Pseudocitrobacter gen. nov., a novel genus of the Enterobacteriaceae with two new species Pseudocitrobacter faecalis sp. nov., and Pseudocitrobacter anthropi sp. nov, isolated from fecal samples from hospitalized patients in Pakistan

Abstract

Four isolates of Gram-negative facultatively anaerobic bacteria, three of them producing NDM-1 carbapenemase, were isolated from hospitalized patients and outpatients attending two military hospitals in Rawalpindi, Pakistan, and studied for their taxonomic position. Initially the strains were phenotypically identified as Citrobacter species. Comparative analysis of 16S rRNA gene sequences then showed that the four strains shared >97%, but in no case >98.3%, 16S rRNA gene sequence similarities to members of the genera Citrobacter, Kluyvera, Pantoea, Enterobacter and Raoultella, but always formed a separate cluster in respective phylogenetic trees. Based on multilocus sequence analysis (MLSA) including partial recN, rpoA, thdF and rpoB gene sequence and respective amino acid sequence analysis it turned out that the strains also here always formed separate clusters. Based on further comparative analyses including DNA-DNA hybridizations, genomic fingerprint analysis using rep- and RAPD-PCRs and physiological tests, it is proposed to classify these four strains into the novel genus Pseudocitrobacter gen. nov. with a new species Pseudocitrobacter faecalis sp. nov. with strain 25 CIT(T) (=CCM 8479(T)=LMG 27751(T)) and Pseudocitrobacter anthropi sp. nov. with strain C138(T) (=CCM 8478(T)=LMG 27750(T)), as the type strains, respectively.

Keywords: 16S rRNA gene; ERIC-, BOX-, (GTG)5-PCR and RAPD-PCR; MLSA; Polyphasic taxonomy; Pseudocitrobacter anthropi gen. nov sp. nov.; Pseudocitrobacter faecalis gen. nov sp. nov..