Positive kidney stone cultures independently predict an increased risk of sepsis after stone percutaneous nephrolithotomy (PCNL), Israeli researchers concluded.

Ohad Shoshany, MD, and colleagues at Tel Aviv University studied 206 consecutive patients undergoing PCNL. Forty-five patients had a positive stone culture (group A). These patients were compared with 161 patients who had a sterile stone culture (group B). 

Postoperative sepsis occurred in 31% of group A versus 5.9% of group B. In multivariate analysis, a positive stone culture was independently associated with a significant 6.9 times increased odds of postoperative sepsis, the researchers reported online Urolithiasis.

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According to the investigators, all patients responded well to treatment and experienced no septic complications. Among the patients with positive cultures, Enterococcus species and Escherichia coli were the most prevalent gram positive and gram negative bacteria, respectively, isolated from 29.4% and 21.6% of patients, respectively.

Researchers ordered a preoperative urine culture for all patients 2–4 weeks prior to surgery. Patients with a negative preoperative urine culture received prophylactic antibiotics with 1 gram cefamezin in accordance to American Urological Association/European Association of Urology guidelines. Those with a positive urine culture or a history consistent with infected stones were treated preoperatively with a full course of antibiotics for a minimum of 7 days, the researchers stated.

Dr. Shoshany’s team reported that quinolone resistance was high in both gram negative and gram positive bacteria.

“One of the important measures to reduce the risk of postoperative infection is the preoperative antibiotic treatment to sterilize the urine,” the authors wrote. “However, infected stone patients pose a specific challenge, as in some patients the urine cannot be sterilized despite repeat antibiotic courses, due to stone colonization and poor antibiotic penetration into the stone.”