Yersinia YERSINIA sp. • Y. pestis • Y. pseudotuberculosis • Y. enterocolitica • Y. intermedia • Y. frederiksenii • Y. aldovae Three species are important pathogens in man: Yersinia pestis – causes plague Yersinis enterocolitica – enteropathogenic Yersinia pseudotuberculosis – enteropathogenic Yersinia enterocolitica –motile at 22-250 C, but non-motile at 370 C –exhibit bipolar staining –grow better at lower temperatures and produce small colonies at 370 C –TSI A/A (sucrose, not lactose fermentation) for Y. enterocolitica –LIA - –Urea + –ODC + for Y. enterocolitica only Yersinia enterocolitica identification – Cefsulodin-irgasan-novobiocin (CIN) agar is a selective media developed specifically for the isolation of Y. enterocolitica from gastrointestinal specimens. » The media also contains mannitol and phenol red to differentiate mannitol from non-mannitol fermenting organisms. » The media is incubated at room temperature and Yersinia are the only Enterobacteriaceae that will grow on the media. » Aeromonas and Pleisiomonas, both members of the Vibrionaceae will also grow. » After 48 hours at RT, Y. enterocolitica and Y. pseudotuberculosis both produce typical pink (from mannitol fermentation) colonies with a bulls-eye appearance. Pathogenesis of Yersinia enterocolitica • Associated with – Contaminated meat or milk – Colder climates during winter months • Gastroenteritis (Food-borne) – Diarrhea, fever, abdominal pain • Lasting for 1-2 weeks • Chronic form can persist for months or year – Can mimic appendicitis, particularly in children – Adults can have septicemia, arthritis, intrabdominal abscess, hepatitis, and osteomyelitis 6 Y. enterocolotica – virulence factors – Enterotoxin similar to E. coli ST (increases cGMP leading to watery diarrhea) – Adhesions – include both fimbrial and non-fimbrial adhesions. » At least four different adhesions have been identified thus far. – Antiphagocytic proteins – include both outer membrane and secreted proteins. » Some are actually injected directly into the host via a type III secretion mechanism. » Some interfere with signal transduction in host cells, thus interfering with the ability of PMNs to respond to signals leading them to the invading bacteria. » Others disrupt the actin cytoskeleton and lead to death of the PMNs. Y. enterocolotica – virulence factors –V antigen - a secreted protein that controls expression of many of the virulence genes plus it appears to have another unknown function that is essential for virulence –Iron capturing ability –Yad A – an outer membrane protein that interferes with C3b binding to bacteria thus preventing the formation of a membrane attack complex. –Endotoxin Yersinia enterocolitica and Y. pseudotuberculosis – clinical significance – Both are acquired by ingestion of contaminated food or water. – Y. enterocolitica is a common cause of human disease, whereas, Y. pseudotuberculosis is mainly a disease of other animals. – Both cause a disease involving fever and abdominal pain. Y. enterocolitica also causes a watery diarrhea. – After ingestion, the bacteria invade the intestinal epithelium by invasion of M cells. » They are transcytosed through the M cells and released at the basal surface. » Once through the intestional epithelium, the bacteria penetrate into the underlying lymphoid tissue, where they multiply both inside and outside host cells. Yersinia enterocolitica and Y. pseudotuberculosis – clinical significance » Multiplication of the bacteria produces an inflammatory response that is responsible for the extreme pain associated with the infections (resembles acute appendicitis) » Fever is due to the activity of the LPS endotoxin. » Sometimes they drain into adjacent mesenteric lymph nodes, causing mesenteric lymphadenitis. – Reactive arthritis may occur in some people following Y. enterocolitica infection. » It is thought to be due to cross reacting T cells or antibodies that attack the joints. Summary of Yersinia infections Identification characteristics of Yersinia enterocolitica(Unknown) Test reaction Oxidase _ KIA K/A TSI A/A Indole _ MR + VP _ citrate _ urease + LIA _(A/A) Arginine _ ornihtine + Motility(37° , 22°) (_/_) ONPG + .