Emergence of carbapenem-resistant enterobacterales co-harboring blaOXA−78 and blaOXA−58 from India.

Background: Carbapenem-Resistant Enterobacterales (CRE) has been categorized as pathogens of critical priority by World Health organization (WHO) as they pose significant threat to global public health. Carbapenemase production considered as the principal resistance mechanism against carbapenems and with the recent surge and expansion of carbapenemases and its variants among clinically significant bacteria in India, the present study reports expansion bla_OXA−78 and bla_OXA−58 of in CRE of clinical origin. Methods: Bacterial isolates were collected from a tertiary referral hospital and identified through VITEK® 2 Compact automated System (Biomerieux, France). Rapidec® Carba NP (Biomerieux, France) was used to investigate carbapenemase production followed by antibiotic susceptibility testing through Kirby-Bauer Disc Diffusion method and agar dilution method. Class D carbapenemase genes were targeted through PCR assay followed by investigation of horizontal transmission of bla_OXA−58 and bla_OXA−78. Whole genome sequencing was carried out using Illumina platform to investigate the genetic context of bla_OXA−58 and bla_OXA−78 genes and further characterization of the CRE isolates. Results: The carbapenem-resistant Escherichia coli (BJD_EC456) and Serratia marcescens (BJD_SM81) received during the study from the tertiary referral hospital were isolated from sputum and blood samples respectively. PCR assay followed by whole genome sequencing revealed that the isolates co-harbor bla_OXA−58 and bla_OXA−78, a variant of bla_OXA−51. Horizontal transfer of bla_OXA−58 and bla_OXA−78 genes were unsuccessful as these genes were located on the chromosome of the study isolates. Transposon Tn6080 was linked to bla_OXA−78 in the upstream region while the insertion sequences ISAba26 and ISCfr1 were identified in the upstream and downstream region of bla_OXA−58 gene respectively. In addition, both the isolates were co-harboring multiple antibiotic resistance genes conferring clinical resistance towards beta-lactams, aminoglycosides, fluroquinolones, sulphonamides, tetracyclines. BJD_EC180 belonged to ST2437 while BJD_SM81 was of an unknown sequence type. The nucleotide sequences of bla_OXA−78 (OQ533021) and bla_OXA−58 (OQ533022) have been deposited in GenBank. Conclusions: The study provides a local epidemiological information regarding carbapenem resistance aided by transposon and insertion sequences associated bla_OXA−78 and bla_OXA−58 genes associated and warrants continuous monitoring to prevent their further dissemination into carbapenem non-susceptible strains thereby contributing to carbapenem resistance burden which is currently a global concern. [ABSTRACT FROM AUTHOR]