Fig. 1. Agarose gel electrophoresis of se gene PCR products. Lanes 1 and 15, molecular weight marker VI, Roche. Lane 2, DNA negative control. Lanes 3–14, PCR products with primers sets for sea (120 bp), seb (478 bp), sec (257 bp), sed (317 bp), see (170 bp), seg (704 bp), seh (495 bp), sei (630 bp), sej (426 bp), sem (300 bp), sen (680 bp), seo (180 bp). Size of molecular weight marker fragments is indicated by arrows in base pairs.

Fig. 2. PFGE separation of SmaI digested macrorestriction fragments of genomic DNA from selected S. aureus isolates. Lane 1, Lambda ladder PFG marker. Lanes 6 and 11, low range PFG marker. (Marker bands indicated in kb.). Lane 2, PFGE pattern 26 (isolate M2). Lane 3, PFGE pattern 25 (isolate M3). Lane 4, PFGE pattern 25 (isolate M4). Lane 5, PFGE pattern 18 (isolate M5). Lane 7, PFGE pattern 49 (isolate M8). Lane 8, PFGE pattern 42 (isolate M9). Lane 9, PFGE pattern 47 (isolate M10). Lane 10, PFGE pattern 52 (isolate M11).

Fig. 3. Selected AFLP patterns generated by AFLP with primer G. Lanes 1, 14 and 24, 1 kb plus marker (Invitrogen) size is indicated by arrows in bp. Lanes 2, 15 and 20, AFLP pattern R (isolates H13, C9 and C17). Lanes 3, 6, 10, 13, 16, 17, 21 and 22, AFLP pattern A (isolates H14, C1, C2, C8, C12, C13, C10 and C14). Lane 4, AFLP pattern P (isolate H15). Lanes 5 and 18, AFLP pattern D (isolates H16 and C15). Lanes 7, 9 and 11, AFLP pattern F (isolates C3, C7 and C4). Lane 8, AFLP pattern O (isolate C6). Lane 12, AFLP pattern L (isolate C5). Lane 19, AFLP pattern G (isolate C16). Lane 23, empty.

Fig. 4. Dendrogram of PFGE patterns showing the relatedness of 92 S. aureus strains examined in this study. Levels of similarity were calculated using Bionumerics software with the Dice coefficient and cluster analysis with UPGMA. Se genotypes are also indicated.

Fig. 5. Dendrogram of AFLP patterns showing the relatedness of 92 S. aureus strains examined in this study. Levels of similarity were calculated using Bionumerics software with the Dice coefficient and cluster analysis with UPGMA. Se genotypes are also indicated.

S. aureus strains used in this study

MIRINZ = Meat Industry Research Institute of New Zealand culture collection, AgResearch Ruakura, Hamilton, New Zealand; DEXCEL cultures kindly gifted by DEXCEL Hamilton, New Zealand; ESR = Institute of Environmental Science and Research culture collection, Wellington, New Zealand.

Primers for the detection of S. aureus se genes

Identification of different se genotypes among S. aureus isolates

ELISA detection of SE's produced by pure cultures of S. aureus and enterotoxin genes by PCR

−, Negative.

+, Positive.

ND, not detected.

NT, not tested (due to negative result with non-specific SE ELISA detection).

AFLP groups, PFGE major clusters (related at 70% similarity level), distinct PFGE pattern types (100% similarity) and se genotypes

Strain designation: H = human source, L = ovine related source, B = bovine related source, C = reference strain (human or food poisoning related source, see Table 1).