CTX-M ESBL are widely found in animal and human infections. For better understanding of CTX-M variations and epidemiology, a total of 2210 CTX-M sequences were retrieved from NCBI as at 20 December 2020. The maximum incidences of CTX-M were reported in China (n = 508), USA (n = 354) and Japan (n = 180). Single amino acid substitution in the domain region of CTX-M ESBL lead to survival benefits to the bacteria. A total of 31 different variations were found of which D240G was the most common followed by A77V and V103I substitutions. The variations in CTX-M enzymes were explained continent-wise revealing the maximum variation reported in America followed by Asia and Europe of which D240G substitution was the most prevalent. India contained only three variations (E166A, P167S D240G) found in New Delhi, Karnataka, West Bengal and Tamil Nadu. The P167 and D240 were under strong positive selection with dN/dS calculation.
Keywords: AMR; Antibiotic resistance; CTX-M; ESBL; β-lactam; β-lactamase.
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