Charm CowSide II Test
for Antibiotic Testing in Milk
Superior Sensitivity
The Charm CowSide II test has superior sensitivity to beta-lactams, sulfonamides,
aminoglycosides and especially tetracyclines.
Breakthrough sensitivity to tetracyclines
makes it the first inhibition test to closely match EU MRL levels.
CowSide II consists of a single service vial that contains pre-measured bacterial spores, media, and a pH indicator. Reagents are unit dosed and compartmentalized
to ensure uniformity. This eliminates reagent transfer steps and prevents inadvertent
contamination and reagent loss.
The starting color in the vial is purple. Milk is added to the vial and incubated. The
spores germinate and grow, generating acid, which is indicated by color change to
yellow. If antibiotics are present in the milk, microbial growth is retarded and/or
inhibited so that no acid is generated. Thus, antibiotic positive samples remain purple.
Simple Procedure
CowSide II Test:
Analyzes for a broad spectrum of antibiotics for the dairy industry
Detects beta-lactams and other antimicrobial drugs near regulatory limits
Features the most sensitive inhibition test for antimicrobial drugs in milk
Produces results that are stable for up to 16 hours
Runs on existing incubator equipment
Requires no expensive reader/analyzer; Easy to read visual color results
ILVOA approved
AILVO-T&V Melle, Belgium
Charm® CowSide® II Test for Beta-lactams and Other Antimicrobial Drugs in Milk
Charm CowSide II Test detects antibiotics in raw, pasteurized, or ultra-pasteurized cow milk and milk powder. Bacteria, cultured in a vial with milk, generate acid and turn a pH indicator from purple to yellow. Dairy samples that prevent a color change are considered positive for antibiotics.
Sensitivity and Selectivity
Selectivity - Antimicrobial drug-free samples should yield 90% negative results with 95% confidence.
Sensitivity – Table 1: Antimicrobial drugs detected as positive compared to regulatory levels.
Antimicrobial Drug1
Concentration2 (ppb3)
US Safe Level/ Tolerance (ppb3)
EU / CODEX MRL4 (ug/kg)
Amoxicillin
3 to 4
10
4/4
Ampicillin
3 to 4
10
4
Cefacetrile
10 to 15
None
125
Cefalexin
75 to 100
None
100
Cefalonium
15 to 20
None
20
Cefazolin
6 to 10
None
20
Cefoperazone
20 to 30
None
50
Cefquinome
40 to 60
None
20
Ceftiofur & Metabolites5
50 to 100
100
100/100
Cefuroxime
20 to 25
None
None
Cephapirin
8 to 10
20
60
Cloxacillin
10 to 25
10
30
Dicloxacillin
5 to 10
None
30
Nafcillin
5 to 10
None
30
Oxacillin
5 to 10
None
30
Penethamate7
2 to 3
None
4
Penicillin G
2 to 3
None
4
Chlortetracycline
200 to 300
300
100/100
Doxycycline
25 to 75
None
06
Oxytetracycline
75 to 100
300
100/100
Tetracycline
50 to 100
300
100/100
Gentamicin
75 to 100
30
100/200
Neomycin
100 to 150
150
1500 to 1500
Sulfadiazine
40 to 60
10
100
Sulfadimethoxine
25 to 50
10
100
Sulfamethazine (Sulfadimidine)
75 to 125
10
100 / 25
Dapsone
1 to 2
None
06
Trimethoprim
200 to 300
None
50
Erythromycin
75 to 100
50
40
Lincomycin
75 to 150
None
150
Pirlimycin
25 to 50
None
100/100
Spiramycin
300 to 400
None
200/200
Tilmicosin
25 to 35
None
&50
Tylosin
20 to 30
50
50/100
1 Antimicrobial drugs listed are representative of their respective drug families. Other drugs will be detected at different levels.
2 Positive 90% of the time with 95% confidence
3 Parts per billion or μg/L
4 Maximum Residue Limit
5 Total parent and metabolites concentration
6 Not for use in animals from which milk is produced for human consumption
7 Penethamate is rapidly converted to benzylpenicillin, the marker residue in milk
Interferences and Cross Reactivity
The Charm CowSide II Test is a broad-spectrum antibiotic screening test.
The following animal drugs, at 100 ppb, show no interference; amphenicols, fluoroquinolones and nitrofurans, or chlorothiazide, dexamethasone, dipyrone, flunixin, furosemide, ivermectin, novobiocin, oxytocin, phenylbutazone, and trichlormethiazide. Other antimicrobials are detected. There are no interferences from high fat (up to 6%), somatic cells at 5 x 105 SCC/mL, or bacteria at 3 x 105 cfu/mL.
