Culture Independent Raman Spectroscopic Identification of Urinary Tract Infection Pathogens: A Proof of Principle Study

Urinary tract infection (UTI) is a very common disease. Up to every second women will experience at least one UTI episode during her lifetime. The gold standard for identifying the infectious microorganisms is the urine culture. However, culture methods are time consuming and need at least 24 h until the results are available. Here, we report about a culture independent identification procedure by using Raman microspectroscopy in combination with innovative chemometrics. We investigated for the first time directly urine samples by Raman microspectroscopy on a single-cell level. In a first step a database of eleven important UTI bacterial species, which were grown in sterile filtered urine, was built up. A support vector machine (SVM) was used to generate a statistical model which allows a classification of this dataset with an accuracy of 92% on species level. This model was afterwards used to identify infected urine samples of ten patients directly without a preceding culture step. Thereby we were able to determine the predominant bacterial species (seven Escherichia coli and three Enterococcus faecalis) for all ten patient samples. These results demonstrate that Raman microspectroscopy in combination with support vector machines allows an identification of important UTI bacteria within two hours without the need of a culture step.