Pseudomonas sediminis CRE-TB-54 carries tmexCD3-toprJ3 in a novel chromosomal region

The emergence of tmexCD-toprJ, coding for a transmissible multidrug resistance efflux pump of the resistance-nodulation-division (RND) family has compromised the usefulness of tigecycline in the treatment of infections caused by multidrug resistant Gram-negative bacteria. Here, we describe the presence of tmexCD3-toprJ3 in a novel chromosomal context in Pseudomonas sediminis CRE-TB-54 isolated from a toilet in a university dormitory in southwestern Nigeria. Antimicrobial susceptibility testing and whole genome sequencing showed that CRE-TB-54 displayed intermediate level resistance to tigecycline and haboured multiple antibiotic resistance genes, including tmexCD3-toprJ3 flanked upstream and downstream by genetic structures not previously reported in association with tmexCD-toprJ. These include insertion sequences IS4 and IS30, and the metal resistance gene czcD upstream, the prophage integrase IntA, the competence associated DNA binding protein gene comEA, and the double stranded DNA repair and homologous recombination gene cluster recBCD downstream. These results provide new insight into the genetic structures surrounding the tmexCD-toprJ cluster and raises concern about toilets as a potential environmental reservoir of bacteria carrying this clinically important gene in a resource-limited setting where tigecycline is not currently used in human or animals.