Open Access Highly Accessed Research article

Molecular epidemiology of extended-spectrum beta-lactamase-producing Escherichia coli in Tunisia and characterization of their virulence factors and plasmid addiction systems

Basma Mnif134*, Hela Harhour14, Jihène Jdidi2, Faouzia Mahjoubi14, Nathalie Genel3, Guillaume Arlet3 and Adnene Hammami14

Author Affiliations

1 Laboratoire de Microbiologie, Hôpital Habib Bourguiba, Sfax, Tunisie

2 Service de médecine préventive, Hôpital Hédi Chaker, Sfax, Tunisie

3 Faculté de Médecine, Site Saint-Antoine, Laboratoire de Bactériologie, Université Pierre et Marie Curie-Paris-6, Paris, France

4 Laboratoire de Microbiologie-Faculté de Médecine de Sfax, Avenue Majida Boulila, 3027, Sfax, Tunisie

For all author emails, please log on.

BMC Microbiology 2013, 13:147  doi:10.1186/1471-2180-13-147

Published: 25 June 2013



Extended-spectrum β-lactamases (ESBLs), particularly CTX-M- type ESBLs, are among the most important resistance determinants spreading worldwide in Enterobacteriaceae. The aim of this study was to characterize a collection of 163 ESBL-producing Escherichia coli collected in Tunisia, their ESBL-encoding plasmids and plasmid associated addiction systems.


The collection comprised 163 ESBL producers collected from two university hospitals of Sfax between 1989 and 2009. 118 isolates harbored blaCTX-M gene (101 blaCTX-M-15 gene and 17 blaCTX-M-14 gene). 49 isolates carried blaSHV-12 gene, 9 blaSHV-2a gene and only 3 blaTEM-26 gene. 16 isolates produced both CTX-M and SHV-12. The 101 CTX-M-15-producing isolates were significantly associated to phylogroup B2 and exhibiting a high number of virulence factors. 24 (23.7%) of the group B2 isolates belonged to clonal complex ST131. Pulsed-field gel electrophoresis (PFGE) typing revealed a genetic diversity of the isolates. 144 ESBL determinants were transferable mostly by conjugation. The majority of plasmid carrying blaCTX-M-15 genes (72/88) were assigned to various single replicon or multireplicon IncF types and had significantly a higher frequency of addiction systems, notably the VagCD module.


This study demonstrates that the dissemination of CTX-M-15 producing E. coli in our setting was due to the spread of various IncF-type plasmids harboring multiple addiction systems, into related clones with high frequency of virulence determinants.

E. coli; ESBL; CTX-M-15; Plasmid; Addiction systems; Virulence