CTX-M-93, a CTX-M Variant Lacking Penicillin Hydrolytic Activity

Genetic Features of MCR-1-Producing Colistin-Resistant Escherichia coli Isolates in South Africa

“…We identified the same clone (ST624) in both hospital-and community-acquired isolates, that clone being identified as an avian pathogenic E. coli isolate causing colibacillosis in poultry in Spain and China (20,21), but also in isolates from patients in France and Japan (22). This feature, together with the identification of the floR gene associated with resistance to florfenicol (that antibiotic being given only in veterinary medicine), further suggests the animal origin of that resistance trait (23).…”

The Continuing Plague of Extended-spectrum β-lactamase–producing Enterobacteriaceae Infections

“…28,48,69,71,73,75,76,[82][83][84][85][86][87][88][89][90] As mentioned, K pneumoniae was the main isolate harboring ESBL genes (most often bla TEM and bla SHV types) during the 1990s. 10 However, a decade later, E coli-producing ESBLs became prevalent in various regions, producing a different class of ESBLs, that is, the CTX-Ms. 75,76,90 The CTX-Ms were discovered over a decade earlier, but were not prevalent initially among ESBL pathogens associated with human infections (with the exception of few alleles, ie, CTX-M-93 91 ). 12,20,92 In recent years, the CTX-M families have seen a tremendous diversification.…”

Kinetic characterization of GES-22 β-lactamase harboring the M169L clinical mutation

“…The presence of a leucine at this position in CTX-M-27 (compared to a glutamine in CTX-M-93) is also associated with higher activity against aztreonam and several penicillins, but lower activity against ceftazidime. 16 SHV-1, which also has a leucine at positon 169, displays a similar pattern of activity: lower activity against ceftazidime, but higher activity against penicillins when compared to SHV-57 (with an arginine at position 169). 15 A C169L substitution in TLA-2 shows increased activity against penicillins.…”

“…15 Also, increased ceftazidime hydrolysis caused by mutations at position 169 have been described in other studies. 16–18 Position 169 is most typically occupied by methionine or leucine in class A β-lactamases, though some exceptions exist (TLA-2, SHV-57, CTX-M-93) (Figure 2). The neighboring residue at position 170 is important in imipenem hydrolysis in GES-type β-lactamases.…”