Laboratory diagnosis of bone, joint, soft-tissue, and skin infections.

The diagnosis of infections of bones, joints, skin, and soft-tissues requires the combined use of a number of laboratory and pathology tests. The diagnosis of most infections requires microbiological cultures, both for isolation and for identification of causative organisms, as well as for antimicrobial susceptibility testing. Chemical analysis of joint fluids and histopathologic examination of infected tissues are often necessary to distinguish infections from other causes of inflammation, as well as to provide information as to the type of infection before the results of cultures are available.

Mucoid Pseudomonas in cystic fibrosis.

Pseudomonas aeruginosa is a frequent and virulent pulmonary pathogen in patients with cystic fibrosis. If colonization is not prevented, P aeruginosa becomes permanently established and nearly always mutates into a mucoid strain. The alginate-containing matrix of the mucoid strain is thought to allow the formation of protected microcolonies and provide increased resistance to opsonization, phagocytosis, and destruction by antibiotics.