Background To 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. Methods Three 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. Results Of 300 isolates tested, 5.7% were pandrug resistant and 29.3% extensively drug resistant. Plazomicin inhibited 87.0% of the isolates at ≤2 mg/L, with MIC 50 /MIC 90 of 0.5/4 mg/L. Apramycin (a veterinary aminoglycoside) inhibited 86.7% of the isolates at ≤8 mg/L and was the second most active drug after plazomicin, followed by gentamicin (S, 43%; MIC 50 /MIC 90 , 4/> 256) and amikacin (S, 18.0%; MIC 50 /MIC 90 , 32/128). Twenty-three (7.7%) isolates (16 KPC-, 6 VIM- and one KPC & OXA-48-producers) exhibited MICs ≥64 mg/L for plazomicin, and harbored rmtB ( n = 22) or armA ( n = 1). AAC(6′)-Іb 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. Conclusions Plazomicin 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. Electronic supplementary material The online version of this article (10.1186/s12879-019-3801-1) contains supplementary material, which is available to authorized users.

No abstract

Dual combinations of carbapenems, including those containing sub-inhibitory concentrations of antibiotics, were synergistic against multidrug-resistant (MDR) and extensively drug-resistant (XDR) K. pneumoniae isolates harbouring blaOXA-48.

No abstract