Actinobaculum schaalii, a common cause of urine tract infections?

Abstract number: P1333

Bank S., Prag J.

Objectives:Actinobaculum schaalii is a slow growing, CO2 demanding, trimethoprim and ciprofloxacin resistent Gram positive rod and has been reported as a cause of urine tract infections, occasionally with bacteraemia. Due to its slow growth, also under optimal conditions A. schaalii is often overgrown with faster growing commensal and patogen bacteria and is therefore only found in monocultures in large quantities. Identification by morphology and biochemistry often takes weeks. Since most microbiological laboratories routinely culture urine overnight at 37°C in ambient air using Columbia blood agar and MacConkey agar A. schaalii is generally overlooked.

We developed a TaqMan real-time quantitative PCR assay targeting the gyrB gene to rapidly detect A. schaalii. The real-time PCR assay has been used to determine the presence and to get a hint to a better understanding of the clinical importance of A. schaalii.

Methods: A universal primer set was used to sequence the gyrB gene from fourteen A. schaalii strains including a A. schaalii reference strain CCUG 27420. The sequences were used to develop a TaqMan real-time quantitative PCR assay targeting the gyrB gene of A. schaalii. The assay was then tested against 37 A. schaalii isolates as well as several genetically related and clinically relevant bacterial strains. Finally the assay was used to screen 150 clinical, consecutive urine samples from patients above 60 years of age.

Results: Of the 150 urine samples 22 were found to harbour a load of more then 10⁵A. schaalii CFU/ml and 11 with less than 10⁵. Of the 33 samples where A. schaalii was detected there were 27 with common patogenic bacteria present in the sample.

Conclusion: Real-time PCR is a fast and reliable method to identify A. schaalii. A. schaalii may be an important co-patogen in many urine tract infections. Patients suffering from chronic UTI are often blindly treated with ciprofloxacin to which some patient respond well whereas others do not show improvements after prolonged treatment. If A. schaalii is the cause of infection other antibiotics are needed to cure the infection. The real-time PCR assay can be used for fast diagnosis which will lead to better antibiotic treatment and thereby faster recovery and lesser admission.