# Presentation: 108575

## Non-O157:H7 STEC:Point of care, population-based, and clinical laboratory-centered analyses.

- P. I. Tarr, MD
- Washington University School of Medicine
- FSIS USDA October 17, 2007

## Perspectives

- USA
- Pediatric
- Systematically collected specimens, in context of patient care

## Background

- Many different *E. coli* serotypes produce Shiga toxin (Stx) 1 (and its variants), 2 (and its variants), or both.
- Only a subset has been demonstrated to be pathogenic to humans.

## Four groupings of STEC

*E. coli* O157:H7
- global; causes epidemics and severe disease, variety of sources, enduring importance
- easily detected in human specimens, using best microbiological diagnostic practices.

## E. coli O157:H7

- Sorbitol MacConkey agar

## Four groupings of STEC

- 2. *E. coli* O157:H-
- focal (esp. Germany, not USA yet); increasingly recovered in other countries
- sources not yet discerned
- less easily detected – because toxin assays needed to find them

## Four groupings of STEC

- Pathogenic non-O157 STEC
- 	(e.g., *E. coli* O26, O111, ...)
- global; variable type distribution; rarely epidemic; epidemiology and sources unclear
- less easily detected – because one needs  toxin assays to find them
- might be transmitted by food

## Four groupings of STEC

- 4.  nonpathogenic STEC:  frequent in animals, environment, food.

## STEC cause HUS (Hemolytic Uremic Syndrome)

- Hemolytic anemia (hct < 30%), Thromobocytopenia (plts <150,000/mm3),
- Renal insufficiency (creatinine > uln for age)
- Occurs 5-13 days after diarrhea begins

## HUS

- 15% of culture + *E. coli* O157:H7 patients < 10 yo will develop HUS
- however, some non-O157 STEC seem particularly virulent  (esp. O157:H-, O111, O113), but in aggregate non-O157 STEC are much less likely to cause HUS

## Diagnosis in humans

*E. coli* O157:H7: at time of HUS, 2/3 of patients can be negative.
- If not found at time of HUS, it does not mean that this pathogen was absent.

## STEC in Humans:  Challenges and Opportunities

- ca. 2.5 episodes of diarrhea/annum
- Vast majority are viral, and self-limiting
- Only about 15 million cultures performed per annum
- Cumbersome technology

## Slide 13

## Slide 14

## Detection and Enumeration Biases

- Bloody diarrhea and HUS patients are disproportionately cultured
- Rural disease, and resources needed to isolate pathogens are often not available at points of presentation

## 	      Archaic, Disjointed Technology

- 	      Archaic, Disjointed Technology

## Slide 17

## Slide 18

## 1/494 episodes + for STEC 

- 1/494 episodes + for STEC
- -Vernacchio, et al, Pediatr Infect Dis J 2006; PID J 25:2 and JPGN 2006; 43:52.

## 0/225 children with acute diarrhea 

- 0/225 children with acute diarrhea
- -Denno, et al, Pediatr Infect Dis J 2005; 24:142

## 15/1926

- Klein, et al, J Pediatr 2002; 141:172
- Klein, et al, unpublished

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

- 1626 ER Stools
- 	 39 signals in Meridian EIA (broth)
- 						Klein, E, et al, J Peds 2002; 172

## 39 EIA positives

	   25 E. coli O157:H7
	   10 non-O157:H7 STEC
	     1 non-O157:H7 STEC + C. jejuni 
	     3 no STEC found

- 	   25 *E. coli* O157:H7
- 	   10 non-O157:H7 STEC
- 	     1 non-O157:H7 STEC + C. jejuni
- 	     3 no STEC found

- 3 more stools + for E. coli O157:H7, not detected by toxin testing

## 39 EIA positives, 11 non-O157:H7 STEC 

	O103:H2 (4)
	O118:H16 (2)
	O26:H11 (1) 
	O111:nm (1)
	O111:H8 (1)
	O121:H19 (1)
	Orough:H11 (1)

- 	O103:H2 (4)
- 	O118:H16 (2)
- 	O26:H11 (1)
- 	O111:nm (1)
- 	O111:H8 (1)
- 	O121:H19 (1)
- 	Orough:H11 (1)

## 39 STECs

- 				non-O157 (11) 	O157 (28)
- Percent of all:	      1.7%			     0.7%
- HUS				0%			     18%
- Bloody		      50%			      92%
- Laboratory blood    22%			      70%

## Seattle STEC, 2003-2005

*	**	*
*	**E. coli* O157:H7: 	11
- 	non O157:H7: 	  4 (O26, O111, O121, O177)
- Klein, et al, unpublished data

## Michigan: 2003-2005

- Shannon, et al, Emerg Infect Dis 2007; 13:318

## Michigan

- 7 STEC from bloody stools, 6 were *E. coli* O157:H7
- 177 *E. coli* O157:H7
- 18 non-O157 STEC (O45, O103)
- 5/177 *E. coli* O157 not detected by EIA

## Pitfalls of focusing on bloody diarrhea

- Laboratory can’t tell what specimens are really bloody
- Many (perhaps most) non-O157:H7 STEC associated with non-bloody diarrhea

## Slide 30

##   Pre-HUS cultures have highest yield

*E. coli* O157:H7 is predominant (> 95%), cause of post-diarrheal HUS in USA, Canada, Japan, UK, and South America.
- 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
-   Pre-HUS cultures have highest yield
-   Antibodies to O157 often present when culture is negative, but short-lived (weeks to months)
-   Absence of proof is not proof of absence!

## But, HUS offers the best chance to find pathogenic non-O157:H7 STEC

- (1-5%, vs. <1% in other series)

## Slide 33

## Five LFs, Seattle children, 1991

- 445 stools probed (colony hybridization)
- 13 *E. coli* O157:H7 (all bloody diarrhea),
- 		9 detected by hybridization
- 5 non-O157:H7 STEC, only 1 had bloody 	diarrhea, but 3 were hospitalized
- Serotypes: O26 (2), O85, O103, O111
- 	Bokete TN, et. al. Gastroenterology 1993; 1724-1731

## Other 1990s series

- Falls Church, VA
- 	6 O157:H7
- 	5 non-O157:H7 STEC (2 with Salmonella)
- Milwaukee, WI
- 	12 O157:H7
- 	  3 non-O157:H7 STEC
- Park, et al, Diagn Microbiol Infect Dis 1996;26:69
- Kehl, et al,  J Clin Microbiol 1997; 35:2051

## St. Louis Children’s Hospital 2003 - 2007

- 	_O157:H7_ (33)         _Non-O157:H7 _(13)
- 2004		6	    2
- 2005	   15	    2
- 2006		8	    7
- 2007		4	    2
- 		                   O103:H2(6), O26, O111:NM, 			                      O145, O165, O174:H21 (1)
- 			No STEC (2)
- HUS		8		 0
- 3 *E. coli* O157:H7 missed by toxin assay

## Falls Church, Atlanta, Salt Lake CityJuly 2005 – September 2006

- 711 specimens
- 19 *E. coli* O157:H7
- 8 non-O157:H7 STEC
- 				Teel, et al, J Clin Microbiol 2007; 45:3377

## Slide 38

## Montana STEC, 1998 – 2000

*	*_*E. coli*__ O157:H7 (31)_	_non O157:H7 (50)_
- Bloody	81%				57%
- ER		56%				28%
- Procedure	22%				16%
- O26 (20), O73 (1), O103 (2), O118 (1), O121 (15), O145 (1), O165 (1), O177 (1), O181 (1), Orough, ONT (7)
- Jelacic J, et. al. J Infect Dis, 2003; 719-729

## Connecticut

- O157: 		278
- Non-O157: 	125
- 	(60% of toxin + assays yielded non-O157:H7 STEC)
- O103 (26)
- O111 (26)
- O26 (18)
- O45 (18)
- 15 other serogroups

- MMWR 2007;56:29

## Connecticut

- HUS not defined, but:

|  | O157:H7 | Other STEC |
| --- | --- | --- |
| Bloody diarrhea | 90% | 56% |
| Hospitalized | 45% | 12% |
| HUS | 9% | 0% |

## Nebraska

- 7 non-O157:H7 STEC
- O26 (2)
- O103 (1)
- O111 (2)
- O145,
- Orough
- 6 O157:H7
- HUS rate not given
- 1 of 6 O157:H7s not detected by EIA

- Fey, et al, Emerg Infect Dis 2000: 6:530

## HUS (ca. 100 cases)

- Culture + rate for *E. coli* O157:H7 in past 15 years (Seattle and St. Louis):
- 	~ 90% positive
- 	~   5% highly suspect to be positive
-    ~   4% nothing found

## Summary

- Human exposure to non-O157:H7 STEC probably common, association with disease is rare
- Human exposure to O157:H7 STEC less common, burden of disease greater

## Summary

- Human diagnostic resources must still focus on *E. coli* O157:H7 in USA, in children
- Some non-O157:H7 serotype predominance in USA:
- 	O26, O103, O111, O118, O121, O145
- Be on the lookout for
- 	O113 – potentially quite virulent – in Canada
- Sorbitol fermenting O157:H- not yet in USA

## Questions

- What is HUS rate for individual serotypes? (series might be biased by focusing on event of HUS)
- What is source of pathogenic non-O157:H7 STEC?

## How should we find these agents? 

- Toxin assays – OK clinically, much background in other settings
- Stx2 – but Stx1+/Stx2- strains have caused disease
*eae* – must include different alleles, and O113 won’t be detected
- O antigen target (side chain or *rfb *loci) for O26, O103, O111, O113, O118, O121, O145