Figure 1.

Relebactam makes Mycobacterium abscessus susceptible to amoxicillin and increases susceptibility to meropenem. (1a) A disk diffusion experiment and corresponding plate map demonstrating enhanced susceptiblity of M. abscessus (NCTC) by zone of inhibition to amoxicillin (1) with the addition of relebactam (2) and meropenem (3) with the addition of relebactam (4). (1b) The disk diffusion experiments were conducted with the NCTC M. abscessus strain along with a panel of clinical isolates, demonstrating enhanced susceptibility by addition of relebactam (REL) to amoxicillin (AMX) and meropenem (MEM). (1c) Growth curves were conducted with M. abscessus NCTC in medium containing 128 mg/L relebactam only and 32 mg/L amoxicillin with and without relebactam at 2 mg/L. Growth inhibition was only observed with relebactam in combination with amoxicillin. Likewise, the inhibitory activity of meropenem was clearly enhanced with the addition of relebactam. A t-test was used for end point analysis between samples +/− relebactam and the results were deemed to be significant with p values of <0.0001 and 0.0152 for amoxicillin and meropenem respectively. (1d) Growth curves were conducted with M. abscessus NCTC in medium containing 0.5 mg/L imipenem and 0.25 mg/L relebactam, with and without amoxicillin at 32 mg/L. The inhibitory activity of imipenem-relebactam was enhanced with the addition of amoxicillin (p = 0.0028). Growth curves were also conducted with M. abscessus NCTC in medium containing 32 mg/L ceftazidime and 32 mg/L avibactam, with and without amoxicillin at 8 mg/L. The inhibitory activity of ceftazidime-avibactam was enhanced by amoxicillin but to a lesser extent than imipenem-relebactam (p = 0.0016).