Multistate Outbreak of Salmonella Serovar Muenchen Infections Associated with Alfalfa Sprouts Grown from Seeds Pretreated with Calcium Hypochlorite

Abstract

During September 1999, a multistate outbreak of Salmonella serovar Muenchen infection associated with eating raw alfalfa sprouts was identified in Wisconsin. Despite use of a calcium hypochlorite sanitizing procedure to pretreat seeds before sprouting, at least 157 outbreak-related illnesses were identified in seven states having sprouters who received alfalfa seed from a specific lot. The continued occurrence of sproutrelated outbreaks despite presprouting disinfection supports the concern that no available treatment will eliminate pathogens from seeds before sprouting and reinforces the need for additional safeguards to protect the public. A lack of consumer knowledge regarding exposure to sprouts documented in this investigation suggests that more-targeted outreach to high-risk individuals may be needed to reduce their risk.Consumption of raw sprouts has emerged as an important risk factor associated with the occurrence of food-borne illness. In the United States, at least 12 reported sprout-related disease outbreaks involving a total of more than 1,500 cases have been reported since 1995. Sprout-related illness has involved infection with 10 different serogroups of Salmonella (12,13,(15)(16)(17)20; E. Mouzin et al

Microbiological quality of organic vegetables produced in soil treated with different types of manure and mineral fertilizer

“…This concern is directed to Salmonella spp. (24,27,40,47,49) and E. coli O157:H7, because cattle is its main reservoir, explaining the risk of transmission by manure (22,34,43,50).…”

Flow cytometry for rapid detection of Salmonella spp. in seed sprouts

“…Remarkably, the doubling time for an S. enterica strain growing on germinating alfalfa seeds has been found to approach that observed for the same strain growing in LB broth, a nutritionally rich medium [16]. It is therefore not uncommon for contaminated sprouts to contain final levels of Salmonella of up to 10 7 CFU g 1 [10,11]. Given the inherent difficulties in effective sampling so that contaminated seed is not used for production of sprouts, or in decontamination of seeds so that Salmonella does not multiply to hazardous levels during the sprouting process, different tactics are needed to help increase the safety of seed sprouts.…”

“…However, the most common source of pathogens in sprout-related disease outbreaks is the seed itself [10,37], which may be distributed widely, with multistate or even multinational outbreaks possible. Further, implicated seeds may be grown anywhere around the globe and may be composited with seeds from several different farms prior to their sale, distribution and use, complicating outbreak traceback efforts [5,11]. Possible modes of seed contamination include contact with animal feces during seed storage (i.e.…”

“…The high incidence of Salmonella contamination of alfalfa sprouts may be rooted in ecological factors, such as the capacity of this pathogen to adhere strongly to sprout surfaces so that it is retained at high levels in the finished product, even after periodic irrigation during the sprouting process [7,8]. Over the years, various serovars of S. enterica have been involved in sprout-borne outbreaks, including Bareilly, Cubana, Enteritidis, Kottbus, Mbandaka, Muenchen, Newport, Saintpaul, Stanley, Weltevreden and others [9,10,11,12]. Despite the availability of long-standing regulatory guidance on best practices for safe production of sprouts [13], outbreaks of salmonellosis due to consumption of contaminated seed sprouts continue to be a chronic food safety problem [3,9,12,14].…”

“…Development of improved seed sanitation treatments as a means to increase sprout safety has been an area of intense effort in the past few years [3,15]. However, no treatment yet developed has been able to completely eliminate Salmonella or other pathogens from seeds [11,15]. The warm, aqueous, nutrient-rich conditions used to sprout the seeds provide an excellent environment for microbial growth [5,6,7,16].…”