Occurrence and traceability of Salmonella spp. in five Sardinian fermented sausage facilities

Abstract

The aims of the present study were to evaluate the presence of Salmonella in five fermented sausage processing plants and their products during the production process, and to trace the possible sources of contamination. A total of 270 samples were collected: mixture of ground pork meat and fat, products at the end of acidification, sausages at the end of ripening and, during production stages, surfaces in contact with meat and surfaces not in contact with meat. For samples of ground meat, product at the end of acidification and sausages at the end of ripening, the pH and water activity (aw), were determined. All the samples were tested for the presence of Salmonella. Thirtytwo Salmonella isolates were obtained, subjected to serotyping and PFGE. The sausages at the end of ripening pH and aw mean values were 5.39±0.24 and 0.91±0.03, respectively. Salmonella was detected in three processing plants with an overall prevalence of 16.7% in food samples and 5.8% in environmental samples. Salmonella prevalence was 24% in ground meat and products at the end of acidification and was also detected in a sample of sausage at the end of ripening (2%). In environmental samples, Salmonella was detected in 6.6% of surfaces in contact with meat and 5% of surfaces not in contact with meat. Five serotypes were identified among 32 isolates: S. Derby (37.5%), S. Typhimurium and S. Rissen (both 25%), S. Give and monophasic S. Typhimurium (both 6.25%). Six different pulsotypes were obtained with PFGE. The serotypes and the PFGE pattern of the strains were specific for each facility with no overlapping between different processing plants. The same observation can be pointed out considering different sampling days for the same processing plants, thus presumably indicating the raw material (ground pork meat and fat) as the source of contamination. The detection of Salmonella in a sample of sausage at the end of ripening highlights the ability of the pathogen to survive during manufacturing process.

Selection of commercial protective cultures to be added in Sardinian fermented sausage to control <em>Listeria monocytogenes</em>

“…As regards pH and a w evaluated during the challenge test, values reported were consistent with what was found by other Authors and typical of the product (Meloni et al ., 2013 ; Piras et al , 2019 ). Significant differences were found in samples added with the protective cultures compared to control samples (negative control) starting from T1 (P<0.01), at T6 (P<0.05) and also at T20 (P<0.05).…”

“…Fermented sausages are usually made using lactic acid bacteria (LAB) and nitrate-reducing coagulase-negative staphylococci (CNS), which are often naturally present in the meat or added by inoculation of starter cultures during the mixing step (Greco et al , 2005 ). The safety of the SFS depends on the application of several sequential “hurdles” at different stages of the fermentation and ripening process (Mangia et al , 2007 ; Meloni, 2015 ; Piras et al , 2019 ). Safety of the final product is therefore ensured by the presence of multiple factors and specific physico-chemical conditions, such as pH, water activity (a w ), sodium chloride, nitrates and nitrites, which interact in limiting microbial growth (Piras et al , 2019 ).…”

“…The safety of the SFS depends on the application of several sequential “hurdles” at different stages of the fermentation and ripening process (Mangia et al , 2007 ; Meloni, 2015 ; Piras et al , 2019 ). Safety of the final product is therefore ensured by the presence of multiple factors and specific physico-chemical conditions, such as pH, water activity (a w ), sodium chloride, nitrates and nitrites, which interact in limiting microbial growth (Piras et al , 2019 ). In SFSs, pH values comprised between 5.3-5.5 and a w values ≤ 0.920 indicate correct acidification drying processes (Greco et al , 2005 ): products reporting these values at the end of ripening can be included in the category of RTE products unable to support the growth of L. monocytogenes (Regulation EC No.…”

Two Faces of Fermented Foods—The Benefits and Threats of Its Consumption

“…were reduced in the early stages of drying, all pathogens were undetectable in chouriço after a longer period (30 days) of this process. In addition to salt concentration, a sufficiently high glucose content, the addition of antimicrobial compounds, or a low pH affect the survival of microorganisms ( Piras et al, 2019 ). The conditions under which fermentation occurs are also important.…”

Genetic diversity and delineation of Salmonella Agona outbreak strains by next generation sequencing, Bavaria, Germany, 1993 to 2018

“…Therefore, attempts were made some years ago to replace this technique by molecular typing methods such as multilocus sequence typing (MLST), which is able to recognise evolutionary relationships with higher resolution [8]. Furthermore, since many years, pulsed-field gel electrophoresis (PFGE), classifying bacteria based on their universal band pattern after chromosomal restriction, is globally used as a standard molecular technique in outbreak investigations [9-11]. However, despite advantages of molecular techniques, traditional serotyping is still universally used and provides an important historical context.…”