Articles on Medical Diseases and Conditions

ARF is a disease that has a specific etiologic agent yet has some similarities to the rheumatoid-collagen-vascular group. The etiologic agent is the beta-hemolytic Lancefield group A Streptococcus. Apparent hypersensitivity or other effect of this organism causes connective tissue changes manifested by focal necrosis of collagen and the development of peculiar aggregates of histiocytes called […]

Pressure Reference values for cerebrospinal fluid (CSF) pressure are 100-200 mm H2O. Elevations are due to increased intracranial pressure. The two most common causes of elevated CSF pressure are meningitis and subarachnoid hemorrhage. Brain tumor and brain abscess will cause increased intracranial pressure in most cases but only after a variable period of days or […]

Varicella-zoster virus (VZV) is a member of the herpesvirus group. Infection is spread through direct contact with skin lesions or through droplet inhalation. The incubation period is about 14 days (range, 9-21 days). Primary infection is usually varicella (chickenpox). The period of skin rash lasts about 4-6 days. This may be preceded by a short […]

The HIVs are retroviruses; their genetic information (genome) is composed of RNA rather than the usual DNA. To reproduce, the virus uses an enzyme known as reverse transcriptase to produce a DNA copy of its genetic RNA and incorporates this material into the host cell genetic material. Some of the copied viral genome also exists […]

Culture. Until the 1980s, except in a relatively few cases the only available laboratory methods were culture and serologic tests for antibodies. There have been significant advances in culture techniques in the past few years, but most virus culture still is difficult and expensive. Culture is performed using living cell preparations or in living tissues. […]

Certain fungi, known as the deep or systemic fungi, are characterized by involvement of visceral organs or penetrating types of infection. Besides true fungi, actinomycetes and nocardiae are bacteria that produce disease resembling deep fungal infection in many ways. These are discussed in the chapter on bacterial infections. The systemic fungi include Blastomyces dermatitidis (blastomycosis), […]

Lyme disease is caused by the spirochete Borrelia burgdorferi by means of several tick vectors, the principal one in the Northeast and North Central United States being the deer tick Ixodes dammini and in the Pacific Coast states, Ixodes pacificus, the Western black-legged tick (both morphologically “hard” ticks). The three major affected areas in the […]

After material has been taken for culture, three steps should be followed. First, the specimen must be taken to the laboratory as soon as possible, since many organisms die on prolonged exposure to air or drying. This is especially true for swab preparations. Swab kits are available that contain a carrier medium into which the […]

Tuberculosis is caused by Mycobacterium tuberculosis (MTB), a rod-shaped bacterium that requires special media for culture and that has the peculiarity of “acid-fastness” (resistance to decolorization by strong acidic decolorizing chemicals such as acid alcohol after being stained by certain stains such as carbol fuchsin). Tuberculosis is still very important and common despite advances in […]

Culture. This is the classic definitive method for detection and identification and will be discussed later in more detail. The major drawback is time; it usually takes 1 full day to grow the organism and then part or all of 1 day to identify it. It may take an additional day to isolate it before […]