Gastrointestinal Information and Courses from MediaLab, Inc.

Endoscopic procedures yield small pinched off tissue samples and are commonly used for biopsies of the gastrointestinal tract. The specimens obtained from endoscopy will most likely be of small dimensions with difficult to see cut edges.It is unlikely that any inked surfaces will be present. In fact, the entire specimen is often colored with eosin to make it more visible. Since the surface will likely appear homogeneous, you will embed these types of biopsies most often on end, so that the tallest side is traveling into the block interior. This allows the greatest number of sections to be obtained from the tiny specimens for multiple levels, special stains, and immunohistochemistry (IHC). Since multiple level section protocols are very common with these types of biopsies, select the smallest mold size that appropriately contains the specimen pieces.

Podschun R. Ullmann U.: Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors Clinical Microbiology Reviews. 11(4):589-603, 1998 Bacteria belonging to the genus Klebsiella frequently cause human nosocomial infections. In particular, the medically most important Klebsiella species, Klebsiella pneumoniae, accounts for a significant proportion of hospital-acquired urinary tract infections, pneumonia, septicemias, and soft tissue infections. The principal pathogenic reservoirs for transmission of Klebsiella are the gastrointestinal tract and the hands of hospital personnel. Because of their ability to spread rapidly in the hospital environment, these bacteria tend to cause nosocomial outbreaks. Hospital outbreaks of multidrug-resistant Klebsiella species, especially those in neonatal wards, are often caused by new types of strains, the so-called extended-spectrum-beta-lactamase (ESBL) producers The incidence of ESBL-producing strains among clinical Klebsiella isolates has been steadily increasing over the past years. The resulting limitations on the therapeutic options demand new measures for the management of Klebsiella hospital infections. While the different typing methods are useful epidemiological tools for infection control, recent findings about Klebsiella virulence factors have provided new insights into the pathogenic strategies of these bacteria. Klebsiella pathogenicity factors such as capsules or lipopolysaccharides are presently considered to be promising candidates for vaccination efforts that may serve as immunological infection control measures.

Citron DM. Appelbaum PC.: How far should a clinical laboratory go in identifying anaerobic isolates, and who should pay? Clinical Infectious Diseases. 16 Suppl 4:S435-8, 1993 Identification of anaerobic bacteria in specimens from sites of infection due to mixed organisms can be time-consuming and expensive. Laboratories should limit anaerobic workups by testing only those specimens that have been properly collected and transported to the laboratory. Use of selective and differential media for initial processing can provide rapid and relevant information to the clinician. Anaerobes isolated from normally sterile sites and sites of serious infection should always be completely identified. Group-or genus-level identifications may suffice in other instances. The Bacteroides fragilis group of organisms should always be identified because of their virulence and resistance to many antimicrobial agents. Some of the other organisms that warrant identification include Clostridium septicum (associated with gastrointestinal malignancy); Clostridium ramosum, Clostridium innocuum, and Clostridium clostridioforme (which are resistant to antibiotics); Clostridium perfringens (a cause of myonecrosis and gas gangrene,potentially serious infection); anaerobic cocci (which may be resistant to metronidazole and clindamycin); and fusobacteria (which may be virulent and resistant to clindamycin and penicillin).

Bernard-Soulier syndrome is a genetic platelet disorder characterized by abnormal platelet function tests, unusually large platelets, and a moderate to severe decrease in platelet count. Clinically, patients present with mucotaneous bleeding of varying severity, as well as having gingival bleeds, epistaxis, purpura, and gastrointestinal hemorrhaging. Treatment can range from the administration of iron supplements up to red cell replacement therapy if the episodic bleeding is severe enough to warrant it.Von Willebrand disease is characterized by a functional defect in von Willebrand factor (vWF) itself. This disease often clinically manifests with a concurrent deficiency of factor VIII. The platelet count is not affected by the disorder, but platelet function assays are abnormal. As far as genetics and inheritance, both men and women are affected equally. VWF is essential for platelet binding. Therefore, a defect in vWF causes impaired platelet adhesion and aggregation. The most commonly used treatment for von Willebrand disease is desmopressin (DDAVP). Crypoprecipitated anti-hemophilic factor (CRYO) can be used as a second-line therapy for patients with hemophilia A and von Willebrand disease, but only in those situations in which safer commercially prepared factor concentrates are not available.

Hereditary hemochromatosis (HH) is a disorder of iron regulation that results in excessive dietary iron absorption through the gastrointestinal tract. Over time, the resultant iron overload and its deposition in tissue may lead to widespread organ damage, a variety of chronic disorders, and even death. Although it is a genetic disorder, clinical symptoms most typically become apparent in middle aged adults. Iron overload occurs in a variety of hereditary and acquired forms, known as iron storage diseases. HH is the most common cause of inherited iron overload. (1) Due to lack of awareness, HH often goes undetected or unrecognized by health care providers. Early detection to prevent the serious complications associated with iron overload has important consequences for reducing morbidity and mortality. Laboratory tests that assess iron levels and molecular assays for genetic mutatations are essential for both its detection and diagnosis.

The PAS staining procedure is most commonly used in the clinical histology laboratory to demonstrate glycogen deposits in the liver. Glycogen granules may also be visible in tumors of the bladder, kidney, ovary, pancreas, and lung. Basement membranes, which are present in various tissues in the body, may also be visualized through the PAS staining procedure. Several disorders can be identified through the demonstration of abnormal basement membranes. The PAS staining procedure can also demonstrate fungi in tissue samples due to the high carbohydrate content of the organisms cellular walls. Neutral mucins in the gastrointestinal tract and some epithelial mucins will also give a PAS-positive staining reaction.

Alcian Blue is used in the clinical histology laboratory to demonstrate acid mucins which can be secreted by various connective and epithelial tissue tumors. It is most commonly used on tissue samples obtained from the gastrointestinal tract. The detection of mucins in certain tissue samples may also be indicative of collagen diseases and atherosclerosis. Alcian Blue may also be used in combination with the PAS staining procedure so that both acid and neutral mucins can be demonstrated in the same tissue sample. Alcian Blue will stain acidic mucins blue and PAS will stain neutral mucins rose red. This technique is particularly useful in diagnosing diseases of the gastrointestinal (GI) tract.

Clostridium difficile is the cause of antibiotic associated diarrhea (AAD) and pseudomembranous colitis (PMC). PMC is an inflammatory disease of the colon caused by toxins of C. difficile.C. difficile produces two potent toxins: Toxin A (TcdA), an enterotoxinToxin B (TcdB), a cytotoxin It is the production of these toxins in the gastrointestinal tract that ultimately leads to disease. There is a relationship between toxin levels, the development of pseudomembranous colitis (PMC), and the duration of diarrhea. For many years, toxin A was regarded as more important than toxin B in the disease process. Later on, disease producing strains producing only toxin B were identified. These strains produced serious disease, and toxin B was found to be responsible for more serious damage to intestinal cells.

Clostridial toxins are among the largest bacterial toxins reported to date and C. difficile produces two potent toxins: Toxin A ((TcdA), an enterotoxin and Toxin B (TcdB), a cytotoxin. It is the production of these toxins in the gastrointestinal tract that ultimately leads to disease. There is a relationship between toxin levels, the development of pseudomembranous colitis (PMC), and the duration of diarrhea. Levels of Immunoglobulin G against TcdA correlate directly with protection from disease following colonization, suggesting that a robust immune response is sufficient for protection from C. difficle-associated diarrhea (CDAD). The role of TcdB is not as well understood. Naturally occurring Toxin A negative/Toxin B positive (TcdA-TcdB+) strains have been identified from clinical isolates, which are capable of causing disease, even extensive PMC, suggesting a role for TcdB in CDAD. Toxin A had always been regarded as more important than Toxin B in infection. However, recent work utilizing mutant C. difficile, strains which did not, or could not produce Toxin A, and which were capable of producing very serious disease has led researchers to completely rethink the roles of Toxin A and Toxin B in CDAD. Toxin B was found to be responsible for the more serious damage to intestinal cells. In addition to the primary virulence factors (Toxin A and Toxin B ), Clostridium difficile also produces a third toxin, binary toxin (CDT). The prevalence of CDT in clinical isolates varies widely and its clinical relevance and role in pathogenicity are still not well defined.

Mr. R.M., a 55-year old male, was admitted to a hospital emergency department with severe lower gastrointestinal bleeding. His history revealed multiple prior transfusions, the last of which he received five years earlier.Physical examination revealed hemodynamic instability (systolic BP 60 mmHg). Blood tests revealed a hemoglobin (Hb) of 8 g/dL (80 g/L) and a hematocrit (HCT) of 28% (0.28). The patient received aggressive fluid resuscitation with Ringer's lactate and was sent to the operating room (OR) for an emergency laparotomy.The physician ordered four units of Red Blood Cells to be crossmatched.Two units of uncrossmatched group O Rh-negative Red Blood Cells were also ordered and authorized for immediate emergency transfusion.