Читать книгу Cases in Medical Microbiology and Infectious Diseases - Melissa B. Miller - Страница 31

Both Chlamydia, a bacterium, and the viruses are obligate intracellular parasites. As such, they do not grow on artificial media, as fungi and other bacteria do. Rather, they can only grow by parasitizing living animal cells (including human cells) that are maintained by continuous tissue culture. Animals such as mice, or chicken eggs, can be inoculated in an attempt to isolate certain viruses, but this approach is rarely done. Tissue culture for Chlamydia may still be attempted, especially in situations where the detection of C. trachomatis is at issue in a legal proceeding, such as a case of sexual abuse of a child. However, molecular detection has become the standard method for diagnosis of C. trachomatis infection.

Tissue culture is still an important technique for the detection of viruses in many laboratories, though laboratories are converting to molecular methods for viral detection at an increasing rate. Herpes simplex virus can be isolated from skin and genital tract lesions, often within the first 24 hours of incubation. Another herpesvirus, varicella-zoster virus, the etiologic agent of chicken pox and herpes zoster, can also be isolated from skin lesions, but it typically requires 3 to 7 days to grow. The enteroviruses are the major etiologic agents of aseptic meningitis and can be isolated from cerebrospinal fluid, but at a significantly reduced rate compared with molecular detection.

A modification of the tissue culture technique is done to detect cytomegalovirus and several respiratory viruses in clinical specimens called rapid centrifugation cultures or shell vial cultures. In this method, the specimen is centrifuged onto tissue culture cells that are growing on a round glass coverslip inside a vial referred to as a shell vial. The cells are incubated for a brief period of time (24 to 72 hours) and then stained with fluorescent antibodies to detect the virus. This technique is much more rapid and sensitive than conventional tissue culture but is still less sensitive than molecular detection.