Gram-negative facultative anaerobe rods (Enterobacteriaceae)

Gram-negative facultative
anaerobe rods
(Enterobacteriaceae)
Dr. Dóra Szabó
Assistant Professor
Semmelweis University
Institute of Medical Microbiology
Gram-negative facultative anaerobic rods
(Positive glucose fermentation)
Oxidase positive Oxidase negative
Vibrioneceae Aeromonadaceae
Vibrio Plesiomonas
Aeromonas
Facultative
pathogenic
Escherichia
Klebsiella
Enterobacter
Proteus
Serratia
Providencia
Morganella
Edwardsiella
Citrobacter
Hafnia
Enterobacteriaceae
Obligate
pathogenic
Salmonella
Shigella
Yersinia
1

Salmonellae
The genus Salmonella was named after
Daniel Elmer Salmon, an American veterinary
pathologist.
While Theobald Smith was the actual
discoverer of the bacteria that causes hog
cholera (Salmonella enterica var.
Choleraesius)
Salmon was the administrator of the USDA
research program and thus the organism was
named after him.
2

Salmonella classification
Classification has been changing in the last few years. Based on
genetic backgound, there two species
S. enteritica, and 7 subspecies: 1, 2 ,3a ,3b ,4 ,5, and 6.
S. bongori
- S. enteritica subgroup 1has only medical importance
- The other subspecies and S. bongori are the parasites of
vertabrae
- 1500 serotypes belong to S. enteritica subgroup 1
- Only cc 12 responsible for most of the human infections
- Earlier these serotypes had their own name: for example: S.
enteritidis, S. typhimurium, S. typhi
Phase variation of Salmonella
3

Biochemistry and serology
Clinically Salmonella isolates are often still reported out as serogroups or
serotypes based on the Kauffman-White scheme of classification.Based
on O and H (flagella) antigens.
O antigens
O antigens are vary variable
Mozaik stucture
Epitop combination, special antigens of the isolate
The H (flagella) antigens
H antigens has a mozaik structure as well
occur in two phases; 1 and 2 and only 1 phase is expressed at a given
time
Polyvalent antisera is used followed by group specific antisera (A, B, C1, C2,
D, and E)
Salmonella typhi also has a Vi antigen which is a capsular antigen.
For serotyping
To determinate the O antigen
To deteminate H (flagella) antigen
To detect the presence or absence Vi antigen
Salmonella
Biochemistry
TSI K/A + gas and H 2 S: S. typhi produces only a
small amount of H 2 S and no gas , and S. paratyphi A
produces no H 2 S
Urea –
Motility +
Citrate +/-
Indole -
4

Salmonella virulence factors
Type III secretion systems and effector molecules – 2
different systems may be found:
One type is involved in promoting entry into intestinal
epithelial cells
The other type is involved in the ability of Salmonella to
survive inside macrophages
Outer membrane proteins - involved in the ability of
Salmonella to survive inside macrophages
Flagella – help bacteria to move through intestinal
mucous
Enterotoxin - may be involved in gastroenteritis
Iron capturing ability
Endotoxin – may play a role in intracellular survival
Capsule (for S. typhi and some strains of S. paratyphi)
Adhesions – both fimbrial and non-fimbrial
Host specificity
Wide host specificity
normal flora in the GI of animal
in human can cause gastroenteritis; zoonosis
S. enteritidits S. typhimurium
Adapted to animal
Serious infection in animal
focal infection in human (mainly kids)
S. cholerasuis
Adapted to human
only in human
S. typhi, S. paratyphi A, B, and C
5

Clinical Significance
Gastroenteritis.
the Salmonella multiply and their presence induces a strong
inflammatory response which causes most of the symptoms seen in
gastroenteritis (mild to moderate fever with diarrhea and abdominal
cramps).
The inflammatory response prevents the spread beyond the GI tract
and eventually kills the bacteria.
Enteric fevers
In enteric fevers (typhoid and paratyphoid) the Salmonella
disseminate before they multiply to high enough levels to stimulate a
strong inflammatory response so the initial symptoms are only a lowgrade
fever and constipation.
GASTROENTERITIS
6

Salmonella-gastroenteritis
Clinical picture
18-48 hours incubation
GASTROENTERITIS, but can be:
dizziness
vomiting
Abdominal pain
The symptoms can be similar to dysentery
The symptoms moderate in a few days
spontan recovery in a week
INVASIVE INFECTION
Sepsis
Meningitis
in very young, or very old, as well as immunocompromised patients
7

Salmonella-gastroenteritis
Epidemiology
The most common cause of foodpoisoning
More than 15 000 know cases per year in Hungary
1-10% of the real cases
Increasing incidence
ZOONOSIS!!
Reservoirs:
Chicken –and duck eggs
Chicken and swine
Insufficient heat treatment is necessary
Salmonella-gastroenteritis
Pathogenesis I.
Mechanism
Bacteria adhere to the epithelial cells
Membrane ruffles will be evolved
The cell incorpotare the bacteria
The role of enterotoxins are not
confirmed
Increased secration because of the
local inflammation
The strains habouring a big plasmid
The size is specific for serotype
Coding serumresistance and survival
in phagocytes
Role in gastroenteritis is not confimed
Role in invasive infections
8

Salmonella-gastroenteritis
Pathogenesis II.
Transient bacteraemia can occur
Permanent bacteraemia:
Very old patient
Very young patient
Immunsuppressed and AIDS patient
Focal infections can occur
lung
brain
In atherosclerotic plaque of aorta
prothesis
Salmonella-gastroenteritis
Pathogenesis III.
Asymptomatic carriers
After recovery carrier status
That patient can be a source of infection later
9

Special characteristics of S.
cholerasuis
The general properties are similar to the
other Salmonella species
S. cholerasuis is tend to cause septic clinical
picture
Microbiological diagnosis
Clinical specimen:
faeces : positive from first week, and may remain + for several weeks
blood for blood-culture: just in 2-4 % (+)
CSF, and food leftover
Direct smear has no value in the diagnosis.
Culture:
Samples are inoculated onto brilliant green and/or bismuth sulphite
selective media.
10

Brillant-green culture media
brillant green – for selection
lactose, dextrose, sacharose
Andrade indicator
(acidic pH → -
Salmonella lactose neg.– no colour
- E. coli lactose+ - red)
Bismuth-sulphite
brillant green – for selection
bismuth salt + sodium sulphite
→ Salmonella H2S production
⇒ Bismuth sulphide (black)
Microbiological diagnosis
n Biochemical identification: (refer to
flow charts) Lactose (-), dextrose
fermentation w/o gas formation, H2S (+)
n Serological identification:
Slide agglutination with specific
antibodies
11

Epidemiological investigations
For strain with similar biochemical and
serological pattern!
Phag typing
Molecular methods
PCR-s (arbritary primed (AP)-PCR, ERIC-PCR)
Pulse-field gel-electrophoresis PFGE
rRNS sequencing
Phage typing
n phage typing of a strain of
Salmonella is done in
epidemiological studies
n the surface of the plate is
inoculated with a broth
culture
n a number of phages are
spotted on the plate
n after incubation the phage
type is determined by the
pattern of lyses
12

Pulde field gel electrophoresis (PFGE)
Therapy
The vast majority of enterocolitis cases do not require
an antibiotic treatment.
After antibiotic treatment carrier status occurs more
frequently.
Antimicrobial treatment of Salmonella infection of
neonates, as well as invasive salmonella infections is
important.
ampicillin
sulfomethoxazole + trimethoprim
fluoroquinolons
3rd generation cephalosporins
susceptibility tests are important
13

1984 Rajneeshee bioterror attack
1984 Rajneeshee bioterror attack
The 1984 Rajneeshee bioterror attack was the food poisoning
ímore than 750 individuals in The Dalles, Oregon, United States
through the contamination of salad bars at ten local restaurants with
salmonella.
A leading group of followers of Osho, then known as Bhagwan
Shree Rajneesh, had hoped to incapacitate the voting population of
the city so that their own candidates would win the 1984 Wasco
County elections.
The incident was the first bioterrorism attack in the United States,
and the single largest bioterrorist attack in United States history.
The attack is one of only two confirmed terrorist uses of biological
weapons to harm humans.
14

Seven hundred and fifty one people
contracted salmonellosis as a result of the
attack, of whom 45 were hospitalized.
There were no fatalities.
Although an initial investigation by the
Oregon Public Health Division and the
Centers for Disease Control did not rule out
deliberate contamination, the actual source of
the contamination was only discovered a year
later.
Enteric fever
15

Salmonella typhi, S. paratyphi A, B, C
gripsdb.dimdi.de
Human pathogen
Antigen
O
H
Vi Ag
Salmonella typhi, S. paratyphi A, B, C
Figure 1. Salmonella typhi, the agent
of typhoid. Gram stain. (CDC)
www.textbookofbacteriology.net
Figure 2. Flagellar stain of a Salmonella
Typhi. Like E. coli, Salmonella are motile
by means of peritrichous flagella. A close
relative that causes enteric infections is
the bacterium Shigella. Shigella is not
motile, and therefore it can be
differentiated from Salmonella on the bais
of a motility test or a flagellar stain. (CDC)
16

Thyphoid fever
caused by S. typhi
a S. paratyphi A, B and C cause the
paratyphus
Milder disease
The source is always human!!
Pathogenesis
First period is the PRIMER BACTERAEMIA
After oral infection the incubation period is two
weeks
Bacteria get through mucosa via the M cells of Peyer
plaques
Infect the local macrophages
S. typhi has no serotype-specific plasmid
Chromosomal genes for survival in
macrophages
Macrophages deliver the bacteria to the mesentarial
lymph nodes
Through the ductus thoracicus and blood stream the
bacteria get to spleen, liver, kidney, lung
The CFU is low
The patient is asymptomatic or subfebrile
SECUNDER BACTERAEMIA
Bacteria multiply in RES
Mainly in Kupffer-cells
Getting out the bactera there is a bacteraemia with
high CFU
Perforation of the terminal ileum and proximal colon
Through bile back to the intestine multiplication in the Payer’s
patches ulceration → bleeding → perforation
Permanent carrier stage
From bile
17

Salmonella
The bacteria move via the lymphatics and bloodstream to the
liver and spleen where phagocytosis and multiplication occurs.
The bacteria re-enter the bloodstream to disseminate throughout
the body to all organs causing fever, headaches, myalgia, and
GI problems.
Rose spots (erythematous, muculopapular lesions) are seen on
the abdomen. Osteomyelitis, cystitis, and gall bladder infections
may occur.
Symptoms of paratyphoid fevers (due to S. paratyphi A, B, or C)
are similar to but less severe than those that occur with typhoid
fever (due to S. typhi)
Clinical signs
headache
fever
Very high in a few days
The sense is typhosus
relative bradycardia
hepatosplenomegalia
Gastroenteritis is NOT characteristic
Roseolas on the chest and abdomen
Blood is characteristic
leukopenia
aneosinophilia
lymphocytosis
18

Typhoid fever (a: petechia, Peyer plaque(b) and necrosis
of the ileum (c), d: perforation of the Peyer-plaque
Typhus abdominalis
Τψπηυσ Τψπηυσ αβδοµιναλισ
gripsdb.dimdi.de
19

Rose spots on abdomen of a patient with typhoid fever
due to the bacterium Salmonella typhi. www.wrongdiagnosis.com
Rose spots on the chest of a patient with typhoid fever
due to the bacterium Salmonella typhi. www.wrongdiagnosis.com
20

Fig. 4.37 Typhoid fever. Numerous ulcers of the small intestine
overlying hyperplastic lymphoid follicles (Peyer’s patches). By courtesy
of Dr. J. Newman.
Fig. 4.39 Typhoid fever. Mononuclear cells and red blood cells in the
stool. Trichrome stain. By courtesy of Dr. H.L. DuPont.
21

Microbiological diagnosis
Clinical specimen:
faeces: positive from the second or third weeks
urine : positive from the second week
bile, bone marrow aspirate
blood for blood-culture : often positive in the first week
Direct smear has no value in the diagnosis.
Culture:
Samples are inoculated onto brilliant green and/or bismuth sulphite
selective media.
Biochemical identification: (refer to flow charts) Lactose
(-), dextrose fermentation w/o gas formation, H2S (+)
Serological identification:
Slide agglutination with specific antibodies to show
presence of S. typhi cells in the culture.
22

Blood serology:
=> Gruber-Widal reaction (Widal`s type tube agglutination): (Ag =
'H' as well as 'O' antigens of the laboratory strain of S. typhi) to
show presence and establish titre of specific antibodies in the
patients` sera.
Treatment
Antibiotics according to susceptibility tests: S. typhi strains are usually susceptible
to
ampicillin,
sulfomethoxazole + trimethoprim,
3rd generation cephalosporins.
Prevention
Specific sanitary measures and control of chronic carriers.
Active immunisation with acetone killed bacterial suspension administered
parenterally is available for high-risk individuals.
An orally administered vaccine of a live avirulent mutant of S. typhi also provides
significant protection.
“Carriers”
3 % of survivors of typhoid become permanent carriers, harboring the organisms
in the gallbladder, biliary tract or urinary tract.
23

Geographical distribution of
the typhoid fever
24

E. coli intestinal infections
Gastroenteritis – there are several
distinct types of E. coli that are
involved in different types of
gastroenteritis:
enterotoxigenic E. coli (ETEC),
enteroinvasive E. coli (EIEC),
enteropathogenic E. coli (EPEC) ,
enteroaggregative E. coli (EAEC),
and
enterohemorrhagic E. coli (EHEC).
ETEC – enterotoxigenic E. coli
Pathogenesis
The organism attaches to the intestinal mucosa
(mainly in small intestine) via colonization factors
(CFA) and then liberates enterotoxin.
Specific to human small intestine
like CFA I, II, III
Structure: :
fimbria
fibrilla
afimbria adhezin
Good antigens, the antibody
Imhibit the adhesion
Good for detection
Enterotoxins – produced by enterotoxigenic strains of
E. coli (ETEC). Causes a movement of water and ions
from the tissues to the bowel resulting in watery
diarrhea. There are two types of enterotoxin:
LT – is heat labile and binds to specific Gm 1
gangliosides on the epithelial cells of the small
intestine where it ADP-ribosylates Gs which stimulates
adenylate cyclase to increase production of cAMP.
Increased cAMP alters the activity of sodium and
chloride transporters producing an ion imbalance that
results in fluid transport into the bowel.
ST – is heat stable, affects the cGMP system.
25

E. coli gastroenteritis
ETEC – enterotoxigenic E. coli
Clinical picture
In developing countries the most common cause of
diarrhea of young kids, less than two years
is a common cause of traveler’s diarrhea
The diarrhea is severe, cholera-like
The disease is characterized by a watery diarrhea,
nausea, abdominal cramps and low-grade fever for
1-5 days.
Transmission is via contaminated food or water.
No specific histology
E. coli gastroenteritis
ETEC – enterotoxigenic E. coli
Diagnostic
Serotyping is not good for diagnostis, lots of
serotype
In vivo animal study
LT in rabbit
ST in newborn mice
Not routine
LT-sensitive cell culture
ELISA for LT and ST
Molecular biology methods for toxins or CFA :
hybridization or PCR
26

Enteropathogenic E. coli (EPEC)
The diarrhea with large amounts of mucous
without blood or pus occurs along with
vomiting, malaise and low grade fever.
Age-specific: just under 1 year old
Adults can be infected with high dose
In developing countries
20 % of diarrheae in hospitalized infants
In fifties, sixties outbreaks is developed countries
Only sporadic
EPEC – enteropathogenic E. coli
Bundle forming pili are involved in
attachment to the intestinal
mucosa.
This leads to changes in signal
transduction in the cells,
effacement of the microvilli, and
to intimate attachment via a nonfimbrial
adhesion called intimin.
The exact mode of pathogenesis
is unclear, the
secretion/absorbtion ratio
changes
27

Enteroinvasive E. coli (EIEC)
The organism attaches to the intestinal mucosa via pili and outer membrane proteins
are involved in direct penetration, invasion of the intestinal cells, mainly in the colon,
and destruction of the intestinal mucosa.
There is lateral movement of the organism from one cell to adjacent cells.
Symptoms include fever,severe abdominal cramps, malaise, and diarrhea followed
by scanty stools containing blood, mucous, and pus.
Virulence genes similar to Shigella
220 kb size virulence plasmid similar to Shigella’s
Biochemistry is similar biokémiai reakciók is hasonlítanak a Shigellákéhoz
O antigens crossreaction
Lactose negative, lysin negative, non-motile
Infective dosis is higher than Shigella’s
Outbreaks were reported
Enteroinvasive E. coli (EIEC)
Diagnostic
15 serotypes
Virulence tests
Serény-test (Shigella)
HeLa-sejt invasion test
ELISA for virulence specific antigens
Molecular biology tests for virulence plasmids
28

Enterohaemorrhagiás E. coli (EHEC)
Epidemiology
In 1982 first case
Most common reason of bloody diarhheae in
developed countries
Calves’s diarrheae or asymptomatic in
animals
Low infective dose, contact persons are
source of infections
Enterohaemorrhagic E. coli (EHEC)
Clinical picture
In mild cases gastroenteritis
Severe colitis
Bloody diarrheae
NOT CHARACTERISTIC:
fever
Mucopurulent secretion
10%
children hemolitic uraemic syndrom (HUS)
Adults with kidney problems
thrombotics trombocytopenic purpura (TTP)
29

Enterohaemorrhagiás E. coli (EHEC)
Pathogenesis
The organism attaches via pili to the intestinal
mucosa and liberates the shiga-like toxin Adhesion
molecule similar to EPEC BFP
AE mechanisms of EPEC
Citotoxins as virulence factors coding by temperated
phages
lizogen konversion
Toxic effect on Vero-cells
Two toxin, one of them is similar to Shiga toxin
Shiga-like toxinoks (SLT)
Enterohaemorrhagiás E. coli (EHEC)
Shiga-like toxinok
Two types: SLT-I AND -II
AB-toxinS
B subunit responsible for adhesion to capillarendothel
A subunit by inhibiting EF-1 blokks the protein
synthesis
Capillar damage
Bloody stool
hemolysis, anaemia
Kidney failure, uraemia
Central nervus system signs
30

E. coli gastroenteritis
enterohemorrhagic E. coli (EHEC).
This is most often caused by serotypes O157:H7.
This strain of E. coli can be differentiated from other strains of E. coli by
the fact that it does not ferment sorbitol in 48 hours (other strains do).
A sorbitol-Mac (SMAC) plate (contains sorbitol instead of lactose) is used
to selectively isolate this organism.
One must confirm that the isolate is E. coli O1547:H7 using serological
testing and confirm production of the shiga-like toxin before reporting out
results.
E. coli gastroenteritis
enteroaggregative E. coli (EAEC),
EAEC – Mucous associated autoagglutinins cause aggregation
of the bacteria at the cell surface and result in the formation of a
mucous biofilm.
Enteroaggregative ST-like toxin – produced by
enteroaggregative strains of E. coli (EAEC) – causes watery
diarrhea.
The organisms attach via pili and liberate a cytotoxin distinct
from, but similar to the ST and LT enterotoxins liberated by
ETEC.
Symptoms include watery diarrhea, vomiting, dehydration and
occasional abdominal pain.
31

E.coli
Antimicrobic therapy- E. coli is usually susceptible
to a variety of chemotherapeutic agents,
Though drug resistant strains are increasingly
prevalent.
It is essential to do susceptibility testing.
Summary of E.coli strains that cause gastroenteritis.
32

Shigella genus
Contains four species that differ antigenically and, to a lesser
extent, biochemically.
Serogroup A: S. dysenteriae (12 serotypes)
Serogroup B: S. flexneri (6 serotypes)
Serogroup C: S. boydii (23 serotypes)
Serogroup D: S. sonnei (1 serotype)
OBLIGATE HUMAN PATHOGEN
33

Shigella species
Antigenic structure
Differentiation into groups (A, B, C, and D) is based on
O antigen serotyping; K antigens may interfere with
serotyping, but are heat labile.
O antigen is similar to E. coli, so it is important to ID as
Shigella before doing serotyping.
Virulence factors
Shiga toxin – is produced by S. dysenteriae and in
smaller amounts by S. flexneri and S. sonnei.
Acts to inhibit protein synthesis by inactivating the
60S ribosomal subunit by cleaving a glycosidic
bond in one of the rRNA constituents.
This plays a role in the ulceration of the intestinal
mucosa.
Shigella species
Outer membrane and secreted proteins
These proteins are expressed at body
temperature and upon contact with M cells
in the intestinal mucosa they induce
phagocytosis of the bacteria into vacuoles.
Shigella destroy the vacuoles to escape
into the cytoplasm.
From there they spread laterally
(Polymerization of actin filaments propels
them through the cytoplasm.) to epithelial
cells where they multiply but do not usually
disseminate beyond the epithelium.
34

Shigella biochemistry and
serology
relative inactive
Lactose-negative
Aexcept S. sonnei
Slowly in some days
Non-motile
Lost of serotypes in S. dysenteriae, S. flexneri and S. boydii species
Based on O antigen
Public health importance
Important S. dysenteriae I-es típusa
Toxin production (Shiga-toxin)
Ressistant to antibiotics and can ause outbreaks
S. sonnei has onyl one O antigen: phase I
Encoded by virulence plasmid
With no virulence plasmid, no O antigens
Roughy colonies
Phase II
Shigella
Clinical significance
Causes shigellosis or bacillary dysentery.
Transmission is via the fecal-oral route.
The infective dose required to cause infection is very low (10-
200 organisms).
There is an incubation of 1-7 days followed by fever, cramping,
abdominal pain, and watery diarrhea (due to the toxin)for 1-3
days.
This may be followed by frequent, scant stools with blood,
mucous, and pus (due to invasion of intestinal mucosa).
It is rare for the organism to disseminate.
The severity of the disease depends upon the species one is
infected with.
S. dysenteria is the most pathogenic followed by S. flexneri, S.
sonnei and S. boydii.
35

Fig. 4.34 Shigellosis.
Sigmoidiscopic view of colonic
mucosa in a fatal case of
infection with S. dysenteriae
type 1 showing extensive
pseudomembranous colitis. By
courtesy of Dr. R.H. Gilman
and Dr. F. Koster.
Fig. 4.33 Shigellosis.
Sigmoidiscopic view of colonic
mucosa in a mild case of infection
due to S. flexneri. Note the thin
whitish exsudate, which is made up
of fibrin and polymorphonuclear
leucocytes. By courtesy of Dr. R.H.
Gilman.
36

Shigella boydii
Blood agar
Microbiological diagnosis
Clinical specimen: faeces, food
leftover
Direct smear has no diagnostic
value
Culture:
Eosine-methylenblue agar
small, round-shaped, colourless
colonies (lactose -)
Desoxycholate-citrate agar ⇒
containing desoxycholic acid,
sodium citrate, lead acetate,
ferrous ammonium sulfate,
lactose, and neutral red
indicator
Shigellae: small, round-shaped,
colourless colonies (lactose -,
H2S-).
www.biologie.de
38

Appearance of Colonies on Salmonella-Shigella Agar
D: Proteus mirabilis
Shigella Shigella
Shigella
Selective –
differentiating
media
www.textbookofbacteriology.net
A. Klebsiella pneumoniae
B. Escherichia coli
Klebsiella pneumoniae &
Escherichia coli are positive
for acid production from
fermentation of the
carbohydrate(s) present.
C: Salmonella sp.
Both Salmonella
sp. & Proteus
mirabilis product
hydrogen sulfide.
The Pseudomonas colonies are nearly colorless.
www.rci.rutgers.edu
E: Pseudomona aeruginosa
39

Fig. 4.18 Positive Serény test. Keratoconjunctivitis in the rabbit
produced by the instillation of shigella microorganism. By courtesy of
Dr. H.L. DuPont.
Shigella
Antimicrobial therapy
Sulfonamides are commonly used as are
streptomycin, tetracycline, ampicillin, and
chloramphenicol.
Resistant strains are becoming increasingly common,
so sensitivity testing is required.
40

Yersinia
Three species are important pathogens in human
Yersinia pestis – causes plague
Yersinia enterocolitica – enteropathogenic
Yersinia pseudotuberculosis – enteropathogenic
41

Yersinia pestis
nonenteric
tiny, gram-negative rod, unusual bipolar
staining & capsules
virulence factors – capsular & envelope
proteins protect against phagocytosis & foster
intracellular growth
coagulase, endotoxin, murine toxin
Yersinia pestis bipolar staining
42

Yersinia pestis Wayson’s stain
Yersinia species
TSI K/A no gas
LIA K/A
Urea –
Guinea pig or mouse pathogenicity studies:
LD 50

Y. pestis
Y. pestis – clinical significance
In man plague occurs in two forms; bubonic and pneumonic
Bubonic plague – transmitted by fleas from an infected rodent (is
endemic in our local mountains).
The bacteria travel in the blood to the nearest lymph node where
they are engulfed by fixed macrophages.
A high fever develops and the lymph nodes in the groin and armpit
become enlarged (buboes) as the bacteria proliferate and stimulate
an inflammatory response.
The bacteria growing in the lymph node leak into the bloodstream.
Lysis of the bacteria releases LPS, causing septic shock.
Subcutaneous hemorrhages , probably due to LPS causing DIC gave
the disease the name, the black death, in the middle ages.
The untreated mortality rate is quite high.
Y. pestis
44

Pathology of plague
3-50 bacilli
bubonic – bacillus multiplies in flea bite, enters lymph,
causes necrosis & swelling called a bubo in groin or
axilla
septicemic – progression to massive bacterial growth;
virulence factors cause intravascular coagulation
subcutaneous hemorrhage & purpura – black plague
pneumonic – infection localized to lungs, highly
contagious; fatal without treatment
treatment: streptomycin, tetracycline or
chloramphenicol
Killed or attenuated vaccine
Buboes
45

Y. enterocolitica growth on CIN
Yersinia species
Yersinia enterocolitica and Y. pseudotuberculosis – clinical significance
Both are acquired by ingestion of contaminated food or water.
Reservoirs : rodents, domestic animals
Y. enterocolitica is a common cause of human disease, whereas, Y.
pseudotuberculosis is mainly a disease of other animals.
Both cause a disease involving fever and abdominal pain. Y.
enterocolitica also causes a bloody diarrhea.
After ingestion, the bacteria invade the intestinal epithelium by invasion of
M cells.
They are transcytosed through the M cells and released at the basal
surface.
Once through the intestional epithelium, the bacteria penetrate into the
underlying lymphoid tissue, where they multiply both inside and
outside host cells.
46

Yersinia species
Multiplication of the bacteria produces an inflammatory
response that is responsible for the extreme pain
associated with the infections (resembles acute
appendicitis)
Fever is due to the activity of the LPS endotoxin.
Sometimes they drain into adjacent mesenteric lymph
nodes, causing mesenteric lymphadenitis.
Immuncomplex formation reactive arthritis, spondylosis
ankylopetica, erythema nodosum may occur in some
people following Y. enterocolitica infection.
It is thought to be due to cross reacting T cells or
antibodies that attack the joints.
- Rare septic case: pneumonia, meningitis
Yersinia Yersinia Yersinia Yersinia enterocolitica
enterocolitica
enterocolitica
enterocolitica
Morphology Gram-negative,
Bipolar rods
www.wadsworth.org
47

Laboratory diagnosis
Sample to be taken: faeces, blood for blood culture,
materials obtained at surgical exploration.
Direct smear: not contributory to the diagnosis.
Culture:
On blood agar at 28 C, aerobically, for 24 hours → colonies
are tiny, round shaped, greyish.
"cold enrichment" (faeces is incubated in buffered, pH 7.6,
saline at 4 oC, for 2 weeks) then inoculated onto
MacConkey agar, or eosine-metyleneblue medium →
colonies are tiny, round shaped and colourless.
Yersinia Yersinia Yersinia Yersinia enterocolitica
enterocolitica
enterocolitica
enterocolitica
www.szu.cz
Véres agar
Blood agar
Blutagar
www.ktl.fi
Y. enterocolitica
O:5,27 CIN-ag
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Y. enterocolitica
Biochemical identification:
lactose (-), but ONPG (+), urease (+), oxidase (-)
Serological identification:
Slide agglutination to identify cultures with specific
antibodies (test serum) based on the 'O' -antigen.
Blood serology:
Tube agglutination (ag = formalin inactivated bacteria) to
show specific antibodies in patients’ serum.
de.wikipedia.org
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•Treatment
In mild diarrhea disease is self-limited, the
benefit of antibiotic therapy is unknown.
In severe cases (sepsis, meningitis), antibiotic
treatment should be started as soon as possible with
3rd generation cephalosporins in combination with
aminoglycosides or with fluoroquinolones.
Prevention
No specific preventive measures are available.
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