Investigation of multidrug-resistant Salmonella serotype typhimurium DT104 infections linked to raw-milk cheese in Washington State.
BACKGROUND
Multidrug-resistant Salmonella Typhimurium DT104 has recently emerged as a cause of human and animal illness in Europe and North America. In early 1997, health officials in Yakima County, Washington, noted a 5-fold increase in salmonellosis among the county's Hispanic population.


OBJECTIVE
To characterize bacterial strains and identify risk factors for infection with Salmonella Typhimurium in Yakima County.


METHODS
Laboratory, case-control, and environmental investigations.


METHODS
Patients with culture-confirmed Salmonella Typhimurium infection living in Yakima County and age- and neighborhood-matched control subjects.


METHODS
Food vehicle implication based on case-control study and outbreak control.


RESULTS
Between January 1 and May 5, 1997, 54 culture-confirmed cases of Salmonella Typhimurium were reported. The median age of patients was 4 years and 91% were Hispanic. Patients reported diarrhea (100%), abdominal cramps (93%), fever (93%), bloody stools (72%), and vomiting (53%); 5 patients (9%) were hospitalized. Twenty-two patients and 61 control subjects were enrolled in the case-control study. Seventeen case patients (77%) reported eating unpasteurized Mexican-style soft cheese in the 7 days before onset of illness compared with 17 control subjects (28%) (matched odds ratio, 32.3; 95% confidence interval, 3.0-874.6). All case-patient isolates were phage definitive type 104 (DT104) (n = 10) or DT104b (n = 12), and 20 (91%) were resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline. The cheese produced and eaten by 2 unrelated patients was made with raw milk traced to the same local farm. Milk samples from nearby dairies yielded Salmonella Typhimurium DT104. The incidence of Salmonella Typhimurium infections in Yakima County returned to pre-1992 levels following interventions based on these findings.


CONCLUSIONS
Multidrug-resistant Salmonella Typhimurium DT104 emerged as a cause of salmonellosis in Yakima County, and Mexican-style soft cheese made with unpasteurized milk is an important vehicle for Salmonella Typhimurium DT104 transmission. We postulate that recent increases in human salmonellosis reflect the emergence of Salmonella Typhimurium DT104 among dairy cows in the region. Continued efforts are needed to discourage consumption of raw milk products, promote healthier alternatives, and study the ecology of multidrug-resistant Salmonella Typhimurium.
Villar
R G
RG
Foodborne and Diarrheal Diseases Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
Macek
M D
MD
Simons
S
S
Hayes
P S
PS
Goldoft
M J
MJ
Lewis
J H
JH
Rowan
L L
LL
Hursh
D
D
Patnode
M
M
Mead
P S
PS
D000293:Adolescent; D000328:Adult; D000668:Ampicillin Resistance; D000818:Animals; D016022:Case-Control Studies; D002611:Cheese / Q000382:microbiology* / Q000506:poisoning; D002648:Child; D002675:Child, Preschool; D002702:Chloramphenicol Resistance; D004196:Disease Outbreaks; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D016521:Electrophoresis, Gel, Pulsed-Field; D004812:Epidemiologic Methods; D005511:Food Handling; D006630:Hispanic or Latino; D006801:Humans; D007223:Infant; D008875:Middle Aged; D008892:Milk / Q000382:microbiology* / Q000506:poisoning; D012307:Risk Factors; D012478:Salmonella Food Poisoning / Q000453:epidemiology* / Q000209:etiology; D012486:Salmonella typhimurium / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification; D012703:Serotyping; D013242:Sterilization; D013307:Streptomycin / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D013753:Tetracycline Resistance; D014861:Washington / Q000453:epidemiology
D013449:Sulfonamides; D013307:Streptomycin