Genus Salmonella - Biology - Lecture Slides, Slides for Biology. Agra University

Biology

Description: Genus Salmonella, Foodborne Disease, Faculatively Anaerobic, Oxidase Negative, Glucose Fermentative, Generally Motile, Biochemical Characteristics, Lactose Negative, Urease Negative, Heat Resistance describes lecture layout.
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1
Microorganisms Causing
F
oodbo
rne Dise
a
se
Microorganisms Causing
F
oodbo
rne Dise
a
se
oodbo aoodbo a
Enterobacteriaceae
Family
Genus
Salmonella
Enterobacteriaceae
Family
Genus
Salmonella
Family
Enterobacteriaceae
Family
Enterobacteriaceae
•Gram-negative
Non-sporeforming rods
Faculatively anaerobic
•Gram-negative
Non-sporeforming rods
Faculatively anaerobic
Faculatively
anaerobic
Oxidase negative
Glucose fermentative
Generally motile
Faculatively
anaerobic
Oxidase negative
Glucose fermentative
Generally motile
Peritrichous flagella
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2
SalmonellaSalmonella
Named after Dr. D. E. Salmon
First described
Salmonella cholerae-suis
Currently only 2 species are recognized
S. bongori
S
enterica
Named after Dr. D. E. Salmon
First described
Salmonella cholerae-suis
Currently only 2 species are recognized
S. bongori
S
enterica
S
.
enterica
6 subspecies
»
enterica
»
salamae
»
arizonae
»
diarizonae
»
houtenae
»
Indica
S
.
enterica
6 subspecies
»
enterica
»
salamae
»
arizonae
»
diarizonae
»
houtenae
»
Indica
Principal biochemical characteristicsPrincipal biochemical characteristics
• Lactose negative
• Lysine decarboxylase positive
•H
2S positive
• Lactose negative
• Lysine decarboxylase positive
•H
2S positive
0.8% of strains can ferment lactose
• A few strains do not produce H2S
0.8% of strains can ferment lactose
• A few strains do not produce H2S
SalmonellaSalmonella
Salmonellae are separated in somatic
groups (O antigens) and flagellar types
(H antigens)
About 2,400 serovars (or serotypes)
have been described
Salmonellae are separated in somatic
groups (O antigens) and flagellar types
(H antigens)
About 2,400 serovars (or serotypes)
have been described
have
been
described
Example of correct nomenclature:
Salmonella enterica
subsp. e
nterica
serovar
Typhimurium
Abbreviated:
Salmonella
Typhimurium
• After having defined by full name
Also there is a phage-based classification
Phage types
have
been
described
Example of correct nomenclature:
Salmonella enterica
subsp. e
nterica
serovar
Typhimurium
Abbreviated:
Salmonella
Typhimurium
• After having defined by full name
Also there is a phage-based classification
Phage types
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Growth characteristicsGrowth characteristics
• Temperature
– Minimum 7°C
– Maximum 47°C
– Optimum 37°C
p
H
• Temperature
– Minimum 7°C
– Maximum 47°C
– Optimum 37°C
p
H
p
– Minimum
• Acetic acid 4.7
• HCl 4.05
–Optimum 7.0
a
w
Minimum 0.93
p
– Minimum
• Acetic acid 4.7
• HCl 4.05
–Optimum 7.0
a
w
Minimum 0.93
Heat resistanceHeat resistance
• Non-thermoduric
S.
Senftenberg 775W is heat resistant
–D
71 in milk = 0.09 min
D
f
S
T hi i i ilk 0 003 i
• Non-thermoduric
S.
Senftenberg 775W is heat resistant
–D
71 in milk = 0.09 min
D
f
S
T hi i i ilk 0 003 i
D
71
f
or
S
.
T
yp
hi
mur
i
um
i
n m
ilk
=
0
.
003
m
i
n
Heating mestruum affects heat resistance
–D
70 for
S.
Typhimurium in chocolate sauce =
11.3 – 17.5 h.
D
71
f
or
S
.
T
yp
hi
mur
i
um
i
n m
ilk
=
0
.
003
m
i
n
Heating mestruum affects heat resistance
–D
70 for
S.
Typhimurium in chocolate sauce =
11.3 – 17.5 h.
EcologyEcology
• Most salmonellae infect a wide range
of animal species
• Some serovars are host adapted
• Most salmonellae infect a wide range
of animal species
• Some serovars are host adapted
S.
Enteritidis PT4,
S.
Pullorum,
S.
Gallinarum in poultry
S. Cholerae-suis in pigs
S. Tiphy in humans
S.
Enteritidis PT4,
S.
Pullorum,
S.
Gallinarum in poultry
S. Cholerae-suis in pigs
S. Tiphy in humans
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Clinical featuresClinical features
• Enteritis
Diarrhea, nausea and fever
• Incubation
p
eriod
• Enteritis
Diarrhea, nausea and fever
• Incubation
p
eriod
p
6 – 48 h
• Infectious dose
–1 to 10
6cells
p
6 – 48 h
• Infectious dose
–1 to 10
6cells
PathogenesisPathogenesis
• Pathogenesis
Adhesion to epithelial cells of the ileum via mannose-
resistant fimbriae
Bacterial uptake by host cells (endocytes)
• Pathogenesis
Adhesion to epithelial cells of the ileum via mannose-
resistant fimbriae
Bacterial uptake by host cells (endocytes)
Passa
g
e throu
g
h epithelial cells within a vacuole,
where the bacterium multiplies
Influx of inflammatory cells leading to the release of
prostaglandins
Prostaglandins activate adenylate cyclase which
produces fluid secretion to the intestinal lumen
Passa
g
e throu
g
h epithelial cells within a vacuole,
where the bacterium multiplies
Influx of inflammatory cells leading to the release of
prostaglandins
Prostaglandins activate adenylate cyclase which
produces fluid secretion to the intestinal lumen
Activity in foodsActivity in foods
•Low
a
w
enhances the survival of
Salmonella
–The lower the
a
w
the greater the survival rate
•Low
a
w
enhances the survival of
Salmonella
–The lower the
a
w
the greater the survival rate
Survival of Salmonella in merin
g
ue powder as
affected by a
w
0
50
100
150
200
250
Days of storage
0.3 0.2 0.1
a
w
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