Biology Reference
In-Depth Information
functional or physiologic assays have been used in the past to identify toxin-
producing bacteria, these have been largely supplanted by immunologic or
molecular-based methods. PCR, DNA probes for genes encoding ST and LT,
ELISA assays for both LT (
Sack et al., 1980
) and ST (
Thompson et al., 1986
)
are used to detect toxins in clinical research settings, with multiplex PCR for LT,
STa, STh emerging as the favored assay to identify ETEC (
Sjoling et al., 2007
).
Unfortunately, none of the current assays is performed routinely in clinical lab-
oratories, nor are they suitable for laboratories in developing countries where
resources may be limited. In the US, ETEC infections are typically diagnosed
during outbreaks when resources of state public health or CDC laboratories are
marshaled to address unexplained cases of diarrhea. Novel rapid point-of-care
technologies that can be easily applied to diagnosing infections in developing
countries remain an unmet need (
Qadri et al., 2005
;
Hauck et al., 2010
).
Treatment
Travelers' diarrhea (TD) caused by ETEC is often treated with antibiotics with
or without adjunctive symptomatic treatment with anti-motility agents such
as loperamide (
DuPont, 2007
). Antibiotics currently in use in adults with TD
include fluoroquinolones, azithromycin, and more recently rifaximin. Azithro-
mycin is the only antimicrobial currently advised for use in children. In general,
when active against the causative strains, all of these drugs appear to shorten
the duration of diarrheal illness by approximately 48 hours. Rifaximin, a non-
absorbable rifamycin antibiotic, appears equivalent to fluoroquinolones and
azithromycin for treatment of sensitive ETEC strains, without systemic side
effects. Emerging resistance to all three antibiotics over time will remain a con-
cern (
Ouyang-Latimer et al., 2011
). Most studies have shown a modest (
Dupont
et al., 2007
;
Ericsson et al., 2007
;
Butler, 2008
) or no (
Taylor et al., 1991
) benefit
to adding loperamide to antimicrobial therapy in adults with travelers' diarrhea,
while loperamide use is not advisable in young children due to concerns over
potential CNS depression.
In severe cholera-like illness, particularly affecting young children in devel-
oping countries, treatment of ETEC infections must focus first on rehydration.
Those with evidence of severe dehydration require initial management with
intravenous fluids followed by oral rehydration therapy (ORT), while milder
forms of illness can be treated with ORT alone. Unlike adult travelers, anti-
microbial administration for ETEC diarrheal illness in children has not been
well-studied.
Immune response
Innate immunity and ETEC
ETEC infections stimulate production of pro-inflammatory cytokines, includ-
ing interleukin-8, a potent chemoattractant for polymorphonuclear leukocytes.
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