Actinotignum schaalii pyelonephritis in a young adult with ureteric calculus: case report

Actinotignum schaalii is a Gram-positive coccobacillus, and a member of the normal human microbiota. A. schaalii is considered as an emerging pathogen causing urinary tract infections among the elderly. Because of an anaerobic growth requirement and lack of knowledge on pathogenic potential following conventional microbiology laboratory techniques, A. schaalii is difficult to identify.

A previously well 24-year-old male presented to a tertiary care unit with fever, left flank pain, and dysuria for two days. He was initially treated with empiric oral ciprofloxacin by the general practitioner. Following admission, blood cultures and urine cultures were done, and empirical intra-venous piperacillin-tazobactam was started. X-ray of the pelvis revealed left-sided pyelonephritis and left ureteric calculi. A nephrostomy tube was inserted to relieve the obstruction which drained pus and was sent to microbiology laboratory in aerobic and anaerobic blood culture bottles. Two days later blood culture flagged positive for Gram-positive bacilli from the anaerobic bottle, and the pus from enriched anaerobic culture grew A. schaalii. The urine culture remained negative. By VITEK 2 anaerobic card and MALDI-TOF analysis, it was identified as A. schaalii. Following clinical improvement, he was discharged with oral doxycycline. Ureteric calculus was removed and remained sterile following 16s DNA analysis.

The urine Gram staining may have a role in detecting and considering anaerobic media to isolate A. schaalii. The novel diagnostic platforms are important to speciate the pathogen. Also, the lack of pathogen-specific breakpoints for antimicrobial susceptibilities made it a problem to decide on appropriate therapy.