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Louisiana Department of Health & Hospitals | Kathy Kliebert, Secretary

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Heterotrophic Plate Count of Water

PHL Location

Central Laboratory, Amite Laboratory, Lake Charles Laboratory, Shreveport Laboratory

CPT Code

N/A

Synonyms

HPC, Standard Plate Count, SPC

Brief Description of Test

Heterotrophic Plate Count, also known as “standard plate count”, is a technique used for estimating the viable bacteria population in a water sample for aerobic and facultatively anaerobic bacteria .

Possible Results

colony count/ ml

Reference Range

30-300 colonies

Specimen Type

Drinking water, vending water, bottled water, dairy waters of all types, including recirculating cooling water and dairy water with glycol.

Specimen Container(s):

Drinking water and dairy water samples are collected in sterile, disposable, 100ml Nasco Whirl-Pak bags, each containing a 10 mg sodium thiosulfate tablet. Bottled waters are submitted in the containers in which they are sold.

Minimum volume accepted:

100 ml

Collection Instructions

N/A

Storage and Transport Instructions

Store and transport sample(s) in clean ice cooler. Dairy water samples must be at 0.0-4.4ºC upon receipt into the laboratory. Maximum time from collection until analysis is 8 hours.

Causes for Rejection

  • Sample > 8 hours old
  • Sample frozen
  • No sample ID
  • Unacceptable collection container
  • Insufficient sample
  • Sample leakage
  • Incomplete sample form

Limitations of the Procedure

Difficult to enumerate when bacterial population of sample is extreme.

Interfering Substances

Excessive chlorine, fungal growth.

References

DOLSOPDWM-02 Hetertophic Plate Count Method for the Enumberation of Heterotrophs in Drinking Water Pour Plate Method SOP of the LA DHH-OPH Laboratory.

Additional Information

Complete a Lab 8 Laboratory Request and Report Form. The following is required Lab 8 information: Sample sequence #’s and project code, name of supply, collected by (name or initials), PWS ID (if applicable), date and time of collection, type of sample and disinfectant residual (if applicable).