Background: There are at least three distinct European leech species used medicinally: Hirudo medicinalis, H. orientalis, and H. verbana. Infection caused by leech microbiota is the most widely reported complication. Few studies have reported the culturable and unculturable bacteria and examined the antibiotic resistances in H. orientalis.
Methods: Following stratified random sampling from a major worldwide leech supplier, Hirudo orientalis leeches were identified by visual comparison and amplification and sequencing the cox1 locus. Combined culture and culture-independent approaches were used to characterize the microbiota of the midgut, and bacterial gyrB sequences from distinct colonies were used to identify the Aeromonas isolates. Nonculturable studies involved clone libraries of 16S rRNA genes, and Etests were used to investigate antibiotic sensitivities.
Results: Analysis of 16S rRNA gene clone libraries revealed the presence of several species in the intraluminal fluid of the crop, including a new finding of Morganella morganii, with Rikenella-like (35 percent) and Aeromonas veronii (38 percent) dominant members. The intestinum contained bacteria not previously isolated from the leech: Magnetospirillium species and Roseospira marina. Etests showed all A. veronii isolates were sensitive to ciprofloxacin, with either a complete or intermediate resistance to Augmentin.
Conclusions: The authors show diverse microbiota in the leech digestive tract. The pathogenic potential of the additional gut symbionts isolated in this study is yet to be elucidated; however, M. morganii, which is a known human pathogen, is a new finding. In addition to adding to the knowledge base regarding antibiotic sensitivities, this article serves as an update to the reconstructive surgeon regarding leech therapy.