Development of microbiological analyzer based on coherent fluctuation nephelometry

Abstract

Rapid antibiotic susceptibility testing of etiologically significant microflora is an actual problem in clinical microbiology. Microbiological analyzers based on traditional nephelometry have a number of limitations. Coherent fluctuation nephelometry (CFN) method is almost insensitive to cuvette quality and allows constructing microbiological analyzers of high usability providing detection of microbial growth starting from 103–104 CFU/ml. CFN based microbiological analyzers were used for rapid antibiotic susceptibility testing of bacterial isolates and urine microflora without isolation within 3-6 hours in two independents studies. In the first study, susceptibility of 18 clinical bacterial isolates to 5 broad-spectrum antibiotics was determined by the disk diffusing method (DDM), the serial dilutions method (SDM) and CFN-analyzer. The pairwise agreement between the results was from 74.6% to 84.6%, the agreement between all three methods was 70%. In the second study, susceptibility of bacteria cultures in 21 urine samples from patients with bacteriuria to 13 broad-spectrum antibiotics was determined by CFN-analyzer without isolating the bacteria, the corresponding isolates were tested by DDM. The agreement between the results was 87.8%. Thus, CFN-method provides the possibility to construct multichannel microbiological analyzers of high sensitivity and usability. Such analyzers allow rapid antibiotic susceptibility testing of both bacterial isolates and urine microflora without bacteria isolating. CFN-analyzer allows implementation of full cycle of analyses, from bacteriuria confirmation to antibiotic susceptibility testing on the day of urine samples collection.