Notably, plasmid analysis identified a sizable diversity of plasmid sizes, including E. coli isolates producing the same CTX-M type (data not shown).
In addition, we observed the dissemination of several clones producing the same CTX-M type enzyme in the hospital, in the community, and in both environments across the boundary between the hospital and the community.
The study showed that the CTX-M-type ESBL was the most common resistance gene type.
The blaCTX-M-15 gene detected in these isolates encodes the most robust CTX-M-type ESBLs described to date and has a wider hydrolytic capability against most cephalosporins, including ceftazidime, than other CTX-Ms.
The TEM-, SHV- and CTX-M-type ESBLs are the most widely distributed worldwide.
Seventy-nine percent of the strains belonged to CTX-M-type, CTX-M-1 and CTX-M-9 constituting the most prevalent types.
Plasmid-mediated ESBLs are most commonly of the TEM-, SHV- or CTX-M-type.
To date, over 60 different CTX-M-type β-lactamases have been described [ 3] and divided into five different clusters that reflect similarity at the amino-acid sequence level, namely bla CTX-M-1, bla CTX-M-2, bla CTX-M-8, bla CTX-M-9, bla CTX-M-25 [ 2], respectively.
Detection by PCR of beta-lactamase (bla) genes encoding KPC-, VIM-, TEM-, OXA- and CTX-M-type enzymes was performed, as described previously [ 14].
For the isolates carrying ESBL genes, 92 carried CTX-M-type genes, two carried SHV-type genes, and one carried both SHV and CTX-M genes.
