Actinobaculum shaalii: a new uropathogen?

Background and Aims. Actinobaculum schaalii is a facultative anaerobic, Gram-positive rod-shaped species phylogenetically related to Actinomyces. A. schaalii is an emerging pathogen causing urinary tract infections (UTI) in both children and adults; although, as part of the human genitourinary tract flora, it is frequently overlooked or considered as a contaminant. While the phenotypic identification of A. schaalii is difficult, the recent Matrix-Assisted Laser Desorption/Ionisation Time-Of-Flight-mass spectrometry (MALDI TOF) technology could represent a promising tool for its identification.
Materials and Methods. This is a retrospective study including all known cases (n=7) of A. schaalii infections occurred (between July 2013 and November 2013) at the Microbiology Laboratory of the A. Cardarelli Hospital, in Campobasso (Italy).
Results. All the 7 A. schaalii collected strains, resulted in vitro susceptible to most of the drugs commonly used for urinary tract infections, but resistant to ciprofloxacin, a first-line antibiotic in the treatment of prostatitis. All isolates were susceptible to amoxicillin, amoxicillin-clavulanic, ampicillin-sulbactam, cefuroxime, gentamicin, piperacillin-tazobactam, vancomicin, tetracycline (no EUCAST breakpoints). All except two isolates were susceptible to cefotaxime; 3/7 and 5/7 strains were clindamicin and levofloxacin resistant, respectively.
Conclusions. As most antibiotics empirically prescribed for UTI (mainly fluoroquinolones or trimethoprim/sulfamethoxazole) are not effective against A. schaalii, the appropriate onset of treatment was delayed by an average of 2.8 days. The implementation of the newer MALDI TOF technology in routine diagnostic procedures may allow a more reliable and rapid identification of A. schaalii in future.