Brucella
• The genus Brucella consists of six species,
four of which cause human brucellosis
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Brucella melitensis
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,
Brucella
suis
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,
Brucella abortus
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, and
Brucella canis
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• Are all intracellular organisms
• Brucella are small (0.4 ～ 0.8
×0.5 ～ 1.5μm), non-motile, non-capasulate, gram-negati ve coccobacilli.
• The organism is aerobic, an
d their nutritional requirem ents are complex.
• All strains grow best in a me
dium enrich with animal ser um and glucose
Antigenic Structure and
classification
• Two main antigen: A and M
• The three main Brucella differ from one another in the amount or the two main antigen they have in common :
B. abortus
•
Bacteria is excreted in genital secretions (in
cluding semen), milk, colostrum.
•
Survival time
:Cheese at 4oC: 180 days !!! Water at 25oC: 50 days
Meat and salted meat: 65 days Manure at 12oC: 250 days !!!!
•
Widespread:
Cattle, Bison, Elk, Deer, Moose, Horse, SB. abortus
• Sources of Human Infection:
Raw milk and products /Direct contact
• Portal of entry:oral mucosa, nasopharynx and
conjunctivae, genital then Xin regional lymph node and spread to RES (nodes of udder, uterus, erythritol...). Placentitis with endometritis. Fetus die with edema /congestion of lung, dissimenated hemorrhages of epicardium and splenic capsule. Bacteria in lung and digestive tract of the fetus. B. abortus
• Bacteria is excreted in genital secretions (including semen), milk, colostrum.
• Survival time:
Cheese at 4oC: 180 days !!!
Water at 25oC: 50 days
Meat and salted meat: 65 days Manure at 12oC: 250 days !!!!
• Widespread: Cattle, Bison, Elk, Deer, Moose, Horse, Sheep, Goat, Swine, Donkey, Dogs, Birds, Hares, Fox, Rats, mice, Camelsand Human.
B. melitensis
• Goat (1886), Sheep, Cow (1905 in
Malta), Swine, Hares, Camels, Buffalo, Impala.
B. suis
• Wild pigs, Rats, Swine. • Abortion,metritis,
bursitis, spondylitis (Lumbar and sacral), arthritis, orchitis, paralysis.
Brucella canis
• Brucella caniswas first described as a cause of abortion in beagles in the USA
• It was subsequently shown to infect dogs in many other countries, irrespective of breed
Incubation period
• Acute or subacute disease follows an incubation per iod which can vary from 1 week to 6 or more mon ths.
• In most patients for whom the time of exposure ca n be identified, the incubation period is between 2 a nd 6 weeks
• The length of the incubation period may be influen ced by many factors
– virulence of the infecting strain – size of the inoculum
– route of infection
Portals of entry
•
Oral entry -
most common route
– Ingestion of contaminated animal products (ofte n raw milk or its derivatives)
– contact with contaminated fingers
•
Aerosols
– Inhalation of bacteria
– Contamination of the conjunctivae
Clinical Manifestations
• The presentation of brucellosis is characteristically
variable
• The onset may be insidious or abrupt
• Influenza-like with fever reaching 38 to 40oC
– Limb and back pains are unusually severe, nigh t sweating and fatigue are marked.
– Anorexia, weakness, severe fatigue and loss of w eight, depression
– Headache
• The leukocyte count tends to be normal or reduced, with a relative lymphocytosis
– Relative leukopenia
COURSE OF BRUCELLOSIS
• If the disease is not treated, the symptoms
may continue for 2 to 4 weeks
– Many patients will then recover spontaneously
– Others may suffer a series of exacerbations
• May produce an
undulant fever
in
which the intensity of fever and
Brucellosis
•
Cyprus fever/Gibraltar fever/Malta
fever/Rock fever/Undulant fever
Undulant fever
39.5
37.0
• Most affected persons
recover entirely within
3 to 12 months
• Some will develop
complications
– involvement of various
organs,
COMPLICATIONS
• Arthritis, often sacroiliitis, and spondylitis
(i
n about 10 percent of cases)
• central nervous system involvement including
meningitis (in about 5%)
• Uveitis, epididymo-orchitis
• Endocarditis very rare
•
In contrast to animals, abortion is not a fea
Population risk
• The main source of infection for the general popula tion is dairy produce prepared from infected milk. • B. melitensis presents the greatest hazard.
• The milk of infected sheep and goats may contain l arge numbers of viable organisms, which become c oncentrated in products such as soft cheeses.
Occupational hazard
• Infection arises from occupational or domestic contact with infected animals or with an
environment contaminated by their discharges • Farmers and their families, abattoir workers,
butchers and veterinarians are particularly at risk
Extending spectrum of zoonosis
• The recent isolation of distinctive Brucella strains, t entatively named Brucella maris, from marine anim als in the United Kingdom and the United States ext ends the ecologic range of the genus and, potentially , its scope as a zoonosis
– seals, sea otters, dolphins and porpoises
• An incident of laboratory-acquired infection suggest s that this type is pathogenic for humans
Sanitary
Prevention
• Eradication of brucellosis in cattle can be attempted by t est and slaughter,active immunization of heifers with avi rulent live strain 19,combined testing,segregation, and i mmunization.Cattle are examined by means of agglutin ation tests
Treatment
• Brucella may be susceptible to tetracyclines or ampicill in.
• Symptomatic relief may occur within a few days after t reatment with these drugs is begun.
• However ,because of their intracellular location,the org anisms are not readily eradicated completely from the host.
Genus Yersinia
• Y. pestis
•
Y. enterocolitica
•
Y. pseudotuberculosis
Enterobacteriaceae
Biological Features
– Small, 0.5-0.8 μm in width 1.0-2.0 μm in length.
– Gram-negative rods.
– Sometimes appearing as cocco bacilli.
Biological Features
• Cultural Features
– Facultative anaerobes.
– Optimal growth temperature range form 28˚C to 30˚C.
– Optimal growth pH: 6.9 布 7.2.
– Growth is more rapid in media containing blood or tissue fluids.
Pathogenicity
Transmission:
Flea
Antigenic Structure
• F1 Antigen:
• V,W Antigen:
• Yersinia Outer membrane Protein (Yop)
• Murine Toxin (MT)
Y. Pestis Virulence factors schematic diagram
F1 Antigen F1 Gene
Plasmid Plasmid
Ca2+ Dependent
Gene V-W Gene
W Antigen
Pathogenesis
Y. pestis Phagocyte
Lymph Nodes
In Groin and Axilla
Enter
Respiratory System
Invade
Pneumonic Plague Bubonic Plague
Invade Blood Stream
Pathogenicity
• Clinical Forms :
– Bubonic Plague: High fever, Swelling,
Bleeding, Necrosis of lymph nodes
– Pneumonic Plague: chills, cough, respiratory
failure, circulatory collapse ——Black Death – Septicemic Plague: Fever (39-40 ˚C) , Shock ,
Y.Enterocolitica & Y.Pseudotuberculosis
• Gram negative, No capsule, No spore, Facultative a naerobes
• V 布 W antigen
• More than 50 serotypes of Y.Enterocolitica 6 serotypes of Y.Pseudotuberculosis
• Diseases:
– Gastroenteritis
– terminal ileitis, appendicitis, mesenteric lymphadenitis, – dermatitis contusiformia, arthritis
– Septicemia
Epidemiology
• Plague
– Probably originated in Asia or central Africa. – One of the earliest record pandemics occurred i
n 542 B.C.
– Three pandemics in the history.
Immunity
Cellular Immunity Humoral Immuni
ty
1) F1 Ag 2) V,W Ag Phagocytose Antibody To:
Diagnosis
•
A. Specimens:
– Aspirates of lymph nodes – Cerebrospinal fluid
– Blood – Sputum
B. Smears:
Giemsa’s stain
Diagnosis
•
C. Culture:
– All materials Cultured on blood agar and MacConkey’s agar and in infusion broth – Positive in 24 hours
– Tentatively identified by biochemical reations Definite identified by immunofluorescence
Diagnosis
• D. Serology:
In patients who have not been previously
vaccinated, a convalescent serum antibody
titer of 1:16 or greater is presumptive
evidence of Y.pestis infection.A titer rise in
two sequential specimens confirms the
Treatment
• Streptomycin
• Tetracycline:
alternative drug
combination with streptomycin
Bacillus Species
• At least 48 species are known but only
• B. anthracis and B. cereus cause defined diseases in humans.
B. anthracis is responsible for the disease anthrax.
This is a disease primarily of animals (zoonosis) but humans can
acquire via handling, inhaling or ingesting contaminated animal products.
B. cereus is predominantly responsible for food
poisoning in humans.
Bacitracin and polymyxin are two well-known
antibiotics obtained from Bacillus species.
Spores of many Bacillus species are resistant to heat, radiation, disinfectants
• It was from studies on anthrax that Koch
established his famous postulates in 1876
• Pasteur (1881) developed a vaccine against
“STICKY” Consistency of
Anthrax infections are classified
by route of entry
•
Cutaneous
•
Gastrointestinal
Cutaneous Anthrax
•
> 95% of naturally occurring cases
> 95% of naturally occurring cases
•
Spores enter breaks in skin after contact with
Spores enter breaks in skin after contact with
contaminated animal products
contaminated animal products
• After a 2- to 3-day incubation period, a small pimple or papule appears at the inoculation site.
• A surrounding ring of vesicles develops
Painless & Edema
• The lesion is painless and is surrounded by marked edema that may extend for some distance
• Pus and pain appear only if the lesion becomes infected by a pyogenic organism
Evolution of an anthrax eschar in
a 4-year-old boy
Evolution of an anthrax eschar in a 4-year-old boy.
(A&B) the lesion when first seen (day 0).Note the arm swollen from the characteristic edema.
(C) Day 6. (D) Day 10. (E) Day 15.
Although penicillin treatment was begun immediately and the lesion was sterile by a bout 24 hours,
Cutaneous anthrax
For cutaneous and gastrointestinal
anthrax, low-level germination
occurs at the primary site,
leading
Inhalation
•
Bacillus
spores are inhaled and ingested
by alveolar macrophages
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• These cells carry the bacteria to the
Gastrointestinal
• Ingestion of contaminated meat produces
systemic symptoms which can lead to death
• Mortality by gastrointestinal anthrax may
Gastrointestinal and pulmonary
anthrax are both more dangerous
than the cutaneous form
because they are usually
PATHOGENESIS
• Anthrax infections result only if the bacteria
produce a
– i) capsule (poly-y-D-glutamic acid polypeptide) – ii) exotoxins
– both encoded on plasmids
•
three proteins
• protective antigen (PA) (82. 7 kDa)
• lethal factor (LF) (90.2 kDa)
ANTHRAX TOXINS
ANTHRAX TOXINS
LF EF PA PA PA LF Host Protease HOST CELL 20 kDaThe complex (PA+LF or PA+EF) is internalized by endocytosis
acidification of the endosome the LF or EF cross the
Effects of anthrax
exotoxins on macrophages
• Edema toxin is acalmodulin 布布布布布
-dependent adenylate cyclase that increases intracellular levels of cyclic AMP (cAMP) on entry into most types of cell
• This is believed to
alter water homeostasis
Effects of anthrax
exotoxins on macrophages
• Lethal toxin is a zinc metallo-protease that
causes a hyperinflammatory condition in macrophages
– activating the oxidative burst pathway
• release of reactive oxygen intermediates – production of
proinflammatory cytokines
• responsible for shock
and death.
•Vegetative anthrax bacilli grow in the lymph node, creating regional hemorrhagic lymphadenitis
•Bacteria spread through the blood and lymph and
increase to high numbers, causing severe septicemia
•In a small number of cases, systemic anthrax can lead to
meningeal involvement by means of lymphatic or hematogenous spread
•In pulmonary anthrax, peribronchial hemorrhagic
lymphadenitis blocks pulmonary lymphatic drainage
• leading to pulmonary edema
Once they have been released from the
macrophages,
there is no evidence
Protective immunity
• Antibodies against protective antigen
• Both the noncellular human vaccines and
live-spore animal vaccines confer protection
by eliciting antibodies to protective antigen
• The poly-g-D-glutamic acid capsule of B
anthracis is poorly immunogenic, and
antibodies to the polysaccharide and other
components of the cell wall are not
Species differences
• Anthrax has been documented in a wide
variety of
warm-blooded animals
• Some species, such as rats, chickens, and
dogs, are quite resistant to the disease
• Others (notably
herbivores
such as cattle,
sheep, and horses) are very susceptible
reservoir of B anthracis is
reservoir of B anthracis is
contaminated soil
• Spores remain viable for long periods
• Herbivores, the primary hosts, become infected when foraging in a contaminated region
• Because the organism does not depend on an animal reservoir, it cannot readily be eradicated from a region
– anthrax remains endemic in many countries • Humans become infected almost exclusively
Cycle of infection in nature
• As a susceptible animal with anthrax approaches death, its
blood contains as many as 109 bacilli/ml
• Necrosis of the walls of small blood vessels during the acute phase of the illness leads to hemorrhages and to characteristic bloody exudations from the mouth, nose, and anus, a highly diagnostic sign
• These exudates carry vast numbers of the bacilli – sporulate on exposure to air
– produce a heavily contaminated environmental site – potentially capable of infecting other animals for
Handling of carcasses
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• Sporulation of B anthracis requires oxygen
– therefore does not occur inside a closed carcass – regulations in most countries forbid
postmortem examination of animals when anthrax is suspected
– The vegetative cells in the carcass are killed
• In endemic areas, animals that die suddenly should be handled cautiously
• Livestock should be vaccinated annually.
Do I look that I am going
to die
Non-Industrial vs Industrial
Anthrax
• Nonindustrial anthrax
• usually affects people who work with animals or animal carcasses
– farmers, veterinarians, butchers – almost always cutaneous
• Industrial anthrax
• acquired from handling contaminated hair, hides, wool, bone meal, or other animal products
Transmission Clinical syndrome Who is at risk
Cutaneous a nthrax
Injured skin or mucous membranes inoculated by spores from the soil or a contaminated animal or carcass
Skin infection begins as a raised itchy bump and within 1-2 days develops into a vesicle and then a painless ulcer, usually 1-3 cm in diameter, with a
characteristic black necrotic area in the center. Lymph glands in the adjacent area may swell.
People in endemic areas in contact with infected anim als of contaminated soils; people who work with ani mals materials (hides, fur, wool, hair) imported from endemic area, such as far mers, veterinarians, knack ers, butchers and laborator ians.
Intestinal anthrax
The ingestion of poorly cooked meat or milk from infected animals
Initial signs of nausea, loss of appetite, vomiting, and fever are followed by abdominal pain,
vomiting of blood, and severe diarrhea.
Pulmonary anthrax
Inhalation of spore-containing dust where animal hair or hides are being handled
Bacillus Cereus
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• B. cereus food poisoning results from the ingesti
on of preformed enterotoxins, producing predo minantly vomiting and diarrhea.
B cereus
virulence factors
• A 38 to 46-kDa protein complex has been shown in animal models: – to cause necrosis of the skin or intestinal mucosa
– to induce fluid accumulation in the intestine – a lethal toxin
• Responsible for the necrotic and toxemic nature of severe B cereus
infections and for the diarrheal form of food poisoning
Bacillus cereus also produces two hemolysins
Phospholipases produced by B cereus may act as exacerbating factors
Bacillus Food Poisoning
Two Distinct Types
• Diarrheal type• diarrhea and abdominal pain
• 8 to 16 hours after consumption of the contaminated food
• Associated with a variety of foods, including meat and vegetable dishes, sauces, pastas, desserts, and dairy products
• Emetic ～～ disease
• nausea and vomiting begin 1 to 5 hours after the
contaminated food is eaten
• Boiled rice that is held for prolonged periods at ambient
temperature and then quick-fried before serving is the
