Modified Assay Medium for the Turbidimetric Assay of Chlortetracycline in Feeds

1976 ◽  
Vol 59 (3) ◽  
pp. 536-539
Author(s):  
Hussein S Ragheb
Keyword(s):  
Growth Rate ◽  
Excellent Agreement ◽  
Test Organism ◽  
Plate Method ◽  
Assay Sensitivity ◽  
Assay Medium ◽  
Turbidimetric Method ◽  
Turbidimetric Assay ◽  
Commercial Feeds ◽  
Lower Recovery

Abstract In previous experiments, the turbidimetric method for determining chlortetracycline-HCI (CTC-HCl) in feeds showed lower recovery than the AOAC plate method. Although the addition of vitamins to the turbidimetric medium improved results, values by the turbidimetric method remained about 10% lower than by the plate method. A modified (1.7 × the weight recommended by the manufacturer) turbidimetric assay medium decreased assay sensitivity but did not significantly change the slope of S. aureus response to CTC-HCl. There was no evidence that vitamin fortification of the modified medium had any significant effect on the growth rate of test organism. Examination of about 100 samples of commercial feeds containing CTC-HCl showed excellent agreement in results between the turbidimetric and plate methods.

Microbiological Assay of Oxytetracycline in Feed: Manual Turbidimetric Assay and Plate Assay

1973 ◽  
Vol 56 (1) ◽  
pp. 23-30
Author(s):  
Hussein S Ragheb ◽  
Anne M Cummings ◽  
Barbara M Browning
Keyword(s):  
Coefficient Of Variation ◽  
Microbiological Assay ◽  
Plate Method ◽  
Turbidimetric Method ◽  
Plate Assay ◽  
Coefficients Of Variation ◽  
Aoac Method ◽  
Turbidimetric Assay ◽  
Turbidimetric Analysis ◽  
Feed Samples

Abstract The useful range for manual turbidimetric analysis of Oxytetracycline (OTC), using K. pneumoniae, was between 0.04 and 0.08 μg/ml in the assay tubes. Laboratory-prepared feeds containing 43.5 and 86.5 g OTC.HCl/ton gave 90–98% recovery by the turbidimetric method and 104–116% by the AOAC method, 38.211–38.213. The coefficients of variation were 9.2–13.0 and 10.2–12.8%, respectively. Feeds containing 50 and 100 g OTC.HCl and neomyein sulfate/ton gave 77% of theory when analyzed turbidimetrically and 95% of theory by the plate method. The coefficient of variation for the turbidimetric method was about 16%, indicating unsatisfactory precision. At 200 g/ton theoretical concentration of each antibiotic, both methods agreed. Commercial premixes and finished feed samples gave almost the same results by both methods. The main advantage of the turbidimetric method over the plate assay is that results can be obtained the same day of analysis.

Determination of Antibiotics in Meat Using Bacillus stearothermophilus Spores

1981 ◽  
Vol 44 (3) ◽  
pp. 194-200 ◽  
Author(s):  
M. BIELECKA ◽  
J. D. BALDOCK ◽  
A. W. KOTULA
Keyword(s):  
Sample Size ◽  
Bacillus Stearothermophilus ◽  
Test Organism ◽  
Optimal Concentration ◽  
Antibiotic Residues ◽  
Plate Method ◽  
Assay Medium ◽  
Organism Growth ◽  
Ph Variations

Ten parameters affecting sensitivity, accuracy and simplicity of the diffusion plate method for determining antibiotic residues in meat were evaluated with spores of Bacillus stearothermophilus as the test organism. Eight antibiotics were studied and included penicillin, bacitracin, tetracycline, chlortetracycline, oxytetracycline, streptomycin, erythromycin and neomycin. Sensitivity of the method was most influenced by concentration of inoculum, quantity of assay medium on the plate and sample size. The optimal concentration of inoculum was established as 2 × 105 spores/ml of medium, quantity of the assay medium on plate/100 mm dia., as 6 ml and quantity of sample poured on disc/12.7 mm dia., as 100 μl. The pH of the assay medium was also important to both antibiotic potency and test organism growth. The activity of streptomycin and erythromycin was the most sensitive to pH variations.

Rapid Automated Turbidimetric Assay for Chlortetracycline Hydrochloride, Using Leuconostoc mesenteroides as the Test Organism

1979 ◽  
Vol 62 (1) ◽  
pp. 160-167
Author(s):  
Dorothy L Mueller ◽  
Shirley J Reed ◽  
John A Barkate
Keyword(s):  
Standard Deviation ◽  
Incubation Period ◽  
Leuconostoc Mesenteroides ◽  
Test Organism ◽  
Turbidimetric Method ◽  
Relative Standard ◽  
Feed Supplements ◽  
Assay Tube ◽  
Label Claim ◽  
Turbidimetric Assay

Abstract A rapid turbidimetric assay has been developed for chlortetracycline hydrochloride (CTC-HC1) in finished animal feeds and feed supplements, using Leuconostoc mesenteroides as the test organism. Two modifications are presented: The incubation period of modification 1 is 2.5 hr and the sensitivity of the assay is 0.03 μg CTC-HC1/assay tube. Modification 2 has a sensitivity of 0.01 μg CTC-HC1/assay tube and requires an incubation period of 3.5 hr. For 21 feed formulations, the turbidimetric method recovered 95.7% of label claim. Recoveries of CTC-HC1 standards from the same feeds ranged from 93.4 to 134% with a mean of 103% . The relative standard deviation among day-to-day duplicates is 3.50% for the faster modification and 1.63% for the more sensitive modification.

Microbiological Plate and Turbidimetric Assays of Chlortetracycline in Feeds: Collaborative Study

1977 ◽  
Vol 60 (5) ◽  
pp. 1119-1124
Author(s):  
Hussein S Ragheb
Keyword(s):  
Statistical Difference ◽  
Collaborative Study ◽  
Plate Method ◽  
Standard Curve ◽  
Turbidimetric Method ◽  
Plate Assay ◽  
Significant Difference ◽  
Turbidimetric Assay ◽  
Swine Feed ◽  
Feed Samples

Abstract The manual and automated turbidimetric assays and a modified official plate assay for Chlortetracycline (CTC-HCl) in feed were collaboratively studied. Three feed samples (swine feed, 100 g CTC-HCl/ton; premix I, 20 g each of CTC-HCl and sulfamethazine/lb, and 10 g penicillin/lb; and premix II, 50 g CTC-HCl/lb) were analyzed at 2 dilutions. Twelve laboratories conducted the plate assay; 8 laboratories, the manual turbidimetric method ; and 7 laboratories, the Autoturb analysis. Within a method, there was no significant difference between dilutions. Between methods, there was a significant difference between the manual turbidimetric plate assays only for swine feed. However, the same sample dilutions or the average values of the 2 dilutions for both methods showed no statistical difference. Among the collaborators, the slope of CTC-HCl standard curve varied between about 2.0 and 3.0 for the plate method. The turbidimetric assay has been adopted as official first action for feeds containing >20 g CTC-HCl/lb.

Turbidimetric and Diffusion Assay of Bacitracin in Feeds

1976 ◽  
Vol 59 (3) ◽  
pp. 526-535
Author(s):  
Hussein S Ragheb ◽  
Lisa Black ◽  
Sherrie Graham
Keyword(s):  
Ion Concentration ◽  
Median Response ◽  
Turbidimetric Method ◽  
Phosphate Ion ◽  
Plate Assay ◽  
Accuracy And Precision ◽  
Turbidimetric Assay ◽  
Zinc Bacitracin ◽  
Diffusion Assay ◽  
And Diffusion

Abstract A manual turbidimetric method for determining zinc or methylene disalicylate bacitracin in feeds was developed. When zinc ions (10−4M) were added to the medium and the phosphate ion concentration in standard solutions was decreased to 1%, the median response of Streptococcus faecalis was about 0.038 unit. Feeds analyzed by the turbidimetric assay should be prewashed with petroleum ether and extracted with pyridine as in 42.204. Zinc bacitracin standards added to swine and broiler rations were recovered at 93.1–102.6% by the turbidimetric method. Excellent agreement between the manual turbidimetric method and the plate assay was also obtained for finished feeds containing the zinc or methylene disalicylate salt of the antibiotic. The turbidimetric method appears to have high accuracy and precision. It is more rapid and less costly than the plate assay.

Microbiological Turbidimetric Analysis of Low Chlortetracycline Concentrations in Feeds

1975 ◽  
Vol 58 (3) ◽  
pp. 602-608
Author(s):  
Hussein S Ragheb ◽  
Linda S Porubcan
Keyword(s):  
Bacterial Growth ◽  
Room Temperature ◽  
Cattle Feed ◽  
Standard Curve ◽  
Turbidimetric Method ◽  
Feed Supplements ◽  
Turbidimetric Assay ◽  
Swine Feed ◽  
Low Levels ◽  
Turbidimetric Analysis

Abstract Recovery studies in which chlortetracycline hydrochloride (CTC-HCl) standard was added to cattle and swine feed supplements at 4.09–9.99 g/ton showed lower antibiotic recovery turbidimetrically (80.6–98.7%) than by the AOAC modified standard as in 38.179(d) (91.2–98.7%) and the plain buffer as in 38.179(b) (93.8-133.0%) methods. Three feeds fortified with a commercial premix at the levels of 5.0 and 10.0 g CTC-HCl/ton showed an overall CTC-HCl recovery of 87.6–110.6% by manual turbidimetric assay. Results were 89.1–108.7% by the AOAC inactivated feed diluent standard and 95.4–125.4% by the plain buffer methods. For some sample extracts (as in cattle feed) the use of heat to stop bacterial growth in the turbidimetric method caused formation of a precipitate. Cooling of cultures to room temperature and rapid reading of sample turbidity followed by standard curve concentrations minimized this interference. The manual turbidimetric assay of low levels of CTC-HCl in feeds appears to offer advantages over other methods.

Comparison of Automatic and Manual Turbidimetric Analyses of Tylosin in Feeds with the Plate Method

1973 ◽  
Vol 56 (2) ◽  
pp. 363-366
Author(s):  
Hussein S Ragheb ◽  
H Latham Breunig ◽  
Robert E Scroggs
Keyword(s):  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Plate Method ◽  
Relative Standard ◽  
Significant Difference ◽  
Aoac Method ◽  
Turbidimetric Assay ◽  
The Mean ◽  
The Difference ◽  
Feed Samples

Abstract Two laboratories participated in a comparison of a manual turbidimetric assay with the AUTOTURB® System and the AOAC method of analysis of tylosin in 4 feed samples. Results showed no significant difference between the 2 turbidimetric assays. When the AOAC method was considered, the difference between laboratories was significant. On an overall basis the turbidimetric methods were significantly higher than the plate method. The relative standard deviation was higher (6.72%) for the plate assay versus turbidimetric assay (4.5%). The mean recovery in both laboratories was significantly less than the labeled amount of tylosin by all 3 methods.

scholarly journals Development and population growth of Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) in the laboratory

2008 ◽  
Vol 68 (2) ◽  
pp. 379-383 ◽  
Author(s):  
FC. Massaro ◽  
O. Rocha
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Generation Time ◽  
Doubling Time ◽  
Test Organism ◽  
Laboratory Culture ◽  
Individual Growth ◽  
Population Doubling ◽  
Population Doubling Time ◽  
The Individual

Hydras, the most representative freshwater Cnidaria, are of common occurrence in bodies of water in every continent except Antarctica. This study was planned with the aim of maintaining a population of Hydra viridissima in laboratory culture to enable the determination of the individual and population growth-rates of this species, as well as its population doubling time and generation time, with a view to employing these common animals as test-organisms in ecotoxicological assays. The organisms were maintained in reconstituted water at 20 ± 2 °C, illuminated at 800 lux with a photoperiod of 12 hours light: 12 hours dark, and were fed on neonates of the cladoceran Ceriodaphnia silvestrii (3 or 4 neonates per hydra, 3 times a week). The individual growth-rate (k) of the species was 0.43, the maximum length of the column 2.53 mm and the generation time 6.6 ± 1.5 days on average. The hydra population showed an intrinsic growth-rate (r) of 0.0468, according to the fitted curve, and a doubling time of 14.8 ± 2.63 days. Hydra viridissima is easy to grow in the laboratory and performs well in the conditions used in this study. It is thus a promising candidate test-organism for ecotoxicological studies.

Evaluation of Two Microbiological Methods for Detecting Residual Antibiotics in Milk

1976 ◽  
Vol 59 (5) ◽  
pp. 1122-1124
Author(s):  
Larry A Ouderkirk
Keyword(s):  
Bacillus Subtilis ◽  
Dairy Industry ◽  
Test Organism ◽  
Plate Method ◽  
Plate Technique ◽  
Whole Milk ◽  
Microbiological Methods ◽  
Aoac Official ◽  
Disk Method ◽  
Official Methods Of Analysis

Abstract Two methods described in the AOAC Official Methods of Analysis for the detection of penicillin residues in whole milk were evaluated to determine the capability of each method to detect residues of 12 antibiotics used in the dairy industry. The first method, a cylinder-plate method that uses Sarcina lutea as the test organism, detected levels of 1 ppm of 8 of the 12 antibiotics tested. The second method, using paper disks with Bacillus subtilis as the test organism, detected approximately 1 ppm of only 4 antibiotics. This disk method was unable to detect <40 ppm of 5 of the antibiotics tested. The data indicate that the S. lutea cylinder-plate technique is more sensitive to more antibiotics than the B. subtilis disk method and is far superior for screening purposes.

Urine contains an inhibitor for turbidimetric determinations of protein.

1982 ◽  
Vol 28 (11) ◽  
pp. 2294-2296
Author(s):  
J Nakamura ◽  
M Yakata
Keyword(s):  
Molecular Mass ◽  
Gamma Globulin ◽  
Gel Filtration ◽  
Relative Molecular Mass ◽  
Sulfosalicylic Acid ◽  
Turbidimetric Method ◽  
Analytical Recovery ◽  
Dye Binding ◽  
Turbidimetric Assay ◽  
Contrast Measurement

Abstract Our examination of urine components separated by gel filtration revealed the presence of an inhibitor that decreases the analytical recovery of protein in a turbidimetric assay involving sulfosalicylic acid as reagent (Proc. Soc. Exp. Biol. Med. 92: 748, 1956). The apparent relative molecular mass of this inhibitor was in the range 160 000-240 000. A study with purified proteins showed a similar inhibition by gamma-globulin, glycoprotein, and beta-lipoprotein in the assay of albumin by the same turbidimetric method. In contrast, measurement of protein by a dye binding method was not affected by these materials. The low values for apparent urinary protein given by the turbidimetric method as compared with those by the dye-binding method are at least partly ascribable to the inhibitor.

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