Influence of antibiotics on Arcobacter-like cells and their biofilm formation

Arcobacters belong to Gram-negative bacteria, the rod cells can be slightly curved into the shape or spiral. Their growth is typical in a microaerophilic environment, but some species are able to grow under aerobic or anaerobic conditions. The purpose of this study was to test the in vitro effect of many antibiotics on planktonic cells and biofilm formation of Arcobacter-like bacteria. The minimum inhibitory concentration (MIC) is the standard assay for testing antibiotic susceptibility of bacteria. So, the MIC of antibiotics were determined by the broth microdilution method. The most of the more than 60 strains showed high susceptibility to gentamicin (98.4%), ciprofloxacin (95.2%) and to erythromycin (93.6%). Biofilm formation in the presence of antibiotics was evaluated by modified Christensen method. All strains were able to form a biofilm after 24 h of exposure. The highest biofilm formation was found in case of A. defluvii LMG 25694 and A. butzleri strains as well as in lower concentration of antibiotics. Biofilm formation ability is often associated with bacterial virulence, environmental survival and increased antibiotic resistance compared to planktonic cells. The biofilm formation represent a potential danger of infections and then a risk to human health, in particular due to antimicrobial-resistant strains.