TOS, JH, KAG, DW, MH and LJH wrote the manuscript. All authors read and approved the final manuscript.”
“Background Escherichia coli belonging to the phylogenic group B2, serotype O25b:H4 and Multi-Locus Sequence Type (ST) 131 (E. coli O25b-B2-ST131), producing extended-spectrum β-lactamase (ESBL) is regarded as a major pandemic clone in community and hospitals causing serious clinical infections such as urinary tract infections and bacteraemia [1]. It has been shown that E. coli O25b-B2-ST131 exhibits a high virulence score compared to other lineages [2] and

is capable of acquiring antibiotic resistance by different mechanisms [3–6]. The fact that E. coli O25b-B2-ST131 is able to exhibit antibiotic selleckchem resistance means that the clinical environment within a hospital or community may actively select certain resistant click here strains [7] making the treatment of these infections increasingly difficult. Analysis by pulsed field gel electrophoresis (PFGE) has identified a high degree of genetic diversity among the E. coli O25b-B2-ST131 isolates; however, some types appear to be more common in certain regions than others [4]. An important cause of resistance in E. coli O25b-B2-ST131 is

the production of β-lactamase enzymes. Some of the most prevalent of these are CTX-M-like enzymes as well as other types specifically TEM-1, TEM-24, SHV-12 and the plasmid-mediated AmpC CMY-2 [8–10]. Furthermore, CTX-M-15 producing strains often co-produce both OXA-1 as well as variants of an aminoglycoside-modifying enzyme that is responsible for reduced susceptibility both to the aminoglycosides and to some fluoroquinolones expressed by aac(6’)-Ib-cr genes [5,6]. Fluoroquinolone

(FQ) resistance in Enterobacteriaceae is usually caused by mutations in the chromosomal genes coding for type II topoisomerases and changes in the expression of efflux pumps and porins. The rise of plasmid-mediated AZD9291 mouse FQ resistance protein Qnr [11] has caused concern in antimicrobial treatment of Enterobacteriaceae whereby carbapenems are considered the best therapeutic option [12]. Nevertheless some Enterobactericeae can produce clinically important carbapenemases; the Ambler class B metallo-β-lactamases (NDM, IMP, VIM), the class A enzymes (KPC) and the class D oxacillinase enzymes (OXA-48). Until recently E. coli was less often affiliated with carbapenemases than Klebsiella pneumoniae, however, the recent emergence of bla NDM gene (New Delhi metallo-β-lactamase) on plasmids in E.coli ST131strains has caused concern [13–15]. The NDM-like enzymes have been identified in different regions [16] including in clinical K. pneumoniae isolates from Kuwait [17] and Oman [18] in the Middle East. The bla OXA-48 carbapenemase is mainly associated with the Tn1999-like transposon inserted into a single 62-kb IncL/M-type plasmid [19]. It has been detected in sporadic cases; E. coli ST1196 (also containing resistance genes: bla CMY-2, bla SHV-12 and bla TEM-1) and E.