African Journal of Biotechnology Vol. 3 (1), pp. 82-87, January 2004

Full Length Research Paper

Laboratory evaluation of the improved tube test detection limits for b-lactam residues in Kenyan milk

Anakalo Shitandi¹* and Gathoni Kihumbu²

¹Antibiotic research laboratory, Dept. of Food Science, Swedish University of Agricultural Sciences, P.O. Box 7051, S- 750 07 Uppsala, Sweden.

²Microbiology laboratory, Guildford Dairy Institute, Egerton University, P.O. Box 536, Njoro, Kenya.

*Corresponding author. E-mail: anakalo.shitandi@lmv.slu.se, ashitandi@eudoramail.com: Tel: 48 67 20 60. Fax: 48 18 67 29 95.

Accepted 22 December 2003

In Kenya there is currently no screening of antimicrobial drug residues in milk. This study evaluated the improved tube test as a possible screening method using seven representatives of the b-lactam antibiotics. The group comprises antimicrobials most frequently used to treat bacterial infections in dairy cows. Each antimicrobial was tested at five concentrations based on established codex alimentarius maximum residue limits (MRLs). Test parameters studied were practicability and limits of detection (LODs) compared to MRLs and repeatability. The LODs established using a logistic regression model were: penicillin G (2 µg /kg), ampicillin (2 µg /kg), amoxicillin (2 µg /kg), oxacillin (30 µg /kg), cefalexin(100 µg /kg), cephapirin(60 µg /kg) and ceftiofur(100 µg /kg) all within codex alimentarius MRLs. The cost per ten samples using the improved tube test was less than 1 USD compared with 5 USD for the Delvo test. The improved tube test is concluded to be an affordable method, which could be used for qualitative identification of residues in low-income countries dairies.

Key words: Improved tube test, b-lactams, Kenyan milk, maximum residue limits.