[Determination of the number of pathogens in bacterial suspensions using laser nephelometry in comparison to the photometry and plate counting method].

We determined the number of bacteria in suspensions of three bacterial species (S. aureus ATCC 25923, E. coli ATCC 25922, P. aeruginosa ATCC 27853) in liquid medium using two optical methods - laser-nephelometry and photometry. These results were compared with the CFU/ml determined by the agar plate test in each suspension. Further we defined the applicable range of measurement of both optical methods. The calculated factor of correlation (r = 0.99) attested the very good conformity of the results obtained by both optical methods. The determination of the number of bacteria in suspensions by laser-nephelometry is a simple though very sensitive method. The results can well be reproduced. A further advantage of this method is the immediate information about the number of bacteria in suspension. All these facts recommend laser-nephelometry as a method useful in any bacteriological routine laboratory for determination of the number of bacteria in suspensions.