Opportunistic pathogens

Opportunistic pathogens are microbes that usually do not cause disease in healthy people, but may become virulent with immuno-compromised and unhealthy individuals. In the last decades several microorganisms normally occurring in foods have emerged as opportunistic pathogens in human and animals. The situation is being complicated by the emergence of multiply antibiotic-resistant strains of such opportunistic pathogens, which in the context of disease makes hospital-acquired infections in susceptible hosts difficult to treat. This is the case for lactic acid bacteria species belonging to the genus Enterococcus, as well as for multidrug-resistant enterobacteria. Also, strains of other lactic acid bacterial species, such as Weissella or Lactobacillus species may be opportunistic pathogens in immunocompromised or hospitalized persons and cause severe infections. In this chapter we will provide an overview of the main opportunistic pathogens occurring in foods and the most promising strategies to control their occurrence in foods.