Survival and antimicrobial resistance profile of Salmonella sp. in stored pig manure

Abstract

This study aimed determine the survival and antimicrobial resistance profile of Salmonella sp. samples isolated from swine manure systems plats with capacity for a minimum period of 120 days of wastewater. Of the 63-manure sample analyzed, Salmonella sp. was recovered only in nine (14.28%) of them, with serovars Typhimurium (79.4%), Panama (11.8%) and Derby (5.9%) and one isolate (2.9%) characterized as S. enterica. The presence at least one sample of Salmonella was determined in six systems, with the greatest number of isolations occurring at 120 days of storage. The antimicrobial resistance profile proved to be variable, and all samples were sensitive to amikacin, gentamicin, amoxicillin, neomycin and ciprofloxacin. Resistance to four or more antimicrobials was present in 20.6% of the isolates. There was a higher percentage of resistance after 120 days of storage in the systems and total multidrug resistance index (MAR) was 0.2. The role that waste treatment plays in the level of resistance of bacteria inhabiting the gastrointestinal tract is still controversial. While some studies point to a bneficial effect, represented by reduction of the resistance level of the samples during treatment, others affirm that the passage through the systems would provide the exchange of genes between bacterial strains resulting in an increase in multiresistance. This fact was observed in the present study, considering that the MAR index above o.2 is considered risk, since these microrganisms could act as reservoirs of resistance genes for other bacteria, including those in contact with the human population. Based on the results, it was concluded that samples of Salmonella survive after 120 days of storage of swine manure, with a tendency to increase in the resistance profile afther this period.