Robust experimental design for optimizing the microbial inhibitor test for penicillin detection in milk.
OBJECTIVE
To use experimental design techniques and a multiple logistic regression model to optimize a microbiological inhibition test with dichotomous response for the detection of Penicillin G in milk.


RESULTS
A 2(3) x 2(2) robust experimental design with two replications was used. The effects of three control factors (V: culture medium volume, S: spore concentration of Geobacillus stearothermophilus, I: indicator concentration), two noise factors (Dt: diffusion time, Ip: incubation period) and their interactions were studied. The V, S, Dt, Ip factors and V x S, V x Ip, S x Ip interactions showed significant effects.


CONCLUSIONS
The use of 100 microl culture medium volume, 2 x 10(5) spores ml(-1), 60 min diffusion time and 3 h incubation period is recommended. In these elaboration conditions, the penicillin detection limit was of 3.9 microg l(-1), similar to the maximum residue limit (MRL). Of the two noise factors studied, the incubation period can be controlled by means of the culture medium volume and spore concentration.


CONCLUSIONS
We were able to optimize bioassays of dichotomous response using an experimental design and logistic regression model for the detection of residues at the level of MRL, aiding in the avoidance of health problems in the consumer.
Cátedra de Biofísica, Departamento de Ciencias Básicas, Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral, Esperanza, República Argentina.
O G
OG
Nagel
M P
MP
Molina
J C
JC
Basílico
M L
ML
Zapata
R L
RL
Althaus
D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis* / Q000494:pharmacology; D001406:Bacillaceae / Q000187:drug effects; D001681:Biological Assay / Q000379:methods; D002417:Cattle; D005506:Food Contamination / Q000032:analysis; D016015:Logistic Models; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D010406:Penicillins / Q000032:analysis* / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D010406:Penicillins