Occurrence of NDM-1 and VIM-2 Co-Producing Escherichia coli and OprD Alteration in Pseudomonas aeruginosa Isolated from Hospital Environment Samples in Northwestern Tunisia

Co-occurrence of genes encoding carbapenemase, ESBL, pAmpC, and Non-β-Lactam resistance among Klebsiella pneumonia and E. coli clinical isolates in Tunisia

This study aimed to investigate the molecular mechanisms of carbapenem and colistin resistance in K. pneumoniae and E. coli isolates obtained from hospitalized patients in Carthagene International Hospital of Tunis. A total of 25 K. pneumoniae and 2 E. coli clinical isolates with reduced susceptibility to carbapenems were recovered. Susceptibility testing and phenotypic screening tests were carried out. ESBL, AmpC, carbapenemase, and other antibiotic resistance genes were sought by PCR-sequencing. The presence of plasmid-mediated colistin resistance genes (mcr-1-8) was examined by PCR and the nucleotide sequence of the mgrB gene was determined. The analysis of plasmid content was performed by PCR-Based Replicon Typing (PBRT). The clonality of isolates was assessed by PFGE and multilocus sequence typing (MLST). All of the isolates produced carbapenemase activity. They showed a great variation in the distribution of ESBL, AmpC, carbapenemase, and other plasmid-mediated resistance determinants. K. pneumoniae isolates carried bla_NDM-1 (n=11), bla_OXA-48 (n=11), bla_NDM-1 + bla_OXA-48 (n=1), bla_NDM-1 + bla_VIM-1 (n=1), bla_OXA-204 (n=1), along with bla_CTX-M , bla_OXA , bla_TEM , bla_CMY , bla_DHA and bla_SHV genes variants on conjugative plasmid of IncL/M, IncR, IncFII_K , IncFIB, and IncHI1 types. Three sequence types ST101, ST307, and ST15 were identified. The mgrB alteration g109a (G37S) was detected in a single colistin-resistant, NDM-1 and OXA-48-coproducing K. pneumoniae isolate. The two E. coli isolates belonged to ST95, co-produced NDM-1 and CTX-M-15, and harbored plasmid of IncFII and IncFIB types. To our knowledge, this is the first report in Tunisia of NDM-1, OXA-48, and CTX-M-15 coexistence in colistin-resistant K. pneumoniae ST15.