Sequence analysis of bla CTX-M-28, an ESBL responsible for third-generation cephalosporin resistance in Enterobacteriaceae, for the first time in India

The most common group of ESBLs not belonging to the bla (TEM) or bla (SHV) families were termed bla (CTX-M), to highlight their ESBLs' greater activity against cefotaxime than against ceftazidime. The presence of nosocomial bla (CTX-M-28)-producing Enterobacteriaceae strains has not been reported earlier in Indian hospitals. The sequences of bla (CTX-M-28) gene from cephalosporin-resistant Enterobacteriaceae were analyzed. The structural gene encodes a 290 amino-acid protein, which is most related to the bla (CTX-M) beta-lactamases. The conserved K-T-G was identified in the bla CTX-M-28 protein sequence, but significantly, two point mutations (N -> T) and (F -> S) were identified in the Y-G-N- and S-T-F-K-conserved motifs respectively. These point mutations were seen in all the three sequenced isolates.