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

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 MeetingRockville, MDApril 12, 2007

SpontaneousResolution

(~85%)

HUS(~15%)

-3 -2 -1 0 1 2 3 4 5 6 7

Diarrhea Bloodydiarrhea

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 ChallengesTarget 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;132:777J 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


39 STECs

O157 (28) non-O157 (11)

HUS 18% 0%

Bloody 92% 50%

Laboratory blood 70% 22%


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 PopulationBloody diarrhea Highly credible, low risk Painful diarrheaHospitalized 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


(~85%)

HUS(~15%)-3 -2 -1 0 1 2 3 4 5 6 7


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

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

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)


(~85%)

HUS(~15%)-3 -2 -1 0 1 2 3 4 5 6 7


Culture

+ culture

Does host injury precede presentation/ diagnosis?

Adapted from: Lancet 2005; 365:1073

ControlUncomplicated

Pre-HUS

38

Fra

gm

en

t 1

+2

(n

mo

l/L

)

A


Pre-HUS

112

t-P

A a

ntig

en

(n

g/m

L)

D


Pre-HUS

20

50

PA

I-1

activi

ty (

IU/m

L)

B


Pre-HUS

710

log

D-d

ime

er

(lo

g n

g/m

L)

E


Pre-HUS

010

t-P

A/P

AI-

1 c

om

ple

xe

s (

ng

/mL

)

C


Pre-HUS

1000

3000

PA

P c

om

ple

xe

s (

ng

/mL

)

F

*

F 1+2: Thrombin generation before HUS

NEJM 2002; 346:23 P<0.01 p<0.001

THROMBIN + F 1+2FXa

PROTHROMBIN

NEJM 2002; 346:23


Pre-HUS

38

Fra

gm

en

t 1

+2

(n

mo

l/L

)

A


Pre-HUS

112

t-P

A a

ntig

en

(n

g/m

L)

D


Pre-HUS

20

50

PA

I-1

activ

ity

(IU

/mL

)

B


Pre-HUS

710

log

D-d

ime

er

(lo

g n

g/m

L)

E


Pre-HUS

010

t-P

A/P

AI-

1 c

om

ple

xe

s (

ng

/mL

)

C


Pre-HUS

1000

3000

PA

P c

om

ple

xe

s (n

g/m

L)

F

D-dimer Before HUS, as Lesion Evolves

**

NEJM 2002; 346:23

Fibrin Degradation

• D-dimer signifies fibrin degradation, infers fibrin presence

D DE D DED D D

Cross-linked fibrin polymers D-DimerPlasmin

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 HUSCHRMC, 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

Copyright ©2005 American Academy of Pediatrics


Fig 1. Timing of critical events during illness

Copyright ©2005 American Academy of Pediatrics

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


Multivariate AnalysisVARIABLE 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

0.3 0.3 0.3

2 3 4

Day of I llness

432

323

365

2 3 4

Day of I llness

275

177

10575

4617 12

34 4368

2 3 4 5 6 7 8 9 10 11

Day of I llness

34 34

30

25

19

26

19

28

25 26

2 3 4 5 6 7 8 9 10 11

Day of I llness

286262

217

4215 17 14 26

9066

143

2 3 4 5 6 7 8 9 10 11 12

Day of I llness

44 45 45

36

28

2523

15

29 28 29

2 3 4 5 6 7 8 9 10 11 12

Day of I llness

286

210

30 28 32 29 33 36

122

221198

281

225

117

150166

254

342

419

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Day of I llness

44 43 4340

28

2219

2421 20

32

2830

36 3633 33 33

36

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Day of I llness

0.5 0.5

1.4

2.3

5.14.9

5.5 5.66.0

5.6

4.3 4.3 4.2

2.9 2.8 2.7 2.7 2.7 2.8

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Day of I llness

32 32 33

2 3 4

Day of I llness

0.4 0.3 0.4

1.3

1.92.2

2

1.3

0.90.7 0.6

2 3 4 5 6 7 8 9 10 11 12

Day of I llness

0.40.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

2 3 4 5 6 7 8 9 10 11

Day of I llness

Pattern 1 Pattern 2 Pattern 3 Pattern 4

Pla

tele

ts

HHe

Hem

atoc

ritC

reat

inin

e

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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Documents

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