Microbiology and Microscopy Testing

The presence/absence (P/A) and Most Probable Number (MPN) for total coliform and E. coli bacteria is analyzed by testing method SM9223B. When the analysis is complete, a change in the color of the sample indicates the presence of bacteria. A specialized sample tray is used to determine MPN. The presence of E. coli is determined using UV light. Enterococci Bacteria is determined by the Enterolert method.


The analyses for bacteria have very short holding times. They differ slightly based on the test and the type of water being sampled. Once the incubation is started, the sample must be read 24 hours later. For this reason, we do not accept samples for these analyses on Fridays or the day before a holiday.  We can provide guidance regarding holding times, testing methods and sampling schedules when you call to request sample containers.


microbiological tests are commonly performed

  • Total Coliform Bacteria (presence/absence and MPN)
  • E. coli Bacteria (presence/absence and MPN)
  • Enterococci Bacteria (presence/absence and MPN)

Microscopy services

The following are some of the microscopy lab services available:

  • mold identification, speciation & viability
  • bacteria counts and identification
  • asbestos PCM & PLM