装饰公司简介MPN、大肠菌群、大肠杆菌原理
United States Food Safety Office of Laboratory QA/QC Division
Department of and Inspection Public Health 950 College Station Road
Agriculture Service and Science Athens, GA 30605
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Laboratory Guidebook
Notice of Change
Chapter new, revid, or archived: MLG Appendix 2.02
Title: Most Probable Number Tables
Effective Date: 7/3/03
Description and purpo of change(s):
The Microbiology Laboratory Guidebook method chapters are currently under revision. The formatting is being changed to meet the requirements of the laboratory document control
system. Tables have been updated to reflect changes in FDA BAM MPN tables. Additional instructions for tube preparation have been added.
QD-F-Micro-0004.01 Approved: Charles Pixley, 2/25/03
Title: Most Probable Number Tables
Effective: 7/3/03
Revision: 02 Replaces: MLG Appendix, Most
Probable Number Tables Volume 1
and 2, Rev.1
APP 2 Procedure
今日工作总结APP 2.1 Introduction
行都APP 2.1.1 For the convenience of analysts using the procedures in this Guidebook, tables of Most Probable Numbers (MPN) are provided in this appendix.
泽泻的副作用
APP 2.1.2 MPN is a procedure to estimate the population density of viable microorganisms in a test sample. It is bad upon the application of the theory of probability to the
numbers of obrved positive growth respons to a standard dilution ries of
sample inoculum placed into a t number of culture media tubes. Positive growth春联七字对联
respon after incubation may be indicated by such obrvations as gas production in
fermentation tubes or visible turbidity in broth tubes, depending upon the type of
media employed. The sample should be diluted in such a manner that higher
dilutions of the sample will result in fewer positive culture tubes in the ries. The
number of sample dilutions to be prepared is generally bad on the expected
population contained within the sample. If particularly high microbial populations
are expected, the sample must be diluted to a range where the MPN can be obtained.
Most reliable results occur when all tubes at the lower dilution are positive and all
tubes at the higher dilution are negative. Generally tenfold rial dilutions are ud
in either a 3, 5 or 10 tube MPN ries. When a higher number of tubes are
inoculated in the ries, the confidence limits of the MPN are narrowed. For
漫天星particularly high microbial populations, the values obtained by MPN are generally
not considered to be as preci as population numbers derived from direct plating
methods; however, it should be emphasized that MPN values are only estimates
while plate counts are direct counts of living organisms expresd in cfu/ml. MPN
values are, however, particularly uful when low concentrations of organisms
(<100/g) are encountered in such materials as milk, food, water and soil where
particulate matter of the matrix may interfere with obtaining accurate colony counts. APP 2.1.3 In application of probability theory to the determination of MPN values, it should be kept in mind that the following assumptions are generally considered to be accepted:
(a) the organisms are randomly and evenly distributed throughout the sample, (b) the
organisms exist as single entities, not as chains, pairs or clusters and they do not
repel one another, (c) the proper growth medium, temperature and incubation
conditions have been lected to allow even a single viable cell in an inoculum to缺点
produce detectable growth and (d) the population does not contain viable, sub-
lethally injured organisms that are incapable of growth in the culture medium ud.
Title: Most Probable Number Tables
Revision: 02 Replaces: MLG Appendix, Most
Effective: 7/3/03
Probable Number Tables Volume 1
and 2, Rev.1
APP 2.1.4 The following 4 tables prent MPN values and corresponding 95% confidence limits for a 3 tube test ries using 4 different, commonly ud ts of inoculum
quantities that should be particularly uful relative to performing the
microbiological analys previously described in various chapters of this Guidebook.
招兵买马The MPN tables may be considered to be abbreviated since not all possible
