Stool bench. Cultures: SARAH

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1 Stool bench The bacteria found in stool are representative of the bacteria that are present in the digestive system (gastrointestinal tract). Certain bacteria and fungi called normal flora inhabit everyone's gastrointestinal tract. They play an important role in the digestion of food and their presence keeps a check on the growth of disease-causing bacteria. Sometimes, the balance of the normal flora may be affected by the administration of broad-spectrum antibiotics; the drugs inhibit the growth of normal flora and allow the bacteria Clostridium difficile that is resistant to the antibiotics to survive and overgrow the digestive tract, leading to symptoms such as diarrhea and abdominal pain. Pathogenic bacteria can enter and infect the digestive tract when someone eats food or drinks water that is contaminated. Examples of contaminated sources include raw or undercooked eggs, poultry or beef, unpasteurized milk, and untreated water from lakes, streams, and (occasionally) from community water supplies. (For more on this, see the article Food and Waterborne Illness.) The stool culture is a test that detects and identifies bacteria that cause infections of the lower digestive tract. The test distinguishes between the types of bacteria that cause disease (pathogenic) and the types that are normally found in the digestive tract (normal flora). The test helps to determine if pathogenic bacteria are the cause of a person's gastrointestinal symptoms (gastroenteritis). Cultures: 1. YERSINIA SELECTIVE AGAR BASE This is a selective medium for the isolation of Yersinia spp. It is made selective by the inclusion of Sodium desoxycholate, Crystal violet and the antimicrobials Cefsulodin, Novobiocin and Irgasan. Mannitol is also included which Yersinia ferments giving a colony that produces a Bull s Eye appearance. The majority of other enteric organisms are inhibited but if they do grow they produce a large pinkish colony with an opaque halo. 1

2 2. Xylose Lysine Deoxycholate (XLD) Agar XLD Agar is a selective differential medium for the isolation of Gramnegative enteric pathogens from fecal specimens and other clinical material. It is especially suitable for the isolation of Shigella and Salmonella species. 3. CAMPYLOBACTER SELECTIVE AGAR Diagnostics Campy CVA Agar contains peptamin which provides carbon, sulfur, and nitrogenous compounds required for growth. Yeast extract supplies B vitamins to the medium, dextrose is incorporated as an energy source. Sheep blood supplements the medium with X-factor and other growth factor requirements. The addition of antimicrobials to the media is required to suppress the growth of normal fecal flora. Cefoperazone is added to inhibit many gram-positive and gram-negative organisms, both aerobic and anaerobic. 2

3 Vancomycin inhibits gram-positive microorganisms. Amphotericin B is incorporated to inhibit the growth of yeast. 4. Hektoen Enteric Agar: Hektoen Enteric Agar (HE) is a selective and differential medium designed to isolate and differentiate members of the species Salmonella and Shigella from other Enterobacteriaceae. Bile salts and the dyes bromthymol blue and acid fuchsin inihibit the growth of most Gram positive organisms. Lactose, sucrose, and salicin provide fermentable carbohydrates to encourage the growth and differentiation of enterics. Sodium thiosulfate provides a source of sulfur. Ferric ammonium citrate provides a source of iron to allow production of hydrogen sulfide from sodium thiosulfate, which provides a source of sulfur. Ferric ammonium citrate also allows the visualiztion of hydrogen sulfide production by reacting with hydrogen sulfide gas to form a black precipitate. Enterics that ferment one or more of the carbohydrates will produce yellow to salmon colored colonies. Non-fermenters will produce blue-green colonies. Organisms that reduce sulfur to hydrogen sulfide will produce black colonies or blue-green colonies with a black center. 3

4 5.Selenite broth: is used as a selective medium for the isolation of Salmonella species. while observing good recovery of Salmonella spp. and reduced growth of fecal coliforms. Selenite Broth is used as a selective enrichment for the cultivation of Salmonella spp. that may be present in small numbers and competing with intestinal flora. This medium must not be autoclaved. Once prepared it is steamed at 100 C for 30 minutes. There should be a very slight red precipitate. To minimise the risk of teratogenicity to workers, sodium selenite must be added separately to the medium. It has a ph of approximately 7.1. Selenite broth gives pale or colourless colonies. 4

5 Tests: C. DIFF QUIK CHEK COMPLETE test is the only rapid cassette assay that simultaneously detects both glutamate dehydrogenase (GDH) antigen and toxins A & B of C. difficile in fecal specimens. The test detects C. difficile antigen, GDH, as a screen for the presence of C. difficile and confirms the presence of toxigenic C. difficile by detecting toxins A and B in fecal specimens from persons suspected of having C. difficile disease. This test is to be used as an aid in the diagnosis of C. difficile disease. 5

6 Devices: Vatic compact machine Vatic is highly automated and allows for the rapid, accurate identification of some bacterial strains in as little as two hours. In addition to being able to identify bacteria, the VITEK2 compact system is able to identify multiple species of yeast. In total, the system s database is capable of identifying a variety of microorganisms. It is technology includes an expanded identification database, the most automated platform available, rapid results, improved confidence, with minimal training time. Features : High discrimination between species Low rate of multiple choice and misidentified specis Minimal number of off-line tests 6

7 Micro scan Is a remains a technology leader in automatic identification and machine vision with extensive solutions for ID tracking, traceability and inspection ranging from basic barcode reading up to complex machine vision inspection, identification, and measurement. The systems advanced Minimum Inhibitory Concentration (MIC) detects emerging resistance as it occurs, providing accurate results without reliance on historical data or virtual MIC. Each system includes our LabPro Information Manager, an easy to use and customizable software that improves lab efficiency from order to LIS transmission. Micros scan panels As the foundation of our identification and antibiotic susceptibility testing (ID/AST) products, Conventional panels deliver accuracy, choice, and flexibility. With the fewest FDA limitations of leading automated ID/AST systems, use of conventional panels reduces supplemental testing costs and reporting delays associated with rapid only systems. 7