Therapeutic potential of highly diluted antibodies in antibiotic-resistant infection.

Klebsiella pneumoniae is one of the main causes of hospital-acquired infections. Its rate of antimicrobial resistance is rapidly increasing, while there are no licensed human vaccines against it. A novel therapeutic approach involves modulation of the host immune response combined with antibiotic treatment. One of the approaches to immunomodulation can be the use of antibodies (Abs) in a specific technological form of high dilutions (hd). The aim of the study was to assess whether hd-Abs could affect the antibacterial activity of AMC against a bacterial strain resistant to it. The study was performed on an in vivo model of K. pneumoniae BAA-1705 multiresistant strain lethal infection in neutropenic RjOrl:Swiss mice. The efficacy of hd-Abs combined with AMC was assessed based on survival and lung bacterial burden. Additionally, we evaluated the direct effect of the drugs on the growth of bacteria in vitro. hd-Abs in combination with AMC increased survival of mice infected with K. pneumoniae up to 50%, whereas all animals in the AMC group died. Hd-Abs had no direct effect on K. pneumoniae sensitivity to AMC in vitro. The survival rate in mice treated with hd-Abs combined with AMC was comparable to that in animals treated with the reference drug gentamicin. Thus, hd-Abs increased the antibacterial activity of AMC against the strain resistant to it. The mechanism of action of hd-Abs remains to be elucidated in future studies.