## 3 Results  
On average, the prevalence of _Salmonella_ spp. in beef and beef products was 1.25% (\(n=5/400\); Confidence interval (CI) = 0.4-3). The samples were mainly of gastrointestinal origin (3/400; 0.75%; CI = 0.2-2; Table 3), followed by beef kidney (\(n=1/400\); 0. 25%; CI = 0-1) and beef rib (\(n=1/400\); 0.25%; CI = 0-1). From these five _Salmonella_ positive samples, five isolates were obtained. The isolates belong to four different serovars, namely \(S\). [PERSON] (\(n=2\)), \(S\). Heidelberg (\(n=1\)), \(S\). Hadar (\(n=1\)) and \(S\). Enteritidis (\(n=1\)) (Table 3).  
Drug resistance was observed for \(S\). Enteritidis only. The \(S\). Enteritidis was resistant to tetracycline and the aminopencillins, which are ampicillin and amoxicillin. The \(S\). [PERSON], \(S\). Heidelberg, and \(S\). Hadar were susceptible to ampicillin, amoxicillin, chloramphenicol, cefotaxime, gentamicin, ciprofloxacin, kanamycin, tetracycline, cefoxitin, and trimethoprim--sulfamethoxazole.  
_Salmonella_ isolates tested positive for a minimum of two virulence genes and some serovars tested positive for up to six out of eight virulence factors (Table 4). The virulence gene profile of each of the isolates was unique, without a repetition of the same combination of virulence genes (Table 4). Virulence gene _agfA_ was predominant, and was observed in all of the five isolates. Both the _invA_ and _hiA_ genes were found in all except one isolate (Table 4). One of the two \(S\). Stanley strains contained six of the eight virulence genes, whilst \(S\). Heidelberg harbored the least (2/8) number of virulence genes. The _spvC_ gene was not detected in any of the six _Salmonella_ isolates in this study.  
_Detection of Virulence Genes Using PCR_  
Figures 2-4 show examples of agarose gel pictures showing PCR amplicons for _invA_, _hiA_ and _sivH_ genes, respectively.  
Lanes: 1: 50 bp DNA ladder; 2; 3 and 5 show PCR amplicons of samples positive for _invA_ gene. Lane 4 shows a negative result for _invA_ (\(S\). Heidelberg). The serovars in lanes 2,3 were \(S\). Stanley and lane 5 contained \(S\). Hadar. The _invA_ gene is 284 bp in length.  
Lane 1 contained the 50 bp DNA ladder and the remainder of the lanes had PCR amplicons run. Lanes 2 (\(S\). Stanley) and 5 (\(S\). Hadar) were positive for the 763 bp _sivH_ gene.  
\begin{table}
\begin{tabular}{c c c} \hline
**Sample Type** & **Serovar** & \multicolumn{3}{c}{**Virulence Gene**} \\ \hline  & _invA_ & _AgfA_ & _LpfA_ & _hiA_ & _sivH_ & _SefA_ & _spvE_ & _spvC_ \\ Beef Intestines & \(S\). Stanley & \(+\) & \(+\) & \(-\) & \(+\) & \(+\) & \(-\) & \(-\) & \(-\) \\ Beef tripe & \(S\). Heidelberg & \(-\) & \(+\) & \(-\) & \(+\) & \(-\) & \(-\) & \(-\) \\ Beef intestines & \(S\). [PERSON] & \(+\) & \(+\) & \(+\) & \(+\) & \(+\) & \(-\) & \(-\) & \(-\) \\ Beef kidney & \(S\). [PERSON] & \(+\) & \(+\) & \(+\) & \(-\) & \(-\) & \(+\) & \(-\) & \(-\) \\ Beef rib & \(S\). [PERSON] & \(+\) & \(+\) & \(+\) & \(+\) & \(-\) & \(+\) & \(+\) & \(-\) \\ \hline \end{tabular} \(\star\): Refers to positive PCR test for the target virulence gene; \(-\): Refers to negative PCR test for the target virulence gene.  
\end{table}
Table 4: PCR results for eight virulence genes from six _Salmonella_ isolates obtained from beef products.  
Figure 3: Image showing example of _hi1A_ gene amplicons observed on agarose gel. Lane 1 contains the 50 bp DNA ladder and lanes 2–4 show positive results for the _hi1A_ gene (497 bp). Lanes 2 and 3 contained amplicons for \(S\). [PERSON] isolates, while lane 4 contained \(S\). [PERSON].  
Figure 2: Image showing examples of _invA_ gene amplicons observed on agarose gel.