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In-Depth Information
may be required in treatment of very young and elderly patients, oral intake can
generally replace these fluid losses.
The antibiotic of choice for treatment of dysentery is trimethoprim-sulfa-
methoxazole (
DuPont, 2005
). However, there is some controversy regarding
the use of antibiotics in treating dysentery. Since the infection is self-limited in
normally healthy patients and full recovery occurs without the use of antibiot-
ics, drug therapy is usually not indicated. In addition, multiple antibiotic resis-
tance among isolates of
Shigella
is becoming more common. Clinical isolates
resistant to ampicillin, trimethoprim-sulfamethoxazole, sulfamethoxazole-
sulfisoxazole, tetracycline, nalidixic acid, chloramphenicol, streptomycin, and
ciprofloxacin have been found and azithromycin is now being used against
highly resistant strains (
Shiferaw et al., 2012
). However, plasmid-mediated
resistance to azithromycin may limit the usefulness of azithromycin for treat-
ment of shigellosis in the near future (
Howie et al., 2010
). Extensive use of
antibiotics selects for drug resistant organisms and, therefore, many believe
that antimicrobial therapy for shigellosis should be reserved only for the most
severely ill patients. On the other hand, there are persuasive public health argu-
ments for the use of antibiotics to manage shigellosis. Antibiotic treatment lim-
its the duration of disease and shortens the period of fecal excretion of bacteria
(
Kabir et al., 1986
). Since an infected person or asymptomatic carrier can be
an index case for person-to-person and food and water borne spread, antibiotic
treatment of these individuals can be an effective public health tool to contain
the spread of dysentery. However, antibiotics are not a substitute for improved
hygienic conditions to contain secondary spread of dysentery. The single most
effective means of preventing secondary transmission is hand washing (
Arvelo
et al., 2009
). It should be noted that, unlike with enterohemorrhagic
E. coli
,
antibiotic treatment of infection with
S. dysenteriae
1 is not contraindicated
as the gene for Shiga toxin in this organism is not encoded on an inducible
bacteriophage.
Despite many years of intensive effort, no licensed vaccine against shigel-
losis has yet been developed. Live-attenuated, inactivated whole-cell, subunit
antigen, and conjugate oligosaccharide vaccines are currently being tested
(
Steele et al., 2012
). An important consideration is whether any vaccine can
afford cross protection against all species and serotypes of
Shigella
as well as
against EIEC.
CONCLUSION
A century of research has yielded significant insights into the mechanisms used
by
Shigella
and EIEC to interact with host tissues. These insights have revealed
a family of pathogens that are master cell biologists that reprogram host cells
and exploit the actions of host phagocytes to serve the needs of the parasite.
Furthermore, the unique evolution of these bacteria has promoted understand-
ing of pathogen evolution and driven discovery of novel evolutionary pathways.
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