Detection of a novel SME-6 Carbapenemase in Serratia ureilytica in Germany

BACKGROUND: Carbapenem resistance in Serratia species is occasionally mediated by the serine carbapenemase Serratia marcescens enzymes (SMEs). During microbiological diagnostics, we identified a carbapenem-resistant Serratia ureilytica isolate in which resistance was not mediated by any known SME variants or other characterized carbapenemases. OBJECTIVES: To identify and characterize the underlying resistance mechanism in a carbapenem-resistant Serratia ureilytica isolate that lacks known SME variants or other characterized carbapenemases. METHODS: Antimicrobial susceptibility testing (AST) was performed using Vitek, gradient strips, broth microdilution, and disc diffusion methods. WGS was performed to identify the resistance mechanisms. Growth curve analysis and RT-qPCR were performed at 30°C and 37°C. RESULTS: WGS identified a novel SME variant, SME-6, which differed from a known variant, SME-2, by two amino acids (G117R and G147E). AST showed carbapenem resistance at 30°C but susceptibility at 37°C. Growth curve analysis showed a shorter lag phase at 30°C compared with 37°C, and RT-qPCR showed a

• Kocer, K.
• Göpel, L.
• Gisch, S.
• Tueffers, L.
• Hauswaldt, S.
• Rupp, J.
• Boutin, S.
• Nurjadi, D.