Impact of four local anaesthetics on growth and viability of in vitro cultured Borrelia burgdorferi sensu stricto, Borrelia bavariensis and Borrelia afzelii.

Many local anaesthetics, including lidocaine, procaine and ropivacaine inhibit bacterial growth. This study investigates potential effects of these local anaesthetics on growth of Borrelia burgdorferi sensu stricto (Bbss), Borrelia bavariensis (Bbav) and Borrelia afzelii (Ba). For this purpose, Borrelia spp. organisms were either continuously or temporarily exposed to one of four local anaesthetics preparations: 20 mg/ml procaine hydrochloride (P); 10 mg/ml ropivacaine hydrochloride (R); 20 mg/ml lidocaine hydrochloride (L1, L2). L2 also contained the preservatives methyl-benzoate and propyl-benzoate, whereas P, R and L1 did not. All four local anaesthetic preparations inhibited in vitro growth of Borrelia spp. depending on concentration and exposure time. There are differences in sensitivity among the Borrelia spp. with Bbav being more susceptible to growth inhibition than Bbss and Ba. When comparing the different local anaesthetic preparations with their regard to inhibition of growth of Borrelia spp. organisms, P showed the lowest impact. It cannot be completely excluded that preservatives present in L2, methyl-benzoate and propyl-benzoate, may be a reason for further inhibition of Borrelia spp. organisms. Concentrations of local anaesthetics used in these experiments may also be present in the skin of patients during regular medical procedures. These are preliminary findings and further experiments, preferably in vivo, are necessary. To minimize the risk to produce false negative results with cultures, we recommend using procaine in a preparation without preservatives for local anaesthesia prior to skin sampling.

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