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e-Medical
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Infection by
Gram + Bacilli include the following:
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ERYSIPELOTHRICOSIS
Infection caused by Erysipelothrix rhusiopathiae
that most often takes the form of erysipeloid, an acute but slowly
evolving skin affliction.
Epidemiology
E. rhusiopathiae (formerly
called E. insidiosa), a gram-positive, capsulated,
nonsporulating, nonmotile, microaerophilic bacillus with worldwide
distribution, is primarily a saprophyte. It may infect a variety of
living animals, including insects, shellfish, fish, birds, and mammals
(especially swine). In humans, infection is chiefly occupational and
typically follows a penetrating wound in persons who handle animal
matter, either edible or nonedible (infected carcasses, rendered
products [grease, fertilizer], bones, and shells). Nondermal infection
is rare, usually occurring as arthritis or endocarditis.
LISTERIOSIS
Infection caused by Listeria sp.
Epidemiology
Listeriaceae are gram-positive, non-acid-fast, noncapsulated,
nonsporulating, motile, facultatively anaerobic bacilli that are found
worldwide in the environment and in the gut of nonhuman mammals,
birds, arachnids, and crustaceans. Only those Listeria sp that
are hemolytic (chiefly L. monocytogenes, rarely L. ivanovii
and L. seeligeri) cause disease in humans and domestic and wild
animals. Incidence in the USA is >= 7 cases/1,000,000 people/yr,
with attack rates highest in newborns and in adults >= 70 yr;
infection peaks from July through August. Infection usually occurs via
ingestion of contaminated dairy products and raw vegetables and is
favored by the ability of L. monocytogenes to survive and grow
at refrigerator temperatures. Infection may also occur by direct
contact (antepartum and intrapartum from mother to child, especially
during abortions [which may be caused by the listerial infection]),
and during slaughter from infected animals to butchers and abattoir
workers. Infection is facilitated by immunoincompetence in up to 2/3
of patients.
ANTHRAX
A highly infectious disease of animals, especially ruminants,
transmitted to humans by contact with the animals or their products.
Epidemiology
The causative organism,
Bacillus anthracis, is a large,
Gram-positive, facultatively anaerobic, encapsulated rod. The spores
resist destruction by disinfectants and heat and remain viable in soil
and animal products for decades. Human infection is usually through
the skin but has occurred very rarely in the GI tract after ingestion
of contaminated meat. Inhaling spores may result in pulmonary anthrax
(woolsorter's disease), which is often fatal.
Biological Warfare and Terrorism:
Biological warfare is the use of microbiological agents for
hostile purposes. Such use is contrary to international law and in
fact has rarely taken place during formal warfare in modern history,
despite the extensive preparations and stockpiling of biological
agents carried out in the 20th century by most major powers.
Currently, the NATO nations have taken biological weapons out of
service. Some other nations (including Iraq, Iran, and North Korea)
are thought to maintain biological warfare capability. For a variety
of reasons--including uncertain military efficacy and the threat of
massive retaliation--experts consider the use of biological agents
in formal warfare unlikely. The area of most concern is the use of
such agents by terrorist groups. Biological agents are thought by
some people to be an ideal weapon for terrorists. These agents may
be delivered clandestinely, and they have delayed effects--allowing
the user to remain undetected.
Potential biological agents include anthrax, botulinum toxin,
brucellosis, encephalitis viruses, hemorrhagic fever viruses (Ebola
and Marburg), plague, tularemia, and smallpox. Each of these is
potentially fatal and, except for anthrax and botulinum toxin, can
be passed from person to person. Of these agents, anthrax is of most
concern. Anthrax spores are relatively easy to prepare, and unlike
most of the other agents can be spread through the air, creating the
potential for distribution by airplane. Theoretically, one kilogram
of anthrax could kill 10,000 people, although technical difficulties
with preparing the spores in a sufficiently fine powder would
probably limit actual deaths to a fraction of this.
Despite these theoretical concerns, the only successful terrorist
use of anthrax -multiple pieces of contaminated mail delivered to a
variety of locations in the United States in 2001 - resulted in only
a handful of deaths and serious infections. A larger number of
people were contaminated with anthrax spores without developing
illness. However, there w as extreme public anxiety related to these
incidents, which may have been a major goal of the terror group
responsible.
In addition to these actual infections, an even greater number of
false threats of anthrax have been reported. In 1999, the FBI
received an average of one false report per day of alleged anthrax
use. False reports, both hoaxes, and alarmed citizens misperceiving
harmless material for anthrax, increased even more following the
2001 anthrax attack in the United States.
The only other successful use of a biological agent by a terror
group in the United States occurred in 1984. In this event, 751
people were stricken with diarrhea resulting from the intentional
contamination with Salmonella of a salad bar in Oregon. The bacteria
were introduced by a religious cult trying to influence the results
of a local election. No one died.
Defense against bioterrorism involves several factors:
intelligence to disrupt the terrorists before they can use the
weapons; early detection; availability of protective antibiotics;
immunization of selected populations (such as the military).
Following entry into the body, the spores germinate inside
macrophages, and the bacteria are transported to regional lymph nodes,
where they multiply. The bacteria produce a variety of toxins;
protective antigen binds to target cells and facilitates cellular
entry of edema toxin and lethal toxin. Lethal toxin triggers a massive
release of cytokines from macrophages, which is responsible for the
sudden death common in anthrax infections.
Although anthrax is an important animal disease, it is rare in
humans and mainly occurs in countries that do not prevent industrial
or agricultural exposure to infected goats, cattle, sheep, and horses
or their products. Anthrax also occurs in exotic wildlife such as
hippos, elephants, and cape buffalo.
Symptoms and Signs
The incubation period varies from 12 h to 5 days (generally, 3 to 5
days).
The cutaneous form begins as a painless,
pruritic, red-brown papule; as it enlarges, it is surrounded by a zone
of brawny erythema and gelatin-like edema. Considerable peripheral
erythema, vesiculation, and induration are present. Central ulceration
follows, with serosanguineous exudation and formation of a black
eschar. Local lymphadenopathy may occur, occasionally with malaise,
myalgia, headache, fever, nausea, and vomiting.
Initial symptoms of pulmonary anthrax are insidious and
resemble influenza. Fever increases, and within a few days, severe
respiratory distress develops, followed by cyanosis, shock, and coma.
Severe hemorrhagic necrotizing lymphadenitis develops and spreads to
the adjacent mediastinal structures. Serosanguineous transudation,
pulmonary edema, and pleural effusion occur. Hemorrhagic
meningoencephalitis and/or GI anthrax may develop. Lung x-ray may show
diffuse patchy infiltration; the mediastinum is widened because of
enlarged hemorrhagic lymph nodes.
In Gastro-intestinal anthrax, the released toxin
induces a hemorrhagic necrosis extending to the draining mesenteric
lymph nodes. Septicemia with potentially lethal toxicity ensues.
NOCARDIOSIS
An acute or chronic, often disseminated,
granulomatous-suppurative infectious disease usually caused by the
aerobic gram-positive bacillus Nocardia asteroides, a soil saprophyte.
Epidemiology
N. asteroides usually enters the body via the lungs and rarely
via the GI tract or skin. Nocardiosis is uncommon and occurs worldwide
in all age groups, but incidence is greater among older adults and
men. Lymphoreticular malignancies, organ transplantation, high-dose
corticosteroid or other immunosuppressive therapy, and underlying
pulmonary disease are predisposing factors, but about half the
patients have no preexisting disease. Nocardiosis also has been
recognized as an opportunistic infection in patients with advanced HIV
infection. Other Nocardia sp sometimes cause localized or,
occasionally, systemic infections.
Symptoms and Signs
Disseminated nocardiosis usually begins as a
pulmonary infection that may resemble actinomycosis, but N. asteroides
is more likely to disseminate hematogenously with abscess formation in
the brain or, less frequently, in the kidney or in multiple organs.
Skin or subcutaneous abscesses occur frequently, sometimes as a
primary site of localized infection. With lung lesions, the most
common symptoms--cough, fever, chills, chest pain, weakness, anorexia,
and weight loss--are nonspecific and resemble those of TB or
suppurative pneumonia. Pleural effusion also may occur. Metastatic
brain abscesses may occur in as many as 1/3 of cases and usually
produce severe headaches and focal neurologic abnormalities. Infection may be acute,
subacute or chronic.
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