Escherichia coli O157 Infection and Hemolytic Uremic Syndrome (HUS), 2009

During 2009, 130 culture-confirmed cases of Escherichia coli O157 infection (2.5 per 100,000 population) were reported. The number of reported cases represents a 20% decrease from the median number of cases reported annually from 1997 to 2008 (median, 162 cases; range, 110 to 219). During 2009, 57 (44%) cases occurred in the metropolitan area. One hundred seven (82%) cases occurred during May through October. The median age of cases was 18 years (range, 9 months to 78 years). Twenty-five percent of cases were 4 years of age or younger. Forty-seven (36%) cases were hospitalized; the median duration of hospitalization was 3 days (range, 1 to 26 days). None died.

In addition to the 136 culture-confirmed E. coli O157 cases, 89 cases of Shiga-toxin producing E. coli (STEC) infection were identified in 2009. Of those, culture confirmation was not possible in 11, and therefore it is unknown if those were O157 or another serogroup. Among the remaining 78 cases of STEC other than O157, E. coli O26 accounted for 19 cases, E. coli O111 for 15, E. coli O777 for 15, and E. coli O103 for 13. These four serogroups represented 79% of all non-O157 STEC.

Eleven E. coli O157:H7 outbreaks were identified during 2009. Ten outbreaks involved foodborne transmission, including six outbreaks with cases in multiple states, and one outbreak involved contact with animals. The 11 outbreaks resulted in a median of only 3 culture-confirmed cases per outbreak (range; 1 to 7 cases).

In April, 1 case of E. coli O157:H7 infection was part of a multi-state outbreak that resulted in 15 cases in 4 states. Pre-packaged lettuce was implicated as the vehicle.

In May, 6 cases of E. coli O157:H7 infection with the same PFGE subtype were part of a multi-state outbreak that resulted in 77 cases in 33 states. Refrigerated cookie dough was implicated as the vehicle. This investigation resulted in a recall of the implicated product.

An outbreak of E. coli O157:H7 infections associated with a graduation party in Mower County occurred in May. Seven culture-confirmed cases were identified. One case who reported developing bloody diarrhea prior to preparing potato salad served at the event was the likely source of contamination.

In June, 2 cases of E. coli O157:H7 infection with the same PFGE subtype occurred in residents of Hennepin County. Both cases reported consuming dishes containing steak at sit down restaurants in the 7 days prior to illness onset. Product invoice information indicated that the cases had consumed the same product that came from the same meat supplier in Kansas.

In June, an infection control preventionist from a Mower County hospital reported that a large number of employees from one company had presented to the emergency room with bloody diarrhea. The company had held an employee lunch catered by a local grocery store the week prior. A total of 7 culture-confirmed cases and 9 probable cases were identified. Three cases were hospitalized. One culture-confirmed case did not attend the company lunch but did consume ground beef purchased at the same grocery store. An inspection of the grocery store suggested that cross-contamination from ground beef used to make meatloaf to ready-to-eat foods served at the lunch could have occurred. However, the specific food vehicle and the source of contamination were not confirmed.

In June, 1 case of E. coli O157:H7 infection was part of a multi-state outbreak that resulted in 23 cases in nine states. Ground beef was implicated as the vehicle. This investigation resulted in a recall of the implicated product.

An outbreak of E. coli O157:H7 infections associated with a daycare in Douglas County occurred in August. Custom slaughtered beef that was served at the daycare tested positive for the E. coli O157:H7 outbreak strain and was implicated as the vehicle; although subsequent person-to-person transmission was also documented. A total of 7 culture-confirmed cases were identified and 1 case developed HUS.

In August, 3 cases of E. coli O157:H7 infection with the same PFGE subtype occurred in Minnesota residents. All three reported eating at locations of a Mexican style restaurant chain. An additional case identified in a Washington state resident also reported eating at one of the restaurant locations in Minnesota. Additional cases identified in California and Colorado did not report eating at the restaurant chain but did report beef exposures. An inspection of the restaurant suggested that cross-contamination from steak could have occurred. However, the specific food vehicle and the source of contamination were not confirmed.

In September, 2 cases of E. coli O157:H7 infection were part of a multi-state outbreak that resulted in 9 cases in six states. Romaine lettuce was implicated as the vehicle.

In October, 2 cases of E. coli O157:H7 infection with the same PFGE subtype occurred in Minnesota residents that had visited an orchard and petting zoo in Scott County. Both cases developed HUS; neither died. Indirect or direct contact with the animals or their manure was the source of the infections.

In November, 5 cases of E. coli O157:H7 infection with the same PFGE subtype were part of a multi-state outbreak that resulted in 25 cases in 17 states. No cases developed HUS; 1 case died. Blade tenderized steaks from a national chain of restaurants were implicated as the vehicle for the national outbreak and resulted in a recall of this product. However, the Minnesota cases did not eat at this restaurant chain and instead reported eating ground beef. A traceback investigation identified a potential common denominator in a company that supplied beef products to multiple plants that in turn supplied steaks or ground beef consumed by cases. However, the traceback investigation was not considered sufficiently strong to conclusively implicate that company.

Hemolytic Uremic Syndrome (HUS)

In 2009, 16 HUS cases were reported. There were no fatal cases. From 1997 to 2009, the median annual number of reported HUS cases in Minnesota was 16 (range, 10 to 25), and the overall case fatality rate was 6.0%. In 2009, the median age of HUS cases was 3 years (range, 1 to 73 years); 13 of the 16 cases occurred in children. All 16 cases were hospitalized, with a median hospital stay of 9 days (range, 2 to 43 days). All 16 HUS cases reported in 2009 were post-diarrheal. E. coli O157:H7 was cultured from the stool of 9 (56%) cases; 2 (13%) additional HUS cases were positive for E. coli O157:H7 by serology. Non-O157 STECs were identified in the stools of 2 (13%) cases, 1 with E. coli O111:NM and 1 with E. coli O121:H19. In 2009, there were 5 outbreak-associated HUS cases.

• For up to date information see:E. coli O157:H7 and HUS
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2009