Antibiotic and heavy metal resistance profiles in avian Escherichia coli isolates from colibacillosis in Central Algeria

Abstract

Although heavy metals are widely used as feed additives in animal production, little attention has been paid to the resistance of pathogenic bacteria to these elements. This study  investigated heavy metal resistance in 215 isolates of avian pathogenic Escherichia coli from a collection of 308 isolates. All collection's strains were also tested against several antimicrobials using the disc diffusion method. Heavy metal resistance was determined by dilution in plates using Mueller Hinton agar incorporated with aqueous solutions of metals at critical concentrations. Except for copper, the study revealed high resistance rates for zinc (79.1 %), lead (59.1 %), and chromium (45.6 %). Lower rates were recorded for silver (17.7 %), cadmium (11.6 %), and mercury (8.4 %). A total of 29 diverse resistance profiles were identified, including 24 multi-resistant metallotypes displaying simultaneous resistance to up to 5 metals with the predominant metallotype involving resistance to zinc, lead, and chromium (20.5 %). Heavy metal resistance has frequently been associated with antibiotic resistance, particularly to beta-lactams and quinolones. This is supported by multiple correspondence analysis and independence test values (chi-square test) (P < 0.05), clearly establishing a link between antibiotic and heavy metal resistance in the tested strains. This is the first study in Algeria to highlight the dissemination of metal resistance among pathogenic E. coli isolates from poultry. The occurrence of heavy metal resistant pathogenic strains with zoonotic potential poses a serious public health threat, largely driven by co-selection pressure.