A 2022 case report (Table 1) and systematic review addressed the growing concern of antibiotic-resistant infections arising from medicinal leech therapy. Historical susceptibility profiles of Aeromonas species have resulted in fluoroquinolones (ciprofloxacin or levofloxacin) being used as the most common antimicrobial prophylactic agents for medicinal leech therapy. However, a number of case reports have raised concern over changing antimicrobial susceptibility in the normal flora of the leech. The reason for the rise of drug-resistant Aeromonas species isolated from medicinal leeches is unclear. One hypothesis suggests the blood used to feed these leeches may contain antibiotics that induce resistance in the leech's normal flora. Similar pathways of antimicrobial resistance have been seen in humans stemming from the agricultural industry (antibiotic use in livestock). Additionally, studies have found that resistant normal flora can be transmitted between leeches, as evidenced by the presence of resistant isolates in the water in which leeches are stored. The development of antimicrobial-resistant Aeromonas species can complicate postoperative recovery in patients receiving medicinal leech therapy. While culturing leeches or the water they are stored in may provide insight into ideal antibiotic prophylaxis regimens, this may not be feasible for all locations, and the susceptibilities may vary among institutions. Double coverage with two prophylactic agents may decrease the risk of infection when using leeches, but the risk must also be balanced with the public health implications of increased use of broad-spectrum agents. Currently, there are no consensus recommendations on ideal prophylactic agents, the timing of administration, or the duration of prophylaxis. [1]
A 2018 qualitative study surveyed 23 French centers regarding their use of medicinal leeches. While there are no guidelines or consensus thoughts on antimicrobial prophylaxis with medicinal leech therapy, most authors suggest starting antimicrobial prophylaxis before or when starting leech application to the patient. Some authors suggest continuing antimicrobial prophylaxis until leech therapy is completed, while others suggest continuing prophylaxis until cicatrization has occurred. The most common prophylactic medications are fluoroquinolones, sulfamethoxazole/trimethoprim, and third-generation cephalosporins; however, there has been growing concern regarding the appropriate selection of agent due to the emergence of drug-resistant Aeromonas species. Amoxicillin/clavulanic acid should be avoided because aeromonads are virtually all resistant to this antimicrobial agent because oxacillinase and/or cephalosporinase are expressed by the vast majority of aeromonads. Other approaches to infection control with medicinal leeches include attempting to sterilize the leech gut by immersing the leeches in an antibiotic solution or eliminating Aeromonas species from the leech by administering an arginine/ciprofloxacin solution; these methods have been unsuccessful and could potentially increase the risk of drug-resistant infections. Another proposed method of infection control involves external decontamination by treating the leeches with chlorhexidine 0.02% for 15 seconds followed by sterile water rinses. [2]
A 2020 case report (Table 2) of multidrug-resistant Aeromonas infection following medical leech therapy prompted an interdisciplinary investigation and subsequent development of infection prevention protocol to proactively monitor for antimicrobial resistance among the institution’s leech supply. One leech from each batch of 50 is sacrificed and 0.5 to 1 mL of leech water collected, both being cultured upon delivery and every 30 days thereafter. The Microbiology lab performs culture and susceptibility testing on Aeromonas hydrophila from leech water and leech gut contents. Upon receiving susceptibility results, antimicrobial stewardship pharmacists will then select the prophylactic antibiotics accordingly. In the absence of ceftriaxone, ciprofloxacin, or meropenem resistance, patients will receive standard antibiotic prophylaxis with ceftriaxone or TMP-SMX if allergic to penicillin. If resistant patterns are detected, the leech batch is quarantined and the leeches ordered will be replaced. If emergent leech therapy is required, pharmacists will recommend antibiotic prophylaxis based on susceptibilities. In case of patients receiving leeches that harbor resistant Aeromonas, infection prevention closely follows up with these patients for any risks of complications. After successful implementation of this protocol, the institution reports no further cases of leech-associated infections. It is worth noting, this proactive monitoring protocol for resistance may not readily apply to all institutions. [3]