Antibiotic Resistance Pattern and Biofilm Formation Ability of Clinically Isolates of Salmonella enterica Serotype typhimurium

Background: The emergence of antimicrobial-resistant bacteria with biofilm formation ability may be a major threat to public health and food safety and sanitation. Objectives: The aim of this study was to determine antibiotic resistance patterns and biofilm production characteristics of Salmonella typhimurium isolated from different species of birds. Materials and Methods: The antibiotic resistance patterns of 38 pre-identified isolates were screened by standard Kirby-Bauer disc- diffusion method performed on Mueller-Hinton agar to a panel of 17 antibiotics. The extent of biofilm formation was measured by Microtiter plate (MTP)-based systems. Results: The highest antimicrobial resistance was detected against nalidixic acid (97%), followed by doxycycline (86%), colistin (84%), streptomycin (84%) and tetracycline (84%). All isolates were sensitive to amikacin (100%) and 97% and 95% of the isolates were sensitive to ceftazidime and ceftriaxone, respectively. Twenty one different antibiotic resistance patterns were observed among S. typhimurium isolates. According to the results of the microtitre plate biofilm assay, there was a wide variation in biofilm forming ability among S. typhimurium isolates. Most of the isolates (60.52%) were not capable of producing biofilm, while 26.31%, 7.89%, and 5.26% isolates were weak, strong and moderate biofilm producers, respectively. Conclusions: It was concluded that nearly all S. typhimurium isolates revealed a high multiple antibiotic resistant with low biofilm forming capabilities which proposed low association between biofilm formation and antibiotic resistance of a major food important pathogen.