Detection and Isolation of Salmonella from Naturally Contaminated Alfalfa Seeds Following an Outbreak Investigation

Inami, Gregory B.; Moler, Silvia

doi:10.4315/0362-028x-62.6.662

Cited by 52 publications

(22 citation statements)

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“…In a naturally contaminated alfalfa seed lot epidemiologically linked to a food-borne disease outbreak, it was estimated that approximately 1 most probable number of S. enterica in 100 g of seed (approximately 1 in 40,000 seeds) actually harbored the pathogen (12). However, as the seeds are germinated, the S. enterica spread through the irrigation water to contaminate the entire batch of sprouts.…”

Section: Discussionmentioning

confidence: 99%

Differences in Attachment of Salmonella enterica Serovars and Escherichia coli O157:H7 to Alfalfa Sprouts

Barak

Whitehand

Charkowski

2002

Appl Environ Microbiol

115

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Numerous Salmonella enterica and Escherichia coli O157:H7 outbreaks have been associated with contaminated sprouts. We examined how S. enterica serovars, E. coli serotypes, and nonpathogenic bacteria isolated from alfalfa sprouts grow on and adhere to alfalfa sprouts. Growth on and adherence to sprouts were not significantly different among different serovars of S. enterica, but all S. enterica serovars grew on and adhered to alfalfa sprouts significantly better than E. coli O157:H7. E. coli O157:H7 was essentially rinsed from alfalfa sprouts with repeated washing steps, while 1 to 2 log CFU of S. enterica remained attached per sprout. S. enterica Newport adhered to 3-day-old sprouts as well as Pantoea agglomerans and 10-fold more than Pseudomonas putida and Rahnella aquatilis, whereas the growth rates of all four strains throughout seed sprouting were similar. S. enterica Newport and plant-associated bacteria adhered 10-to 1,000-fold more than E. coli O157:H7; however, three of four other E. coli serotypes, isolated from cabbage roots exposed to sewage water following a spill, adhered to sprouts better than E. coli O157:H7 and as well as the Pseudomonas and Rahnella strains. Therefore, attachment to alfalfa sprouts among E. coli serotypes is variable, and nonpathogenic strains of E. coli to be used as surrogates for the study of pathogenic E. coli may be difficult to identify and should be selected carefully, with knowledge of the biology being examined.Numerous food-borne diseases caused by Salmonella enterica and Escherichia coli serovar O157:H7 have been associated with contaminated alfalfa, clover, and bean sprouts (3, 13, 15, 17-19, 24, 27). For food production, seeds are grown into sprouts at ambient temperature in trays or rotating drums and are watered regularly during sprouting. The constant moisture, nutrients released by the sprouting seeds, and warm temperatures are conducive to the growth of human bacterial pathogens such as S. enterica and E. coli O157:H7 (1,4,5,8,11,22).Numerous studies have reported the growth of S. enterica and E. coli O157:H7 on sprouting seeds. We recently demonstrated that S. enterica strains grow to significantly higher levels on sprouting alfalfa seeds than E. coli O157:H7 when irrigation water is regularly refreshed (5). Our results suggested that S. enterica might reach higher numbers of bacteria on alfalfa sprouts in part because it adheres better to alfalfa sprouts and thus is not washed from the sprouts when the sprouts are irrigated. In this study, we have compared the adherence to alfalfa sprouts of the human pathogens S. enterica and E. coli and the plant-associated bacteria Rahnella aquatilis (10), Pseudomonas putida (7), and Pantoea agglomerans (10). We also have compared how these human pathogens and plantassociated bacteria colonize sprouting alfalfa seeds. MATERIALS AND METHODSBacterial strains, plasmids, and growth media. Strains used in this study are listed in Table 1. S. enterica serovar Newport 96E01153C-TX and E. coli F4546 are clinical isolates from sp...

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Section: Discussionmentioning

confidence: 99%

Differences in Attachment of Salmonella enterica Serovars and Escherichia coli O157:H7 to Alfalfa Sprouts

Barak

Whitehand

Charkowski

2002

Appl Environ Microbiol

115

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“…Viable pathogens can persist not only on the surface but also in the inner tissue and stomata of cotyledons of sprouts experimentally contaminated with bacteria (11). Low numbers of culturable Salmonella may not be detected in seed even with methods that provide the greatest potential for detection and recovery (10). While several chemical treatments can reduce Salmonella populations up to 3.2 log 10 CFU/g on alfalfa seeds, as analyzed by direct plating, no chemical treatment will eliminate the pathogen, as evidenced by detection in enrichment samples (21).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2001

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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

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“…In 2001, serovar Newport was the third highest cause of Salmonella-associated human gastroenteritis, behind serovars Typhimurium and Enteritidis, and linked to nearly 10% of human cases of Salmonella infection (www.cdc.gov/ncidod/dbmd/phlisdata/salmtab /2001/SalmonellaAnnualSummary2001.pdf). The incidence of serovar Newport infections has increased probably as a result of multiple reservoirs for serovar Newport (8,11,16,19,22,26) and the emergence of multidrug-resistant strains (12). The ability of serovar Newport to attach to cells from a number of different host species may be a function of the fimbriae produced by this organism (2, 7), allowing for many carriers.…”

Section: Discussionmentioning

confidence: 99%

“…Runoff from agricultural crops may also contribute to the increase of Salmonella contamination in summer, since most crops are irrigated with recycled water, which may contain fecal and Salmonella contaminants, as stated by the United States geological survey (http://water.usgs.gov/pubs/pp/pp1655 .html). It has been documented that alfalfa sprouts also contain Salmonella spp., including serovar Newport (16,26). If Salmonella is present when the crops are irrigated, the runoff goes into local streams.…”

Section: Discussionmentioning

confidence: 99%

Prevalence of Salmonella spp. in Oysters in the United States

Brands¹,

Inman²,

Gerba

et al. 2005

Appl Environ Microbiol

135

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Food-borne diseases such as salmonellosis can be attributed, in part, to the consumption of raw oysters. To determine the prevalence of Salmonella spp. in oysters, oysters harvested from 36 U.S. bays (12 each from the West, East, and Gulf coasts in the summer of 2002, and 12 bays, four per coast, in the winter of 2002-2003) were tested. Salmonella was isolated from oysters from each coast of the United States, and 7.4% of all oysters tested contained Salmonella. Isolation tended to be bay specific, with some bays having a high prevalence of Salmonella, while other bays had none. Differences in the percentage of oysters from which Salmonella was isolated were observed between the summer and winter months, with winter numbers much lower probably due to a variety of weather-related events. The vast majority (78/101) of Salmonella isolates from oysters were Salmonella enterica serovar Newport, a major human pathogen, confirming the human health hazard of raw oyster consumption. Contrary to previous findings, no relationship was found between the isolation of fecal coliforms and Salmonella from oysters, indicating a necessity for specific monitoring for Salmonella and other pathogens rather than the current reliance on fecal coliform testing.

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Detection and Isolation of Salmonella from Naturally Contaminated Alfalfa Seeds Following an Outbreak Investigation

Cited by 52 publications

References 0 publications

Differences in Attachment of Salmonella enterica Serovars and Escherichia coli O157:H7 to Alfalfa Sprouts

Differences in Attachment of Salmonella enterica Serovars and Escherichia coli O157:H7 to Alfalfa Sprouts

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

Prevalence of Salmonella spp. in Oysters in the United States

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