaminated with oral secretions. An ear swab, likewise, collects material from the ear canal, which is also not a sterile environment. Hence, the urine collected via catheter stands out as the only specimen type directly obtained from a sterile anatomical site.