Analisis ecometrico

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The performance of Gram-negative ŽGN. broth with Ž10 mgrml. and without novobiocin, Shigella broth ŽSB. with 0.5
and 3.0 mgrml novobiocin, all incubated at 37 8C ŽSBwith 3.0 mgrml novobiocin also at 42 8C. and buffered brilliant
green bile glucose ŽEE. broth with 1.0 mgrml novobiocin incubated at 37 and 42 8C were evaluated forresuscitation and
growth of Shigella sonnei and S. flexneri Žeight strains; unstressed, chill-stressed and acid-stressed. and non-shigellae Ž11
strains.. GN broth withor without novobiocin supported significantly less growth of Shigella sp. No significant differences
in growth of shigellae were obtained between the other culturemedia. Performance depended more on the Shigella strain
used. None of the tested media were significantly superior for suppressing the competitive flora.
Electivity andselectivity of MacConkey agar ŽMAC., tergitol-7 agar ŽT7., desoxycholate citrate agar ŽDCA., xylose
lysine desoxycholate agar ŽXLD., Salmonella Shigella agar andHektoen enteric agar ŽHEA. were determined by ecometric
testing. HEA confirmed to be a high selective medium for both non-shigellae and stressed Shigella sp. Klebsiellasp.,
Enterobacter sp., Citrobacter sp., Salmonella sp. and the Escherichia strains can mask the presence of shigellae.
In vitro competition experiments and experimentswith artificially contaminated foods showed higher resistance of S.
sonnei than S. flexneri towards the stress imposed by the food matrix and its indigenous flora.Reliable detection, however,
of shigellae in foods with the current enrichment and isolation media was not achieved. q2001 Elsevier Science B.V. All
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