A highlight for Non-Escherichia coli and Non-Salmonella sp. Enterobacteriaceae in dairy foods contamination

Abstract

Dairy products are the base of the diet of many families in all social classes worldwide. However, the high content of milk nutrients and their derivatives, in addition to the near neutral pH and high water activity, provide an ideal environment for the growth of many microorganisms in dairy products (Oladipo and Omo-Adua, 2011). Moreover, during its manufacturing, processing, storage, distribution, and marketing, dairy products may be subject to inadequate hygiene conditions, which can promote spoilage and contamination with pathogenic microorganisms, including Enterobacteriaceae (Cusato et al., 2013; Freitas et al., 2013). Several studies have reported the contamination of dairy products by Salmonella sp. and Escherichia coli; however, few studies have described the presence of Enterobacter, Klebsiella, and Serratia species, particularly with regard to the presence of these genera in foods and milk products. In addition, although most studies performed with these bacteria have focused on quantification and identification, some studies have also explored antimicrobial resistance (Samaržija et al., 2012; Zhang et al., 2015) and other virulence factors, such as biofilm (Cherif-Antar et al., 2016), proteolytic enzymes (Chove et al., 2013), and lipolytic enzymes (Masiello et al., 2016). Cheese is a major dairy product that can be manufactured using nonpasteurized milk; this process is often carried out at farms and small establishments, increasing the potential for contamination by microorganisms, including Enterobacteriaceae (Zhang et al., 2015). Even in products subjected to the pasteurization process, the absence of contaminants is not guaranteed because of possible flaws in the process or after pasteurization. In Brazil, the most commonly consumed fresh cheese, "Minas frescal," has undergone changes in its composition, particularly after campaigns pushing for sodium reduction. However, such changes in composition can exacerbate problems with contamination because sodium is effective in controlling some pathogenic and deteriorative microorganisms, including Enterobacteriaceae family members, directly affecting the shelf life of the product and potentially altering its rheological and sensory features (Doyle and Glass, 2010; Cruz et al., 2011; Damaceno et al., 2015). Contamination in dairy products is not restricted to fresh products. Infant milk formulas and milk powder, which are subjected to various moisture removal processes, have also been reported to be contaminated with representatives of this family. Isolates of Klebsiella pneumoniae, Citrobacter freundii, Enterobacter cloacae, and other members of the E. cloacae complex have been found in these foods (Oonaka et al., 2010; Sani and Yi, 2011; Yao et al., 2012).