Occurrence of Extended Spectrum Cephalosporin-, Carbapenem- and Colistin-Resistant Gram-Negative Bacteria in Fresh Vegetables, an Increasing Human Health Concern in Algeria.

The aim of this study was to screen for extended spectrum cephalosporin-, carbapenem- and colistin-resistant Gram-negative bacteria in fresh vegetables in Batna, Algeria. A total of 400 samples of fresh vegetables were collected from different retail stores. Samples were immediately subjected to selective isolation, then the representative colonies were identified using matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS). Phenotypic and genotypic analyses were carried out in terms of species identification and relative antibiotic resistance. Transferability of the carbapenemase and mcr -bearing plasmids was verified by conjugation. The clonal relationships of carbapenemase and mcr -positive Escherichia coli isolates were studied by multi-locus sequence typing (MLST). Sixty-seven isolates were characterised and were mostly isolated from green leafy vegetables, where the dominant species identified included Citrobacter freundii , Klebsiella pneumoniae , Enterobacter cloacae , Stenotrophomona maltophilia , E. coli and Citrobacter braakii . PCR and sequencing results showed that E. coli was the bacterial species presenting the highest antibiotic resistance level in parallel to bla TEM ( n = 16) and bla CTX-M-15 ( n = 11), which were the most detected genes. Moreover, five isolates carried carbapenemase genes, including the bla OXA-48 and/or bla VIM-4 genes. The mcr-1 gene was detected in two E. coli isolates. MLST analysis revealed three different E. coli sequence types: ST101 ( n = 1), ST216 ( n = 1) and ST2298 ( n = 1). Conjugation assays confirmed the transferability of the bla OXA-48 and mcr-1 genes. In this study we report, for the first time, the detection of the bla OXA-48 gene in E. coli and C. braakii isolates and the bla VIM-4 gene in vegetables. To the best of our knowledge, this is the first report on the detection of mcr-1 genes from vegetables in Algeria.