Searching for carbapenemases in zoo animals

Abstract

Searching for novel carbapenemases in zoo animals Degree project, Programme in Medicine Martin Thorslund 2018, Institute of Biomedicine, Gothenburg, Sweden 1.1 Introduction Carbapenems, a class of “last resort” antibiotics, are threatened by resistant pathogens producing carbapenemases. There is increasing evidence that the environmental/commensal bacteria act as a source of antibiotic resistance genes that can be picked up by pathogens. Sampling animal microbiota could increase the probability of finding genes that have the potential to migrate the pathogens. 1.2 Aim To screen for novel carbapenemases in the stool of animals never purposely exposed to carbapenems. 1.3 Methods and results By inoculating fecal samples from 43 zoo animals in meropenem-supplemented broths, 31 meropenem-resistant strains were isolated; the majority could be identified as opportunistic bacteria by MALDI-TOF. Seventeen isolates were positive in Carba NP and imipenem-EDTA synergy tests, indicating carriage of genes encoding carbapenemases of the metallo-β- lactamase (MBL) class. Total DNA was isolated from meropenem-supplemented broths with visible growth and sequenced. Through newly developed hidden Markov models, 19 novel MBLs were found, 13 novel B1 and 6 novel B3 genes, by screening the sequenced DNA. 2 PCR could link 6 novel B1 and 3 novel B3 MBLs to specific isolates. Samples was also pooled into five groups according to their animal origin, 11 novel B1s and 4 novel B3s could be linked to one or more of these animal groups. 1.4 Conclusion/implications MBLs were readily detectable in the gut flora of the sampled zoo animals, including previously unknown ones, even though relatively selective methodology was applied. Their presence in gut commensals/opportunists should reduce some barriers for transfer to pathogens. Next step is to sequence the isolates to gain knowledge about mobility and possibly origin of the novel carbapenemase genes found.