Detection, identification, and typing of Listeria species from baled silages fed to dairy cows

Abstract

Anaerobiosis, critical for successful ensilage, constitutes a challenge in baled silages. The loss of complete anaerobiosis causes aerobic deterioration and silages undergo dry matter and nutrient losses, pathogen growth, and mycotoxin production. Silage may represent an ideal substrate for Listeria monocytogenes, a pathogen of primary concern in several cheeses. The aim of this research was to investigate the occurrence of Listeria in baled silage fed to cows producing milk for a protected designation of origin cheese, and to characterize isolates by repetitive sequence-based PCR. Listeria spp. were detected in 21 silages and L. monocytogenes in 6 out of 80 of the analyzed silages; 67% of positives were found in molded zones. Results of the PCR typing showed genotypic homogeneity: 72.9 and 78.8% similarity between strains of Listeria spp. (n = 56) and L. monocytogenes (n = 24), respectively. Identical profiles were recovered in molded and nonmolded areas, indicating that contamination may have occurred during production. The application of PCR allowed the unambiguous identification of Listeria isolated from baled silages, and repetitive sequence-based PCR allowed a rapid and effective typing of isolates. Results disclose the potential of the systematic typing of Listeria in primary production, which is needed for the understanding of its transmission pathways.

Silage fermentation—updates focusing on the performance of micro‐organisms

“…Thus, these micro‐organisms also act in the phase of aerobic deterioration of silage (Nucera et al . ). Despite L. monocytogenes being the most important species, it is not always the most frequent.…”

“…Some authors have verified the predominance of L. innocua (Nucera et al . ). Fenlon () and Santos et al .…”

“…; Nucera et al . ) (Table ). Listeria monocytogenes is the most worrisome and causes listeriosis, a type of feed‐borne infection with a high mortality rate; clinical manifestations include encephalitis, abortion and septicaemia in several animals and humans (Dunière et al .…”

“…Oxygen is important to the survival and growth of this bacterium in silage (Fenlon 1986). The species L. monocytogenes, L. innocua, L. welshimeri, L. grayi, L. seeligeri and L. ivanovii have been identified in different types of silage (Ryser et al 1997;Santos et al 2013;Durmaz et al 2015;Nucera et al 2016) (Table 4). Listeria monocytogenes is the most worrisome and causes listeriosis, a type of feed-borne infection with a high mortality rate; clinical manifestations include encephalitis, abortion and septicaemia in several animals and humans (Duni ere et al 2013).…”

“…Some species or strains have a strong ability to survive the silage environment (anaerobiosis and acidity); and even if they cannot grow, they tend to survive when the oxygen enters the ensiled mass. Thus, these micro-organisms also act in the phase of aerobic deterioration of silage (Nucera et al 2016). Despite L. monocytogenes being the most important species, it is not always the most frequent.…”