Direct microscopic count techniques

2022 ◽  
pp. 19-30
Author(s):  
Osman Erkmen
Keyword(s):  
Microscopic Count

Pyruvate as an Indicator of Quality in Grading Nonfat Dry Milk1

1982 ◽  
Vol 45 (6) ◽  
pp. 561-565 ◽  
Author(s):  
R. T. MARSHALL ◽  
Y. H. LEE ◽  
B. L. O'BRIEN ◽  
W. A. MOATS
Keyword(s):  
Geometric Mean ◽  
Regression Line ◽  
Skim Milk ◽  
Plate Count ◽  
Department Of Agriculture ◽  
Standard Plate Count ◽  
Geometric Average ◽  
Dry Milk ◽  
Standard Plate ◽  
Microscopic Count

Samples of skim milk and nonfat dry milk (NDM) made from it were collected, paired and tested for pyruvate concentration, [P], and Direct Microscopic count (DMC). The skim milk was tested for Standard Plate Count (SPC) and Psychrotrophic Plate Count (PPC). The geometric average DMC of skim milk was more than three times higher than that of the paired NDM samples. However, [P] of NDM was not significantly different from that of the skim milk. Although [P] of skim milk was poorly correlated with SPC and PPC, r = .31 and .26, respectively, it was relatively well correlated with DMC, r = .64. Data were widely dispersed around the regression line when [P] was ≤ 4.0 mg/L. However, [P] increased rapidly when DMCs were > 106/ml. A limit of 10 mg/L of [P] in NDM reconstituted 1:9 was chosen to represent the current U.S. Department of Agriculture Standard for DMC in NDM. This limit failed to classify about 10% of the samples correctly, assuming that each geometric mean DMC was correct. However, the probability that samples meeting the DMC standard would be rejected by the pyruvate test was quite low and the probability was moderate that samples which would be acceptable by the pyruvate test would be rejected by the DMC. For the latter, 28% of the samples having DMCs of ≥ 107/ml contained < 10 mg/L of pyruvate. No sample having ≥ 10 mg/L of pyruvate had a DMC of ≤ 107/ml. Pyruvate concentration in NDM did not change during storage at 5 or 32°C for 90 days.

Rapid Detection of Psychrotrophic Bacteria In Manufacturing Grade Raw Milks

1991 ◽  
Vol 54 (11) ◽  
pp. 861-867 ◽  
Author(s):  
S. R. TATINI ◽  
P. MEKALA ◽  
A. EL-HABAZ ◽  
M. W. GRIFFITHS
Keyword(s):  
Rapid Detection ◽  
Bacterial Count ◽  
Raw Milk ◽  
Plate Count ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Microscopic Count ◽  
Direct Epifluorescent Filter Technique ◽  
Native Microflora

Methods to rapidly assess the bacteriological quality of raw milk were investigated. Whereas direct microscopic count, modified psychrotrophic plate count, and direct epifluorescent filter technique (DEFT) did not correlate well with initial psychrotrophic bacterial count of raw milk, improvements were obtained after preincubation of the milk samples. The best preincubation conditions were identified as 30°C for 6 h, 21°C for 10 h, 13°C for 15 h, 13°C for 20 h, or 7°C for 37 h. The “square root” equation was applied to the data, and a model was produced for predicting growth of the native microflora of raw milk. Using this equation, a DEFT count after preincubation of the milk at 21°C for 10 h could accurately predict the initial psychrotroph count and the count after storage of the milk at 6°C for 48 h.

A COMPARISON OF SIX METHODS OF PREPARING AND USING THE METHYLENE BLUE STAIN FOR BACTERIAL COUNTS BY THE DIRECT MICROSCOPIC METHOD*

1954 ◽  
Vol 17 (6) ◽  
pp. 179-184 ◽  
Author(s):  
Nathan Mantel ◽  
A. H. Robertson
Keyword(s):  
Methylene Blue ◽  
Federal State ◽  
Cooperative Study ◽  
Microscopic Method ◽  
Bacterial Counts ◽  
Blue Stain ◽  
Microscopic Count

A cooperative study, involving 12 federal, state, local, and private laboratories throughout the country, was conducted to evaluate six methods of preparing and using the methylene blue stain for the direct microscopic count of bacteria in milk. Three of the six methods were found superior, yielding significantly higher bacteria counts, at the same time providing greater ease in counting. These three methods are: Levine and Black's acid-and-water-free stain; North's aniline oil stain; and Anderson's polychrome stain.

THE DIRECT MICROSCOPIC COUNT ON PRESERVED MILK SAMPLES: AN EFFECTIVE MEASURE FOR UNIFORM STATE-WIDE CONTROL*

1951 ◽  
Vol 14 (3) ◽  
pp. 105-108 ◽  
Author(s):  
F. B. Claiborne ◽  
K. E. Cox
Keyword(s):  
Statistical Analysis ◽  
Wide Area ◽  
Central Laboratory ◽  
Large Area ◽  
Effective Measure ◽  
Milk Samples ◽  
Evaluation Of Performance ◽  
Uniform State ◽  
Microscopic Count ◽  
Comparative Results

A survey is presented of the use of preserved milk samples shipped from a state-wide area to a central laboratory for examination. Statistical analysis of comparative results on a large number of samples proved that within 3 days there was no significant change in grade of preserved milk samples from the grade of the identical samples immediately before preservative was added. This method is suggested for uniformity of the laboratory aspects of milk grading programs throughout a large area, and for evaluation of performance of laboratories engaged in this work.

A VISCOMETRIC METHOD FOR THE ESTIMATION OF MILK CELL COUNT

1970 ◽  
Vol 33 (8) ◽  
pp. 351-354
Author(s):  
W. G. Whittlestone ◽  
L. R. Fell ◽  
H. De Langen
Keyword(s):  
Cell Count ◽  
Correlation Coefficient ◽  
Coefficient Of Variation ◽  
Rolling Ball ◽  
Simple Apparatus ◽  
Microscopic Count ◽  
Rolling Ball Viscometer

The use of a rolling ball viscometer to estimate the cell count of milk treated with California Mastitis Reagent is described. The method compares favorably with the direct microscopic count and requires relatively simple apparatus and unskilled operators. A correlation coefficient for mean count and log viscometer time of 0.93 with a coefficient of variation of 8.1% were obtained. The repeatability of viscometer readings was 0.97.

EFFECT OF PASTEURIZATION ON THE DIRECT MICROSCOPIC COUNT OF EGGS

1971 ◽  
Vol 34 (4) ◽  
pp. 209-211 ◽  
Author(s):  
H. E. Hall ◽  
D. F. Brown ◽  
R. B. Read
Keyword(s):  
Methylene Blue ◽  
Bacterial Count ◽  
Bacterial Cells ◽  
Bacterial Counts ◽  
The North ◽  
Counting Chamber ◽  
Blue Stain ◽  
Microscopic Count ◽  
Whole Egg

When pasteurized whole eggs from breakers were examined by the Direct Microscopic Count (DMC) procedure, the bacterial count frequently appeared to be too low to correlate with the observed state of decomposition. The DMC of whole egg was found to decrease during pasteurization. To determine why, DMC's were done using the North Aniline Oil - Methylene Blue Stain and the Levowitz-Weber modification of the Newman-Lampert stain. Total bacterial counts also were made using the Petroff-Hausser counting chamber. Results indicated that the reduction in count resulted from lysis of some of the bacterial cells in egg rather than to loss of stainability. Crystalline lysozyme at the concentration found in egg and whole egg preparations produced similar reductions in the DMC of bacteria isolated from egg.

A COMPARISON OF SCREENING TESTS TO DETECT ABNORMAL MILK1

1969 ◽  
Vol 32 (9) ◽  
pp. 365-368 ◽  
Author(s):  
G. Nageswararao ◽  
H. E. Calbert
Keyword(s):  
Optical Density ◽  
Catalase Activity ◽  
Screening Tests ◽  
Milk Samples ◽  
California Mastitis Test ◽  
Fresh Milk ◽  
Bulk Milk ◽  
Microscopic Count ◽  
Insignificant Correlation

The results of the Feulgen-DNA-color optical density and score, the California mastitis test (CMT) score, viscosity developed in milk samples by addition of equal volume of CMT reagent, the catalase test, the (direct microscopic count bf leucocytes, and the proportion of live leucocytes were compared using fresh, quarter, and bucket milk samples and 1 to 2 day old bulk milk samples. The Feulgen-DNA-color gave. good correlations with all the tests in all types of samples, except with the CMT of bulk samples. The CMT score and viscosity gave good correlations with all the tests on fresh milk samples and insignificant correlation with stored milk samples. The catalase test gave good correlations with all other tests in fresh samples and low but significant correlations with stored samples. Quarter and bucket milk samples contained 71% and 74% live leucocytes and bulk milk samples contained 42% live leucocytes. Holding of milk at 5 C for 5 days did not significantly change the Feulgen-DNA-color and catalase activity, slightly increased total leucocyte counts, but gradually decreased the CMT score, the viscosity, and the proportion of live leucocytes. The Feulgcn-DNA-color of milk samples containing few millions of leucocytes and the direct microscopic count of total, leucocytes gave poor reproducibility.

scholarly journals The influence of media on the recovery of bacteria from the normal mouse caecum

1982 ◽  
Vol 16 (4) ◽  
pp. 364-368
Author(s):  
J. P. Koopman ◽  
H. M. Kennis
Keyword(s):  
Normal Mouse ◽  
Viable Count ◽  
Potassium Salts ◽  
Lower Yield ◽  
Solid Agar ◽  
The Media ◽  
Agar Media ◽  
Microscopic Count ◽  
Quantitative Recovery

3 diluting fluids and 6 agar media were compared for the culture of caecal micro flora of mice. The efficiency of the media in the growth of caecal bacteria was determined by comparing the quantitative recovery (expressed as percentage of the total microscopic count) from the specimens. Of the diluting fluids saline resulted in a low yield (11·47%). Addition of potassium salts increased the yield (23·25%). A broth medium resulted in the highest recovery (44·44%). The influence of storing the caecal micro flora in 3 different diluting fluids on the yield was studied. In all diluents the viable count of caecal bacteria decreased with time, but did so least in broth medium. 6 solid agar media were tested. When saline was used as the diluting fluid, no significant differences in yields were found with all 6 media. When broth medium was used as diluting fluid and yields up to 60% were obtained, no significant differences were shown between the results with 5 media but one medium resulted in a lower yield (32·59%).

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