Characterization of antibiotic resistance in Salmonella enterica isolates determined from ready-to-eat (RTE) salad vegetables

Abstract

In the last decade, ready-to-eat (RTE) salad vegetables are gaining increasing importance in human diet. However, since they are consumed fresh, inadequate washing during processing can bring on some foodborne illnesses, like salmonellosis, since these food items have natural contamination from soil and water. During 2009–2010, a total of 81 samples were purchased arbitrarily from local markets in Ankara, and were examined for Salmonella contamination. Salmonella screening was performed by using anti-Salmonella magnetic beads system and polymerase chain reaction (PCR) identification of the suspected colonies. Then, the antibiotic resistance profiles of four Salmonella strains identified (strains RTE-1, RTE-2, RTE-3, and RTE-4) were also investigated, since the mechanism by which Salmonella spp. have accumulated antibiotic resistance genes is of interest. All strains showed resistance against sulfonamides (MIC > 128 mg/L). Further results suggested that associated sulfonamide resistance genes were encoded by the 55.0 kb plasmid of strain RTE-1 that involves no integrons. As a result of using two primers (P1254 and P1283) in randomly amplified polymorphic DNA-PCR (RAPD-PCR) analysis, two common amplicons (364 bp and 1065 bp) were determined. The findings of this study provide support to the adoption of guidelines for the prudent use of antibiotics in order to reduce the number of pathogens present on vegetable and fruit farms. Besides, since it is shown that these bacteria started to gain resistance to antibiotics, it is necessary to further investigate the prevalence of them in foods.

Cross-Sectional Survey of Indicator and Pathogenic Bacteria on Vegetables Sold from Asian Vendors at Farmers’ Markets in Northern California

“…As shown in Figure 2, identical strains of Salmonella clustered by commodity within location, similar to the level of spatial clustering observed for strains of Salmonella isolated from salad vegetables purchased from markets and retail premises from across the city of Ankara, Turkey (36). Surprisingly, there were several examples in our study of similar PFGE pattern isolates of Salmonella obtained from different commodities at different markets.…”

“…Elsewhere, researchers have traced outbreaks of Salmonella to contaminated lettuce (12,26) and other vegetables from Mexico (30), Turkey (3), Canada (2), and Brazil (33,37). Although minimal baseline information exists for the prevalence of foodbome pathogens for specialty crops sold at farmers' markets in some countries, including Brazil (21), Canada (5,28), Nigeria (25,31), Togo (1), Turkey (36), and the United States (18,39), many countries (including the United States) have not conducted detailed cross-sectional surveys of specialty crops grown on small to medium-sized farms and sold at local retailers, by direct marketing, and at urban and peri-urban farmers' markets (15). Given that bacterial pathogens represent a common cause of produce-associated foodbome illness (4,14,24) and that little information exists on the microbiological quality of ethnic-specific commodities such as yardlong beans and bitter squash from direct retail operations, we conducted a crosssectional survey of bacterial pathogens and indicators for a variety of specialty commodities at farmers' markets in northern California during summer 2013.…”

Antimicrobial resistance surveillance of Salmonella isolates from the First People’s Hospital of Yunnan Province, China

“…This is different from what had been reported previously for Typhimurium infection in Spain and enteric fever in India, where most of the isolates (76% and 90.2%, respectively) were recovered from children [3,4]. Humans may be exposed to Salmonella through consumption of contaminated water and food [5]. With the rising public standard of living, a gradual reduction in the frequency of Salmonella isolation was observed during the study period (Figure 1), which may be due to the reduced the likelihood of exposure to contaminated water and food.…”

Microbiological Quality of Ready-to-Eat Leafy Green Salads during Shelf-Life and Home-Refrigeration

“…[ 21 ], Listeria monocytogenes [ 22 , 23 ] and Escherichia coli O157: H7 [ 5 , 24 ]. Furthermore, RTESs may have an important role in the spread of bacteria of clinical interest carrying antibiotic resistance genes [ 25 , 26 ].…”