Improved methods for the enumeration of heterotrophic bacteria in bottled mineral waters

At this time the European Union regulations require that the heterotrophic plate counts (HPC) of mineral waters be assessed at two recovery temperatur es: 22 degreesC for 72 h and 37 degreesC for 24 h. This procedure is time c onsuming and expensive. Development of new rapid methods for microbiologica l assessment of the microbial flora in the bottled water is an industry-dri ven need. The objectives of this work were to develop a method for the HPC that utili ses only one recovery temperature and one incubation period and evaluate th e use of. the LIVE/DEAD(R) BacLight(TM) Bacterial Viability Kit, 5-cyano-2, 3-ditotyl tetrazolium chloride (CTC) and impedance methods to enumerate via ble bacteria in bottled mineral water. Results showed that incubation at 30 degreesC could be used instead of incu bation at 22 degreesC and 37 degreesC. Good correlation exists between coun ts at 30 degreesC and counts at 22 degreesC (r > 0.90) and all the pathogen s important in mineral water analyses grow similarly at 30 degreesC and 37 degreesC during 24 h. It was demonstrated that impedance methods might be useful to the mineral w ater 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. (C) 2001 Published by Elsevier Science B.V.