We report a high prevalence of MCR-1 and CTX-M-1-producing Escherichia coli in three Tunisian chicken farms. Chickens were imported from France or derived from French imported chicks. The same IncHI2-type plasmid reported to carry those genes in cattle in France and in a food sample in Portugal was found in Tunisian chickens of French origin. This suggests a significant impact of food animal trade on the spread of mcr-1-mediated colistin resistance in Europe.

The emergence of colistin-resistant (CoR) is a public health concern, since this antibiotic has become the last line of treatment for infections caused by multidrug-resistant (MDR) Gram negatives. In this study, we have investigated the molecular basis of colistin resistance in 13 MDR strains isolated from 12 patients in a teaching hospital in Sousse, Tunisia. Whole-genome sequencing (WGS) was used to decipher the molecular mechanism of colistin resistance and to identify the resistome of these CoR isolates. It revealed a genome of ca. 5.5 Mbp in size with a G+C content of 57%, corresponding to that commonly observed for These isolates belonged to the 5 different sequence types (ST11, ST15, ST101, ST147, and ST392), and their resistome was composed of acquired β-lactamases, including extended-spectrum beta-lactamase and carbapenemase genes (, ,, and genes), aminoglycoside resistance genes [('), (″)-, ()-, and ()-], and fosfomycin (), fluoroquinolone (-like), chloramphenicol, trimethoprim, and tetracycline resistance genes. All of the isolates were identified as having a mutated gene. Mapping reads with reference sequences of the most common genes involved in colistin resistance revealed several modifications in, , and operons (deletions, insertions, and substitutions) likely affecting the function of these proteins. It is worth noting that among the 12 patients, 10 were treated with colistin before the isolation of CoR No plasmid encoding to genes was found in these isolates. This study corresponds to the first molecular characterization of a collection of CoR strains in Tunisia and highlights that the small-transmembrane protein MgrB is a main mechanism for colistin resistance in .

The basis of the ␤-lactam resistance of 39 multidrug-resistant Acinetobacter baumannii isolates recovered from hospitalized patients was studied. These isolates were collected from 2001 to 2005 at the Sahloul Hospital in Sousse, Tunisia. They belonged to two distinct clones. One clone that grouped 19 isolates produced a carbapenem-hydrolyzing oxacillinase, OXA-97, that differed from OXA-58 by a single amino acid substitution and conferred the same ␤-lactam resistance profile as OXA-58. The bla OXA-97 gene was located on plasmids that varied in size in 18 isolates and was chromosomally located in a single isolate. Cloning and sequencing identified genetic structures surrounding the bla OXA-97 gene similar to those reported to be adjacent to the bla OXA-58 gene. In addition, the novel ISAba8 element (which is of the IS21 family) was identified. This is the first report of the nosocomial spread of carbapenemase producers in A. baumannii isolates in Africa.

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