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INTESTINAL BLEEDING AND STEC O127: H21 INFECTION INTESTINAL BLEEDING AND OCCLUSION ASSOCIATED
WITH SHIGA TOXIN-PRODUCING ESCHERICHIA COLI O127: H21 MARTA RIVAS1, ELIZABETH MILIWEBSKY1, LAURA BALBI2, BEATRIZ GARCIA2, NELIDA LEARDINI1, MONICA TOUS1, GERMAN CHILLEMI1, ARIELA BASCHKIER1, LILIANA STRUGO2 Instituto Nacional de Enfermedades Infecciosas, ANLIS Dr. Carlos G. Malbrán, Buenos Aires; 2 Hospital Pediátrico Dr. Humberto Notti, Mendoza Resumen Hemorragia y oclusión intestinal asociadas a Escherichia coli O127:H21 productor de toxina Shiga. Se presenta el caso de un niño de 9 años, eutrófico, perteneciente a una familia de bajo nivel socioeconómico en Mendoza, que ingresó al hospital con vómitos, fiebre y dolor abdominal y al cual se le practicó apendectomía, aislándose Escherichia coli O127:H21, productor de toxina Shiga (STEC) en el coprocultivo. A las 48 horas post-cirugía, el paciente presentó vómitos biliosos y dos episodios de hemorragia intestinal. El hematocrito fue de 35% y la uremia de 0.22 g/L. La diuresis fue normal. Al día siguiente estaba afebril, alerta, hidratado, pero con el abdomen distendido y doloroso. Fue enviado nuevamente a cirugía con diagnóstico de oclusión intestinal, observándose durante la misma, sangrado intestinal y múltiples adherencias en yeyuno e íleo, que fueron manualmente removidas. El paciente continuó con distensión abdominal y presentó dos deposiciones sanguinolentas, el hematocrito disminuyó a 29% y la urea en sangre se elevó a 0.32 g/L. STEC O127:H21 eae(-)/Stx2/Stx2vh-b(+)/E-Hly(+) fue aislado de la materia fecal. El niño fue dado de alta después de 10 días de hospitalización sin presentar complicaciones como SUH o PTT. Esta es la primera comunicación sobre el aislamiento de E. coli O127:H21 de un caso de enterocolitis hemorrágica, con los factores de virulencia que caracterizan a STEC. Este serotipo era reconocido como perteneciente a la categoría de E. coli enteropatógeno no clásico. Teniendo en cuenta que las infecciones por STEC pueden mimetizar otras patologías infecciosas o no infecciosas, es importante utilizar distintos criterios diagnósticos, para evitar prácticas médicas o tratamientos innecesarios.
Abstract We report a case of a nine-year old boy with vomiting, abdominal pain and fever, who underwent surgery with a diagnosis of appendicitis in Mendoza and from whom a Shiga toxin-producing Escherichia coli (STEC) O127:H21 strain was recovered. Forty-eight hours after surgery he presented bilious vomiting and two episodes of intestinal bleeding. Laboratory findings included: hematocrit, 35%; blood urea nitrogen, 0.22 g/L. The urinary output was normal. The following day physical examination showed an alert mildly hydrated child, without fever but with distended and painful abdomen. The patient was again submitted to surgery with a diagnosis of intestinal occlusion. Bleeding and multiple adhesions in jejunum and ileum were found. The patient still had tense and painful abdomen and presented two bowel movements with blood; hematocrit fell to 29% and blood urea nitrogen rose to 0.32 g/L. STEC O127:H21 eae(-)/Stx2/Stx2vh-b(+)/E-Hly(+) was isolated from a stool sample. He was discharged after 10 days of hospitalization and no long-term complications such as HUS or TTP were observed. This is the first report, to our knowledge, on the isolation of E. coli O127:H21, carrying the virulence factors that characterize STEC strains, associated to an enterohemorrhagic colitis case. This serotype was previously characterized as a non-classic enteropathogenic E. coli (EPEC). STEC infections can mimic infectious or noninfectious pathologies. Therefore an important aspect of clinical management is making the diagnosis using different criteria thereby avoiding misdiagnoses which have occasionally led to invasive diagnostic and therapeutic procedures or the inappropriate use of antibiotics. Key words: Escherichia
coli
O127:H21 infection, intestinal bleeding, intestinal occlusion
Shiga
toxin-producing Escherichia coli (STEC), previously referred
to as Shiga-like toxin or verocytotoxin– producing E. coli.1, is the
causative agent of hemorrhagic colitis (HC), a bloody diarrhea that
usually occurs without fecal leucocytosis or fever. E. coli
O157:H7 is the predominant serotype isolated in outbreaks of HC in
many countries, including the USA, UK, Canada and Japan. However,
more than 25 other serotypes (O5:NM; O26:H11; O111:H8; O113:H21;
O128:NM; O145:NM; among others) that share a similar pathogenic
potential, have been isolated from HC cases2.
The group is called enterohemorrhagic E. coli (EHEC). The
illness typically begins with severe abdominal cramps and non-bloody
diarrhea, which may become grossly bloody by the second or third day
of illness. About half the patients have nausea and vomiting. Other
infectious causes of diarrhea (Shigella, Salmonella,
Campylobacter, Yersinia enterocolitica, Clostridium difficile)
must be considered in making the diagnosis. However, unlike most
bacterial enteric diseases, a low-grade fever or the absence of
fever usually characterizes O157:H7 infection. This feature may lead
clinicians to suspect noninfectious causes, such as inflammatory
bowel disease, ischemic colitis, or in children, intussus-ception.
Because the abdominal pain and tenderness may be severe, an acute
condition requiring surgery may be the initial diagnosis, leading to
exploratory laparotomy3. Stools
from patients with E. coli O157:H7 infection are sometimes
described as all blood and no stool simulating gastrointestinal
hemorrhage. Edema and submucosal hemorrhage in the ascending and
transverse colon may be demonstrated by a thumbprinting pattern on
barium-enema examination. At endoscopy, the colonic mucosa appears
edematous and hyperemic, sometimes with superficial ulcerations.
Pseudomembranes may be present making it difficult to distinguish
between C. difficile pseudomembranous colitis and infection
with STEC4. Numerous
epidemiological studies have demonstrated an association between HC
and STEC infection. Life threatening systemic complications can also
result from infection including the hemolytic uremic syndrome (HUS)
and thrombotic thrombocytopenic purpura (TTP). A triad of acute
renal failure, microangiopathic hemolytic anemia and
thrombocytopenia characterizes HUS. Patients with HUS are also at
increased risk of neurological symptoms including lethargy, severe
headache, convulsions and encephalopathy. HUS following STEC
infection is recognized as the most common cause of pediatric acute
renal failure in many countries, including Argentina5.
TTP, which is identical in its clinicopathological features to HUS,
occurs more often in infected elderly patients. In addition, more
prominent central nervous system abnormalities are reported to occur
with TTP2. STEC
strains elaborate potent bacteriophage-encoded cytotoxins called
Shiga toxins (Stxs)1.
There are two main types of Stx: Stx1 and Stx2, and within the Stx2
family there are various sub-types produced by human STEC isolates.
The toxins may be present alone or as a combination of two toxins
(typically Stx1; Stx2 or Stx2/Stx2v). Apart from Stx, EHEC strains
generally express other virulence-associated factors, which may be
linked to their ability to cause severe disease. These factors
include a novel hemolysin called enterohemolysin (EHEC-Hly)6
encoded by a 60MDa plasmid (pO157), and intimin, an outer membrane
protein encoded by the chromosomal eae gene7
that is involved in intimate attachment to its receptor (Tir) on the
host cell and effacement of microvilli of colonic mucosa (AE
lesion). Both genes (eae and tir) are located in the
locus of enterocyte effacement (LEE) pathogenicity island. At
present, there is no vaccine to protect against STEC infection nor
are there effective interventions to treat STEC-induced diseases. In
fact, antibiotic therapy may be a risk factor for developing
complications of STEC infection8
because antibiotics increase toxin release from the periplasm of the
bacterium. Current therapy for STEC-associated illnesses consists of
supportive care. We
report a case of intestinal bleeding and occlusion associated with
STEC O127:H21, a serotype previously considered a non-classic
enteropathogenic E. coli (EPEC), in a well nourished child
nine-years old, belonging to a low socioeconomic family. He was
admitted to the Hospital Regional Antonio J. Scaravelli, Mendoza,
Argentina, on 19 August 1995 with vomiting, abdominal pain and
fever. Appendectomy was performed after clinical diagnosis of acute
appendicitis. No pathologic studies were carried out. Twenty-four
hours after surgery, the patient presented abdominal distention with
generalized pain without fever and vomiting. Plain abdominal
radiograph demonstrated multiple air-fluid levels throughout the
abdomen with thickening of the bowel wall. Nasogastric and rectal
decompression was done. Forty-eight hours later, he presented
bilious vomiting and had suffered two episodes of intestinal
bleeding, of around 300 ml each at 72 hours. Laboratory
findings included: White blood cells (WBC) count, 7,100/ml;
hematocrit, 35%; prothrombin, 85%; blood urea nitrogen, 0.22 g/L.
The urinary output was normal. Therapy with ampicillin 100 mg/kg/day
and gentamicin 5 mg/kg/day was started. Rectal digital examination
showed an empty rectum for feces, it was followed for a discharge of
fresh blood. A new plain abdominal radiograph was requested and the
patient was immediately derived to the Hospital Pediátrico Dr.
Humberto J. Notti on 22 August. Physical examination showed an alert
mild hydrated child, without fever but with distended and painful
abdomen. He was treated with penicillin 100,000 U/kg/day, gentamicin
5 mg/kg/day and metronidazole 25 mg/kg/day. WBC count was 7,200/ml;
hematocrit, 33%; platelet count, 280,000/ml and blood urea nitrogen,
0.22 g/L. Plain
abdominal radiograph showed a progressive distention (Fig. 1) but
abdominal sonography, barium-enema examination and/or abdominal
computed tomography scan were not considered in making the
diagnosis. The patient was submitted to surgery with presumptive
diagnosis of intestinal occlusion. During exploratory laparotomy,
intestinal bleeding and multiple adhesions in jejunum and ileum were
found. They were manually liberated and after surgical procedure
intestinal motility returned to normal. The patient still had tense
and painful abdomen and presented two bowel movements with blood in
feces on 23 August. Hematocrit fell to 29% and blood urea nitrogen
raised to 0.32 g/L. After forty-eight hours the patient was in good
conditions with only minimal blood in feces and 24 hours later the
antimicrobial therapy was suspended. The patient recovered from the
infection and did not go to develop either HUS or TTP. He was
discharged to his home on 29 August. A
fecal sample was collected on 23 August. In addition to be cultured
for E. coli, the stool was also routinely cultured for Salmonella,
Shigella, Yersinia, Vibrio, Campylobacter, and Clostridium species
with negative results. The stool was not evaluated for C.
difficile toxins A and B. Sorbitol-fermenting colonies were
observed on sorbitol-MacConkey agar. Biochemical reactions were
positive for b-glucuronidase,
indole production, methyl red test, glucose acid production,
D-mannitol, raffinose and trehalose fermentation, lysine and
ornithine decarboxylase. Six colonies identified as E. coli
were positive for Stx2 production in cytotoxic assays on Vero cells9
using Stx1 and Stx2 specific monoclonal antibodies (MAb 13C4 and
BC5BB12, respectively), provided by NA Strockbine, Center for
Infectious Diseases, Atlanta, GA. The
strains were positive for stx2 gene and EHEC virulence
plasmid analyzed by colony blot hybridization assays with specific
digoxigenin labeled gene probes (provided by Drs J Kaper and J
Nataro, Center for Vaccine Development, University of Maryland,
School of Medicine, Baltimore, MA) under stringent conditions10. The strains were negative for the eae factor and the bundle
forming pilus (bfp) and did not adhere to HeLa cells11.
The PCR test for amplification of stx gene sequences was
performed with the oligonucleotide primers described by Pollard et
al12. Amplified products of the stx2 gene (346-bp fragment) were
obtained. The strains were characterized as Stx2/Stx2vh-b by the
PCR-RFLP (Restriction Fragment Length Polymorphism) genotyping
method of Tyler et al13. The
strains were positive for E-Hly on the sheep blood agar assay6.
They were serotyped by agglutination with specific O and H antisera
(Denka Seiken CO., Ltd., Japan) and identified as E. coli
O127:H21. They were susceptible to ampicillin, cefixime, cefotaxime,
cefuro-xime, cephalotin, colistin, chloramphenicol, gentamicin,
nalidixic acid, norfloxacin, streptomycin and tetracyclin as
determined by Kirby Bauer method. Human
pathogenicity of E. coli strains belonging to the STEC group
varies according to serotypes, virulence attributes and others
unknown factors. Serotype O127:H21 carrying the virulence factors
than characterize STEC strains, as far as we know, has not been
previously reported as a cause of HC. E.
coli
O127:H21 eae(-)/Stx2/Stx2vh-b(+)/E-Hly(+) was isolated from a
child with diagnosis of appendicitis, who suffered intestinal
bleeding and occlusion and underwent two surgeries. He did well
following the discharge and no long-term complications such as HUS
or TTP were observed. E.
coli
O127:H21 was previously characterized as a non-clasic EPEC with the
ability to cause gastroenteritis in very young children and rarely
in adults. On the other hand, EPEC are found in human populations
throughout the world and constitute one of the main causes of
infantile diarrhea in developing countries, including Argentina14. A
new STEC serotype could conceivably have arisen when an E. coli
O127:H21 strain became lysogenized with one or more Stx-encoding
bacteriophages or acquired virulence factors, such as Shiga-toxin,
plasmid-encoded adhesins and enterohemolysin, via horizontal
transfer and recombination from an EHEC strain. The direct
involvement of such mobile elements in transmission of stx
genes has yet to be demonstrated. However, one study has identified
an IS element adjacent to an stx1 operon in an O111:H-
STEC strain, there was no duplication of target sequence at the
insertion site, which raised the possibility that the segment of DNA
containing the toxin gene was part of a transposon. Involvement of
bacteriohages and transposons may help to explain why many STEC
strains readily lose their stx genes after subcultivation in
vitro15. STEC
infections can mimic infectious or noninfectious pathologies.
Therefore an important aspect of clinical management is making the
diagnosis using different criteria such as colonic biopsy, abdominal
sonography, barium-enema examination and/or abdominal computed
tomography scan, thereby avoiding misdiagnoses which have
occasionally led to invasive diagnostic and therapeutic procedures
or the inappropriate use of antibiotics. Acknowledgements:
The authors are grateful to Dr. Luis E. Voyer, for helpful
discussion and review of the manuscript. The technical assistance of
Ana Garbini and Natalia Martinez is acknowledged. This work was
partially supported by a grant from CONICET (Consejo Nacional de
Investigaciones Cientí-ficas y Técnicas) (PIA N° 7237/97). References
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Paton AW, Paton JC. Characterization of IS 1203, an insertion
sequence in Escherichia coli O111:H-. Gene 1994; 150: 67-70. Received: 10-XI-1999 Accepted: 5-I-2000 Postal
address: Dr. Marta Rivas,
Servicio Fisiopatogenia, Instituto Nacional de Enfermedades
Infecciosas ANLIS Dr. Carlos G. Malbrán, Av Vélez Sarsfield 563,
1281 Buenos Aires, Argentina Fax: (54-11) 4303-1801
e-mail: rivasmarta@hotmail.com Fig.
1.– Plain abdominal radiograph demonstrating multiple air-fluid
levels throughout the abdomen with thickening of the bowel wall in a
child with intestinal bleeding and occlusion associated with Shiga
toxin-producing Escherichia coli O127:H21. - - - - Creo que la fortuna es árbitra de la mitad de nuestras acciones, pero nos deja gobernar la otra mitad a nosotros. Nicolás Maquiavelo (1469-1527) El
príncipe
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