Carbapenemase and virulence factors of Enterobacteriaceae in North Lebanon between 2008 and 2012: evolution via endemic spread of OXA-48.

OBJECTIVES

To investigate the resistance to carbapenems in Enterobacteriaceae and the underlying resistance mechanisms in North Lebanon between 2008 and 2012.

METHODS

A total of 2767 Enterobacteriaceae isolates recovered from clinical samples collected in Nini Hospital (North Lebanon) were screened for a decrease in susceptibility or resistance to ertapenem (MIC >0.25 mg/L). Enterobacteriaceae were similarly screened from 183 faecal samples obtained from non-hospitalized patients. The bacterial isolates were assigned to clonal lineages by PFGE and multilocus sequence typing. Carbapenemase genes, their genetic environment and virulence genes were characterized by molecular approaches.

RESULTS

The rate of Enterobacteriaceae exhibiting a decrease in susceptibility or resistance to ertapenem increased from 0.4% in 2008-10 to 1.6% in 2012 for the clinical isolates recovered from hospitalized patients. Of these isolates, scattered among seven enterobacterial species, 88% produced OXA-48 carbapenemase. However, Escherichia coli represented 73% of the OXA-48-producing Enterobacteriaceae collected in 2012 at this hospital. During the faecal carriage study performed in non-hospitalized patients, E. coli was the only species producing OXA-48. The bla(OXA-48) gene was mainly found within Tn1999.2-type transposons inserted into E. coli chromosomes or in ∼50, ∼62 or ∼85 kb plasmids. The plasmids and chromosomal inserts were related to pOXA-48a. Molecular typing of the isolates revealed clonal diversity of E. coli and Klebsiella pneumoniae producing OXA-48. OXA-48 was observed in all major E. coli phylogroups, including D and B2, and isolates harbouring virulence genes of extra-intestinal pathogenic E. coli. Although not belonging to highly virulent capsular genotypes, the OXA-48-producing K. pneumoniae harboured genes associated with virulence or host colonization.

CONCLUSIONS

Horizontal transfer of related plasmids has facilitated the spread of the bla(OXA-48) gene into several Enterobacteriaceae species, including virulent E. coli. Their clonal diversity and the presence of faecal carriers in the community suggest an endemic spread of OXA-48.