## 4 Discussion  
A wide range of methodologies are available for the bacteriological isolation and characterization of _Salmonella_, which demands the harmonization of results across the EU member states for _Salmonella_ surveys and enforcement of regulations. This harmonization was enforced by the mandatory use of ISO 6579-1:2017. However, our observations show that the efficacy of the ISO needs further validation. Such problems with existing bacteriological methods and the need for faster reliable results promote research into the development of molecular methods. However, for fecal and environmental samples derived from pigs, molecular methods are still in the early stages of development with regard to giving consistent results. For now, the adoption of new methods in routine laboratory monitoring control programs is a compromise between improved sensitivity, specificity and selectivity, speed, ease of use, and economic benefits. However, compromise may result in the loss of some 'exotic' _Salmonella_ serovars, negatively affecting their prevalence and eventually the effectiveness of control programs. Thus, the growing availability of studies held periodically to determine the sensitivity of the various new culture media show that some perform better than others. Their performance is, perhaps, influenced by the kind of sample (e.g., food, feed, feces, environmental sources) or the species of the pathogen [32] infecting swine, with no culture method likely to be safely reliable in recovering all serovars [33; 34; 35; 36; 37; 38; 39; 40]. Hence, recovery of _Salmonella_ spp. from swine samples can be significantly different between culturing methods, with MSRV used for enrichment of swine feces improving recovery because it inhibits growth of most fecal bacteria species, increasing in this way the sensitivity of XLD and BGA agars [12; 20; 36]. Their sensitivity after the use of MSRV is increased to 96% (in naturally contaminated food samples) compared to the standard methods [41]. In the present work, 47 (7.64%) of 615 samples cultured on MSRV showed extensive swarming indicative of _Salmonella_'s migration through the MSRV medium and expressed as turbidity (whitening of the medium). Unfortunately, of the 509 samples producing minimal turbidity, nine (9) were eventually identified as _Salmonella_, a number reducing the specificity of MSRV for _Salmonella_ spp., which proved to be very poor for this specific medium (81.3% false positive results on the factor of inhibiting growth of non-_Salmonella_ species). The reduction of specificity necessitates complementary testing, increasing labor and costs, in order to differentiate salmonellae from other microorganisms. Perhaps, pre-enrichment needs optimization according to a sample's suspected microbial burden, which may also help the recovery of damaged or slow-growing _Salmonella_. Of interest was also the direct recovery of three _Salmonella_ isolates from non-selective pre-enrichment broth. These isolates had been lost on enrichment media (MSRV) as their inability to grow on this medium was confirmed. MSRV medium had, perhaps, a killing effect on this isolates that affected the prevalence of _Salmonella_ spp. in an animal population or food stuff. This finding implies that maximum detection can result from the combination of selective enrichment and direct plating from pre-enrichment media. This is, however, unacceptable for routine testing when large numbers of samples are tested. It was also evident that the choice of differential plating culture media significantly affects recovery. This study confirmed that most but not all _Salmonella_ serovars grow adequately on XLD, SS, BG, and SCA. With the exception of the three rare _Salmonella_ serovars, SCA appeared as a medium with better specificity than the combination of XLD, SS, BGA, and TSI.