This study aimed to compare the prevalence of antibiotic-resistant coliforms and Escherichia coli strains between industrial and antimicrobialfree poultry manure. The mean counts of high-level antibiotic-resistant coliforms were determined using the spread plate technique. Metal and antibiotic resistance of Escherichia coli strains in manure samples was compared using plate dilution and CLSI procedures, respectively. Several multi-drug resistant Escherichia coli strains were screened for plasmids using alkaline lysis method as well. The relative abundance of high-level antibiotic-resistant coliforms was significantly (p < 0.05 and 0.001) higher in industrial manure than in antimicrobial-free manure. Metal analysis indicated that the concentrations of copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) in manure samples were significantly (p < 0.05) correlated with the percentage of coliforms resistant to several antibiotics. The number of multidrug-resistant Escherichia coli strains was significantly (p < 0.001) higher in industrial manure (97.4%) than in antimicrobial-free manure (80.7%). Four out of twelve screened Escherichia coli strains harbored plasmids. Considering the high number of drug-resistant isolates in both samples, reductions in co-selecting agents is essential for the effectiveness of antibiotics, along with controlling the activities which cause the spread of resistance.
