While antibiotic therapy is most commonly determined by blood cultures, Dr. Bradley and her colleagues sought to understand if stone culture is, in fact, a better method by which to select antibiotic therapy.
A retrospective analysis of 181 PCNL procedures revealed that 32 patients (17.7%) experienced postoperative systemic infectious complications. As depicted in the figure below from Dr. Bradley’s poster, stone cultures were positive in 83% of these patients, which was significantly higher than that for blood cultures (23%). Additionally, while each of these patients had a positive preoperative midstream specimen of urine (MSSU), not all patients with a positive preoperative MSSU went on to develop a postoperative infection.
Figure 1 - Positive blood and stone cultures in patients with SIRS following PCNL
The group of investigators concluded that stone culture, instead of blood culture, should be used to guide antibiotic selection. Many members of the audience had their own experience with obtaining stone cultures, which led to a hearty discussion regarding the practice. Dr. Bradley stated that it is standard practice to obtain stone cultures on PCNL patients at her institution; however, one gentleman in the audience felt that, based on his experience, selectively obtaining stone cultures based on patients with risk factors was more cost-effective and yielded positive results more often.
Another audience member spoke to the strength of obtaining stone cultures, as they are obtained at the time of PCNL rather than after a patient has manifested symptoms of systemic infection, the latter being when blood cultures are obtained. Thus, stone cultures may expedite appropriate antibiotic selection and prevent the confounding effects that empirically given antibiotics may have on blood cultures. Other members of the audience engaged in a discussion regarding the promise of DNA cultures for stones, which can provide data within 24 hours and can provide information regarding bacterial resistance and presence of fungal organisms. There certainly seemed to be a consensus among audience members that there is value in obtaining stone cultures, though the frequency that this practice should be done remains debatable.
Presented by: Caroline Bradley, MD, Academic Foundation Year 2, NHS Greater Glasgow and Clyde, Glasgow, Scotland, United Kingdom
Co-Authors: Lynne Kerr, ST5, NHS Greater Glasgow and Clyde, Glasgow, Scotland, United Kingdom, Jane Hendry, Gareth Jones, Glasgow, Scotland, United Kingdom
Written by: Frank Jefferson, Department of Urology, University of California-Irvine, medical writer for UroToday.com at the 36th World Congress of Endourology (WCE) and SWL - September 20-23, 2018 Paris, France