Janina Noster (Oldenburg / DE), Lukas Schaffarczyk (Oldenburg / DE), Janko Sattler (Köln / DE), Stephan Göttig (Frankfurt a. M. / DE), Yvonne Stelzer (Oldenburg / DE), Sören G. Gatermann (Bochum / DE), Axel Hamprecht (Oldenburg / DE)
Introduction
Morganella spp., Serratia spp. and Providencia spp. (MSP) are Enterobacterales that cause infections of the urinary tract, wounds and bloodstream among others. Currently, the epidemiology of carbapenemases in MSP is largely unknown.
Goals
To determine the epidemiology of carbapenemases in MSP and performance of diagnostic assays.
Materials & Methods
In total, 131 clinical carbapenemase-producing MSP patient isolates were included (Serratia marcescens, n=107; Morganella morganii, n=13; Providencia spp., n=11). MSP were isolated from clinical samples at the University Hospitals Cologne, Frankfurt and the German National Reference Centre for multidrug-resistant Gram-negative bacteria. Susceptibility was determined by broth microdilution (BMD). Carbapenemase production was assessed by modified zinc-supplemented carbapenem inactivation method (mzCIM). Growth on carbapenem agar (mSuperCarba) was additionally determined. Resistance genes were analysed by whole genome sequencing.
Results
OXA-48-like were the most frequent carbapenemases (n=112; 85.5%), followed by KPC (n=10; 7.6%), IMP (n=6; 4.5%) and GES (n=3; 2.3%). KPC and GES were only detected in S. marcescens. Interestingly, only 29 isolates (22.1%) co-produced an ESBL, with CTX-M-15 being the most frequent (n=21). In contrast, genes coding for AmpC beta-lactamases were detected in 92 isolates (70.2%). Despite carbapenemase production, susceptibility (S/I) was observed for piperacillin-tazobactam in one isolate, ceftazidime in 61, ertapenem in 10 and meropenem in 42 isolates. All isolates were correctly identified as carbapenemase-producers by mzCIM, but only 120 grew on the selective carbapenem agar.
Summary
Carbapenemase production in MSP was mostly observed in S. marcescens and OXA-48-like were by far the most common carbapenemases. Further carbapenemases and ESBL production were less frequent compared to other Enterobacterales species. Despite carbapenemase production, MSP isolates frequently tested susceptible for ceftazidime and meropenem, which could result in insufficient detection in the routine microbiology laboratory.