title: Improved methods for the enumeration of heterotrophic bacteria in bottled mineral waters.
abstract: At this time the European Union regulations require that the heterotrophic plate counts (HPC) of mineral waters be assessed at two recovery temperatures: 22 degrees C for 72 h and 37 degrees C for 24 h. This procedure is time consuming and expensive. Development of new rapid methods for microbiological assessment of the microbial flora in the bottled water is an industry-driven need. The objectives of this work were to develop a method for the HPC that utilises only one recovery temperature and one incubation period and evaluate the use of, the LIVE/DEAD(R) BacLight Bacterial Viability Kit, 5-cyano-2,3-ditotyl tetrazolium chloride (CTC) and impedance methods to enumerate viable bacteria in bottled mineral water. Results showed that incubation at 30 degrees C could be used instead of incubation at 22 degrees C and 37 degrees C. Good correlation exists between counts at 30 degrees C and counts at 22 degrees C (r>0.90) and all the pathogens important in mineral water analyses grow similarly at 30 degrees C and 37 degrees C during 24 h. It was demonstrated that impedance methods might be useful to the mineral water industry as a rapid indicator of microbiological quality of the water. Results obtained with BacLight and CTC were similar to those obtained with plate counts.
authors.affiliation: Escola Superior de Biotecnologia, R. Dr. António Bernardino de Almeida, 4200-072, Porto, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Ramalho
authors.forename: J
authors.initials: J
authors.lastname: Cunha
authors.forename: P
authors.initials: P
authors.lastname: Teixeira
authors.forename: P A
authors.initials: PA
authors.lastname: Gibbs
mesh_terms: D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification*; D001431:Bacteriological Techniques; D015169:Colony Count, Microbial / Q000379:methods; D017097:Electric Impedance; D008900:Mineral Waters / Q000382:microbiology*; D011933:Reagent Kits, Diagnostic; D013696:Temperature; D013778:Tetrazolium Salts / Q000378:metabolism
chemical_list: D008900:Mineral Waters; D011933:Reagent Kits, Diagnostic; D013778:Tetrazolium Salts; C075453:5-cyano-2,3-ditolyltetrazolium