A Modified Selective Medium Containing Benzalkonium Chloride (BKC) for the Isolation of <i>Pseudomonas aeruginosa</i>from Raw Milk
- 1 Department of Food Engineering, Faculty of Engineering, University of Ankara, Diskapi, Ankara 06110, TURKEY
- 2 Institute of Biotechnology, University of Ankara, Golbasi, Ankara 06830, TURKEY
- 3 Department of Food Engineering, Faculty of Engineering, University of Ankara, Diskapi, Ankara 06110, TURKEY
Abstract
A modified selective medium (modified Cetrimide Agar, mCA) consisting of 200 μg/mL benzalkonium chloride (BKC) was developed for the isolation of Pseudomonas aeruginosa from raw milk. Initially, a total of 55 isolates were obtained from 14 raw milk samples collected from several dairy plants in Ankara, Turkey. Among these isolates, 19 were identified as Pseudomonas aeruginosa , 28 as Pseudomonas fluorescens , 4 as Acinetobacter baumannii , 2 as Enterobacter intermedium , 1 as Enterobacter agglomerans , and 1 as Escherichia coli using Microbact biochemical test kit. BKC was chosen as a selective agent to suppress growth of competitive flora because it is very effective against a wide range of Gram-negative bacteria while P. aeruginosa is resistant. MICs (minimum inhibitory concentration) for BKC were determined by agar dilution method. The concentration of 200 μg/mL BKC inhibited competitive flora, while 90% of P. aeruginosa strains were resistant. When the results of enumeration of P. aeruginosa and other Gram (-) bacteria in Cetrimide Agar (CA) and mCA were compared, it was observed that mCA was more selective than the standard CA in preventing the growth of competitive flora especially of P. fluorescens .
- S. Flint and N. Hartley, “A Modified Selective Medium for the Detection of Pseudomonas Species that Cause Spoilage of Milk and Dairy Products,” International Dairy Journal, Vol. 6, No. 2, 1996, pp. 223-230. doi:10.1016/0958-6946(95)00007-0
- T. S. Gunasekera, M. R. Dorsch, M. B. Slade and D. A. Veal, “Specific Detection of Pseudomonas spp. in Milk by Fluorescence in Situ Hybridization Using Ribosomal RNA Directed Probes,” Journal of Applied Microbiology, Vol. 94, No. 5, 2003, pp. 936-945. doi:10.1046/j.1365-2672.2003.01930.x
- M. L. Martins, C. L. O. Pinto, R. B. Rocha, E. F. Araújo and M. C. D. Vanetti, “Genetic Diversity of Gram-Negative, Proteolytic, Psychrotrophic Bacteria Isolated from Refrigerated Raw Milk,” International Journal of Food Microbiology, Vol. 111, No. 2, 2006, pp. 144-148. doi:10.1016/j.ijfoodmicro.2006.06.020
- B. Do?an and K. J. Boor, “Genetic Diversity and Spoilage Potentials among Pseudomonas spp. Isolated from Fluid Milk Products and Dairy Processing Plants,” Applied and Environmental Microbiology, Vol. 69, No. 1, 2003, pp. 130-138. doi:10.1128/AEM.69.1.130-138.2003
- W. Dwight, J. R. Lambe and P. Stewart, “Evaluation of Pseudosel Agar as an Aid in the Identification of Pseudomonas aeruginosa,” Applied Microbiology, Vol. 23, No. 2, 1972, pp. 377-381.
- R. Ramalho, J. Cunha, P. Teixeira and P. A. Gibbs, “Modified Pseudomonas Agar: New Differential Medium For the Detection/Enumeration of Pseudomonas aeruginosa in Mineral Water,” Journal of Microbiology Methods, Vol. 49, No. 1, 2002, pp. 69-74. doi:10.1016/S0167-7012(01)00365-7
- L. Laine, J. D. Perry, J. Lee, M. Oliver, A. L. James, C. De La Foata, D. Halimi, S. Orenga, A. Galloway and F. K. Gould, “A Novel Chromogenic Medium for Isolation of Pseudomonas aeruginosa from the Sputa of Cystic Fibrosis Patients,” Journal of Cystic Fibrosis, Vol. 8, No. 2, 2009, pp. 143-149. doi:10.1016/j.jcf.2008.11.003
- H. A. Lilly and E. J. L. Lowbury, “Cetrimide-Nalidixic Acid Agar as a Selective Medium for Pseudomonas aeruginosa,” Journal of Medical Microbiology, Vol. 5, No. 1, 1972, pp. 151-153. doi:10.1099/00222615-5-1-151
- G. Szita, V. Tabajdi, A. Fabian, G. Biro, O. Reichard and P. S. K?rm?czy, “A Novel, Selective Synthetic Acetamide Containing Culture Medium for Isolating Pseudomonas aeruginosa from Milk,” International Journal of Food Microbiology, Vol. 43, No. 1-2, 1998, pp. 123-127. doi:10.1016/S0168-1605(98)00104-4
- P. H. McCay, A. A. Ocampo-Sosa and G. T. A. Fleming, “Effect of Subinhibitory Concentrations of Benzalkonium Chloride on the Competitiveness of Pseudomonas aeruginosa Grown in Continuous Culture,” Microbiology, Vol. 156, No. 1, 2010, pp. 30-38. doi:10.1099/mic.0.029751-0