The greatest concentration of gut bacteria is in the colon, while the small intestine is normally near sterile.

There are several types of collecting apparatus, but the general design uses a tube with a normally sterile inner liner and hard outer shell.

Various forms of instrumentation, including ventilation, inhibit the usual means of clearing organisms from normally sterile epithelial surfaces.

By reflux or suction of material from the nasopharynx into the normally sterile middle ear space, the fluid may then become infected - usually with bacteria.

If, however, it is grown from sites which would be normally sterile (e.g., blood), then it usually represents true infection.

Confirmed Case: Meet the probable case definition plus have pneumococcal infection confirmed by blood culture or other isolation of pneumococci from normally sterile site.

It can be grown in Sabouraud dextrose broth, a liquid medium used for cultivation of yeasts and molds from liquid which are normally sterile.

Specimens that are normally sterile, such as blood, urine or spinal fluid, are cultured under conditions designed to grow all possible organisms.

The region of the uterus and fallopian tubes is normally sterile.

Since blood is normally sterile, this process does not normally lead to the isolation of bacteria.