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Gram Positive Rods
Gram positive rods
Spore forming
Aerobic
Bacillus spp
Non spore forming
Anaerobic
Clostridium spp
Corynebacterium
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There are four Genera of gram positive rods:
Bacillus
Clostridium
Corynebacterium
Listeria
Bacillus and Clostridium form spores while
Corynebacterium and Listeria do not.
Members of the genus bacillus are aerobic
while members of Clostridium are anaerobic.
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Central: Bacillus anthracis
Subterminal: Present near the end
Terminal: Present at the end
SPORES
Bacillus anthracis
Clostridium tetani
Bacillus anthracis causes Anthrax disease
and Bacillus cereuscauses food poisoning
Bacillus anthracis: causes Anthracis
 Important disease in animals, but rare in
humans
 ( potential biological weapon)
Human disease occur in three main forms
which are cutaneous, pulmonary and
gastrointestinal
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Large gram positive rod with square ends,
Frequently found in chain.
Its ant phagocytic capsule is composed of
D- glutamate) the other bacterial capsule
are polysaccharide
Its non motile
Anthrax toxin is encoded on one plasmid
and the polyglutamate capsule is encoded
on a different plasmid
Spores of the organism can persist in soil for years; therefore:
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Human contact with the spore hides in the environment such
as from hides, bristles and wool.
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Inhalation of spores into the respiratory tract
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Pulmonary anthrax occurs when spore are inhaled into lungs
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Gastrointestinal anthrax occurs when contaminated meat are
ingested
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Inhalation anthrax is not communicable from person
to person despite the severity of the infection. After the
organism being inhaled into lungs, it moves rapidly to the
mediastinal lymph nodes , where it causes hemorrhagic
mediastinitis. Because it leaves the lungs so rapidly, it
is not transmitted by respiratory route to others.
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Consisted of two factors:
edema factor and lethal factor each consisted
of two proteins in an A-B sub unit
configuration. The B, or binding subunit is the
protective antigen.
Edema factor is an adenylade cyclase causes
outpouring of fluid from cell into the
extracellular space which manifest as edema
Lethal factor cleaves the phosphokinase that
activates the mitogen-activated protein and
inhibit cell growth.
Protective antigen forms pores in the human
cell membrane that allows edema factor and
lethal factor to enter into cell.
Infection
 Primarily a disease of animals ( sheep,
cattle, horses)
 Humans affected rarely
 Infection is by entry of spore through
injured skin or mucous membranes, rarely
by inhalation into lungs
 In animals the portal entry is mouth and GIT
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Spores in soil may be taken up with spiny or
irritating vegetation
In humans scratches in the skin or
inhalation leads to infection (woolsorter
disease) – rapidly fatal
Germination of spores occurs in tissue at
site of entry – leads to formation of
gelatinous edema
Spread & multiplication
 – via lymphatics to the blood stream.
 Multiply in blood and tissue shortly
before and after animal dies.
 Toxic anthrax factor has demonstrated
to kill when studied on animal models
 Toxic anthrax factor can be neutralised
with anthrax antiserum
anthrax toxin:
1)
Protective antigen –has antigenic
properties
2)
Edema factor
3)
Lethal factor
Toxin production is controlled by presence
of a
specific plasmid, its absence means
absence of
toxin
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Spores from the dust of wool hair etc
germinate in the lungs, or in the trachea,
broncho lymph nodes
Results in hemorrhagic mediastinitis,
pneumonia, meningitis
It is rapidly fatal
In susceptible organisms
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Bacteria proliferate at site of entry
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Bacterial capsule remain intact
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Bacteria surrounded by large amount of
proteinaceous fluid containing few
leukocytes
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Bacteria rapidly disseminate and reach the
blood stream
In resistant organisms
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Bacteria proliferate for a few hours, then
there is massive accumulation of
leukocytes
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Bacteria remain localized
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Malignant pustule at site of infection on
skin
A papule develops 13 – 36 hrs
Papule rapidly changes into vesicle, then a
pustule and finally a necrotic ulcer, from
which the bacteria may disseminate giving
rise to septicemia
Inhalation anthrax
 Early manifestation may include
mediastinitis, sepsis, meningitis, or
haemorrhagic pulmonary edema
 Haemorrhagic pneumonia with shock is a
terminal event
Specimen
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Fluid or pus from local lesion, blood,
sputum - demonstration of large gram
positive rods
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Immunofluorescence staining techniques
can also be used
Culture
Blood agar – is useful
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Some animals (guinea pig) are highly
susceptible, others (rats) are very resistant
to anthrax infection.
Resistance factors:
Leukocyte activity
Bactericidal action of blood
Polypeptides – that kill anthrax ( synthetic
polysine has similar effect)
Active immunity to anthrax
Can be induced to susceptible animals by
vaccination ( live attenuated bacilli,
spore suspension or protective antigens
from culture filtrates)
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Ciprofloxacin/Penicillin is satisfactory
except against inhalation anthrax (
inhalation anthrax remains to have high
mortality rate)
Some may produce beta lactamase and
thus resist penicillin. Tetracycline,
Erythromycin or Clindamycin may be
effective.
In prevention the disease to develop for
those exposed Ciprofloxacin and
Doxycycline can be used as prophylaxis.
Carcasses - dead animals ( source of
spore)
pH – 6.5 can allow spore germination in the
soil.
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Grazing – animals are infected through
injured mucous membranes
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Contact with infected animals or their
hide, hair, bristles
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Control measures
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Disposal of animal carcasses – burning or
deep burial in lime pits
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Decontamination of animals products
(autoclave)
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Protective clothing, gloves for handling
potentially infected materials
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Active immunization of domestic animals
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People exposed occupationally should be
vaccinated
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Is an ubiquitous soil organism found in
grains, vegetables and dairy product
Causes food poisoning
Transmission: spores on grains such as
rice survive steaming and rapid frying. The
spore germinate when rice is kept warm
for hours (eg reheated fried rice). The
portal of entry is the gastrointestinal tract.
Is caused by preformed heated stable
enterotoxin ingested in reheated foods
eg rice beans
Manifested by:
 Nausea
 Vomiting
 Abdominal cramps
 Occasionally diarrhea
 Is self limiting, recovery within 24 hrs
 Begins 1-5 hrs after ingestion of rice,
or pasta dishes
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Has incubation period of 1 -24 hrs
Profuce diarrhea
Abdominal pain and cramps
Fever & vomiting uncommon
Toxin may be preformed in the food or
produced in the intestine
Organism introduced into eye by foreign
bodies associated with trauma
Endocarditis
 Meningitis
 Osteomyelitis
 Pneumonia
Obs!
Presence of medical device intravenous drug use predisposes to
these infections
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Prevention
Refrigeration of food after cooking: spores
survive initial cooking and will germinate
into toxin producing vegetative cells if
foods are not well s refrigerated properly;.
Later reheating in activate heat labile toxin
but does not affect vegetative cells or heat
stable toxin.
Supportive therapy eg replenish fluids and
electrolytes.
C. tetani
C.perfregent
C.botulinum
C.defficile
organism
Disease
Transmission Action of
/predisposing toxin
factor
1 C. tetani
Tetanus
Spore in soil
enter wound
Blocks
Toxoid
release of
vaccine
inhibitory
transmitter
s eg
glycine
2 C.
Botulism
Exotoxin in
food is
ingested
Blocks
Proper
release of
canning:
acetycholin cook food
e
3 C.
1.Gas
gangrene
2.food
poisoning
Spore in soil
enter wound
Exotoxin in
food is
ingested
Lecithinase Debride
wounds
superranti Cook food
gen
Pseudomem
Antibiotic
Cytotoxin
botulinun
perfringes
4 C. difficile
prevention
Appropriat
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Large anaerobic gram (+ve)
Many decompose proteins or produce toxins,
some do both
Their natural habitat is the soil or intestinal
tract of humans and animals (saprophytic
life)
Pathogenic strains include those that cause
botulism, tetanus, gas gangrene,
pseudomembranous colitis
C. tetani
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a gram-positive rod
commonly found in the soil, dust and animal
feces, rusted iron materials
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Commonly found in the soil, dust and animal feces
Contamination of wounds, which provide anaerobic
conditions, can lead to spore germination and
tetanus frequently fatal disease.
Tetanus is also know as lockjaw because of the
patient's inability to open the mouth as a result of
muscle paralysis.
In developing countries, (about half) of tetanus
cases are in neonates where the unhealed umbilical
stump becomes infected, or circumsion often as a
result of cutting the area with a contaminated
knife
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Small rods with tennis racquet shape due to
presence of terminal spore
Strict anaerobic that is very sensitive to
oxygen
C. tetani
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Infection usually occurs when spores enter
wounds and scratches where they
germinate and produce tetanus toxin
The exotoxin (tetanospasmin) binds to
ganglioside receptors and bocks the
release inhibitory mediators (eg. Glycine)
at the spinal synapsesin central nervous
system and this stops nerve impulse
transmission to muscle leading to spastic
paralysis.
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The toxin can act at
peripheral motor nerve end
plates, the brain, spinal cord
and also in the sympathetic
nervous system.
Because inhibitory neurons
are involved, the result is
unopposed muscle
contraction
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Tetanolysin - heat and oxygen labile/lyse
RBC/
Tetanospasmin - heat and oxygen
stable/highly lethal (for mice 0.0000001
mg) dies within 1 - 2 days get easily
neutralize with antitoxin
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· Headache.
· Jaw cramping.
· Sudden, involuntary muscle tightening –
often in the stomach (muscle spasms)
· Painful muscle stiffness all over the body.
· Trouble swallowing.
· Jerking or staring (seizures)
· Fever and sweating.
· High blood pressure and fast heart rate
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disseminates systemically
binds to ganglioside receptors
 inhibitory neurones in CNS, signal
stopped
muscles keep on working
spastic (rigid) paralysis
glycine, neurotransmitter
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GABA GLYCINE
A severe case of tetanus.
muscles, back and legs are rigid
muscle spasms can break bones
can be fatal (e.g respiratory failure)
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In generalized tetanus, the most common form, the
patient typically experiences lockjaw
Stiffness of the jaw muscles - inability to open the
mouth or swallow leading to the appearance of a
sardonic smile (risus sardonicus).
Speech as a result of spasm of the vocal cords may be
affected.
Continued severe muscle contractions, which can
even cause broken bones
The patient often experiences a fever (a rise of 2 to 4
degrees) with sweating,
elevated heart rate blood pressure.
Aspiration pneumonia is often a late complication.
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About eight days after infection
symptoms of tetanus appear (though
the incubation period can be a short as
three days and as long as three weeks).
Incubation period seems to depend on
the distance of the infection site from
the central nervous system.
In neonates the average latent period is
about a week
Cephalic tetanus
a rare infection involving the middle ear. It
can affect cranial nerves.
Local tetanus
rare and manifests itself as localized muscle
contractions in the area of infection
Few cases are fatal
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Vaccination with Tetanus toxoid (formaldehyde inactivated
toxin) administered as a part of DPT vaccine.
Booster shots required every ten years and recommended
after probable exposure.
Treatment for unvaccinated individuals
 Supportive care eg muscle relaxants, oxygen to reduce
spasms and maintain breathing until circulating toxin is
metabolized.
 Passive immunization with human antitoxin
immunoglobulin to neutralize circulating tetanospasmin
 Debridement of the primary wound and penicillin therapy
to eliminate clostridial cells
If infants receive the complete vaccination regimen, virtually
100% protection is achieved
Boosters should be given every ten years
• infant
• DPT (diptheria, pertussis, tetanus)
• tetanus extremely uncommon in US
• tetanus toxoid
– antigenic
– no exotoxic activity
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Causes wound colonization – gas
gangrene after soil, and food poisoning to
a lesser extent intestinal tract after
swallowing contaminated food
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Term gas gangrene refers to swelling of tissues
due to release of gas, as fermentation products, of
clostridia.
Is caused by C perfringes . Can also be caused by
other histotoxic clostridai such as Clostridium
histolyticum, Clostroridium septicum and C. novyi.
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The organism produces several tissue
degrading enzymes (including
lecithinase [alpha toxin], proteolytic
and saccharolytic enzymes).
Necrosis and destruction of blood
vessels and the surrounding tissue,
especially muscle, result.
This creates an anaerobic environment
in adjacent tissue and the organism
spreads systemically.
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Pain, edema, and cellulitis occurs in the
wound area.
Crepitation indicate presence of a gas in
tissue. Hemolysis and jaundice are common,
are blood, -tinged exudates.
Shock and death can ensue.
Mortality rate are high.
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Treatment (including antitoxin, antibiotic therapy) is
extremely effective and
amputation and death is
rare.
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production of lecithinase is important in
laboratory identification of the organism.
C. Botulinum
- Causes Botulism
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Spores wide distributed in soil, contaminated
vegetables, and meats. When these foods are
canned or vacuum – packed without adequate
sterilization, spores survive and germinate in
the anaerobic environment. Toxin is produced
within the canned food and ingested
preformed.
The highest risk food are:
-a) alkaline vegetables such as green beans,
peppers, and mushroom
 -b) smoked fish
 The toxin is relatively heat-labile, it is inactivated by
boiling for several minutes. This disease can be
prevented by sufficient cooking.
Botulinum toxin is absorbed from the gut and
carried via blood to peripheral nerve synapses
where it blocks release of acetylcholine.
It is a protease that cleaves the proteins involved in
acetylcholine release.
The toxin is a polypeptide encoded by a lysogenic
phage.
It is the most toxic known as tetanus.
There are 8 immunological types of toxin. Type A, B,
and E are most common in human illness.
FIND THE OTHERS ( ASSIGNMENT)
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toxin binds to receptors on peripheral nerves, where
acetylcholine is the neurotransmitter.
toxin inhibits nerve impulses and flaccid paralysis and
often death (from respiratory and/or cardiac failure) results.
The organism does not grow in the gut, but pre-formed
exotoxin from prior germination of spores may be present
in inadequately autoclaved canned food (usually at
home).
 Wound
botulism can occur but is
even rarer.
 C. botulinum does not readily
grow in the adult intestine due to
competition with the normal flora
and their requirement for an
anaerobic, low acidity
environment.
 In the neonate, where the flora is
not established, colonization with
C. botulinum can easily occur.
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usually with a day or two but sometimes
there may be a period of up to a week
before they appear.
Vision and swallowing are affected
patient may become nauseated and
constipated.
Muscle paralysis ensues, usually starting at
the head and, when the respiratory muscles
are affected, death can result.
Eating honey contaminated by spores is
one source.
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The organism is usually NOT cultured . The
Botulinum toxin is demonstrated in uneaten
food and the patient serum by mouse
protection test. Mice are inoculated with a
sample of the clinical specimen and will die
unless protected by antitoxin.
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Adults includes an enema to clear the
gastro-intestinal tract of the toxin and
injection of
It is important that the anti-toxin is given
early to neutralize the toxin and protect
nerve endings from damage. Trivalent
antitoxin A, B and E is given with
respiratory support.
Antibiotics are not used to treat botulism,
although they may be used in secondary
infections, because of the possibility of
more toxin being released as bacteria are
lysed.
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Supportive treatment of infants is
based on helping them breath
and on tube feeding.
Adults may also require a
respirator.
Complete recovery from botulism
usually occurs over a period of
months as the damaged nerve
endings are replaced.
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Proper sterilization and proper techniques
in canning by adequate heating.
Food must be adequately
cooked to inactivate the toxin.
Swollen can must be discarded.
C. difficile
• Is part of intestinal normal
flora
– greatly decreased
• colonization occurs
• exotoxin A (enterotoxin)
• exotoxin B (cytoxin)
• pseudomembanous colitis
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C. difficile………
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When the normal flora of the intestine is
altered by antibiotic therapy, this organism which is present in the gastro-intestinal tract
of many babies - can grow and colonize.
 C. difficile produces an enterotoxin and
pseudomembranous colitis can result.
EPIDEMIOLOGY
PATHOGENESIS
Clinical Findings
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abdominal cramps
watery diarrhea, start some days (4 to 8) after
initiation of antibiotic therapy.
In mild cases, there is no blood in the diarrhea
but, in severe cases, bloody diarrhea
a distended tender abdomen
fever can occur.
Treatment
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Discontinuation of the implicated antibiotic
(e.g. ampicillin).
Severe cases require specific antibiotic therapy
(e.g. metronidazole and vancomycin).