antibiotic resistance of salmonella and escherichia coli isolated from chicken in shiraz area

antibiotic resistance pattern of salmonella and e. coli isolated from chickens against several antibiotics was determined. a total of 150 samples from chickens were isolated and identified using various enrichment and special media. disc diffusion antibiotic susceptibility test was performed and mic and mbc of doxycycline were also determined using serial dilution method. sixty nine bacterial isolates were obtained from which 58 isolates were e. coli and 11 isolates were salmonella. the percentage of resistance against tylosin and erythromycin, doxycycline, enrofloxacin, oxytetracycline, and chloramphenicol were 100, 79.7, 69.5, 76.8 and 24.6, respectively.mic values for e. coli and salmonella were obtained to be 8-64 and 1-64 µg/ml, respectively. the lowest resistance obtained belongs to chloramphenicol (24.6%). one should expect a higher degree of resistance against chloramphenicol, as this antibiotic is used in human medicine and cross resistance may also occur between chloramphenicol/tetracyclines and chloramphenicol/erythromycin. doxcycline is also used in chicken production. considering the fact that cross resistance may occur among members of tetracyclines, the result obtained in this respect, is not far from expectation.