Enterohemorrhagic and other Shigatoxin-producing Escherichia coli - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 120

non- E.coli O157 serotypes are O111 (13.7%) and O26 (11.1%) ( Vally et al.,
2012 ). New Zealand, Australia's nearest neighbor has a higher rate, e.g. 3.3
cases per 100,000 in 2009 ( Leotta et al., 2008 ; Vally et al., 2012 ).
Among Asian countries, STEC disease is most prevalent in Japan (0.74 cases
per 100,000 in 1999-2004), where multiple outbreaks occur every year ( Sakuma
et al., 2006 ). Although other serogroups, such as O26 and O111, have been
reported to cause outbreaks, serogroup O157 is the predominant serogroup in Japan
( Table 5.1 ). In 1996, multiple STEC O157 outbreaks throughout Japan affected
11 826 people and caused 12 deaths. Indeed, one of the largest reported E. coli
O157:H7 outbreaks in history occurred that year in Sakai City, affecting approxi-
mately 8000 people, although with very low mortality (i.e. two deaths) ( Izumiya et al.,
1997 ). Until recently, only a few studies on STEC epidemiology have been done in
other Asian countries. Human cases of STEC have been reported in India, Thailand,
Vietnam, and Bangladesh. In 2006, the prevalence of STEC in Dhaka, Bangladesh
was estimated to be 0.5% among hospitalized patients. Interestingly, no STEC O157
strains were isolated from these patients; the common serotypes isolated included
O32: H25, O2: H45, O76: H19, ONT: H25, and ONT: H19 ( Islam et al., 2007, 2008 ).
Because of the low incidence of severe disease and complications such as HUS, the
STEC strains in these developing countries are believed to be less virulent.
Economic impact
STEC outbreaks inflict a severe global economic burden both on the public and
on the food industry due to costs associated with illness, product recalls, and
compensations. The Economic Research Service of the USDA estimated the
annual cost of illness due to STEC in the US at $1 billion in 2000. As of 2009,
illness due to STEC O157 alone was estimated to cost $478 million in the US
( Frenzen et al., 2005 ). Additionally, the total cost of each outbreak is amplified
by legal costs and losses due to product recalls. For instance, a 1996 outbreak
associated with an apple juice outbreak in the US resulted in $1.5 million in fed-
eral fines, $6.5 million in losses due to a product recall, and $12 million in claim
settlements ( Pennington, 2010 ). In Canada, the annual economic impact of STEC
O157 illness alone is CAD$21 million, and more than CAD$82 million due to
product recalls and other associated costs (George Morris Study Excerpt, 2007 ).
Illness from STEC illnesses costs €9.1 million annually in the Netherlands ( Tariq
et al., 2011 ), and the 2011 German STEC outbreak accrued a total cost of $2.84
billion throughout the EU. Additionally, EU farmers claimed to have lost $600
million per week during the outbreak period ( Kirk, 2011 ).
MOLECULAR PATHOGENESIS
The molecular pathogenesis of EHEC has been the subject of intense study due
not only to its global clinical significance but also its diversity of pathogenic
strategies that serve as models for other bacterial infections. As outlined below,