Shewanella spp. are commonly known as environmental bacteria and are most frequently isolated from aquatic areas. Currently, diseases syndromes and multidrug resistance have increasingly been reported in the genus Shewanella. Some species are associated with various infections, such as skin and soft tissue infections, as well as bacteremia. Generally, these bacteria are opportunistic and mostly affect people with an impaired immune system. This genus is also a probable vehicle and progenitor of antibiotic resistance genes. In fact, several resistance genes and mobile genetic elements have been identified in some resistant species isolated from environmental or clinical settings. These genes confer resistance to different antibiotic classes, including those used in therapies such as β-lactams and quinolones, and are generally located on the chromosome. Recently, a multidrug-resistant (MDR) plasmid harboring several drug resistance genes associated with transposons and integrons has been identified in Shewanella xiamenensis. These antibiotic resistance genes can circulate in the environment and contribute to the emergence of antibiotic resistance. This review describes different aspects of Shewanella, focusing on the infections caused by this genus, as well as their role in the propagation of antibiotic resistance via mobile genetic elements.

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The whole genome sequencing of extensively drug-resistant Shewanella xiamenensis T17 isolated from hospital effluents in Algeria revealed the presence of a novel 268.4 kb plasmid designated pSx1, which carries several antibiotic-resistance genes in the novel Tn1696 derivative (Tn6297), in addition to the chromosomal bla-like gene (bla). The presence of the plasmid was confirmed by nuclease S1-PFGE analysis and transformation by electroporation into Escherichia coli DH10B. Tn6297 contains an In27 class 1 integron harboring the dfrA12-orfF-aadA2 array, msr(E) and mph(E) associated with IS26; a new efflux pump multidrug resistance composite transposon delimited by two ISEc29s; Tn-tet harboring tetR and tetA(C); a class 1 integron with the qacG gene cassette; qnrVC6 and dfrA23 associated with ISCR1; and a complex class 1 integron In4-like containing aacC1, aadA1, bla, catA2, sul1Δ, cmlA9, tetR, tetA(G), aac(6')-II, and bla. Its mer operon carries merB, but lacks merC, in contrast to Tn1696 and Tn21. This study represents the first characterization of a multidrug-resistant transposon and multidrug resistance plasmid in Shewanella and is the first report of bla in Algeria, providing evidence that Shewanella spp. could be an important reservoir and vehicle for drug resistance genes.

We analyzed 254 Shigella species isolates collected in Québec, Canada, during 2013 and 2014. Overall, 23.6% of isolates showed reduced susceptibility to azithromycin (RSA) encoded by mphA (11.6%), ermB (1.7%), or both genes (86.7%). Shigella strains with RSA were mostly isolated from men who have sex with men (68.8% or higher) from the Montreal region. A complete sequence analysis of six selected plasmids from Shigella sonnei and different serotypes of Shigella flexneri emphasized the role of IS26 in the dissemination of RSA.