Nationwide epidemiology of carbapenem resistant Klebsiella pneumoniae isolates from Greek hospitals, with regards to plazomicin and aminoglycoside resistance

BackgroundTo evaluate the in vitro activities of plazomicin and comparator aminoglycosides and elucidate the underlying aminoglycoside resistance mechanisms among carbapenemase-producing K. pneumoniae isolates collected during a nationwide surveillance study in Greek hospitals.MethodsThree hundred single-patient carbapenemase-producing K. pneumoniae isolates were studied, including 200 KPC-, 50 NDM-, 21 VIM-, 14 KPC & VIM-, 12 OXA-48-, two NDM & OXA- and one KPC & OXA-producing isolates. Susceptibility testing was performed by broth microdilution, and minimum inhibitory concentrations (MICs) interpreted per EUCAST breakpoints. Carbapenemase-, aminoglycoside modifying enzyme- and 16S rRNA methylase- encoding genes were detected by PCR.ResultsOf 300 isolates tested, 5.7% were pandrug resistant and 29.3% extensively drug resistant. Plazomicin inhibited 87.0% of the isolates at 2mg/L, with MIC50/MIC90 of 0.5/4mg/L. Apramycin (a veterinary aminoglycoside) inhibited 86.7% of the isolates at 8mg/L and was the second most active drug after plazomicin, followed by gentamicin (S, 43%; MIC50/MIC90, 4/>256) and amikacin (S, 18.0%; MIC50/MIC90, 32/128). Twenty-three (7.7%) isolates (16 KPC-, 6 VIM- and one KPC & OXA-48-producers) exhibited MICs 64mg/L for plazomicin, and harbored rmtB (n=22) or armA (n=1). AAC(6)-b was the most common aminoglycoside modifying enzyme (84.7%), followed by AAC(3?)-IIa (25.3%), while those two enzymes were co-produced by 21.4% of the isolates.ConclusionsPlazomicin retains activity against most carbapenemase-producing K. pneumoniae isolated from Greek hospitals, with MICs consistently lower than those of the other aminoglycosides, even in the presence of aminoglycoside modifying enzymes. Dissemination of 16S- rRNA methylases in 8% of the isolates is an unwelcome event that needs strict infection control measures and rigorous stewardship interventions.