Charm provides the only Bacicillus
stearothermophilus Disc Assay
officially approved for bulk tank
milk† and producer samples‡
The Charm Bacillus stearothermophilus
Disc Assay (BSDA) is a microbial inhibition
test designed to detect penicillin G,
ampicillin, amoxicillin, and cephapirin
at or below the established Safe Levels/
Tolerances. This method has been
performance tested and validated by
an independent laboratory. The test is
designed for use by dairy, veterinary,
laboratory, field, and regulatory personnel.
†Appendix N of the Pasteurized Milk Ordinance (PMO)
‡Section 6 of the Pasteurized Milk Ordinance (PMO)
Bacillus stearothermophilus Disc Assay (BSDA) AT A GLANCE
Objective and quantitative by zone size
measurement. No questionable color changes.
Detects penicillin G, ampicillin, amoxicillin, and
cephapirin close to Safe Level/Tolerance.
More resistant to natural inhibitors than other
microbial inhibition assays..
Certified 1OO x 1O6 spores per tablet.
No colony counting/spore titre.
No glass ampules.
Stable up to a year at room-temperature.
No autoclaving of PMI agar.
Beta-Iactamase tablets for confirmation.
Includes 5 ppb Penicillin G standard made
from USP Reference Standard
Charm® B. stearothermophilus Tablet Disc Assay for Amoxicillin, Ampicillin, Cephapirin, and Penicillin G for Raw Commingled and Finished Cow and Goat Milk
The Bacillus stearothermophilus Disc Assay (BSDA) is a microbial inhibition test to detect beta-lactam drugs. This method has been performance tested by an independent laboratory and validated for detection of these drugs at or below the established safe level/tolerance. The test is designed for use by dairy, veterinary, laboratory, field, and regulatory personnel.
Finished Milk - The Charm BSDA has been evaluated by the FDA and has been found to be acceptable for testing the following drugs at or below the Safe Level/Tolerance in pasteurized, homogenized white milk (0% fortified to 3.5% fat): amoxicillin, ampicillin, cephapirin, and penicillin G.
Sensitivity and Selectivity
Selectivity – 60 negative milk samples were evaluated by an independent laboratory and 0 of these samples tested positive with the Charm B. stearothermophilus Tablet Disc Assay.
Table 1. Sensitivity – Results of sensitivity evaluations are presented below. The drugs indicated by an asterisk (*) have demonstrated 90% positive with 95% confidence level which is at least 25% less than the Safe Level/Tolerance.
CONCENTRATION (ppb‡)
DRUG
Amoxicillin
*Ampicillin
*Cepharin
*Penicilin G
1
0%
2
0%
0%
0%
0%
3
0%
4
10%
3%
0%
55%
5
100%
6
30%
67%
8
90%
100%
0%
10
100%
100%
14
100%
20
100%
Calculated 90/95% detection level (ppb)
7.5
6.7
11.7
3.8
Safe Level/Tolerance (ppb)
10
10
20
5
‡parts per billion
Interferences and Cross Reactivity
There are no known interferences from the following animal drugs at 100 ppb: chlorothiazide, chlortetracycline, doxycycline, oxytetracycline, tetracycline, desfuroylceftiofur (DFC) related metabolites, dexamethasone, dipyrone, erythromycin, furosemide, gentamicin, neomycin, streptomycin, ivermectin, oxytocin, PABA, phenylbutazone, sulfadiazine, sulfadimethoxine, sulfamethazine, sulfanilamide, sulfapyridine, sulfathiazole, trichlormethiazide, and thiabendazole.
