Food Protection Trends - April 2011 - (Page 218)

TABLE 1. Incidence of enterohemorrhagic Escherichia coli (E. coli O157:H7) in cheese analyzed under the Domestic and Imported Cheese Compliance Program between January 1, 2004 and December 31, 2006 Year 2004 2004 2005 2005 2006 2006 Total Category Domestic Imported Domestic Imported Domestic Imported No. positive/ No. tested (%) 0/478 (0) 2/1070 (0.2) 0/317 (0) 1/699 (0.1) 0/210 (0) 0/586 (0) 3/3360 (0.09) Mexican-style soft Mexico Mexican-style soft Soft-ripened Mexico Honduras Cheese type Country of origin shown in Table 1, only 3 (0.09%) of these tested positive: 2 samples of Mexicanstyle soft cheese imported from Mexico (one in 2004 and one in 2005), and one sample of soft-ripened cheese imported from Honduras in 2004. No cheese samples tested in 2006 were positive for E. coli O157:H7 and no domestically produced cheeses tested positive in any year. Given that E. coli O157:H7 was the pathogen of concern that prompted the FDA to consider mandatory pasteurization of all milk intended for cheesemaking, as well as a ban on importation of cheeses made from raw milk, the results are remarkable. Although a major pathogen of concern, E. coli O157:H7 was detected in only 0.09% of cheese samples analyzed by the FDA between 2004 and 2006, and not a single sample of domestically produced cheese tested positive for this organism. These data are in agreement with those presented by Bowen and Henning (4), who failed to recover E. coli O157:H7 in 50 retail samples of natural cheese. Similarly, no E. coli O157 was detected in 153 soft and semi-soft cheeses made with raw cow, ewe or goat milk in a survey conducted in Belgium (41). In addition to the low incidence in cheese, only seven of the 183 (4%) foodborne E. coli O157:H7 outbreaks reported in the U.S. from 1982 to 2002 were attributed to dairy products, and of these seven, four were linked to the consumption of unpasteurized fluid milk (31). The only well publicized domestic outbreak linked to the consumption of cheese oc- curred in Wisconsin in 1998, when vats used to make raw milk Cheddar cheese were inadvertently used to make fresh cheese curds (13). Throughout the same period, the FDA examined 2,181 cheese samples for the presence of L. monocytogenes. A total of 52 samples (2.4%) were positive for this pathogen (Table 2). As can be seen from Table 2, more than half (52%) of the samples positive for L. monocytogenes were from Mexican-style soft cheese (17 positive samples) or soft-ripened cheese (10 positive samples). When data from all years are combined, the overall incidence of L. monocytogenes in domestic cheese samples (1.2%) is seen to be notably lower than that in imported products (3.2%). The incidence of L. monocytogenes in imported samples decreased from 4.25% in 2004 to less than 1% by 2006, suggesting increased control and/ or regulatory compliance by cheese producers abroad. These results are in agreement with a review of FDA records by the World Health Organization Working Group on Foodborne Listeriosis which, according to Norton and Braden (27), revealed the presence of L. monocytogenes in 12 of 658 (1.82%) domestic cheese samples analyzed in 1986. The following year, in a sampling of domestic aged natural cheese manufactured from raw milk, only one of 181 (0.55%) samples was positive for L. monocytogenes (27). These data could represent a low incidence of L. monocytogenes in cheese or could simply be an artifact of the extensive recalls of contaminated cheese in the U.S. prompted by intensive FDA surveillance. Based on the results of multiple surveys, Norton and Braden (27) reported incidence rates below 5% for cheeses manufactured in France (4.5%), Germany (4.4%), Italy (3%) and Switzerland (4.9%), with contamination most commonly observed in soft, followed by semi-soft and hard, varieties. A slightly higher incidence, 6%, was reported by Loncarevic and others (21) for soft and semi-soft cheeses at retail in Sweden. More recently, a Listeria spp. prevalence of 3.49% was reported for fresh soft cheeses purchased at retail in Italy (29). The results of the present review indicate that soft and semi-soft cheese varieties continue to pose the greatest risk in terms of L. monocytogenes contamination. No information was provided as to whether or not cheeses tested were manufactured from pasteurized, heat treated or raw milk. This is an important factor to consider, as soft and semi-soft cheeses made from raw milk may have a higher risk of L. monocytogenes contamination than those made from milk that has undergone heat treatment (21). However, Listeria is an environmental pathogen, and the majority of cheeses contaminated by Listeria result from post-process environmental recontamination. In a study of smear rind style cheeses, for example, Rudolf and Sherer (35) found a higher incidence of L. monocytogenes in cheeses made from pasteurized (8%) versus raw (4.8%) milk. The data reviewed in the pres- 218 FOOD PROTECTION TRENDS | APRIL 2011

Table of Contents for the Digital Edition of Food Protection Trends - April 2011

Food Protection Trends - April 2011
Contents
Sustaining Members
Reflections of Your President
Commentary from the Executive Director
Prevalence of Ivermectin Residues in Cattle Slaughtered in Federally Inspected Abattoirs in Nuevo Leon, Mexico
FDA’s Domestic and Imported Cheese Compliance Program Results: January 1, 2004 —December 31, 2006
New Members
What’s Happening in Food Safety
Industry Products
Special Contributors and Sponsors
Preliminary Program
Ivan Parkin Lecture
John H. Silliker Lecture
Activities
General Information
Registration Rates
Coming Events
Advertising Index
Journal of Food Protection Table of Contents
Booklet Order Form
Membership Application
Celebrating 100 Years of IAFP: 1960s

Food Protection Trends - April 2011