# Presentation: 357480

## The Connecticut Experience with non-O157 STEC“Seek and Ye Shall Find”

**Sharon Hurd, MPH**
**October 17, 2007**

**Connecticut Emerging Infections Program**
**FoodNet**

## BackgroundShiga toxin-producing Escherichia coli (STEC)

**STEC infections are an important public health problem**
***E. coli***** O157 most widely recognized STEC in U.S.**
**Clinic-based studies suggest infection caused by non-O157 STEC may be as prevalent as O157**
**Standard culture methods for O157 do not detect non-O157 STEC**
**Incidence and trends of infection with non-O157 STEC not well established**
**Increasing use of Shiga toxin (ST) testing by clinical laboratories provides an opportunity to evaluate occurrence of non-O157 STEC and monitor trends over time**

## Objectives

**Describe how/why Connecticut (CT) began testing for STEC**
**Describe the frequency of non-O157 STEC compared to O157 STEC**
**Describe trends in incidence of STEC infections over past seven years of surveillance**
**Describe some clinical and epidemiologic features of non-O157 vs. O157 infections**
**Share preliminary data from the STEC laboratory survey**
**Make recommendations based on findings**

## E. coli  in Connecticut1999

**Several clinical laboratories began using Shiga toxin testing in place of culture for O157**
**ST-positive results not reportable at time**
**No isolates available for further testing (serotyping, PFGE)**
**Impacted ability to detect/investigate outbreaks**
**Outbreak of *****E.coli***** O121*  **
**11 cases, including 3 cases of HUS**
**Illness associated with swimming in lake and swallowing water while swimming**
***E.coli***** O121:H19 isolated from a toddler who swam in lake**
**6 cases serologically confirmed (O121 antibody titers)**
**Outbreak possibly detected sooner if ST screening was done**
**1****st**** outbreak of non-O157 STEC in Connecticut**

- *McCarthy et. al., *Pediatrics, *Vol. 108, No. 4, 2001

## Laboratory Methods 

***E. coli***** O157 reportable since early 1990’s**
**ST-positive tests made reportable in 2000**
**Laboratories required to submit ST-positive broths to the State Laboratory**
**Broths plated on SMAC & CT-SMAC**
**Sorbitol-negative colonies tested for O157**
**If O157-negative, sorbitol-positive colonies and sweep of plate tested for ST**
**Non-O157 STEC isolates sent to CDC for serotyping**

## Laboratory Surveillance for STEC Connecticut 2000 – 2006

**478 STEC infections**
**	****214**** ****(45%)**** ****O157**** ****	****       ****  264 (55%) Shiga toxin (+) broths**
**     ****culture isolates****	****	****	**
**	****	****	****	****	****105 (40%)**** ****	****	****159 (60%)****	****	****	****       O157 STEC****	****    non-O157 STEC**
**	****	****	****	****	****	****	****      ****24 serogroups**

## Incidence* of STEC Infections by Year Connecticut 2000-2006

|  | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | % Change from 2000 to 2006 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| All STEC Infections | 2.9 | 1.9 | 1.8 | 1.9 | 1.6 | 1.8 | 2.2 | - 45% |
| E. coli O157 | 2.5 | 1.1 | 1.3 | 1.1 | 0.9 | 1.3 | 1.2 | - 52% |
| Non-O157 STEC | 0.4 | 0.7 | 0.5 | 0.8 | 0.7 | 0.6 | 1.0 | + 150% |

- *Rate per 100,000 population

## Trends in STEC Isolates by YearConnecticut 2000-2006

|  | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | p-value* |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| All STEC isolates | 97 | 63 | 62 | 63 | 55 |   63         | 75 |  |
|  % E. coli O157 | 87% | 59% | 73% | 59% | 56% | 68% | 55%         | <0.001 |
|  % ST (+) broth | 33% | 52% | 47% | 65% | 64% | 59% | 76%        | <0.001 |
| ST broth isolates  | 32 | 33 | 29 | 41 | 35 | 37 | 57 |  |
|  % E. coli O157 | 59% | 24% | 41% | 37% | 31% | 46% | 40%      | n.s. |
|  % Non-O157
     STEC | 41% | 76% | 59% | 63% | 69% | 54% | 60% | n.s. |
| O157 Isolates | 84 | 38 | 45 | 37 | 31 | 43 | 41 |  |
| Overall % from Broth | 23% | 21% | 27% | 41% | 35% | 40% | 56% | <0.001 |

- *Chi-square for trend

## Non-O157 STEC Incidence and Percent of O157 Isolates from ST Tests by Year Connecticut 2000-2006

**Non-O157 STEC Incidence and Percent of O157 Isolates from ST Tests by Year ****Connecticut 2000-2006**

- p= 0.000*

- * Chi-square for trend

- Year

- Percent

- Rate/100,000

## Top Six Non-O157 Serogroups (N=159)Connecticut 2000-2006

| 
Serogroup | 
Percent |
| --- | --- |
| O103 | 20% |
| O111 | 20% |
| O26 | 17% |
| O45 | 12% |
| O121 | 4% |
| O145 | 3% |

**Top Six Non-O157 Serogroups ****(N=159)****Connecticut 2000-2006**

## Epidemiology

**STEC patients reported between 4/1/04 and 12/31/06 interviewed regarding:**
**Symptoms and potential exposures**
**Differences between patients with non-O157 and those with O157 STEC were assessed**

## Relative Severity of DiseaseDue to O157 and Non-O157 STEC 2000-2006

|  | Non-O157 
n=159 | O157 
n=319 | p-value |
| --- | --- | --- | --- |
| Hospitalized | 15% | 45% | < 0.0001* |
| Hemolytic uremic syndrome | 0 | 9% |  |
| Died | 0 | 2% |  |

-  *RR 3.0 95%CI (2.0, 4.4)
** **

## Symptoms Reported by Interviewed Patients Connecticut, April 2004 – December 2006

|  | Non-O157 
(n=52) | O157 
(n=99) | p-value |
| --- | --- | --- | --- |
|      Bloody stool | 71% | 89% | 0.02 |
|      Diarrhea | 96% | 98% | n.s. |
|      Cramps | 87% | 87% | n.s. |
|      Nausea | 31%  | 50% | 0.05 |
|      Fever | 31% | 43% | n.s. |
|      Vomiting | 15% | 38% | 0.01 |

##  Comparison of Non-O157 and O157 Patients by Selected Exposures 

| Selected Exposures | Non-O157 | O157  | p-value |
| --- | --- | --- | --- |
|  | % exposed | % exposed |  |
| Ate hamburger  | 53% | 51% | n.s. |
| Ate ground beef | 21% | 30% | n.s |
| Visited farm/petting zoo | 14% | 9% | n.s. |
| Ate at restaurant, preceding 7 days | 71% | 81% | n.s |
| International travel | 12% | 7% | n.s. |
| Suburban residence | 29% | 58% | 0.002 |

## Clinical Laboratory Testing of STEC,10 FoodNet sites  

**STEC lab survey addressed practices related to culture and non-culture based testing**
**        ****- Media, methods, test kits used**
**  ****- Circumstances for testing (eg., routine, MD request) **
**Preliminary data:**
**668 laboratories surveyed (only labs testing on-site were analyzed)**
**437 labs (65%) test on site for STEC; **
**401 (92%) do culture based testing**
**28 (7%) do non-culture based testing for O157**
**45 (13%) do non-culture based testing for all STEC**
**24 (6%) set up culture and non-culture simultaneously**
**Most labs do EIA testing; only 2 report using RT-PCR**
**Lateral flow method gaining attention**
**	****	**

## Clinical Laboratory Testing of STEC, Connecticut

**STEC lab survey conducted in 32 clinical labs**** **
**Results:**
**27 labs (84%) test on site for any STEC**
**15 (55%) do only culture based testing**
**	****   ****- all report routine testing**
** ****12 (45%) do non-culture based testing for STEC**
**     ****-   all use EIA methods**
**	****  ****-   6 (50%) report routine testing**
**5 (19%) report using both culture and non-culture based methods (3 do so simultaneously) **
**Interest expressed in using the new lateral flow test**
**	****	**

## Clinical Laboratory Testing of STEC, Connecticut 

| # of labs doing Shiga toxin testing |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| 2000 | 2001 | 2002 | 2003 | 2004 | 2005     2006 |
| 4 | 4 | 5 | 6 | 8 |  10          12* |

**Since 2000, clinical labs in CT are required to report positive ST results and submit all positive ST broths to the CT PHL**

- *Since the survey was completed, 2 additional labs began
- using a non-culture (EIA) method bringing the total number of labs
- performing testing which would capture non-O157 STEC to 52%

## Conclusions

**An increasing number of clinical laboratories are conducting ST testing **
**By 2006, 56% of all O157 in CT found through ST testing **
**Incidence of non-O157 has increased**
**Increase in non-O157 likely due to an increase in ST testing **
**Positive ST tests are consistently more often associated with non-O157 STEC than O157**
**While the severity of illness from non-O157 is somewhat milder, there appear to be no differences between non-O157 and O157 in frequency of exposure to known cattle-beef risk factors for O157**

## Conclusions

**Diagnostic testing has an impact on public health activities**
**Surveillance activities are an important component for outbreak detection and disease prevention**
**Isolates are important to successful investigations**
**Clinical laboratories are increasing their use of non-culture methods**

## Recommendations

**Clinicians should consider non-O157 STEC infection when evaluating patients with diarrhea**
**	****-****	****continued education regarding ordering and ****	****interpreting test results**
**Clinical labs currently only culturing for O157 should consider also using ST testing **
**Public health departments must assure that all labs doing ST testing follow up positive ST tests with culture for at least O157 and/or submission to PHL for isolation of an organism **
**Ongoing surveillance for both O157 and  non-O157 STEC needed to better describe trends and epidemiology of STEC infections**
**Continued surveys of clinical labs to monitor testing trends**

## Acknowledgements

**Emerging Infections Program (EIP), FoodNet **
**Connecticut Department of Public Health**
**CDC Foodborne and Diarrheal Diseases Reference Laboratory**