Brucella
? The genus Brucella consists of six species,
four of which cause human brucellosis 布
鲁菌病,Brucella melitensis 羊布鲁菌,
Brucella suis 猪布鲁菌,Brucella abortus
牛布鲁菌,and Brucella canis 犬布鲁菌
? Are all intracellular organisms
? B,neotomae; B,ovis
? Brucella are small (0.4～ 0.8
× 0.5～ 1.5μ m),non-motile,
non-capasulate,gram-
negative coccobacilli,
? The organism is aerobic,
and their nutritional
requirements are complex,
? All strains grow best in a
medium enrich with animal
serum and glucose
? 5-10% carbon dioxide
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, A:M=20:1
B.melitensis,A:M=1:20
B.suis,A:M=2:1
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,Camels and Human,
B,abortus
? Sources of H uman Inf ec t i on,
R aw milk and p r oducts / Dir ec t cont ac t
? Port al o f en t r y, or a l mucos a,n as oph ary n x and
conjunctiva e,genit al t hen X in r egional ly m ph
node and s pr e ad to RE S ( nodes of udder,uter us,
ery thr itol,..), P lace ntiti s with endometrit is, F etus
die with edem a /cong e s tion of lung,dis s imen ated
hemorr hage s of epic ardium and s pleni c c aps ule,
B ac t eria in lung and di ges tive tr a ct of the f et us,
B,abortus
? B act eri a i s e xcr et e d in ge nit a l se cre t i ons
( i ncl ud i ng sem en ),m i l k,co l ost ru m,
? Surviv al t i me,
C hee s e at 4
o
C, 180 days ! ! !
Wa ter at 25
o
C, 50 days
M ea t and s alted meat,65 da ys
M anure at 12
o
C, 250 days ! ! ! !
? Wi desprea d, Ca tt le,B ison,El k,De e r,M oos e,Hor s e,
Shee p,Goat,Sw ine,Donke y,Do gs,Bi rds,H a re s,F o x,Ra ts,
m ice,C amel s a nd Hum a n.
B,melitensi s
? G oat ( 1886 ),Shee p,
C ow ( 1905 i n
Ma l t a),S w i ne,
H are s,Came l s,
B uff a l o,Im pa l a,
B,suis
? Wild p igs,Rat s,S wi n e,
? Abort ion,m e t riti s,
b u rs it is,s p on d y lit is
( L u m b ar and s acr al),
arth riti s,orc h it is,
p araly s i s,
Br ucella can i s
? Bruce l l a ca ni s w as f i r st des cribed as a cau se of
abo r t i on i n be agl es i n t he USA
? I t was sub seq uen t l y sho w n t o i nf ect dogs i n m an y
ot her cou nt r i es,i r r e spe ct i ve o f br eed
? A n oc cas i ona l ca use of br uce l l osi s i n h u m ans
Spread of Brucella in the body
Incubation period
? Acute or subacute disease follows an incubation
period which can vary from 1 week to 6 or more
months,
? In most patients for whom the time of exposure
can be identified,the incubation period is between
2 and 6 weeks
? The length of the incubation period may be
influenced by many factors
– virulence of the infecting strain
– size of the inoculum
– route of infection
– resistance of the host
Portals of entry
? Oral entry - most common route
– Ingestion of contaminated animal products
(often raw milk or its derivatives)
– contact with contaminated fingers
? Aerosols
– Inhalation of bacteria
– Contamination of the conjunctivae
? Percutaneous infection through skin
abrasions or by accidental inoculation
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,
night sweating and fatigue are marked,
– Anorexia,weakness,severe fatigue and loss of
weight,depression
– Headache
? The leukocyte count tends to be normal or reduced,
with a relative lymphocytosis
– Relative leukopenia
? On physical examination,splenomegaly may be the
only finding,
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
symptoms recur and recede at about 10
day intervals,
Brucellosis
? Cyprus fever/Gibraltar fever/Malta
fever/Rock fever/Undulant fever
U n d u l a n t f e ve r
3 9, 5
3 7, 0
? Most affected persons
recover entirely within
3 to 12 months
? Some will develop
complications
– involvement of various
organs,
– a few may enter an ill-defined
chronic syndrome,
COMPLICATIONS
? Arthritis,often sacroiliitis,and spondylitis
(in 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
feature of brucellosis in pregnant women,
LARGE JOINTS
SPONDYLITIS脊椎炎
SACROILIITIS 骶髂关节炎
Chronic Brucellosis- Depression
Population risk
? The main source of infection for the general
population is dairy produce prepared from
infected milk,
? B,melitensis presents the greatest hazard,
? The milk of infected sheep and goats may contain
large numbers of viable organisms,which become
concentrated in products such as soft cheeses,
? Indeed,soft cheese has been recognized as a
major vehicle of infection in the Mediterranean
region,the Middle East and Latin America
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
? Infected animals that have recently aborted or
given birth present the greatest hazard
Extending spectrum of zoonosis
? The recent isolation of distinctive Brucella strains,
tentatively named Brucella maris,from marine
animals in the United Kingdom and the United
States extends 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
suggests that this type is pathogenic for humans
? Infection could result from occupational contact
with infected seals or cetaceans,
CLINICAL DIAGNOSIS
Sanitary
? Pasteurization of dairy products and use of
protective clothing prevent human infection,
More importantly,systematic identification
and elimination of infected animals and
vaccination of animals reduces the reservoir,
Prevention
? Eradication of brucellosis in cattle can be attempted by
test and slaughter,active immunization of heifers with
avirulent live strain 19,combined testing,segregation,
and immunization.Cattle are examined by means of
agglutination tests
? Active immunization of humans against brucella
infection is experimental.Control rests on limitation of
spread and possible eradication of animal
infection,pasteurization of milk and milk products,and
reduction of occupational hazards wherever possible,
Treatment
? Brucella may be susceptible to tetracyclines or
ampicillin,
? Symptomatic relief may occur within a few days
after treatment with these drugs is begun,
? However,because of their intracellular location,the
organisms are not readily eradicated completely from
the host,
? For best results,treatment must be
prolonged.Combined treatment with streptomycin
and a tetracycline may be considered
YERSINIA
Genus Yersinia
? Y,pestis
? Y,enterocolitica
? Y,pseudotuberculosis
Enterobacteriaceae
Genus Escherichia
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,
– Bipolar Staining:Retaining
stain at the ends of cells,
Biological Features
? Cultural Features
– Facultative anaerobes,
– Optimal growth temperature range form 28?C
to 30?C,
– Optimal growth pH,6.9～ 7.2,
– Growth is more rapid in media containing
blood or tissue fluids,
– Nonmotile when grow at temperatures above
30 ?C,
Pathogenicity
Transmission,
Flea Respiratory Tract Bite
Antigenic Structure
? F1 Antigen,
? V,W Antigen,
? Yersinia Outer membrane Protein (Yop)
? Murine Toxin (MT)
0.3%-0.4% formaldehyde Toxoid
? Endotoxin (LPS)
Y,Pestis Virulence factors schematic diagram
F1 Antigen F1 Gene
Plasmid Plasmid
Ca2+ Dependent
Gene V-W Gene
W Antigen
V Antigen LPS
Pathogenesis
Y,pestis Phagocyte
Lymph Nodes
In Groin and
Axilla
Enter
Respiratory System
Invade
Pneumonic Plague Bubonic Plague
Invade Blood Stream
Septicemic Plague meningitis
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,
DIC
Y.Enterocolitica & Y.Pseudotuberculosis
? Gram negative,No capsule,No spore,Facultative
anaerobes
? V－ 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
? Sanitary precautions,Antibiotic
Epidemiology
? Plague
– Probably originated in Asia or central Africa,
– One of the earliest record pandemics occurred
in 542 B.C,
– Three pandemics in the history,
– 1989－ 1998,5440 cases,681 dead,
Immunity
Cellular
Immunity
Humoral
Immunity
1) F1 Ag 2) V,W Ag Phagocytose
Antibody To,
Promote phagocytose,agglutinate and kill bacteria
Diagnosis
? A,Specimens,
– Aspirates of lymph nodes
– Cerebrospinal fluid
– Blood
– Sputum
?B,Smears,
?Giemsa’s stain
?immunofluorescent 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
CAUTION,All cultures are highly infectious and must be
handled with extreme caution
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
serologic diagnosis,
Treatment
? Streptomycin
? Tetracycline,
alternative drug
combination with streptomycin
essential for control early in disease
? Sulfonamides
Summary of Yersinia infections
Bacillus
Spore-Forming Gram-Positive Bacilli,
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
and desiccation
? It was from studies on anthrax that Koch
established his famous postulates in 1876
? Pasteur (1881) developed a vaccine against
anthrax
B,anthracis Gram stain
demonstrating spores
B,anthracis,
Colony on SBA
“STICKY” Consistency of
B,anthracis’ Colony on SBA
Anthrax infections are classified
by route of entry
? Cutaneous
? Gastrointestinal
? Respiratory
Cutaneous Anthrax
? > 95% of naturally occurring cases
? Spores enter breaks in skin after contact with
contaminated animal products
? Papule丘疹 - Vesicle水泡 - Ulcer - Eschar焦痂
? Up to 20% case fatality rate if untreated
? Mortality with treatment < 1%
? After a 2- to 3-day incubation period,a small
pimple or papule appears at the inoculation
site,
? A surrounding ring of vesicles develops
? Over the next few days,the central
papule ulcerates,dries,and blackens
to form the eschar
Vesicles & Black Eschar
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
? Similarly,marked lymphangitis淋巴管炎 and fever usually
point to a secondary infection,
Evolution of an anthrax eschar in
a 4-year-old boy
DAY 6
DAY 10 - 15
?
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
about 24 hours,
it continued to evolve and resolve as seen,
Cutaneous anthrax
Differential diagnosis
Ect hy ma gan gre no sum
Rat - bit e fe ver
Ul cero gla nd ula r tu lare mi a
Pl agu e
Gl and ers
Rick ett sialp ox
Orf
St aph ylo cocc al l ym ph aden iti s
Cut aneo us t ub ercu losi s
Lep rosy
Bur uli ul cer
Pseu do mo na s aeru gin osa
Stre pto ba cil lus mo nil ifo rmis,
Sp iril lum mi no r
Fra nci sella tu l aren sis
Ye rsini a p estis
Pseu do mo na s pseu do ma lle i
Ri cket tsia aka ri
Pa rap ox vir us
Sta ph ylo cocc us a ureu s
My ocb act eriu m t ub ercul osis
My cob act eriu m l epra e
My cob act eriu m u lcera ns
Cutaneous anthrax
?For cutaneous and gastrointestinal
anthrax,low-level germination occurs at
the primary site,leading to local edema
and necrosis
Inhalation
? Bacillus spores are inhaled and ingested by
alveolar macrophages肺泡巨噬细胞
? These cells carry the bacteria to the
regional lymph nodes,causing necrotic
hemorrhaging which leads to death
Gastrointestinal
? Ingestion of contaminated meat produces
systemic symptoms which can lead to death
? Mortality by gastrointestinal anthrax may be
50%
Gastrointestinal and pulmonary
anthrax are both more dangerous
than the cutaneous form
because they are usually
identified too late for treatment
to be effective
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)
? edema factor (EF) (88.9 kDa)
ANTHRAX TOXINS
LF
EF
PA
PA
PA
LF
Host
Protease
HOST CELL
20 kDa
The complex (PA+LF or
PA+EF) is internalized by
endocytosis
acidification of the endosome
the LF or EF cross the
membrane into the cytosol via
PA-mediated ion-conductive
channels
Effects of anthrax
exotoxins on macrophages
? Edema toxin is a
calmodulin钙调节蛋白 -
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
– resulting in massive
edema
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,
? MAPKK denotes mitogen-
activated protein kinase
kinase
?Endospores
are
phagocytosed
by macrophages
and germinate
?Macrophages
containing
bacilli detach
and migrate to
the regional
lymph node,
?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
?High levels of exotoxins are produced that are
responsible for overt symptoms and death,
?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
Death results from septicemia,toxemia,or pulmonary
Once they have been released from the
macrophages,there is no evidence that an
immune response is initiated against
vegetative bacilli
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
protective,
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
? Humans have intermediate susceptibility,
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
through contact with infected animals or animal
products
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
many years
Handling of carcasses动物尸体
? 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 a few days by the process of putrefaction,
? 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
– higher chance of being pulmonary as a result of the inhalation of
spore-laden dust
Transmission
Clinical syndrome Who is at risk
Cutaneous
anthrax
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
animals of contaminated
soils; people who work
with animals materials
(hides,fur,wool,hair)
imported from endemic
area,such as farmers,
veterinarians,knackers,
butchers and laboratorians,
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
begins abruptly with high
fever and chest pain,
progresses rapidly to a
systemic hemorrhagic
pathology
Bacillus Cereus蜡样芽胞杆菌
? B,cereus food poisoning results from the
ingestion of preformed enterotoxins,producing
predominantly vomiting and diarrhea,
? The vomiting form is most often associated
with ingestion of a heat stable toxin from
contaminated rice,while the diarrheal form is
most often associated with ingestion of a heat
labile toxin from contaminated meat or
vegetables
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
by degrading host cell membranes following exposure of their
phospholipid substrates in wounds or other infections
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呕吐 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
usual offender,although dairy products or other foods are
occasionally responsible,
