Use chemometric techniques in the optimization of a specific bioassay for betalactams in milk.

摘要

Aims: A microbiological bioassay using Geobacillus stearothermophilus was optimized to detect betalactams at concentrations near to the maximum residue limits (MRLs), with low cross-specificity for tetracycline. Methods and Results: A factorial design (3 x 4) was used to evaluate the effects of concentration of spores (2 0 x 106, 4 0 x 106 and 8 0 x 106 spores ml--1) and incubation time (3 0, 3 5, 4 0 and 4 5 h) on the response of the bioassay. Then, desirability function to raise the detection capabilities (CC _beta) of tetracyclines and increase sensitivity to betalactams was implemented. Significant effects of Log[S] and incubation time [It] on the CC _beta of betalactams and tetracyclines were observed. Finally, high value of global desirability (D = 0 853), adequate betalactams CC _beta (3 8 mug l--1 of penicillin "G", 27 mug l--1 of oxacillin, 8 1 mug l--1 of ampicillin, 48 mug l--1 of cloxacillin) and high tetracyclines CC _beta (5260 mug l--1 chlortetracycline, 1550 mug l--1 of oxytetracycline, 1070 mug l--1 of tetracycline) were calculated. Conclusions: The application of chemometric tools allows the optimization of a bioassay that detects betalactam residues in milk. The more robust conditions have been achieved in Log[S] = 6.30 and [It] = 4. 20 h. Significance and Impact of the Study: The logistic regression model and the desirability function are adequate chemometric techniques to improve the properties of the methods, because it is possible to increase sensitivity and decrease cross-specificity simultaneously. copyright 2011 The Authors. Letters in Applied Microbiology copyright 2011 The Society for Applied Microbiology.