Prevalence, Risk Factors, Antimicrobial Resistance and Molecular Characterization of Salmonella in Northeast Tunisia Broiler Flocks

Abstract

This study was conducted in northeastern Tunisia to estimate both the prevalence and the risk factors of Salmonella in broiler flocks as well as to characterize the isolated multidrug-resistant (MDR) Salmonella strains. In the present study, a total number of 124 farms were sampled; Salmonella isolates were identified by the alternative technique VIDAS Easy Salmonella. The susceptibility of Salmonella isolates was assessed against 21 antimicrobials using the disk diffusion method on Mueller–Hinton agar using antimicrobial discs. Some antimicrobial resistance genes were identified using PCR. The prevalence rate of Salmonella infection, in the sampled farms, was estimated at 19.9% (64/322). Moreover, a total number of 13 different serotypes were identified. High rate of resistance was identified against nalidixic acid (82.85%), amoxicillin (81.25%), streptomycin (75%), and ciprofloxacin (75%). Alarming level of resistance to ertapenem (12.5%) was noticed. A total of 87.5% (56/64) of isolated strains were recognized as MDR. Three MDR strains were extended-spectrum β-lactamases (ESBL)-producers and three MDR strains were cephalosporinase-producers. The blaCTX-M gene was amplified in all the three ESBL strains. The qnrB gene was not amplified in fluoroquinolones-resistant strains. The tetA and tetB genes were amplified in 5% (2/40) and 2.5% (1/40) of tetracycline-resistant strains, respectively. The dfrA1 gene was amplified in five of the 20 trimethoprim-resistant strains. The mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5 genes were not amplified in any of the phenotypically colistin-resistant strains. In terms of integrase genes int1 and int2, only gene class 2 was amplified in 11% (7/64) of analyzed strains. Risk factors, such as the poor level of cleaning and disinfection, the lack of antimicrobial treatment at the start of the breeding, and a crawl space duration lower than 15 days, were associated with high Salmonella infection in birds. These data should be considered when preparing salmonellosis control programs in Tunisian broiler flocks.

Colistin Resistance Genes in Broiler Chickens in Tunisia

“…Colistin resistance has been detected in Escherichia coli isolates from both apparently healthy chickens or poultry meat [ 16 , 25 , 31 , 32 , 33 ] and chickens that died due to colibacillosis [ 34 ], as well as in Salmonella spp. isolates in broiler flocks [ 35 ].…”

“…To our knowledge this study is the first investigation conducted in Tunisia in which all the mcr gene types known so far have been examined. In this regard, previous studies have shown a mismatch between phenotypic colistin resistance and the detection of mcr genes in some bacterial isolates [ 16 , 35 ]. The lack of evidence of mcr genes in DNA from colistin resistant isolates could be attributed to classic chromosomal mutations as well as the presence of untested mcr variants.…”

Prevalence and Antibiotic Resistance of Salmonella spp. and Staphylococcus aureus Isolated from Broiler Chicken Meat in Modern and Traditional Slaughterhouses of Morocco

“…The skin and meat of carcasses are frequently infected with the pathogen during slaughter and processing (FAO, 2022). several studies have reported Salmonella prevalence in broiler farms as 34.37%, 24%, 19.9%, in Algeria, Morocco, and Tunisia, respectively (Chaiba and Rhazi Filali, 2016;Djeffal et al, 2018;Oueslati et al, 2021). Therefore, it is important to consider farm contamination, which represents a critical stage in the development of Salmonella, both in terms of its impact on public health and the significant economic repercussions it can generate (Chaiba and Rhazi Filali, 2016).…”

Serotype Occurrence, Virulence Profiles, Antimicrobial Resistance and Molecular Characterization of Salmonella Isolated from Hospitalized Patients with Gastroenteritis in Great Tunisia between 2010 and 2020

“…The global spread of S. Kentucky, especially in Europe, Africa and Asia, has been illustrated by the isolation of a particular epidemic clone (S. Kentucky ST198-X1) in different reservoirs of livestock, especially in poultry, chicken and turkey farms. For this purpose, poultry are considered the main potential vectors of human infection [ 26 , 27 ].…”

“…Gene amplicons were visualized in 1.5% agarose gel stained with ethidium bromide and photographed under UV transilluminate. Positive and negative controls represented by Salmonella strains isolated in a previous study [ 27 , 52 ] and distilled sterile water were added in each PCR run, respectively.…”