Antimicrobial Resistance of Salmonella enteritidis and Salmonella typhimurium Isolated from Laying Hens, Table Eggs, and Humans with Respect to Antimicrobial Activity of Biosynthesized Silver Nanoparticles

Abstract

Salmonella enterica is one of the most common causes of foodborne illness worldwide. Contaminated poultry products, especially meat and eggs are the main sources of human salmonellosis. Thus, the aim of the present study was to determine prevalence, antimicrobial resistance profiles, virulence, and resistance genes of Salmonella Enteritidis (S. enteritidis) and Salmonella Typhimurium (S. Typhimurium) isolated from laying hens, table eggs, and humans, in Sharkia Governorate, Egypt. The antimicrobial activity of Biosynthesized Silver Nanoparticles (AgNPs) was also evaluated. Salmonella spp. were found in 19.3% of tested samples with laying hens having the highest isolation rate (33.1%). S. Enteritidis) (5.8%), and S. Typhimurium (2.8%) were the dominant serotypes. All isolates were ampicillin resistant (100%); however, none of the isolates were meropenem resistant. Multidrug-resistant (MDR) was detected in 83.8% of the isolates with a multiple antibiotic resistance index of 0.21 to 0.57. Most isolates (81.1%) had at least three virulence genes (sopB, stn, and hilA) and none of the isolates harbored the pefA gene; four resistance genes (blaTEM, tetA, nfsA, and nfsB) were detected in 56.8% of the examined isolates. The AgNPs biosynthesized by Aspergillus niveus exhibit an absorption peak at 420 nm with an average size of 27 nm. AgNPs had a minimum inhibitory concentration of 5 µg/mL against S. enteritidis and S. typhimurium isolates and a minimum bactericidal concentration of 6 and 8 µg/mL against S. enteritidis and S. typhimurium isolates, respectively. The bacterial growth and gene expression of S. enteritidis and S. typhimurium isolates treated with AgNPs were gradually decreased as storage time was increased. In conclusion, this study indicates that S. enteritidis and S. typhimurium isolated from laying hens, table eggs, and humans exhibits resistance to multiple antimicrobial classes. The biosynthesized AgNPs showed potential antimicrobial activity against MDR S. enteritidis and S. typhimurium isolates. However, studies to assess the antimicrobial effectiveness of the biosynthesized AgNPs in laying hen farms are warranted.

Occurrence of virulence factors and carbapenemase genes in Salmonella enterica serovar Enteritidis isolated from chicken meat and egg samples in Iraq

“…In this study, the presence of tetA (87.1%)/ tetB (87.1%) and dfrA1 (77.6%)/ sul1 (83.6%) genes may be contributed to the high resistance rates against tetracycline and trimethoprim-sulfamethoxazole, respectively. In line with our findings, in a previous study by Abou Elez et al [ 18 ] from Egypt, high resistance rates were observed against ampicillin (100.0%) and tetracycline (88.0%). They stated that the presence of the tet genes may be responsible for this high resistance rate to tetracycline.…”

“…In recent years, ESBLs have spread among Salmonella species in different countries [ 24 , 25 ]. The lower resistance rates against carbapenems including imipenem and meropenem in comparison with other antibiotic classes may be as a result of limited use of these antimicrobials in poultry farms that was consistent with previous reports from Bangladesh [ 9 , 26 ] and Egypt [ 18 ].…”

“…Zoonotic pathogens including Salmonella serovars are commonly transmitted by chickens and eggs [ 18 ]. S. Enteritidi s is an important Salmonella serovar which causes zoonotic infections.…”

“…Various countries have different hygienic control and management programs, which may explain the differences in S. Enteritidis contamination rates of food products [ 6 ]. The Salmonella species in infected poultry feces may contaminate the eggshells and penetrate the interior of eggs, causing bacteria to grow inside [ 18 ]. Another reason for these differences may be due to the detection method, sample size, and sample types.…”

“…They stated that the presence of the tet genes may be responsible for this high resistance rate to tetracycline. In their study, the most S. Enteritidis isolates (84.0%, n = 21/25) harbored tetA gene, whereas the tetB gene was only found in 2 isolates [ 18 ]. However, in another report by Shittu et al [ 27 ] from Nigeria, the tetA and tetB genes were not detected in any S. enterica serovars including S. Enteritidis isolates that was in contrast to our results.…”