Graphene derivatives potentiate the activity of antibiotics against Enterococcus faecium, Klebsiella pneumoniae and Escherichia coli

Antibiotic resistance in bacteria is developing at a faster rate than new antibiotics can be discovered. This study investigated the antimicrobial activity of several carbon-based derivative compounds alone and in combination with clinically relevant antibiotics against key ESKAPE pathogens Enterococcus faecium, Klebsiella pneumoniae and Escherichia coli. Three compounds, graphite, graphene and graphene oxide, in conjunction with ciprofloxacin (CIP), chloramphenicol (CHL) and piperacillin/tazobactam (TZP) were examined using fractional inhibitory concentration (FIC) testing. CIP combined with graphene demonstrated additive antimicrobial activity against E. faecium compared to individual application. Furthermore, CIP supplemented with graphene, graphene oxide or graphite showed additive activity with ∑FIC values of 1.0 against K. pneumoniae, whereas only TZP showed ∑FIC values <1.0 with graphene oxide. For E. coli, the antibiotic activity of CIP was enhanced with graphene, graphene oxide or graphite, whereas only graphite and graphene enhanced the activity of CHL and TZP respectively. Graphite and graphene oxide caused significant antagonism (∑FIC ˃ 4.0) in conjunction with TZP against E. coli. In conclusion, the results demonstrate the potential to supplement clinically relevant antibiotics with carbon-based graphene, graphene oxide derivative or graphite for use as an additive supplement for novel systemic or topical treatment solutions against key priority pathogens.