Salmonella Species

There are over 2000 serotypes of the genus salmonella that cause human disease [48]. According to the CDC, there are an estimated 1.4 million cases annually, with an estimated 500 fatalities [48]. Approximately half of all cases are caused by serotypes Enteritidis or Typhimurium [48].

Salmonella infections are more commonly associated with animal-derived foods, such as meat, seafood, dairy, and egg products, rather than juices. However, outbreaks associated with fresh juice have occurred as far back as 1922 [1]. Early outbreaks resulting in typhoid fever were associated with poor hygiene by asymptomatic S. Typhi shedding food handlers. As disinfection of water, sanitation procedures, and hygiene practices have improved, outbreaks of typhoid fever have become far less common in developed countries. Nonetheless, given the dramatic increase of fresh fruit imported from developing countries, typhoid fever outbreaks associated with these commodities remain a concern [49]. More recent outbreaks of nontyphoidal salmonellosis in fresh juice have been attributed to fecal-associated contamination of fruit or poor processing practices [50-52].

Both E. coli O157:H7 and salmonella are tolerant to extreme acid environments. As with E. coli O157:H7, tolerance in salmonella is inducible and increases when cells have been adapted either to acid conditions or are in stationary phase [4,7]. For S. Typhimurium, two major acid tolerance systems were identified, one associated with log phase and one associated with stationary phase [2]. Not surprisingly, survival in juice for extended periods has been observed. Goverd et al. reported survival of S. Typhimurium in apple cider [25]. Survival in juice above pH 3.6 held at 22°C was reported as greater than 30 days. Survival was decreased by lower pH and lower temperature. Survival in orange juice by various salmonella serovars was studied by Parish et al. [53]. Salmonella serovars Gaminara, Hartford, Rubislaw, and Typhimurium were inoculated at log 6CFU/ml into orange juice at pH 3.5, 3.8, 4.1, and 4.4. Survival (to below levels of detection) at pH 3.5 ranged from a low of 14.3 ± 0.9 days for S. Typhimurium to a high of 26.7 ± 4.0 days for S. Hartford.

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