Antibiotic resistance of Salmonella isolated from commercial chicken feeds in Dar es Salaam, Tanzania
Salmonella resistance to antimicrobials is rapidly growing worldwide. Antibiotics are commonly used in prevention of bacterial infections as well as treatment of infected chickens in Tanzania. A study on Salmonella was conducted in commercially produced chicken feeds from feed mills in Dar es Salaam, Tanzania, between May 2015 and June 2016 with the objective of estimating the prevalence of Salmonella contamination and their antibiotic susceptibility patterns. Feed samples were collected from a total of 384 randomly selected feed bags of different types from six feed mills. Cultural and biochemical tests were performed for identification of Salmonella in the samples. All isolates were subjected to eight commonly used antibiotics for sensitivity test using disc diffusion method. The overall prevalence of Salmonella in the study was 22.1%. Prevalence of Salmonella contamination was 22.2%, 39.1%, 14.7%, 0.0%, 25% and 42.9% of the samples from feed mills named A, B, C, D, E and F respectively. Significantly higher (p = 0.001) prevalence of Salmonella contamination was recorded in feed mill B. Although Salmonella isolates were less resistant to ciprofloxacin (14.1%), the resistance increased towards amikacin (63.4%), sulphamethoxazole/trimethoprim (85.9%), gentamicin (87.1%), kanamycin (88.2%), streptomycin (96.5%), amoxycillin (98.8%) and tetracycline (100.0%). Isolation of Salmonella from commercial chicken feeds in Dar es Salaam connotes the importance of hygienic processing and handling of feeds for effective control of Salmonella contamination in both humans and farms. The antibiogram pattern shows the presence of antibiotic resistant Salmonella species hence; suitable measures should be implemented to avoid indiscriminate use of antibiotics in chicken feed chain.
Keywords: Salmonella, Poultry mash, feed mills, antibiogram, antibiotic sensitivity