Index NA oxidase test Aeromonas species Plesiomonas shigelloides Bacterial pathogens TCBS medium Yersine selective agar Mannitol3a Bacterial pathogens Salmonella sp. It causes a variety of human diseases called salmonellosis. The disease ranges from mild, self-limiting gastroenteritis to the more severe form with the possibility of bacteremia or typhoid fever, which can be life-threatening. Severe disease associated with S.typhi and S.paratyphi A and S. paratyphi B while the other 2,300 or more strains are associated with gastroenteritis. S.typhi is unique because only humans carry it. This intracellular parasite can cause typhoid fever, characterized by fever, diarrhea, and inflammation of infected organs. Other symptoms include headache, abdominal cramps and vomiting. Gram-negative, rod-shaped, motile, facultatively anaerobic bacterium On XLD, Salmonella sp. Produces red colonies, usually with a black center. Is agglutination with polyvalent O, H and Vi antiserum followed by additional O sub-antisera and H sub-antisera performed when biochemical tests suggest it? Salmonella sp. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original assay Positive S.paratyphi A, B & C and S.typhi agglutination is transferred to the CAT III laboratory and API 20E and EUCAST sensitivities are performed. The isolate is sent to the reference laboratory for confirmation of ID and serotype. Salmonella sp produces acid from glucose usually with gas production and is oxidase, indole and urea negative. Most produce hydrogen sulfide, except S. paratyphi A and Salmonella typhi, which is a weak producer. The presumptive positive identification of Salmonella sp is sent to MALDI for manual identification and sensitivity performed for Shigella sp. People infected with Shigella develop diarrhea, fever, and abdominal cramps. The severity of the disease varies from mild to very severe diarrhea. Diarrhea is bloody in 25-50% of cases and most often contains mucus. Illness begins 12 hours to 6 days after exposure. Dehydration is a common symptom of Shigella infection. Based on the serological antigen, the disease is classified into 4 species. Serotype A- S.dysenteriaeSerotype B- S.flexneriSerotype C- S.boydiiSerotype D- S.sonnei non-motile, facultative anaerobes, Gram-negative rods. On XLD agar, Shigella sp. Appears as red colonies (no black centers). Shigella sp. can be divided based on their somatic (cell wall) antigens or OSdysenteriae contains 12 serotypes, S.flexneri contains 8 serotypes, S,boydii 18 serotypes and S.sonnei 1 serotype. Positive agglutination of Shigella dysenteriae type 1 is transferred to the cat III laboratory and API20E and EUCAST sensitivities are performed. The isolate is sent to the reference laboratory for confirmation of ID and serotype. Shigella sp. it is oxidase, indole and urea negative and does not decarboxylate lysine and all except S.dysenteriae type 1 are catalase positive. Most Shigella sp. With the exception of S.flexneri 6 and S.boydii 13 and 14 they ferment sugars without producing gas. S.sonnei and S.dysenteriae type 1 are the only ONPG positive species. Presumptive positive identification of Shigella sp. is sent to MALDI for identification and manual sensitivity carried out Campylobacter sp. Campylobacter sp. it is the most common cause of enteritis in the UK. Initial symptoms may be severe with fever and abdominal pain suggesting appendicitis. Stools often contain mucus with blood and leukocytes. Severe infection can cause reactive arthritis, bursitis, endocarditis, and neonatal sepsis. Curved Gram negative rods have the appearance of a spiral. Cefoperazone deoxycholate agar withcharcoal (CCDA) incubated in microaerobic mode at 42°C for 48 hours. If necessary, the culture can be incubated for an additional 24 hours. On selective agar, colonies are grey/white or creamy gray and have a moist appearance. They are mobile, microaerophilic (optimal 5 -10% oxygen).NA Oxidase TestCampylobacter sp. It is oxidase positive. If positive MALDI is performed for identification. For confirmation, colonies are subcultured onto blood agar and incubated aerobically at 37°C for 24 hours. The absence of growth on BA after 24 hours confirms the Campylobacter sp.Vibrio species. The disease is associated with ingestion of contaminated water or seafood. The diarrhea causing sp. the most frequently isolated are the parahaemolytic vibrios. Symptoms range from mild to bloody diarrhea (often accompanied by abdominal cramps and vomiting) to explosive diarrhea. The main symptoms of cholera are the passage of abundant watery diarrhea with mucus but no blood, which gives the appearance of "rice water". Fluid loss and dehydration are the main causes of death. The incubation period ranges from a few hours to a few days. V.cholerae 01 and 0139 are producers of cholera toxin (CT). V. parahaemolyticus associated with consumption of contaminated seafood, particularly shellfish. Gram-negative curved rods, characteristically comma-shaped. This characteristic appearance is not always observed when the organism is Gram stained from solid media. Vibrio sp. they are facultative anaerobes, motile thanks to a single polar flagellum. On blood agar colonies have a diameter of 2-3 mm. Some strains may be hemolytic. After 18-24 hours of incubation, colonies on TCBS have a diameter of at least 2 mm and are yellow in the case of sucrose fermenters (V.cholerae) and green non-sucrose fermenters (V.parahaemolyticus) Serology and sensitivity to pteridine O129Most part of the Vibrio sp. they are sensitive with 150 µg but the species differ with 10 µg discs. V. cholerae O1 depends on the detection of O1 antigens on the surface of the bacterium. Presumptive identification of V.cholerae is sent to MALDI for identification and sensitivities are performed using EUCAST. The isolate is sent to the reference laboratory. Oxidase test and API 20EVibrio species are oxidase positive. It is necessary to subculture colonies in blood agar for the oxidase test because a false oxidase test may result on carbohydrate-containing media. Ecoli O157 (VETEC O157) E.coli O157 is one of the verocytotoxin-producing organisms. The toxin is similar to the shiga toxin of Shigella dysenteriae and is associated with hemorrhagic colitis, uramic hemolytic syndrome, and thrombocytopenic purpura (TTP) which causes renal failure, hemolytic anemia, and thrombocytopenia. The infection ranges in severity from mild to bloody diarrhea and can occur in any age group, however it is more common in children. Gram negative rods. On Macconkeys sorbitol agar (SMAC) containing cefixime and tellurite, colonies are colorless and 2-3 mm in diameter. VETC O157 differs from other members of the Escherichia genus in that it does not usually ferment sorbitol. Plates are usually incubated in air at 35-37ºC for 16-24 hours. Maldi is used for ID on both SMAC plates, once positively identified for E. coli. The sample and all plates are transferred to CAT III.API20E, susceptibility testing is performed in CAT III, and the isolate is sent to the reference laboratory. E.coli 0157 strains are oxidase negative, indole positive, urea and citrate negative. Yersinia sp. The infection is usually acquired orally from contaminated food, milk, or water. Pigs are a frequently identified source of infection. The infection occurs more often in young (<6 years) and elderly people.After ingestion, the organism proliferates in the lymphoid tissue of the small intestine where it can cause hyperemia, neutrophil infiltration, and ulceration. The incubation period is between 4 and 7 days. Occasionally, hematogenous spread occurs, producing septicemia with abscess formation in organs such as the liver and spleen. Yersiniosis can therefore present with various clinical conditions such as acute diarrhea, mesenteric lymphadenitis, terminal ileitis, “pseudoappendicitis”, septicemia, metastatic infection and immunological sequelae (e.g. reactive arthritis). Gram negative rods On CIN agar, colonies of suspected Yersinia sp. Shows typical pink bullseye colonies at 30ºC under aerobic conditions. NA Yersina sp. Sonourea positive and oxidase negative. The presumptive positive Yersinia identification is sent to MALDI for identification and manual sensitivities are performed. The isolate is sent to the reference laboratory. Other organisms of potential importance in enteric pathogens Aeromonas species Aeromonas sp. have been implicated as the causative organisms of bloodless watery diarrhea. Young children and elderly patients may be more susceptible to infections. Although the organisms have been linked to food- and water-borne outbreaks, their significance is still uncertain. Pseudomonas sp. must be excluded by confirmation of growth on pseudomonas agar/MALDI. Aeromonas and plesiomonas show pink, oxidase positive colonies on XLD. Aeromonas can also grow on TCBS forming bluish green colonies. Possible identification of Aeromonas and Plesiomonas sp. are sent to MALDI for confirmation and sensitivities are performed in PHOENIX. Furthermore, an isosensitest agar is inoculated with the addition of a 0129 disc (150 µg)Aeromonas = ResistantPlesiomnas = SusceptibleAeromonas sp. and Plesiomonas sp. may produce false negative oxidase results if tested for Macconkey's form and therefore oxidase should be performed from the BA subculture. Plesiomonas shigelloides Plesiomonas shigelloides has been isolated from patients with diarrhea and abdominal cramps. It has been linked to outbreaks of food- and water-borne gastrointestinal infections. Bacterial Pathogens Explain the composition and method of action on each type of media used on the stool bench Media used on the stool bench Composition Method of action XLD (Xylulose lysine dextrose medium) Lysine, xylose, lactose, sucrose, sodium deoxycholate, sodium thiosulfate , iron ammonium citrate, phenol red. It uses sodium deoxycholate as a selective agent and inhibits Gram positive microorganisms. Xylose fermentation differentiates Shigella sp. from other enteric pathogens. Due to this decarboxylation the pH changes and the colony appears pink with a neutral red indicator. If the organism produces hydrogen sulfide, the colony appears pink with a black center. Selenite medium Tryptone Lactose Disodium phosphate L-cystine This is enrichment medium for Salmonella sp. Which inhibits the growth of coliforms and other fecal streptococci. Lactose is added as a fermentable carbohydrate to prevent an increase in the pH value during incubation. Sorbitol – Macconkey'sMediumPeptone, sorbitol, sodium chloride, neutral red, potassium tellurite and cefixime. The medium is intended primarily for the sorbitol non-fermenting organism E.coli O157. This medium contains the major supplements cefixime and potassium tellurite, which inhibit the growth of other sorbitol non-fermenting organisms without any inhibitory effect on E. coli O157. The medium is used for screening purposes only as some non-sorbitol fermentants can grow on this medium. TCBS Medium Bacteriological Peptone, Sodium Thiosulfate, Sodium Citrate, Ox Bile, Sucrose, Sodium Chloride, Ferric Citrate, Bromothymol Blue, Blue.