CTX-M-137, a hybrid of CTX-M-14-like and CTX-M-15-like β-lactamases identified in an Escherichia coli clinical isolate

hThe carbapenem resistance determinant bla NDM-1 has been found in various Gram-negative bacteria and upon different plasmid replicon types (Inc). Here, we present four patients within two hospitals in Pakistan harboring between two and four NDM-1-producing Gram-negative bacilli of different species coresident in their stool samples. We characterize the bla NDM-1 genetic contexts of these 11 NDM-1-producing Gram-negative bacilli in addition to other antimicrobial resistance mechanisms, plasmid replicon profiles, and sequence types (STs) in order to understand the underlying acquisition mechanisms of carbapenem resistance within these bacteria. Two common plasmid types (IncN2 and IncA/C) were identified to carry bla NDM-1 among the six different bacterial species isolated from the four patients. Two of these strains were novel Citrobacter freundii ST 20 and ST 21. The same IncN2-type bla NDM-1 genetic context was found in all four patients and within four different species. The IncA/C-type bla NDM-1 genetic context was found in two different species and in two of the four patients. Combining genetic context characterization with other molecular epidemiology methods, we were able to establish the molecular epidemiological links between genetically unrelated bacterial species by linking their acquisition of an IncN2 or IncA/C plasmid carrying bla NDM-1 for carbapenem resistance. By combining plasmid characterization and in-depth genetic context assessment, this analysis highlights the importance of plasmids in antimicrobial resistance. It also provides a novel approach for investigating the underlying mechanisms of bla NDM-1 -related spread between bacterial species and genera via plasmids.

Section: Figmentioning

confidence: 99%

Genetic Contexts of bla _NDM-1 in Patients Carrying Multiple NDM-Producing Strains

Wailan

Sartor

Zowawi

et al. 2015

“…More than 95% identity is often observed within the same cluster, whereas less than 90% identity is detectable between clusters (2). Several hybrids of the CTX-M-1 and -9 groups, namely, CTX-M-64, CTX-M-123, CTX-M-137, and CTX-M-132, have also been identified recently (3)(4)(5). Formation of these hybrid CTX-M enzymes was suggested to be the result of recombination between bla CTX-M- 15 and bla CTX-M-14 , the two most dominant variants detectable worldwide (1,6).…”

mentioning

confidence: 99%

“…This suggests that recombination may take place between bla CTX-M- 14 and bla CTX-M-55 , producing various hybrid enzymes. Interestingly, all three published hybrids, CTX-M-64, CTX-M-123, and CTX-M-137, confer relatively high ceftazidime MICs compared to the majority of other CTX-M-type ESBLs (3)(4)(5). Conversely, the hydrolytic activities of CTX-M-55, CTX-M-123, and CTX-M-132 enzymes have not been described.…”

mentioning

confidence: 99%

Residues Distal to the Active Site Contribute to Enhanced Catalytic Activity of Variant and Hybrid β-Lactamases Derived from CTX-M-14 and CTX-M-15

Chiou

Zeng

et al. 2015

A variety of CTX-M-type extended-spectrum ␤-lactamases (ESBLs), including hybrid ones, have been reported in China that are uncommon elsewhere. To better characterize the substrate profiles and enzymatic mechanisms of these enzymes, we performed comparative kinetic analyses of both parental and hybrid CTX-M enzymes, including CTX-M-15, -132, -123, -64, -14 and -55, that are known to confer variable levels of ␤-lactam resistance in the host strains. All tested enzymes were susceptible to serine ␤-lactamase inhibitors, with sulbactam exhibiting the weakest inhibitory effects. CTX-M-55, which differs from CTX-M-15 by one substitution, A 77 V, displayed enhanced catalytic activity (k cat /K m ) against expanded-spectrum cephalosporins (ESCs). CTX-M-55 exhibits higher structure stability, most likely by forming hydrophobic interactions between A 77 V and various key residues in different helices, thereby stabilizing the core architecture of the helix cluster, and indirectly contributes to a more stable active site conformation, which in turn shows higher catalytic efficiency and is more tolerant to temperature change. Analyses of the hybrids and their parental prototypes showed that evolution from CTX-M-15 to CTX-M-132, CTX-M-123, and CTX-M-64, characterized by gradual enhancement of catalytic activity to ESCs, was attributed to introduction of different substitutions to amino acids distal to the active site of CTX-M-15. Similarly, the increased hydrolytic activities against cephalosporins and sensitivity to ␤-lactamase inhibitors, clavulanic acid and sulbactam, of CTX-M-64 were partly due to the amino acids that were different from CTX-M-14 and located at both the C and N termini of CTX-M-64. These data indicate that residues distal to the active site of CTX-Ms contributed to their enhanced catalytic activities to ESCs.T he rapid dissemination of CTX-M-type extended-spectrum ␤-lactamases (ESBLs) in Enterobacteriaceae poses a huge threat to both human and animal health. To date, more than 150 different CTX-M-type ESBLs have been identified (http://www .lahey.org/studies/other.asp#table1). Based on the genetic relatedness, CTX-Ms can be divided into six clusters, including CTX-M-1, -2, -8, -9, and -25 and the KLUC groups (1). More than 95% identity is often observed within the same cluster, whereas less than 90% identity is detectable between clusters (2). Several hybrids of the CTX-M-1 and -9 groups, namely, CTX-M-64, CTX-M-123, CTX-M-137, and CTX-M-132, have also been identified recently (3-5). Formation of these hybrid CTX-M enzymes was suggested to be the result of recombination between bla CTX-M-15 and bla CTX-M-14 , the two most dominant variants detectable worldwide (1, 6). However, the genetic environments of bla CTX-M-123 and bla CTX-M-64 were highly similar to that of bla CTX-M-55 identified in pHN1122-1, the second-most prevalent bla CTX-M variant in China (7). This suggests that recombination may take place between bla CTX-M-14 and bla CTX-M-55 , producing various hybrid enzymes. Interestingly, all three p...

“…PCR analyses were performed to identify various resistance genes, including MBL genes (bla NDM , bla IMP , bla VIM , bla SPM , bla SIM , bla GIM , and bla AIM ) (1), non-MBL carbapenemase genes (bla KPC , bla OXA-48-like , bla , bla OXA-40-like , bla OXA-51-like , and bla OXA-58 ) (11), and various other genes (12). PCR products were sequenced on both strands with an ABI3700 instrument (Applied Biosystems, Foster City, CA), and bla NDM-1 was identified in all three isolates.…”

Section: Dm-1 (New Delhi Metallo-␤-lactamase [Mbl]mentioning

confidence: 99%

“…Cloning experiments and PCR mapping were performed to detect the genetic environment of bla NDM-1 in the three isolates (12). From A. baumannii GB661, we obtained an ϳ12-kb fragment containing bla NDM-1 and its environment.…”

Section: Dm-1 (New Delhi Metallo-␤-lactamase [Mbl]mentioning

confidence: 99%

NDM-1-Producing Citrobacter freundii, Escherichia coli, and Acinetobacter baumannii Identified from a Single Patient in China

Huang

Zhong

Zhang

et al. 2015

Self Cite

eWe identified New Delhi metallo-␤-lactamase (NDM-1)-producing Citrobacter freundii GB032, Escherichia coli GB102, and Acinetobacter baumannii GB661 in urine and stool samples from a single patient in China. Plasmid profiling and Southern blotting indicated that bla NDM-1 from GB032 and that from GB102 were likely located on the same plasmid, while bla NDM-1 from GB661 was located on a very large (>400-kb) plasmid. This case underscores the broad host range of bla NDM-1 and its potential to spread between members of the family Enterobacteriaceae and A. baumannii.