Prevalence and serovar diversity of Salmonella spp. in primary horticultural fruit production environments

Abstract

Increases in foodborne disease outbreaks associated with fresh produce have necessitated the need to identify potential sources of microbial contamination in produce and agricultural environments. The present study evaluated Salmonella prevalence and serovar diversity in fruit (225), water (140) and surface (126) samples, from three commercial farms and associated packhouses, located in different farming regions in South Africa. Fruit and water samples were collected from both orchards and packhouses, while surface samples were collected from conveyer belts and hands of packhouse employees. Salmonella was detected in 26 of the 491 (5.3%) samples. Environmental samples (water and surfaces) recorded a slightly higher proportion (3.1%; 15/491) of positive samples compared to fruit samples (2.2%; 11/491). Salmonella was not detected on employee hands and river water samples. A total of 263 Salmonella isolates were obtained from the 26 positive samples by standard culture methods, preliminarily identified through matrix-assisted laser desorption ionisation-time of flight mass spectroscopy (MALDI-TOF MS) and API 20E, and confirmed by invA gene. Of the 39 representative isolates serotyped the serovars Muenchen (33.3%), Typhimurium (30.8%), Heidelberg (20.5%), Bsilla (7.7%), Salmonella subspecies IIb: 17: r: z (5.1%) and one untypable strain were identified. Most samples had multiple serovars with orchard water form one site recording the highest serovar diversity (4 serovars). Our findings show the potential of agricultural fruit production environments to act as reservoirs of clinically important Salmonella serovars.