Isolation, Identification, and Genetic Characterization of Antibiotic Resistance of Salmonella Species Isolated from Chicken Farms

Abstract

<i>Salmonella</i> is a major cause of foodborne outbreaks. It causes gastroenteritis in humans and animals. This micro-organism causes severe illness in chickens and has a major impact on chicken productivity and the poultry industry. This study aimed to address the prevalence of <i>Salmonella</i> infection in broiler chicken farms in Kafrelsheikh, Gharbia, and Menofeya provinces in Egypt during 2020-2022. This work also aimed to evaluate the genetic characterization and antibiotic resistance of the isolated <i>Salmonella</i> strains. Clinical signs and mortalities were observed and recorded. In total, 832 samples were collected from 52 broiler flocks, including 26 from both one-week-old and 6-week-old chicken farms from different organs (liver, intestinal content, spleen, and gallbladder). The prevalence of <i>Salmonella</i> infections was reported in the study region to be 36.54%. Of the 26 one-week-old farms surveyed, 11 (42.31%) and 8/26 (30.77%) of the six-week-old broiler chicken farms had <i>Salmonella</i> infections. Recovered isolates were serotyped as 9 (47.37%) <i>S. enteritidis</i> O 1,9,12, ad monophasic H: g, m: -, 6 (31.58.%) <i>S. shangani</i> 2, (10.53%) <i>S. gueuletapee</i> 1, (5.26%) <i>S. II (salamae)</i>, and 1 (5.26%) untypable. The results showed that <i>Salmonella</i> infection was predominant in one-week-old chicks compared to infection in six-week-old and uninfected flocks. All <i>Salmonella</i> isolates were resistant to ampicillin and erythromycin, while all isolates were sensitive to ciprofloxacin, chloramphenicol, and levofloxacin. The isolates also contained 10.53% (2/19) streptomycin, 10.53% (2/21) gentamicin, 15.79% (3/19) doxycycline, and 26.32% (5/19) lincomycin and colistin. The phenotypically resistant <i>Salmonella</i> samples against ampicillin, erythromycin, and macrolide harbored <i>bla</i> _TEM <i>, bla</i> _SHV <i>, erm</i>B<i>, ere</i>A<i>, mph</i>A, and <i>erm</i>B, respectively. This baseline data on <i>Salmonella</i> spp. prevalence, serotyping, and antibiotic profiles are combined to define the antimicrobial resistance to this endemic disease. Elucidation of the mechanisms underlying this drug resistance should be of general importance in understanding both the treatment and prevention of <i>Salmonella</i> infection in this part of Egypt.