EPIDEMIOLOGY AND ANTIMICROBIAL RESISTANCE OF ESCHERICHIA COLI ISOLATED FROM PNEUMONIA IN CALVES

Abstract

Escherichia coli (E. coli), a Gram-negative bacterium, is widely recognized as a commensal of the digestive system and as a pathogen in various intestinal and extraintestinal infections. In calves, pathogenic strains of E. coli are linked to severe lung infections, such as pneumonia, which cause considerable economic impacts due to reduced growth, treatment costs and mortality rates. These infections are often linked to control failures, such as insufficient colostration, high population density and environmental stress. The pathogens have particular virulence factors, such as genes that encode adhesins (fimH, papC), siderophores (iroN, iucD) and immune-resistant proteins (iss, ompT, traT), which are crucial for colonization and evasion of the host’s defences. At the same time, the increase in antimicrobial resistance in E. coli is a result of the excessive use of antimicrobials in animal production systems. This favors the spread of resistant genes, such as mcr-1 and blaCTX-M, commonly propagated by mobile plasmids and integrons. Studies in Brazil highlight the presence of resistant E. coli in calves and in the agricultural environment, including feces, water and flies, which act as reservoirs and propagators of resistance. These elements highlight the connection between improper management practices and the continuation of bacterial infections that are complex to treat. Therefore, to effectively control these infections and minimize AMR, integrated strategies are needed, including biosecurity, monitoring of resistant genes and appropriate use of antimicrobials, as well as greater awareness of the environmental impact of livestock practices.