Incidence of Enterohemorrhagic Escherichia coli, Escherichia coli O157, Salmonella, and Listeria monocytogenes in Retail Fresh Ground Beef, Sprouts, and Mushrooms

Abstract

The objective of this study was to determine the prevalence of enterohemorrhagic Escherichia coli (EHEC), E. coli O157, Salmonella, and Listeria monocytogenes in retail food samples from Seattle, Wash. A total of 2,050 samples of ground beef (1,750 samples), mushrooms (100 samples), and sprouts (200 samples) were collected over a 12-month period and analyzed for the presence of these pathogens. PCR assays, followed by culture confirmation were used to determine the presence or absence of each organism. Of the 1,750 ground beef samples analyzed, 61 (3.5%) were positive for EHEC, and 20 (1.1%) of these were positive for E. coli O157. Salmonella was present in 67 (3.8%) of the 1,750 ground beef samples. Of 512 ground beef samples analyzed, 18 (3.5%) were positive for L. monocytogenes. EHEC was found in 12 (6.0%) of the 200 sprout samples, and 3 (1.5%) of these yielded E. coli O157. Of the 200 total sprout samples, 14 (7.0%) were positive for Salmonella and none were positive for L. monocytogenes. Among the 100 mushroom samples, 4 (4.0%) were positive for EHEC but none of these 4 samples were positive for E. coli O157. Salmonella was detected in 5 (5.0%) of the mushroom samples, and L. monocytogenes was found in 1 (1.0%) of the samples.

Presence and Characterization of Shiga Toxin-Producing Escherichia coli and Other Potentially Diarrheagenic E. coli Strains in Retail Meats

“…Contamination of beef by STEC has been examined by other researchers around the world. In the United States, a recent study by Samadpour et al reported STEC in 3.5% of 1,750 retail ground beef samples collected from stores in Seattle, WA (45). In other countries, STEC was detected in 4% of beef samples in France (43) and 3% of raw beef samples in Australia (11).…”

“…Such variations could lead to a big difference in results, since isolation of STEC from stx-positive samples was found to be relatively difficult due to the small number of bacterial cells or the occurrence of free stx-carrying phages in meat samples (43,45). In terms of isolation method, instead of picking multiple colonies randomly from one plate and testing each of them (17,26), colony hybridization with a stx probe would more conveniently detect any STEC in all colonies on each plate and yield more accurate results (18,45). The level of STEC contamination (Ͻ1%) in the NARMS ground beef appeared low compared to reports from other investigators, but caution should be exercised in interpreting this low prevalence.…”

“…Culture confirmation is also an important factor affecting the results from different studies. In some research, samples were consid- (43,45), while in other studies, culture confirmation was performed to assess the real occurrence of STEC in meat samples (6,17). Such variations could lead to a big difference in results, since isolation of STEC from stx-positive samples was found to be relatively difficult due to the small number of bacterial cells or the occurrence of free stx-carrying phages in meat samples (43,45).…”

“…In some research, samples were consid- (43,45), while in other studies, culture confirmation was performed to assess the real occurrence of STEC in meat samples (6,17). Such variations could lead to a big difference in results, since isolation of STEC from stx-positive samples was found to be relatively difficult due to the small number of bacterial cells or the occurrence of free stx-carrying phages in meat samples (43,45). In terms of isolation method, instead of picking multiple colonies randomly from one plate and testing each of them (17,26), colony hybridization with a stx probe would more conveniently detect any STEC in all colonies on each plate and yield more accurate results (18,45).…”

Listeria spp. em carpaccio de carne bovina e perfil de resistência aos agentes antimicrobianos

“…A baixa ocorrência de L. monocytogenes também foi reportada no trabalho de Yücel et al (2005), que relataram uma frequência reduzida dessa espécie em carnes bovinas, moídas e inteiras, e carne de frango, sendo que somente 6,16% das amostras estavam contaminadas. Samadpour et al (2006) e Mantilla et al (2007 também observaram uma quantidade pequena de carnes moídas contaminadas com L. monocytogenes, 3,5 e 6,7% respectivamente. Apesar das baixas ocorrências, verifica-se que esses alimentos ainda representam risco para saúde dos consumidores.…”