Biofilm development capacity of Salmonella strains isolated in poultry risk factors and their resistance against disinfectants

Prevention of Salmonella contamination of poultry products requires detailed knowledge of the most important risk factors associated with its presence in the production system. The aim of this study was to identify the risk factors for Salmonella contamination in 44 broiler and 51 layer farms and determine the biofilm development capacity of the strains isolated. Then, glutaraldehyde (50% vol/vol), formaldehyde (37% vol/vol), and hydroxide peroxide (35% vol/vol) were applied to evaluate their capacity to remove Salmonella, biofilm and nonbiofilm strains, isolated from each risk factor in an artificial contamination test in field conditions. Samples of feces, dust, surfaces, meconium, delivery-box liners, water tank, water dispensers, litter, vectors (rodents, flies, and beetles), and surfaces of the slaughter trucks were taken throughout the rearing period. All samples were analyzed in accordance with ISO 6579:2002 (Annex D). To evaluate biofilm development, a screening method based on the fluorescence of Salmonella colonies on calcofluor agar plates was used. In the artificial contamination test, the chemical solutions were prepared at a concentration of 1.0% and applied at exact times (1, 15, or 60 min). Our results showed that the most important risk factors for Salmonella contamination were dust, surfaces, and feces. Moreover, day-old broiler chicks reached the farm highly contaminated, and wild carriers played an important role in the recirculation of Salmonella in laying hen houses. The serotype most commonly isolated from each risk factor was Salmonella enteritidis, and irrespective of the origin of different serotypes, around 50% were able to produce biofilm. Finally, the use of glutaraldehyde, formaldehyde, and peroxygen at a concentration of 1.0% in field conditions are inadequate for Salmonella elimination irrespective of the serotype, the biofilm development capacity, and the disinfectant contact time.