Articles on Medical Diseases and Conditions

Febrile agglutinins are serologic tests for a group of unrelated infectious diseases that are sometimes responsible for so-called fever of unknown origin. They include typhoid and enteric (Salmonella) fever, certain rickettsial diseases, brucellosis, and tularemia. Since organisms causing these diseases are potential causes of fever of unknown origin, and since relatively simple slide agglutination serologic […]

One controversial area in microbiology is the reliability of blood cultures drawn from an indwelling vascular catheter. In general, investigators have encountered higher rates of contamination when drawing culture specimens from vascular catheters, due to colonization of the catheter tip or other areas of the apparatus, such as the stopcock, reservoir, or hub. However, not […]

Gram staining provides a presumptive diagnosis and some indication of the organism involved without waiting for culture results. On occasion, Gram stain may reveal organisms that (for technical reasons) do not grow when cultured. Best information comes from areas that are normally sterile. Gram staining is considered a routine procedure for CSF in possible meningitis, […]

The usefulness of sputum culture is controversial. This method of diagnosis has evoked the same spectrum of emotions and suffers from most of the same potential drawbacks as Gram stain of sputum. Various studies have demonstrated that either sputum or bronchoscopic specimens are frequently contaminated by upper respiratory tract bacteria. Some of the contaminants, such […]

Contamination of urine specimens by vaginal or labial bacteria is a serious problem. The most reliable way to obtain the specimen, especially in young children, is by suprapubic puncture and aspiration of the bladder with a needle and syringe. However, this technique has never become popular. Catheterization is another way to solve the difficulty, but […]

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 […]

It is useful to know certain technical information involved with isolation and identification of bacteria. This information may improve physician understanding of the microbiology laboratory, to the mutual benefit of physician and laboratory. If a culture is ordered, it usually takes at least 48 hours, and often longer, for definitive diagnosis—1 day to culture the […]

Certain bacteria that ordinarily are nonpathogenic (such as normal inhabitants of certain areas) frequently appear in cultures and are traditionally considered contaminants, presumably introduced by faulty culture technique. The major species are Staphylococcus epidermidis and the diphtheroids. Occasionally there are others, such as Bacillus subtilis. However, under certain circumstances, especially when the patient is immunocompromised, […]

Whipple’s disease. This is a rare systemic illness that involves the small intestine mucosa but also may have low-grade fever, arthralgias, lymphadenopathy, and CNS symptoms (confusion, loss of memory, vision abnormalities, and symptoms referable to involvement of one or more cranial nerves). The GI symptoms are primarily those of malabsorption similar to sprue; with steatorrhea, […]

Corynebacteria These organisms are gram-positive aerobic rods of varying length, frequently arranged on smear in sheafs (palisades) or Chinese letter-type configurations. The most important member of this genus is Corynebacterium diphtheriae, which causes diphtheria. Infection usually becomes established in the pharynx. Corynebacterium diphtheriae produces a toxin that affects the heart and peripheral nerves. There is […]