- Known and Unknown Pathogens –
(show number of pathogens found in 10 years
to assess what we likely don’t know and prove that we’ll never have the ability
to identify them all or enforce zero tolerance on them)
The rate of discovery of new microbes, and
the new associations of microbes with health and disease, has accelerated over
the past two decades. Many factors are implicated. New pathogens have truly
emerged wit the globalization of travel and trade, changes in demographics and
land use, susceptibility to opportunistic organisms associated with
immunosuppression, and climate change. Environmental, ecological, and
demographic factors, with the ongoing evolution of viral and microbial variants
and selection for drug resistance suggests that infections will continue to
emerge and probably increase and emphasizes the urgent need for effective
surveillance and control. (1)
Types of pathogens are viral, bacterial,
fungal, other parasites and prionic (e.g. mycobacterium tuberculosi (a
causative agent for most tuberculosis) and Fungus (affect Athlete’s Foot). A
pathogen is a harmful organism that causes disease in its host and any foreign
organism, which is not part of the body, and presents inside the body, mainly
in the blood stream, but antigen is a part of the body. (2)
- Weaknesses in Testing Methodology –
(tests can’t tell between live/dead cells,
can’t identify everything)
- Adherence to Testing Protocol –
(Regulators don’t follow protocol)
- Global Experts Weigh-In –
International experts opinions on zero
tolerance policy including recommendations for alternatives)
- A particular concern for the group was the use of criteria
implying a zero tolerance for Salmonella and suggesting complete absence of the
pathogen. The notion can be interpreted differently by various stakeholders and
was considered inappropriate because there is neither an effective means of
eliminating Salmonella from raw poultry nor any practical method for verifying its
absence.
An example is the different criteria (and subsequent actions in
the case of noncompliance) addressing the presence of Salmonella on raw
chicken, all of which depend on the stage in the food chain, the sensitivity of
the sampling plan and method, and the analytical method used.
Increasingly, risk-based concepts are being adopted for both
domestic policy and international trade, despite sometimes being poorly
understood and not always applied consistently or with transparency.
A recent risk assessment of Salmonella contamination in Belgian
chicken meat preparations revealed that levels greater than 1 CFU/g were most
likely to be associated with human salmonellosis (185).
Legislation has been introduced that makes testing compulsory
and specifies deadlines for establishing the required targets in chicken
breeders, layers, and broilers and in turkeys (56, 57)
Serovar-specific control measures. In some parts of the world,
strategies have been adopted to target specific Salmonella serovars associated
with both poultry and human salmonellosis. Salmonella Enteritidis caused a
pandemic of human illness from infected layer and broiler flocks beginning in
the 1980s (3). Particular strains of Salmonella TABLE 1. Prevalence of
Salmonella-positive broiler flocks in the EU, 2005 and 2006 (61) Member state
No. of flocks sampleda % flocks positive for Salmonella Austria 365 7.7 Belgium
373 15.3 Cyprus 248 10.9 Czech Republic 334 22.5 Denmark 295 3.1 Estonia 131
2.2 Finland 360 0.3 France 381 8.9 Germany 377 17.2 Greece 245 27.3 Hungary 359
65.7 Ireland 351 27.9 Italy 313 30.4 Latvia 121 9.1 Lithuania 156 5.1 Poland
357 57.7 Portugal 367 42.8 Slovakia 230 8.3 Slovenia 326 3.1 Spain 388 42.3
Sweden 291 0.0 The Netherlands 362 10.2 United Kingdom 382 10.7 a The number of
samples taken was statistically determined. Pooled fecal samples were obtained
from boot swabs, and five swabs per flock were tested. J. Food Prot., Vol. 73,
No. 8 SALMONELLA ON RAW POULTRY 1569 Enteritidis with an apparent predilection
for the reproductive tract of the laying hen were responsible for contamination
of egg contents, resulting in vertical transmission
For Salmonella Enteritidis and Salmonella Typhimurium in
particular there is a clear linkage between human illness and poultry
consumption. Conversely, although all Salmonella serovars are considered to be
potentially pathogenic to humans, some of those found in poultry are rarely if
ever associated with human illness. A classical example is Salmonella serovar
II 1,4,12,[27]:b:[e,n,x], also known as Salmonella Sofia, which is often
isolated from chicken in Australia but rarely from human salmonellosis cases
there (146).
Predominant poultry serovars differ among countries and can
change over time within a single country or region (76), and successful control
of one serovar may allow another to predominate. For example, epidemiological
evidence suggests that Salmonella Enteritidis may have filled the ecological
niche occupied previously by the antigenically related Salmonella Gallinarum,
which was eradicated in most of the major poultry producing countries by the
1970s (148).
Feed can be a latent source of Salmonella for food animals
because it is made from a wide range of potentially contaminated ingredients
(44, 151). When present in dry feed, Salmonella can survive for more than 1
year, and even low numbers may be significant because for some strains ,1 cell
per g is sufficient to colonize young chicks (157).
The heat sensitivity of nonsporulating bacteria, including
Salmonella, is influenced by the temperature and time and the prevailing water
activity of the feed. The heating process aims to eliminate Salmonella during
pelleting, expansion, or extrusion and minimize any adverse effect on the
nutritional quality of the feed (42, 50, 104, 119, 126). However, there is a
significant risk of recontamination during post-pelleting stages of the milling
operation and during storage and transport of feed. Because of this risk,
various chemical treatments have been considered, e.g., addition of certain short-chain
fatty acids, such as formic and propionic acids. These acids have many of the
attributes that are desirable in a feed treatment (92, 113, 151, 189, 195).
Instead of depending on extensive product testing, a better
alternative is to apply good manufacturing practices (GMPs) and hazard analysis
critical control point (HACCP) principles to the manufacturing process.
Effective implementation of the HACCP system requires measures
to prevent recontamination of the feed after heat treatment. As with raw ingredients,
these measures involve adequate storage conditions (including rigorous dust
control), appropriate control of transport vehicles, regular cleaning and
disinfection of the vehicles, and protection of the load up to and including
the point of delivery.
when used with water-immersion chilling systems, reduces the
organic load in the chill water (168), making any added chlorine more
effective. However, the removal of bacteria from carcasses in the spray washing
process is not enhanced by using chlorine and/or hot water (137), probably
because organisms that become firmly attached to the tissues are protected from
the effects of these agents and are not easily removed (118, 138).
Chilling of poultry carcasses to about 4uC or lower ensures that
any Salmonella present will be unable to multiply…or exposure to cold air
either by passing carcasses through an air blast system or holding them in a
chill room. The continuous immersion system has a washing effect that reduces
microbial contamination by up to 1 log unit (131).
The U.S. system (170) also includes a zero-tolerance policy for
visible fecal contamination on carcasses entering the chilling process (181)
and the need for a HACCP plan to ensure that avoidance of fecal contamination
is a critical control point (182). Otherwise, the determination of critical
control points is a matter for the individual company, and their number and
location are likely to differ among establishments (180).
No feasible sampling plan can guarantee the absence of Salmonella,
but sampling on a regular basis will reveal changes in infection or
contamination so that corrective action can be taken, as required. The sampling
strategy should be defined according to the public health risk involved, the
anticipated prevalence of the target organism, the desired level of confidence
in the results obtained, and the general principles of statistical control,
which will indicate the degree of confidence offered by negative results. Other
factors to consider are the stage in the food chain at which samples should be
taken, the type of sample in each case, how many samples to take at any one
time, how often material is collected, and what quantity of the material to
collect. Standardized methods of analysis should always be used; methods
advocated for international adoption are provided by organizations such as the
International Organization for Standardization (ISO) and the World Organization
for Animal Health (OIE). There also is the question of who should carry out the
sampling, although regulations may specify that sampling must be done, at least
in part, by a competent authority (71). An effective control strategy requires
detailed consideration of the nature of the food chain and the points at which
sampling will provide the most meaningful information. No single sampling site
is ever sufficient. Testing for Salmonella at any stage should always have a
clear objective that is related to control of the organism, allowing
appropriate action to be taken on the basis of the results obtained. Other
factors include the likelihood of infection or contamination at a particular
stage and whether there are practices or interventions that might minimize the
risk. Resources can then be allocated appropriately and cost effectively in
relation to the risk involved. However, feasible levels of sampling are not
usually sufficient to determine fully the effectiveness of a specific control
measure.
In monitoring the mill environment, Jones and Richardson (104)
noted that TABLE 2. Sampling for Salmonella at different stages of the supply
chain Stage in supply chain What to sample When to sample Feed manufacture Bulk
ingredients Before use Mill environment and equipment Finished feed Grandparent
or parent flocks Litter Sampling should be more intensive for grandparent
stock; sample before and just after moving to production house Dead birds Dust
Feces Surfaces and equipment After cleaning and disinfection Hatchery Internal
surface of hatching cabinet After hatching Chick box liners Eggshells Meconium
Dead-in-shell chicks Culled chicks Surfaces and equipment After cleaning and
disinfection Broiler flocks Litter Before slaughter Dust Feces Surfaces and
equipment After cleaning and disinfection Slaughter and processing Neck skin or
carcass rinse After carcass chilling Plant environment and equipment After
cleaning and disinfection Portioning and deboning Meat surface and skin As
required Plant environment and equipment After cleaning and disinfection
Wholesale (fresh and frozen) Meat surface and skin As required Retail Meat
surface and skin As required J. Food Prot., Vol. 73, No. 8 SALMONELLA ON RAW
POULTRY 1575 dust was consistently contaminated with Salmonella throughout the
mill and especially near pellet coolers, which draw in large amounts of air.
Thus, sampling of dust and the mill environment is much more effective than
monitoring the end product, and the sampling should be done as part of a HACCP
program (63, 197).
Sampling at retail. Testing products at the retail stage rather
than during processing is more relevant to the exposure of consumers to
Salmonella via raw poultry meat. The results obtained can be of greater value
in assessing the human health risk, which is required in risk assessments, and
in verifying the effectiveness of Salmonella control measures for different
types of product. This information will provide a scientific basis for any new
criteria that are deemed necessary. The sampling strategy should be based on
statistical methods and related to the sources of Salmonella exposure for the majority
of the population, i.e., it should be largely focused on retail products that
are on display in major towns and cities and in the principal retail outlets
from which most poultry meat is sold. All the main forms in which poultry
products are marketed should be sampled, e.g., whole carcasses, portions, meat
preparations, and fresh and frozen products, and it will be important to
distinguish between domestic and imported products
The adoption of quantitative risk assessment practices in
microbiological food safety underscores the reality that zero risk is
unattainable for all raw foods, a reality in everyday events and everyday life.
The choice of zero tolerance, implying the complete absence of a hazard, may be
regarded as the expression of a regulatory preference for the precautionary
principle and has little to do with food safety and human health (80, 176). In
the United States, the Committee on the Review of the Use of Scientific
Criteria and Performance Standards for Safe Foods formed under the National
Research Council (135) noted that the term ‘‘zero tolerance’’ is commonly used
but generally poorly defined or understood. Use of this language in expressing
objectives is troublesome because the terminology has different meanings for
different audiences, as highlighted by the definition the Committee offered for
its own purposes: ‘‘lay audience perception of the absence of a hazard that
cannot be scientifically assured, but is operationally defined as the absence
of a hazard in a specified amount of food as determined by a specific method.’’
To some people, zero tolerance implies a notional concept of zero risk
associated with the food or zero prevalence of a pathogen in the food
commodity. Such a misunderstanding could easily arise from the pending EU
requirement for the absence of Salmonella in 25 g of fresh (raw) poultry meat
(56) because no details are given on how this requirement would be interpreted.
In the absence of any means of eliminating the pathogen from a raw food
product, the ‘‘zero’’ concept is misleading to those consumers who may
interpret such regulations as implying no risk; these consumers would have
unrealistic expectations of the effectiveness of regulatory action. If a hazard
exists, there is some probability it will cause an adverse effect, no matter
how small (85). Zero tolerance may also imply that both minor and major
deviations from a policy will be treated with the same severity. This is
obviously not a sensible approach to identifying and resolving problems.
Internationally, there is no consistency in interpreting the concept and what
action should result from any deviations. The purpose of a zero tolerance
policy should be to provide an alert, leading to a review of control policies
and procedures while permitting distribution of the final product to the
marketplace in situations where withdrawal would not give a risk reduction
proportional to cost and other practical considerations. Little is to be gained
when dealing with food safety management practices based on microbiological
criteria for end product testing alone (accept or reject) because even when a
process is completely under control some, albeit small, probability exists for
exceeding the established parameters (191, 203). Without knowledge of the
degree of variability in a process or product or of where the uncertainties of
a food process lie, the likelihood of exceeding the limits is unknown. Several
other challenges exist to applying a zero tolerance policy for Salmonella in
poultry meat: defining the accuracy, sampling intensity, sampling material, and
method sensitivity. At which point is the assessment to be made, preharvest or
postharvest, who bears the repercussions for enforcement, and who has and what
is the enforcement capacity? Ultimately, regulatory choices in establishing
control policies must be verified through scientific evidence for their
effectiveness for reducing risk so that social costs can be made transparent
(80).
The term ‘‘zero tolerance’’ for specific pathogens such as
Salmonella in food products is interpreted differently by scientists and other
stakeholders in different countries and therefore has been confusing,
misleading, and misapplied. All countries signing the international WTO
agreements are entitled to establish sovereign levels of protection. However,
with regard to sanitary measures that include MCs, the most appropriate and
legally defensible approach is to define such criteria by limits of detection
according to the analytical method imposed and confidence limits of sampling and
testing. Using terms such as ‘‘zero tolerance’’ or ‘‘absence of a microbe’’ in
relation to raw poultry should be avoided unless these terms are defined and
explained by international agreement. New metrics, such as POs that are linked
to human health outcomes based on risk assessment, should be used throughout
the food chain and will define the resultant public health risk.
In addition to principal authors listed above, members of the
Salmonella on Raw Poultry Writing Committee include Raphael Andreatti Filho,
Sao Paulo State University, Sao Paulo, Brazil; Roy Biggs, Tegel Foods Ltd.,
Auckland, New Zealand; Jeff Buhr, U.S. Department of Agriculture, Agricultural
Research Service, Athens, GA, USA; Sarah Cahill, Food and Agriculture
Organization of the United Nations, Rome, Italy; John Cason, U.S. Department of
Agriculture, Agricultural Research Service, Athens, GA, USA; Thongchai
Chalermchaikit, Chulalongkorn Univeristy, Bangkok, Thailand; Hector Hidalgo,
University of Chile, Santiago, Chile; Charles Hofacre, University of Georgia,
Athens, GA, USA; Henk Hupkes, Meyn Food Processing Technology, B.V., Oostzaan,
The Netherlands; Mogens Madsen, Dianova, Aarhus, Denmark; Roel Mulder,
Spelderholt Poultry Consulting and Research, Burg, The Netherlands; Lars Plym
Forshell, National Food Administration, Uppsala, Sweden; Martha Pulido
Landinez, Universidad National de Colombia, Bogota´, Colombia; Jason
Richardson, The Coca-Cola Co., Atlanta, GA, USA; Douglas Smith, North Carolina
State University, Raleigh, NC, USA; Yvonne Vizzier Thaxton, Mississippi State
University, Mississippi State, MS, USA; Hajime Toyofuku, National Institute of
Public Health, Japan; Pirkko Tuominen, Finnish Food Safety Authority, Helsinki,
Finland; Mieke Uyttendaele, Ghent University, Ghent, Belgium; Sian Ming Shi,
Shanghai Jiaotong University, Shanghai, China; and Marcel Zwietering,
Wageningen University, Wageningen, The Netherlands.
