Natural Resources Defense Council, Inc. et al v. United States Food and Drug Administration et al

Filing 33

DECLARATION of Jennifer A. Sorenson in Support re: 19 MOTION for Summary Judgment.. Document filed by Center For Science In The Public Interest, Food Animal Concerns Trust, Natural Resources Defense Council, Inc., Public Citizen, Inc., Union Of Concerned Scientists, Inc.. (Attachments: # 1 Exhibit A, # 2 Exhibit B, # 3 Exhibit C, # 4 Exhibit D, # 5 Exhibit E, # 6 Exhibit F, # 7 Exhibit G, # 8 Exhibit H, # 9 Exhibit I, # 10 Exhibit J, # 11 Exhibit K, # 12 Exhibit L, # 13 Exhibit M, # 14 Exhibit N, # 15 Exhibit O, # 16 Exhibit P, # 17 Exhibit Q, # 18 Exhibit R, # 19 Exhibit S, # 20 Exhibit T, # 21 Exhibit U, # 22 Exhibit V, # 23 Exhibit W, # 24 Exhibit X, # 25 Exhibit Y, # 26 Exhibit Z, # 27 Exhibit AA, # 28 Exhibit BB, # 29 Exhibit CC, # 30 Exhibit DD)(Sorenson, Jennifer)

EXHIBIT G
TO DECLARATION OF
JENNIFER A. SORENSON
Excerpt from Seattle-King County Department of Public Health 1984 Report

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SURVEILLANCE OF THE FLOW
OF SALMONELLA A D
CAMPYLOBACTER IN
A COMMUNITY
Prepared for .
United States Department of Health and Human Services
Public Health Service
Food and Drug Administration
Bureau of Veterinary Medicine

By:
mom

Communicable Disease Control Section
Seattle-King County Department of Public Health
Contract Number: 223-81-7041
August, 1984 -

City of Seattie

King County

Charles Royer Randy Revelle
Mayor County Executive

0000000840

I. ABSTRACT
In an effort to learn more about possible linkages between
human infection with Salmonella and Campylobactor jejuni and
contamination of food by those bacteria, a two-pronged surveillance system was established. Food of animal origin from retail
outlets in King County was systematically cultured for Salmonella
and C. jejuni'for a period of 20 months. Simultaneously, cases
of Salmonella and C. jejuni enteritis diagnosed in enrollees at
Group Health Cooperative of Puget Sound, a 320,000 member health
maintenance organization, were investigated. A case/control
study was included in the evaluation of the C. jejuni infections.
Salmonella and C. jeluni isolates from food'and human cases
were subjected to antibiotic susceptibility testing, plasmid
analysis,. and serotyping in an effort to identify phenotypic
characteristics which might facilitate comparisons between the
two groups of isolates.
The predominant finding in the food surveillance system was
contamination of retail poultry by C. jejuni; 192 (22.3%) of 862
specimens cultured C. jejuni, only 30 (3.5%) cultured Salmonella.
Other types of retail meat had, at most, negligible contamination
by either bacterium.
In the population under study, C. jejuni was found to be a
more common enteric pathogen than Salmonella. During the period
of case surveillance, 218 C. jejuni cases (matched with 526
controls) and 72 Salmonella cases were diagnosed and investi-

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polm
_gated. The case/control study disclosed that a number of expo- (-**)
sures during the 7days prior tib the onset of illness were associated with cases more frequently than with controls, thus implicating those exposures as risks for C. jejuni infection. The
most prominent of those exposures were travel to undeveloped
countries, drinking raw milk, consumption of chicken, exposure to
untreated water, contact with humans ill with enteritis, and
contact with pets, particularly dogs, with diarrhea.
Calculatton of the "etiologic fraction," the proportion of
all . cases attributable to specific exposures, revealed that consumption of chicken was responsible for 48.2% of cases of C.
•■••■■••

jejuni enteritis in the Group Health population during the period
of study.
The information provided by the case/control study showing
that chicken consumption was the predominant risk factor associated with C. jejuni enteritis was supported by microbiological
study of C. jejuni isolates. Thus, isolates fiom human cases and
those from retail poultry had similar antibiotic susceptibility
patterns including prevalences of 29.7% and 32.8%, respectively,
of tetracycline resistance, which was found to be plasmid-mediated. In addition, the distribution . of the six most frequent
Lior serotypes of isolates of C. jejuni from retail poultry was
identical to that-among isolates from humans.
In summary, work performed under Contract #223-81-7041 indicates that enteritis due to Campylobacter jejuni is more common
than that due to Salmonella. Furthermore, C. jejuni does appear
to flow from chickens to man via consumption of poultry products.

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0000nn0848

DiMbgioN
Details of the total scope of work performed under Contract
#223-81-7041 can appropriately be discussed in relation to the
four stipulated objectives of the contract. One objective was
to determine the magnitude and the character of the problem of
human illness caused by Salmonella and C. jejuni in a defined
population. The present study was well designed to accomplish
that objective, because its case-surveillance system was
established at Group Health Cooperative of Puget Sound (GHC), a
320,000 member health maintenance organization serving residents
of western Washington. Survetllance of the two diseases of
interest at GHC permitted the derivation of incidence rates
because of the availability of patient enrollment statistics to .
serve as denominators to match case infdrmation or numerator
data.
The overall incidence of C. jejuni infection at GHC was 71.5
cases diagnosed per 100,000 population per year, some two and
one-half times the incidence of Salmonella infection
-(27.7/100,000/year). Other investigators'have reported C. jejuni
infections to be more frequent than salmonellosis (11, 46), and
this newly recognized infection may in fact, be more common than
the tvio traditionally predominant bacterial infections, salmonellosis .and.shige1losis combined (46).
Only two reportable diseases, gonorrhea, with an incidence
of 415 per-100,000 and chicken pox, with a rate of 72.2 per
100,000, were reported in the U.S. in 1982 at

en

incidence

greater than that of C. jejuni (47). To provide further com165

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(Th
parison,' ih 1982 the incidence of tuberculosis in the U.S. was
11.0 per 100,000, that of syphilis, 32.7 per 100,000 (47).
A difference was also noted in the age-specific incidence of
C. jejuni infection as compared to that for salmonellosis. Along
with a peak in incidence in infants, very similar to that of
Salmonella infection, there was with C. jejuni a second distinct
peak in the young adult years, ages 20-39, which was entirely
-absent in salmonellosis.
This distinctive diphasic curve that comprises the agespecific incidence for C. jejuni infections has also been noted
in Great Britain (48). The absence of a male preponderence of
cases witilin the peak in the young adult years suggests that male
homosexuals, known to acquire C. jejuni , anorectal infections
(49), do not account for a large proportion of cases in the GHC
population. Nevertheless, this observed difference between C.
• jejuni amA Salmonella age-speCific rates suggests fundamental
differences in the epidemiology of the two infections, which are
currently viewed by many to have common pathways of transmission
to
. . and among humans.
•

Clinically, C. jejuni and Salmonella enteritis produced
- -illnesses that were virtually indistinguishable. Nearly all
•patients with both infections had diarrhea and cramps, with a
substantial minority suffering from bloody diarrhea. Fortunately, it

Waa'

necessary to hospitalize only a small fraction of

patients with both infections, and none died.
In-comparing the morbidity of C. jejuni and Salmonella
enteritis two facts suggested that the former was more severe.

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blrst, a . significantly larger proportion of patients with C.

fl

jejuni Infecti.oil experienced weight loss with their illness, and
secondly, the mean duration of symptoms was significantly longer.
One estimate- of the magnitude of the problem caused by C.
jejuni is a derivation of days lost to normal activities due to
the infection. The mean duration of C. jejuni illness was 13.52
days in the present study. If it is assumed that approximately
half of that time, or 7 days, was lost to normal activity such as
employment, then one can calculate that 40 person-weeks of normal
activity would be lost per 100,000 population per year due to C.
jejuni infection. In a city of one million population, therefore, 400 person-weeks or 7.69 person-years of normal activity
such *as employment, would be lost due to this infection.
Furthermore, if it is true that C. jejuni infection is more
ptevalent than salmonell6sis and produces as great or greater
morbidity, then it is possible to make crude estimates on the
importance of C. jejuni infection based upon statistics derived •
for salmonellosis. For example, it has been estimated by the
Centers of Disease Control that as many as two million cases of
ialmonellosis occUr annually in the U.S., at a cost of more than
a billion dollars to the U.S. economy (1). An infection such as
C. jejuni enteritis, which occurs twice as frequently as salmonellosis and is at least as severe, might be expected to produce
an economic_impact twice that of salmonellosis, or two billion
dollars a year upon the U.S. As crude as these estimates are,
it can be appreciated that the potential quantitative impact of
C. jejuni upon a population similar to that where the current
case sur- veillance system was conducted is considerable whether
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viewed in - terms of disease morbidity or economic burden.
It should be kept in mind that all the foregoing estimates
were made without consideration of related C. jejuni infections
within a family. Our culture surveillance in family contacts of
cases and our casa/control study documented that the organism is
prevalent in the environment of cases, and that contacts of cases
' are at increased risk for the illness, but the morbidity asso•ciated with these findings is yet to be determined.
Two of the three remaining objectives of Contract #223-817041 may be considered together as a basis for further discussion
of the present study because the two objectives are closely
related. The first was to define the character of the movement
of bacteria from animals to man, using as markers Salmonella and
C. jejuni in foods from animals; the second, to utilize specific
microbiological markers to link human illness caused by

SalMonella and C. jejuni to specific animal sources. With respect to the use of C. jejuni and Salmonella as "markers" for
bacterial contamination of animal-derived food, the present study

is the

first, to our knowledge, to report comparative contamina-

tion rates for these two pathogens in the same pool of food
.products. C. jejuni was isolated over four times more frequently
than Salmonella but was found almost exclusively in poultry
products. Thus, in retail poultry at least, C. jejuni appears to
provide 'a'better marker for bacterial contamination than does

Salmonella.
Becadse C. jejuni contamination of poultry products was the
only significant positive finding in the food surveillance compo-

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nent of thts study, further discussion of possible linkages
between food contamination and human illness will be restricted
to considerations relating to that phenomenon.
Considerable effort was extended in the present project to
characterize all C. jejuni isolates from food and human cases
with respect to three specific microbiological markers which
might, to paraphrase the contract objective under question, link
a human illness, C. jejuni enteritis, to a specific animal
source, poultry. The three markers were antibiotic susceptibility testing, plasmid analysis, and serotyping (as noted in Results
Section H, serotyping of C. jejuni isolates was performed by the
Centers for Disease Control, Atlanta,'GA).
The most interesting observations to emerge from the study
of these phenotypic markers of C. jejunk was a relationship
between tetracycline resistance and plasmid carriage. First, a
surprisingly high rate of tetracycline resistance was noted in
• pouitry products (32.8%) and in human cases (29.7%). Secondly,
there . was a strong correlation between tetracycline resistance
and plasmid carriage; 93% of tetracycline resistant strains har:bored plasmids: Thirdly, 30 of 31 plasmid-containing isolates
w.ere able to transfer the tetracycline resistance phenotype,
confirming the fact that the resistance gene is located on extrachromOsomal elements. Finally, there were no differences in the
MIC's 'of tetracycline for the isolates tested with and without
pre-exposure to the antibiotic, which suggests that tetracycline
resistance-is not inducible in Campylobacter species, and therefore not located on the bacterial chromosome.
Previous work with R-factors obtained from cynomologous
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monkeys . ( 35) ..and Taylor.and asS68iates' early studies with human
isolates (50) suggested that the R-factors mediating tetracycline
resistance . in C. jejuni would be of a single type and size, since
both of the above reports describe a conjugal 57 kilobase plasmid. However, during the present study, it became apparent that
C. jejuni plasmids both larger and smaller than 57 kilobase were
capable of transferring resistance to tetracycline within Campy-

' lobacter species% Although the BgIII and BcII endonuclease patterns.of these plasmids were highly diverse, further analysis
revealed that several fragments were highly conserved. These
data confirm and extend the data recently published by Taylor and
associates (50), who also noted a high degree of nucleotide
homology among Campylobacter R-factors. Further studies are
needed to explain the reasons for the diversity in size of these
closely related C. jejuni plasmids.
. Further work must .also be done to determine the relationship
between carriage of a tetracycline R-factor by C. jejunk and
tetracycline supplementation of poultry feed; the present study
. did not address this issue directly. However, we did observe
c

variation, unlikely to be due to chance, between tetracycline
-resistance of C. jejuni cultured from Washington-reared poultry
and that of poultry.originating in other states. It is tempting
to speculate that geographic variability in plasmid mediated
tetracyóiine 'resistance of C. jejuni could be related to regional
differences in poultry feeding patterns. Further specific study
should 'be undertaken to unravel any relationships that may exist
between poultry feeding practices and C. jejuni plasmid profiles

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anu susceptibility patterns in a given region. It is noteworthy
that the strain specific analysis preformed as a part of the
case/control study showed that humans were no more likely to
acquire tetracycline-resistant than tetracycline-susceptible C.
jejuni infections from poultry. This finding suggests that
poultry does not serve as the only reservoir of tetracyclineresistant C. jejuni infection.
Also yet to be determined is the clinical significance of
tetracycline resistance in C. jejuni. Most patients with C.
jejuni infection do not receive antibiotic therapy (51), and
tetracycline is not the drug of choice should an antibiotic be
needed (10). Furthermore, preVious studies (50) and work done
under . the present contract all demonstrate that the C. jejuni Rfaptors could not be introduced into E. coli by conjugation or
transformation. This suggests that these plasmids are incapable
Of replicating at least in E. coli and probably in the Enterobacteriaceae in general. Whether these plasmids could be transferred and Maintained in other members of the bowel flora, such
as in Bacteroides species, remains to be tested. It is possible,
-therefore, that there is little practical'clinical significance
to the finding of a related family of C. jejuni R-factors, even
-should they ultimately be traced to poultry feeding practices.
To conclude a review of microbiological markers identified
in the . prasent study, one other interesting phenomenon was
noted: C. jejuni isolates from human cases and retail poultry
possessed. distributions of the six most frequent Lior serotypes
that were virtually identical. This correlation has been noted
previously with Salmonella serotypes isolated from human and non171

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human

sOuiCes (2),

and has been used as evidence that human

Salmonella infections arise from an animal reservoir, presumably
through contamination of animal-derived food (3).
However, a word of caution must be raised against the casual
use of microbiological markers to link bacteria from different
sources, or more specifically, to prove that human C. jejuni
infections arise from animal-derived food, as the two contract
objectives under . question stipulate.
The precedence for the use of phenotypic bacterial markers
to identify sources of human disease Originated with the study of
foodborne outbreaks. In that setting, laborataory tests often
show similarities between pathogenic bacteria isolated from food
eaten by ill individuals and those isolated from the patients
themselves. In fact, the investigation of the single C. jejuni
foodborne outbreak in the present projbct (Appendix B) fit.this
..pattern perfectly, with. the outbreak-associated bacterial
strains, isolated from all implicated patients and from several
goats at the implicated dairy, showing virtual homology among the
. following tests: . susceptibility to five antibiotics, plasmid
pattern, and Lior serotype.
However informative bacterial phenotypic markers may be in
the evaluation of foodborne outbreaks, it is quite a different
matter to presume that they will be useful in identifying sporadic, l. oiated infections as being foodborne. Similar phenotypic
markers in C. jejuni isolates from retail poultry and patients
could,*taken alone, as easily support a hypothesis that chic-kens
were infected by humans, or perhaps more reasonably, that chick-

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et.. and humans derived their C. jejuni isolates from another
large envibrnitiefital reservoir.
For purposes

of

linking C.

jejUni

isoiates from different

groups, it would have been helpful had significant C. jejuni
contamination of another type of meat been detected. In that
case, isolates from humans could have been compared to those of
the two meat species by analysis of the microbiological markers
and perhaps subsequently labeled as more similar to isolates
found in one meat species than to those of the other. This was
not the case, although C. jejuni isolates from retail poultry did
show closer marker similarities to human strains than did those
from processor products.
This dilemma concerning appropriate interpretations of data
on microbiological markers of C. jejuni was largely resolved by
information gained frgm the case/control study of C. jejuni .
infections in humans. Case/control analysis is one of the tools
Z'outinely applied by epidemiologists to address questions of
cause and effect in human disease. The dual approach employing
microbiological and epidemiologiCal (case/control) methodologies
.employed in this study has recently been proposed by the CDC to
determine the cause(s) of sporadic cases of salmonellosis (con,
respondence from John C. Feeley, Acting Director, Division of
Bacterial Diseases, CDC, to State and Territorial Epidemiologists
dated JuneA, 1984. Subject: Salmonella antimicrobial
resistance patterns

in

the United States).

Because, the epidemiology of human C. jejuni infection is so
poorly understood, it was considered essential'to explore numerous potential causal factors by means of an extensive inquiry
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into ttie:backgrounds of-affected and unaffected persons. During
this process, a wide variety of potential food exposures and
habits were sought in order to maximize the likelihood of addressing a prime objective of Contract #223-81-7041, which was to
link human illness caused by C. jejuni to specific animal sources
through food derived from those animals.
There were a number of exposures that were more frequent
- among cases than among controls during the week prior to the
onset . of symptoms. Consequently those exposures were identified
as potential causes of C. jejurii enteritis. It is noteworthy
that many of the previously implicated types of transmission of
C. jejuni infection to humans summarized from the literature in.a
recent epidemiological review (45) were also found to be risk
factors for sporadic C. jejuni enteritis-in the present study.
.Among those were trave/ to an undeveloped country, consumption of
drinking . raw mllk, consumption of untreated surface
water, contact with humans ill with enteritis, and contact with
pets, particularly dogs, with diarrhea.
.The most surprising food exposure found to have an elevated
• relative risk in the present study was mushroom consumption.
- -Mushrooms have not previously been implicated as a vehicle for C.
jejuni infection. However, •that vegetable is grown commercially
in high concentrations of animal manure, including that of chickens. ThUS, C. jejuni proliferation is plausible in this setting.
Furthermore, because mushroom eating is a common exposure, there
is cons1derable potential profit for disease . prevention in establishing a causal relationship. Further work should be done to

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svostantiate this finding.
- •
Cohsidering the objectiVes of COntraCt #223-81-7041, it is
appropriate to focus critical attention upon chicken consumption,
found in our study to have an elevated relative risk. Is this
association, in fact, a causal one?
Several well-accepted observational criteria for causation
of associations found in case/control studies (52) may be applied to that between eating chicken and C. jejuni enteritis.
First, the temporal sequence must be consistent: a causal event
precedes its effect. In the present study, the questions on food
exposures applied specifically to the 7-day period prior to onset
of illness. This time interval was chosen because existing
infotmation suggested that the incubation period for C. jejuni
infection ranges between two and seven days. Assuming no recall
bias was present, the . temporal sequence criterion appears to have
been satisfied for the association under question.
• -• A second condition for causation is that the association
under question should be consistently observed under different
conditions. As previously noted, there is now an accumulating
" boiiy Of evidence that eating chicken is a risk factor for C.
jejuni infection. Brouwer et al. (53) described an outbreak in a
military academy which affected 89 of 123 first year cadets
during a survival exercise. Each cadet had killed, skinned, and
prepared hAp own chicken over a wood fire. In several recent
case/control studies . (24,25,54,55), the cases reported greater
frequencies. of chicken consumption (25,54,55), handling of chtcken during meal preparation (24,55), and greater frequency of
shorter cooking time (55), than did controls.
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rm
Thiraly, the strength of the association provides evidence
for causation. In the present study, the relative risk for
chicken consumption was not large, as cases were only two and
one-half times as likely as controls to have named that exposure
in the week prior.to onset of illness. It is probable that the
strength of the association would have been much greater had it
been possible to ascertain the consumption of C. jejuni- contaminated chicken, found in our food surveillance study to represent
approximately 22% of all retail specimens. According to this
evidence, almost 80% of chicken eaters were not at risk for C.
jejuni enteritis because the chicken that was eaten was not
contaminated. This fact led to considerable dilution of the
association between chicken consumption and C. jejuni enteritis,
and produced the relatively modest relative risk.
A final important condition supporting causatioh of an ob- .
. :served association is consonance of the association with existing
knowledge. It is in this context that the microbiological information acquired in our study assumes importance. The association
- of chicken eating with C. jejuni infection is strongly supported
by the observation in this and previous studies (11-14) that
retail poultry products are frequently contaminated with C.
jejuni because this.is a plausible mechanism by which eating
chicken could "cause" C. jejuni infection.
.-- •
Furthermore, the similarities in antibiograms, plasmid content, and serotypes of C. jejuni isolates from retail poultry and
humans ' found in the present study would be expected should a
substantial fraction of human C. jejuni infections derive from

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t pool of . organisms that are found in poultry. In addition,
the similar se .isOnal patterns of C. jejuhi Contamination of
retail poultry and human C. jejuni cases, with a summer-fall
peak, is evidence for a causal association. It should also be
noted that the absence of C. jejuni isolation from the other
major meat species, beef and pork, supports the lack of association of those foods with C. jejuni illness in the case/control
study.
The fourth and last objective of Contract #223-81-7041 was
to determine the proportion of human salmonellosis and C. jejuni
enterities which has its origin from animal foods obtained from
poultry, swine, and beef. For . C. jejuni this proportion was
estimated, in the determination of the "etiologic fraction," to
be 48.2% for ISoultry and none for either beef or swine.
The etiologic fraction of a disease is viewed as the expected reduction in the . disease following removal of the exposure. Thus, we estimate that almost SO% of C. jejuni infections.
at Group Health Cooperative during the period of study would not
have occurred had no poultry been consumed. We have no reason to
believe that the same effect would not accrue to the general
population if C. jejunk

contamination

of retail poultry were

controlled.
Thus, work performed by Seattle-King County Health Department and

kts.

subcontractors under Contract #223-81-7041 provides

•
an important insight into the epidemiology of infections due to
Camplylobacter jejuni by showing that almost half of cases in 4
defined population over an 18-month period were attributable to
eating poultry. This information, derived from the case/control
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study, -wea supported by results Of food surveillance showing that
over 20 percent of poultry products sampled at King County retail
.outlets over the same period were contaminated with C. jejuni.
Furthermore, C. jejuni isolates from those human cases and retail
poultry were similar with respoct to antibiotic susceptibilities,
plasmid carriage, and serotype.
The food surveillance component of the present study sug- gested several possible strategies for at least reducing C.

jejuni contamination of poultry. For example, isolation rates for
C. jejuni in retail markets were lowest on Mondays, when display
shelves were cleanest and products had been freshly received. On
the other hand, handling of poultry at tile retail level appeared
to increase the likelihood of culturing C. jejuni. The most
dramatic effect on C. jejuni contamination of poultry was movement of products from processor, where the isolation rates ap7
.:proached 60%, to retail sites, where it fell to just over 20%.
Observations such as these provide hypotheses for studies aimed
at reducing C. jejuni contamination in retail poultry.

•--

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