# Presentation: 108574

## Human infections with E. coli O157:H7 and other Shiga toxin-producing bacteriaP. I. Tarr, M.D.Washington University School of MedicineFDA AIDAC MeetingRockville, MDApril 12, 2007

## Spontaneous

- Resolution
- (~85%)

- HUS
- (~15%)

- Diarrhea

- Bloody
- diarrhea

- Culture

- + culture

- HCT < 30%
- Plts < 150K
- Cr > ULN

- Adapted from: Lancet 2005; 365:1073

## Opportunities

- About 90% are seen by a physician pre-HUS
- Toxemic disorder

## Challenge – Assess therapies to prevent HUS 

- Identify infected patients
- Quickly, accurately
- Low incidence, sporadic epidemiology, rural predominance
- Many sites of presentation
- Narrow window to prevent sequelae
- Vascular injury already is underway
- What is outcome of interest?
- HUS vs. severe HUS
- Informed consent in urgent situation, multi-site randomization

## Challenges – Use of an approved therapeutic 

- Safety
- Efficacy
- Cost
- Carrying Costs to Institution

## Diagnostic Challenges

- Target pathogen:
- 	All STEC?
- 	Only *E. coli* O157:H7?
- USA, Canada, Japan, UK, and South America:
*E. coli* O157:H7 predominant, and nearly exclusive (> 95%), cause of HUS.
- Pediatrics. 1987;80:37
- J Infect Dis. 1990;162:553
- J Pediatr. 1998;132:777
- J Infect Dis. 2001;183:1063
- J Pediatr. 2002;141:172
- Foodborne Pathog Dis. 2006;3:88
- Epidemiol Infect. 2007 Mar 5 (epub)1-7

## EIA vs. SMAC, point of care,1998-2001

- 1626 ER stools, 225 from private practice (all children)
- 	 39 signals in Meridian EIA (broth) (in ER)
- 						Klein, E, et al, J Peds 2002; 172

## 39 EIA positives

11 non-O157:H7 STEC (> 1/5 colonies)
O103:H2 (4), O118:H16 (2), O26:H11, O111:nm, O111:H8, O121:H19, Orough:H11 (1 each) (1 with C. jejuni)

 3 signals, no STEC (20 colonies and broth tested)

 25 E. coli O157:H7

- 11 non-O157:H7 STEC (_>_ 1/5 colonies)
- O103:H2 (4), O118:H16 (2), O26:H11, O111:nm, O111:H8, O121:H19, Orough:H11 (1 each) (1 with C. jejuni)
-  3 signals, no STEC (20 colonies and broth tested)
-  25 E. coli O157:H7

- Klein, E, et al, J Peds 2002; 172

## 39 STECs

- 				O157 (28) 	non-O157 (11)
- HUS				18%			  0%
- Bloody		        92%			50%
- Laboratory blood     70%			22%

- Klein, E, et al, J Peds 2002; 172

## Why not test stool for toxin?

-   Difficult analyte
-   Often not there, _especially when patient subsequently develops HUS_
- _  _Test misses about 10% of patients infected with E. coli O157:H7
- Cornick NA, et. al., J Infect Dis, 2002; 57-63

## Is EIA signal for real, if SMAC is negative?

- Prior probability: Probability of disease before performing a diagnostic test
- If high, then positive result likely to be valid
- If low, then positive test less likely to be valid

## EIA+, SMAC no O157

- Test applied to:
- ER Population
- Bloody diarrhea	Highly credible, low risk
- Painful diarrhea
- Hospitalized diarrhea
- Signal from pathogenic STEC (i.e., O26, O45, O103, O111, O113, O118, O121, O145, 177)

## STEC Testing

- Test applied to:
- Chronic diarrhea
- Infantile diarrhea	Not highly credible
- Non-painful, non-	if positive
-     bloody diarrhea
- No STEC recovered, non-major serogroup isolated

## Summary of Diagnostic Challenges

-  O157 preferential testing should be performed before action
-  Direct stool tests insensitive
-  Choose population well (i.e., not large volume commercial laboratories)
-  Time to positive critical

## Spontaneous

- Resolution
- (~85%)

- HUS
- (~15%)

- Diarrhea

- Bloody
- diarrhea

- Culture

- + culture

## Bloody Diarrhea

- Diagnose, then treat, or ...
- Treat all bloody diarrhea (would miss ~20% of E. coli O157:H7 patients, and most (> 90%) won’t have target infection)
- Syndromic profiling to increase specificity

## Syndromic Profiling – Bloody Diarrhea as entry criteria

- Diarrhea for X days
- X > 1
- X < 5-7
- ≥ 3 bowel movements/day
- 9 months – 10 years
- No documented fever in health care setting
- Abdominal pain, especially when defecating

## Syndromic Profiling

- Best in high acuity venues
- Will miss ~ 20% of cases
- Will have ~ 2-3:1 false positive rate
- Must be coupled with expeditious testing
- If in research setting, needs support for negatives

## Presymptomatic/Contacts

- Epidemics, household
- 10% of cases are 20, but few (of many) contacts become 20 cases
- Massive outbreaks on wane at time of “discovery.”  Few symptomatic subjects subsequently come to light.

## Early in Timeline(Pre-Bloody Stage)

- Contact of known case (but most symptomatic contacts are not infected)
- Strain – specific replicates

## Onsest

|  |  |  |  |
| --- | --- | --- | --- |

- Presentation

- HUS

## 10,000 diagnosed cases per annum
  2,500 cases < age 10
48 cases < age 10 per week, of whom 7 will develop HUS (15% rate)
One child in the US daily develops HUS. 
Today, two children in the US are in the  opportune post-presentation, pre-deterioration, window.
Today, 14 children are in that window but will not develop HUS 

-   2,500 cases < age 10
- 48 cases < age 10 per week, of whom 7 will develop HUS (15% rate)
- One child in the US daily develops HUS.
- Today, two children in the US are in the  opportune post-presentation, pre-deterioration, window.
- Today, 14 children are in that window but will not develop HUS

- Extrapolations

## First Encounter 

- High acuity setting (ED)
- ‘Primed’ point of care
- Research projects focusing on diarrhea, bloody diarrhea, and *E. coli* O157:H7
- Outstanding microbiology

## ER KINETICS

Inter-defecation interval (O157:H7+):  206 min 

70% chance of producing stool on site if in ER for 4 hours

- Inter-defecation interval (O157:H7+):  206 min
- 70% chance of producing stool on site if in ER for 4 hours

## CHRMC ED, 1998 - 2001

- 4799 children with “diarrhea” or “gastroenteritis”
- 1626 “enrolled”
- 39 STEC
- 28 *E. coli* O157:H7 	(every 39 days)
- 5 HUS (all O157:H7) 	(every 219 days)
- Klein, EJ, J Pediatrics (2002) 141:172; Clin Infect Dis (2006) 43:7

## CHRMC ED, 1998 - 2001

- 4799 children with “diarrhea” or “gastroenteritis”
- 1626 “enrolled” (34%)
- 28 (1.7%) + for O157:H7
- 372 specimens submitted as cups; 5.4% +
- 1254 non-cups (largely swabs); 0.6% +
- Klein, EJ, J Pediatrics (2002) 141:172; Clin Infect Dis (2006) 43:7

## Target Population

- Bloody diarrhea → culture + 	→ 22/237 	9.3%
- (miss 6) (once every 7 weeks)
- Bloody diarrhea → HUS 	→ 4/237 	1.7%
- (miss 1) (once every 39 weeks)

## Spontaneous

- Resolution
- (~85%)

- HUS
- (~15%)

- Diarrhea

- Bloody
- diarrhea

- Culture

- + culture

- Does host injury precede presentation/ diagnosis?

- Adapted from: Lancet 2005; 365:1073

## *

- F 1+2: Thrombin generation before HUS

- NEJM 2002; 346:23

- P<0.01 		 p<0.001

- THROMBIN

- +

- F 1+2

**FXa**

- PROTHROMBIN

- NEJM 2002; 346:23

## D-dimer Before HUS, as Lesion Evolves

- D-dimer Before HUS, as Lesion Evolves

- *

- *

- NEJM 2002; 346:23

## Fibrin Degradation  

**D-dimer signifies fibrin degradation, infers fibrin presence**

- D

- D

- E

- D

- D

- E

- D

- D

- D

**Cross-linked fibrin polymers  **

- D-Dimer

**Plasmin**

## LABORATORY VALUES  - ALL GROUPS

- 			Normal	Uncomp	  Pre-HUS
- HCT (%)		 36  3  	   37  3 	   38  5
- Plts (k/mm3)   	321  70 	 317  74   322  97
- Cr (mg/dL)   	0.4  .1	  0.4  .1	   0.4  .2

- NEJM 2002; 346:23

## Stx vanishing from Stool

**DOES SHIGA TOXIN IN STOOL RELATE TO HUS RISK?**
**	****	****	****Stx Frequency****	****Titer**
**Pre-HUS: ****	****	****        40%****	****	****320 (160-1280)**
**Uncomplicated:              48%****	****           1689 (160-40 K)**
**At HUS: ****	****	****        16%****	****	****	**
**Cornick, N., J Infect Dis. 2002;186:57**
**	**

## Additional Pre-HUS findings and host perturbationsStx not on circulating PMNs(“PMN are not acting as transporter for Stx in the pathogenesis of HUS.”)(Nephrol Dial Transplant 2007; 22:749) PAF activated(Pediatr Nephrol 2002;17:1047)Platelets activated(Blood 2006; 108:167)vWF multimers show signs of shear-induced cleavage (? from nascent thrombi)(Pediatr Res 2001; 49:653)

## Outcome Definition

**Hemolysis:** Packed cell volume <30%, smear evidence of intravascular erythrocyte destruction
**Thrombocytopenia:** Platelets <150,000 mm-3
**Renal insufficiency:** Creatinine > ULN age
- Urinalysis not in criteria (difficulty obtaining a reliable specimen, non-functional data)

## Outcome Subgroups

- Mild HUS: transfusions, no dialysis,
- 	_nonanuric_.  LOS: 6 days
- Severe HUS: dialysis, anuria, LOS: 12 days
- Anuric HUS: best predictor of chronic renal injury (JAMA 2003; 290:1360; J Pediatr 1991; 118:195)

- Ake, J. A. et al. Pediatrics 2005;115:e673

## Anuric vs. Non-anuric HUSCHRMC, 1997-2003

- 16 children with anuric HUS
- 13 children with non-anuric HUS
- All *E. coli* O157:H7 +
- Variable routes of enrollment (syndromic profiling (2), contact (1), culture + (19), arrive with HUS (7))
- All pre-HUS variables examined

## Fig 1. Timing of critical events during illness

- Copyright ©2005 American Academy of Pediatrics

- Ake, J. A. et al. Pediatrics 2005;115:e673

**Fig 1. Timing of critical events during illness**

## Fig 2. Volume and characteristics of fluids that were administered during first 4 days of illness

- Copyright ©2005 American Academy of Pediatrics

**Fig 2. Volume and characteristics of fluids that were administered during first 4 days of illness**

- Ake, J. A. et al. Pediatrics 2005;115:e673

## Multivariate Analysis

| VARIABLE | ADJUSTED RELATIVE RISK
(95% C.I.) | P |
| --- | --- | --- |
| Age (yr) | 1.9 (.8-4.4) | 0.15 |
| Female sex | 1.5 (.1-19.4) | 0.77 |
| Pre-HUS antibiotics | 1.1 (0.1-17.0) | 0.95 |
| Free water in IVF (mL/m2) | 1.0 (.999-1.001) | 0.49 |
| Na in IVF (mmol/m2) | 0.994 (.989-.999) | .017 |

- Pediatrics. 2005 Jun;115(6):e673-80

- Ake, J. A. et al. Pediatrics 2005;115:e673

## Target Population

- Bloody diarrhea → culture + 	→ 22/237 	9.3%
- (miss 6) (once every 7 weeks)
- Bloody diarrhea → HUS 	→ 4/237 	1.7%
- (miss 1) (once every 39 weeks)
- Bloody diarrhea → anuric HUS → 0/237

## Four patterns of outcome

- Tarr, PI, et al, in Yamada, T., Textbook of Gastroenterology, Blackwell, 5th ed., in press

## Trial Specifications

- Diagnose early, accurately
- Intervene early
- Support all patients with aggressive volume expansion (IV)
- Collect data in usable fashion for subsequent users
- Benefits (what outcomes are to be averted?) to be weighed against risk
- Address important consent issues re urgent enrollment
- Might need to address Stx2c

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- Eileen J. Klein, MD, MPH, Jennifer R. Stapp, BS, Carla R. Clausen, PHD, Daniel R. Boster, BS, Joy G. Well, MS, Xuan Qin, PhD, David L. Swerdlow, MD, and Philip I. Tarr, MD. Shiga toxin-producing *Escherichia coli* in children with diarrhea: A prospective point-of-care study. The Journal of Pediatrics 2002;172-178.

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