As part of FoodNet, case-control and other epidemiologic
studies are conducted to determine the proportion
of foodborne diseases that are caused by specific
foods or food preparation and handling practices.
By determining this proportion, health officials can
make prevention efforts more specific and document
their effectiveness. These large epidemiologic studies
will provide more precise information about which
food items or other exposures might be risk factors
for infections with these organisms. To allow the
most precise classification of the isolates from the
patients in these studies, Salmonella, E.
coli O157, and Campylobacter isolates
from these patients are sent from FoodNet sites to
CDC for further study, including antibiotic resistance
testing, phage typing, and molecular subtyping.
Cases of the pathogens under study are ascertained
through hospitals and laboratories in the FoodNet
catchment area. Patients reported through FoodNet
surveillance are contacted by FoodNet staff and administered
the questionnaire if eligible for the study. Outbreak-associated
cases are excluded from these studies.
Salmonella Case-Control Study
In 1996, the FoodNet Salmonella case-control
study was conducted to determine the proportion of
culture confirmed cases of non-typhoidal Salmonella
serogroups B and D infections that are attributable
to eating meat, egg, poultry, and other products,
and the proportion of infections attributable to pet
ownership. More than 60% of Salmonella infections
in the United States are caused by serogroups B and
D Salmonella.
Eating chicken and undercooked eggs was associated
with sporadic Salmonella Enteritidis and
Salmonella Heidelberg infections. Antimicrobial
use in the month before illness was associated with
multidrugresistant Salmonella Typhimurium
DT104 infections. Reptile contact was associated with
salmonellosis. Breast-feeding was found to be protective
against infant salmonellosis.
E. coli O157 Case-Control Studies
The 1997 FoodNet E. coli O157 case-control
study was conducted to determine the proportion of
culture confirmed cases of E. coli O157 infections
that are attributable to eating meat, poultry, and
other products. The case-control study found that
visiting a farm, living on or visiting a farm that
had cattle, eating pink hamburger (either at home
or away from home), eating at a table-service restaurant,
and obtaining beef through a private slaughter arrangement
were the principal risk factors for these infections.
In 1999 a second E. coli O157 case-control
study was conducted. This study included subtyping
of isolates by pulsed-field gel electrophoresis (PFGE),
evaluated the role of undercooked ground beef and
examined risk and prevention factors for E. coli
O157 infections.
Campylobacter Case-Control Study
In 1998, FoodNet conducted a case-control study
to determine risk and prevention factors for Campylobacter
infection and enrolled more than 1463 case-patients
and 1317 controls. The objectives of the study include
determining the proportions of culture-confirmed cases
of sporadic Campylobacter infections, and
specific antimicrobial susceptibility patterns, that
are attributable to eating meat, poultry, and other
products, and the proportion of infections attributable
to contact with farm or companion animals. The burden
of illness associated with Campylobacter
infections as measured by the number of culture-confirmed
cases and by the number of days of hospitalization
for each culture-confirmed case will be determined.
Cryptosporidium Case-Control Study
In 1999, FoodNet began a 2 year case-control study
to determine sources and risk factors for Cryptosporidium
infection. Specific objectives for this study include
determining the estimate of the burden of illness
associated with Cryptosporidium infections
in the population under study and determining the
proportion of laboratory confirmed cases of sporadic
Cryptosporidium infections attributable to
consuming certain foods or water, and the proportion
of infections attributable to contact with recreational
water or farm animals.
Listeria monocytogenes Case-Control
Study
FoodNet began a case-control study in February 2000
to determine sources and risk factors for listeriosis.
Eight FoodNet sites are participating in this study.
Specific goals of the study include identifying dietary,
medical, and behavioral risk factors for listeriosis,
describing the spectrum of illness in patients with
listeriosis and describing the antimicrobial resistance
patterns and molecular subtypes of L. monocytogenes
isolates from these patients.
Case-Control
Study Abstracts & Publications Search |
