BACKGROUNDS: Different susceptibility rates of pathogenic bacteria to antimicrobial agents are considered major factors in the choice of drugs and the success of treatments. Concerns have been raised regarding the emergence of antimicrobial resistance among pathogenic bacteria that may result in unpredictable antimicrobial susceptibilities and therapy failure.OBJECTIVES: The purpose of this investigation was to determine the antimicrobial susceptibility of 1, 000 bacterial isolates to five antibacterial agents commonly used in the Iranian poultry industry.METHODS: From July 2008 to June 2009, the antimicrobial susceptibility of 1, 000 bacterial isolates to five antibacterial agents was tested. These agents that are commonly used in the Iranian poultry industry include colistin, doxycycline, enrofloxacin, florfenicol, and sulfamethoxazole+ trimethoprime. The data were provided by 19 laboratories in eight Iranian provinces.RESULTS: The bacterial species belonged mainly to Escherichia coli and Salmonella spp. Of all tested samples, 55.5% were resistant to colistin, 61.5% to doxycycline, 41.5% to enrofloxacin, 34.5% to florfenicol, and 65.5% to sulfamethoxazole+trimethoprime.CONCLUSIONS: The findings of this survey represent the high frequency of resistance to antimicrobial agents commonly used in the Iranian poultry industry. They also highlight the need for the implementation of a national monitoring program for antimicrobial resistance and for a rational use of antimicrobial drugs.