Rapid and economical identification and antimicrobial susceptibility test methodology for urinary tract pathogens

Abstract

To decrease the time and cost of processing urine cultures, a critical pathway to identify and perform antibiotic susceptibility tests on commonly isolated microbial pathogens within 6 h of growth detection was devised. The strategy was based on eliminating expensive kits and automated procedures when not required. A pathway utilizing a statistical matrix and 3 rapid biochemical tests required to identify the most common pathogen, Escherichia coli, was developed. This species, which represented 82% of urinary isolates, was identified in 1 h for < 10% the cost of a commercial kit. The specificity of the 1 h E. coli identification battery was .gtoreq. 99.9% with a sensitivity of 93%. This critical pathway, adapting published methods, permitted the identification of other enteric pathogens, group D streptococci and Pseudomonas aeruginosa within 4-6 h. It accounted for other microbes that required longer periods of incubation. The pathway also included a rapid disc diffusion sensitivity test. Utilizing the critical pathway strategy, 76% (E. coli frequency of 0.82 .times. E. coli sensitivity of 0.93) of all urinary pathogens were identified within 1 h; 98% were identified within 4 h with an antibiotic sensitivity test available within 6 h after the observation of growth. Costs were reduced from 2.5 to 5.0 times. This methodology is applicable to other specimen types.