Bacterial Information and Courses from MediaLab, Inc.

The following table lists the various cell types and macroscopic descriptions of CSF, and the patient conditions that could cause those properties to be present in the patient's CSF: Predominant Cell Appearance Conditions lymphs variable; clear - turbid viral meningitis tubercular meningitis multiple sclerosis drug abuse lymphoma leukemia Guillain-Barré syndrome chronic alcoholism neutrophils variable; clear - turbid bacterial meningitis mycotic meningitis early tuberculosis hemorrhage cerebral abscess tumors monocytes variable chronic bacterial meningitis partial treatment of meningitis tumors macrophages clear - turbid or clear - xanthochromic bloody tuberculosis fungal meningitis following hemorrhage blood contamination eosinophils variable parasitic meningitis fungal meningitis allergic reaction medications shunts dyes tumor cells variable metastatic carcinoma blast cells variable leukemia lymphoma normal to increased lymphs clear - xanthochromic benign tumor spinal cord brain ependymal or orchoid cells (often clumped) variable; may be xanthochromic bloody trauma spinal tap Adapted from Saunders Manual of Clinical Laboratory Science. Craig A. Lehrmann, Ed. WB Saunders, 1998.

Many lymphocytes are present in this field. Two larger, atypical lymphocytes with intact cytoplasm and slightly indented nuclei are seen near the center of this slide. Two other large cells with irregular, trailing cytoplasm are macrophages (histiocytes). Increased lymphocytes may be seen in viral meningoencephalitis, partially treated bacterial meningitis, multiple sclerosis, Guillian-Barre's syndrome, or polyneuritis.

Reasons for acidic urine pH include: a high-meat diet, respiratory/metabolic acidosis, and hypochloridemia. A urine with a high concentration of glucose may also have a lower pH. An alkaline pH may be the result of a vegetarian diet, respiratory/metabolic alkalosis, or a bacterial infection caused by urease-producing bacteria. Urine that contains bacteria can become more alkaline if the specimen remains at room temperature for an extended period of time.

A false positive nitrite test result may occur when a urine specimen has remained at room temperature for an extended period of time, allowing bacterial contaminants to multiply and produce measurable levels of nitrites. Interference from some medications that cause the urine to become red or orange may lead to an incorrect reading of positive for nitrite.

Tuomanen EI.: Pathogenesis of pneumococcal inflammation: otitis media Vaccine. 19 Suppl 1:S38-40, 2000Pneumococci cause damage to the ear in otitis media with an association with bacterial meningitis. The pathogenesis of injury involves host response to cell wall constituents and the pore-forming toxin, pneumolysin.Release of cell wall constituents, particularly during antibiotic-induced bacterial lysis, leads to an influx of leukocytes and subsequent tissue injury. The signal transduction cascade for this response is becoming defined and includes CD14, Toll-like receptor 2, NFkB, and cytokine production.The second source of injury is the cytotoxicity of the pore forming toxin, pneumolysin.Decreasing the sequelae of otitis can be achieved by an increased understanding of the site-specific mechanisms of pneumococcal-induced inflammation.

Listeria monocytogenes is optimally motile at 25C; and is non-motile at 35-37C.Motility may be directly assessed by observing bacterial cells with a tumbling motion in a direct mount preparation.In soft motility agar, the identification can be made by observing for a thin, umbrella-like lateral extension of growth from the stab line (see photograph).

Low JC. Donachie W.: A review of Listeria monocytogenes and listeriosis. Veterinary Journal. 153:9-29, 1997Following the initial isolation and description in 1926, Listeria monocytogenes has been shown to be of world-wide prevalence and is associated with serious disease in a wide variety of animals, including man.Our knowledge of this bacterial pathogen and the various forms of listeriosis that it causes has until recently been extremely limited, but recent advances in taxonomy, isolation methods, bacterial typing, molecular biology and cell biology have extended our knowledge. It is an exquisitely adaptable environmental bacterium capable of existing both as an animal pathogen and plant saprophyte with a powerful array of regulated virulence factors.Most cases of listeriosis arise from the ingestion of contaminated food and in the UK the disease is particularly common in ruminants fed on silage.Although a number of forms of listeriosis are easily recognized, such as encephalitis, abortion and septicaemia, the epidemiological aspects and pathogenesis of infection in ruminants remain poorly understood. The invasion of peripheral nerve cells and rapid entry into the brain is postulated as a unique characteristic of its virulence, but relevant and practical disease models are still required to investigate this phenomenon.

Rouquette C. Berche P. The pathogenesis of infection by Listeria monocytogenes Microbiologia. 12:245-58, 1996 Listeria monocytogenes is a Gram-positive bacterium responsible for severe infections in human and a large variety of animal species. It is a facultative intracellular pathogen which invades macrophages and most tissue cells of infected hosts where it can proliferate. The molecular basis of this intracellular parasitism has been to a large extent elucidated. The virulence factors, including internalin, listeriolysin O, phospholipases and a bacterial surface protein, ActA, are encoded by chromosomal genes organized in operons. Following internalisation into host cells, the bacteria escape from the phagosomal compartment and enter the cytoplasm. They then spread from cell to cell by a process involving actin polymerisation. In infected hosts, the bacteria cross the intestinal wall at Peyer's patches to invade the mesenteric lymph nodes and the blood. The main target organ is the liver, where the bacteria multiply inside hepatocytes. Early recruitment of polymorphonuclear cells lead to hepatocyte lysis, and thereby bacterial release This causes prolonged septicaemia, particularly in immunocompromised hosts, thus exposing the placenta and brain to infection. The prognosis of listeriosis depends on the severity of meningoencephalitis, due to the elective location of foci of infection in the brain stem (rhombencephalitis). Despite bactericidal antibiotic therapy, the overall mortality is still high (25 to 30%).

The Gram stain reaction, shape, and arrangement of bacteria, and the presence or absence of intracellular organisms must be noted on the worksheet.Examples:Gram positive cocci in chains are present.Gram negative diplococci, intracellular, are present within white blood cells.Quantitate by approximating the average number of each cell type seen in 10 oil immersion fields, and record as:Many = More than 15/fieldModerate = 4-15/fieldFew = 1-3/fieldOccasional = 2-10/10 fieldsRare = 0-2/10 fields

Direct smear results are generally reported in the same way that they are read, except that bacterial cell arrangement (ex: clusters, chains, pairs) may be misleading and is generally not reported except in the case of intracellular diplocci in genital smears.

The process of culture, isolation and identification of microorganisms is basic to medical microbiology. When a culture shows signs of growth, the process of identification includes examining the following characteristics:appearance of the colonies in the culture mediumstaining reactionappearance of stained organismssizeshapearrangement of bacterial cellsThis type of preliminary identification may help the physician to initiate the appropriate antibiotic treatment.