## 4 Discussion
In this study, 59.34% of _Salmonella_ strains (five serotypes) exhibited the rdar morphotype, indicating the presence of curli fimbiae and cellulose, extracellular matrix components of the biofilm; however, temperatures of 22 and 35 \({}^{\circ}\)C did not cause any differences (\(p>0.05\)). Similar results were also observed by [PERSON] et al. [6], who reported the rdar morphotype at 28 and 35 \({}^{\circ}\)C in 55.2% of _Salmonella_ spp. isolated from raw poultry. In addition, [PERSON] et al. [4] and [PERSON] et al. [38] reported the rdar morphotype on CRA at 28 \({}^{\circ}\)C in monophasic _Salmonella_ Typhimurium, _Salmonella_ Anatum, _Salmonella_ Baildon, _Salmonella_ Braenderup, _Salmonella_ Javiana, _Salmonella_ Montevideo, and _Salmonella_ Newport isolated from water sources, feed, the environment, and feces. In contrast, [PERSON] et al. [28] reported that _Salmonella_ Newport isolated from humans and _Salmonella_ Typhimurium and _Salmonella_ Enteritidis isolated from irrigation water exhibited the sar morphotype, while _Salmonella_ Daytona isolated from irrigation water exhibited the bdar morphotype on CRA. Our results show variations of the morphotypes pdar (2.19%) and bdar (27.47%). This could be associated with the set of genetic machinery behind these morphotypes or with environmental factors such as the nutrients, temperature, pH, and oxygen that regulate the expression of genes involved in the synthesis of cellulose and fimbiae (curli). [PERSON] et al. [40] and [PERSON] et al. [41] argued that _csgD_ regulates curli fimbia biosynthesis and _bcs_ is responsible for cellulose biosynthesis in biofilm formation by _Salmonella_. Consequently, the medium correlation (0.453) between _Salmonella_ serotype morphotypes and multidrug-resistant morphotypes in our study may be related to the extracellular polymeric substances (EPS) of the matrix of the biofilm, such as curli fimbiae, cellulose, extracellular DNA (eDNA), and extracellular polysaccharides that link cells together and confer resistance to antibiotics. In addition, fimbiae and cellulose are coexpressed by _Salmonella_; a matrix of tightly packed cells produces a spatial organization in which cells in the biofilm cluster in microcolonies [3, 42]. Therefore, it is complex to establish an association between multidrug resistance and the formation of a biofilm. In fact, the mechanisms of resistance and tolerance to antibiotics are associated with the bacterial strain and species that generate the biofilm, the formation stage and component of the biofilm (eDNA), antibiotic-degrading enzymes, efflux pumps, and quorum sensing [31, 43, 44]. All four serotypes of _Salmonella_ used in this study had a high ability to develop biofilms in TSBS (8.39-9.63 log\({}_{10}\) CFU/cm\({}^{2}\)) and TSBA (7.81-8.98 log\({}_{10}\) CFU/cm\({}^{2}\)) on PP at 35 \({}^{\circ}\)C (Table 4). Furthermore, _Salmonella_ Infants-9 showed a higher cell density that the other serotypes (\(p<0.05\)). Similar results were also observed by [PERSON] et al. [45], who reported a biofilm of _Salmonella_ Newport (mango isolate; 7.2 log\({}_{10}\) CFU/coupon) and _Salmonella_ Thompson (cilantro outbreak, isolate; 7.5 log\({}_{10}\) CFU/coupon) cells suspended in 2% lettuce juice extract on stainless steel. Likewise, [PERSON] et al. [46] showed the formation of a biofilm by _Salmonella_ Typhimurium (ST1 and ST2) isolated from vegetables on different surfaces used in the food industry, including PVC (polyvinyl chloride) pipes (ST1 6.2 log\({}_{10}\) CFU/g; ST2 4.5 log\({}_{10}\) CFU/g) and polyethylene bags (ST1 5.8 log\({}_{10}\) CFU/g; ST2 4.2 log\({}_{10}\) CFU/g); they concluded that PVC pipes are more likely to be colonized by biofilms. [PERSON] et al. [6] reported weak biofilm formation (65.5%) by _Salmonella_ spp. isolated from raw poultry on PVC at 35 \({}^{\circ}\)C in BHI (brain heart infusion). Generally, the development of biofilms by _Salmonella_ serotypes responds to limitation of nutrients through the use of the simplified culture media TSBS and TSBA (\(p<0.05\)).