Direct count is one of many techniques used to measure bacterial growth. In this method, individual bacterial cells are directly observed and counted using a Petroff-Hausser counting chamber. 

Limitations of direct microscopic count

• Unable to differentiate viable and nonviable cells so both living and dead cells are counted
• Is not sensitive to populations of less than 1 million cells
• The particles in the samples and the cells are mixed together 
• Precision is difficult to accomplish 
• Some cells are likely missed because of the difficulty in being able to see smaller cells under the microscope
• Higher susceptibility to eye fatigue
• When using a sample that is not stained, a phase contrast microscope is needed