Abstract
AbstractThe objective of this study was to use matrix-assisted laser desorption ionisation–time of flight mass spectrometry (MALDI-TOF MS) for the identification of ovine-associated staphylococci. Presumptive Staphylococcus isolates were recovered from ovine udder surface (US), individual raw milk, bulk tank milk, and cheese samples and were characterised by conventional phenotypic methods. A total of 69 bacterial isolates were further confirmed by MALDI-TOF MS. Forty-two (60.9%) of 69 isolates were successfully identified on genus and species level. Two thirds (n = 28) of the 42 identified isolates were shown to be Staphylococcus spp. These 28 staphylococcal isolates formed two clusters, one consisting of 22 Staphylococcus aureus strains and the other composed of 6 non-aureus staphylococci, including S. simulans (n = 3), S. auricularis, S. equorum, and S. haemolyticus. MALDI-TOF MS has proven to be a reliable tool for the identification of staphylococci from raw sheep's milk, especially bulk tank milk; however, currently it appears to be less useful for the identification of bacterial isolates originating from ovine US samples. This is the first study to evaluate the applicability of MALDI-TOF MS for identification of Staphylococcus spp. in ovine raw milk, cheese, and US samples in Hungary.
Highlights
Staphylococci are Gram-positive and facultative anaerobic bacteria belonging to the family Staphylococcaceae
MALDI-TOF MS has proven to be a reliable tool for the identification of staphylococci from raw sheep’s milk, especially bulk tank milk; currently it appears to be less useful for the identification of bacterial isolates originating from ovine udder surface (US) samples
As for the distribution of staphylococcal isolates according to source, 10.7% were recovered from US (n 5 3), 50% from individual raw milk (IRM) (n 5 14), 28.6% from bulk tank milk (BTM) (n 5 8), and 10.7% from cheese samples (Table 2)
Summary
Staphylococci are Gram-positive and facultative anaerobic bacteria belonging to the family Staphylococcaceae. Their cells are spherical in shape and form grape-like clusters. The coagulasepositive Staphylococcus aureus is a major pathogen responsible for intramammary infections in dairy ruminants (Bergonier et al, 2003; Peles et al, 2007). This species is found naturally on the mucous membranes and skin of warm-blooded animals and humans (Irlinger, 2008). It is highly prevalent in both individual and bulk-tank ovine milk (Marogna et al, 2010; de Garnica et al, 2011)
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