Document Type


Publication Date




In order to improve the identification of common aerobic urine cultures as well as antimicrobial susceptibility testing (AST) setup at an Academic Medical Center, work-flow modifications and MALDI-TOF technology were incorporated. Previously, the majority of species identification was achieved with conventional identification/antimicrobial susceptibility combo panels. All urine cultures, regardless of laboratory receipt time, were previously read once per day on 1st shift.


The initial workflow modification involved addition of a 2nd shift urine culture reading. Urine specimens received from 8:00 AM to 4:00 PM were read on 1st shift, while urine specimens received from 4:00 PM to 8:00 AM were read on 2nd shift. Additionally, urine cultures were sorted into categories: no growth (NG) at 24 hours, no growth at <24 hours, single colonies of growth, multiple colonies of growth, and potential contaminants. No growth cultures were signed out at 24 hours. No growth cultures at < 24 hours were reincubated to be read on subsequent shift. Cultures with growth were set aside as either single colony types or multiple colony types. Cultures of probable contaminants were signed out. Once cultures were sorted, the isolated colonies underwent MALDI-TOF analysis (Bruker) and antimicrobial susceptibility testing (AST) as appropriate. Individual technologists setup the MALDITOF target plate map and spotted the associated target plate. AST was setup at the same time. The MALDI-TOF was then operated by a central technologist and results reported by the original technologist reading the culture.


Retrospective pre-workflow (September-November 2013) and post-workflow (May, June, October 2014) modification turn-around-times were compared for 16 commonly isolated pathogens. These pathogens consisted of common urine pathogens as noted in Table 1. Staphylococcus aureus was previously identified in our laboratory by a positive coagulase test and not included in this analysis. The average turn-around-times, standard deviations and the p-values for each organism are indicated in Table 1.


Converting from conventional identification methods to MALDI-TOF, in conjunction with workflow modifications such as a 2nd culture reading, notably improved urine culture turn-around-time for identification and AST.