Antibiofilm Activity of β-Lactam/β-Lactamase Inhibitor Combination against Multidrug-Resistant Typhimurium.

This study was designed to assess the effect of β-lactam/β-lactamase inhibitor combinations on the inhibition of biofilm formation of Typhimurium. The anti-planktonic and anti-biofilm activities of ampicillin (AMP), ceftriaxone (CEF), and combination treatments of antibiotics and sulbactam (AMP + SUL and CEF + SUL) were evaluated against antibiotic-sensitive . Typhimurium ATCC 19585 (ST) and clinically isolated multidrug-resistant (MDR) . Typhimurium CCARM 8009 (ST). Compared to the control, the minimum inhibitory concentrations (MICs) of AMP against ST and CEF against ST were decreased from 32 to 16 μg/mL and 0.25 to 0.125 μg/mL, respectively, in the presence of SUL. The numbers of ST treated with AMP + SUL and CEF + SUL were effectively reduced by more than 2 logs after 4 h of incubation at 37 °C. The β-lactamase activities of ST and ST treated with AMP and CEF were reduced from 3.3 to 2.6 μmol/min/mL and from 8.3 to 3.4 μmol/min/mL, respectively, in the presence of SUL. The biofilm cell numbers of ST and ST were reduced at all treatments after 24 h of incubation at 37 °C. The biofilm cell numbers of ST and ST were reduced by more than 2 logs in the presence of SUL compared to the AMP and CEF alone. The lowest relative fitness level was 0.6 in ST treated with AMP + SUL, while no significant differences in the relative fitness were observed in ST. This study suggests that β-lactamase inhibitors (BLIs) could be used for controlling biofilm formation of β-lactamase-producing multidrug-resistant . Typhimurium.