INTRODUCTION
•
The genus salmonella consists of
bacilli that parasitise the intestines of
a large of vertebrate sp and infect
human beings leading to enteric fever,
gastroenteritis, septicemia
•
The most important member of genus is
salmonella typhi the causative agent of
typhoid fever.
•
2000 serotypes or species.
•
For practical purpose they may be
divided into 2 groups:
The enteric fever group.
2. The food poisoning group.
1.
MORPHOLOGY
•
•
•
•
•
Gram-negative rods
Peritrichate flagella
Non capsulated
Non sporing
Fimbriated
CULTURAL CHARACTERS
•
Aerobic and facultatively anerobic
NUTRIENT AGAR:- Large, circular low
convex and smooth.
MACCONKEY AGAR:- Non lactose fermentor.
WILSON & BLAIR BISMUTH SULPHITE
MEDIUM:- jet black colonies with a metallic sheen
are formed due to production of H2S.
BLOOD AGAR
Mac CONKEY AGAR
WILSON BLAIR AGAR
XYLOSE-LYSINE-DEOXYCHOLATE
(XLD) AGAR
BIOCHEMICAL REACTIONS
•
•
•
•
•
•
•
Ferment glucose, mannitol, maltose
forming acid and gas.
Lactose ,sucrose and salicin are not
fermented.
Indole-negative
MR-positive
VP-Negative
Citrate-positive
Urease-negative
INDOLE
MR
VP
CITRATE
RESISTANCE
•
•
•
Killed at 55˚C in one hour.
Boiling or chlorination of water and
pasteurisation of milk destroy the
bacilli.
There are killed within 5 mins by
mercuric chloride or 5 % phenol.
ANTIGENIC STURCTURE
•
Three antigens are identified:-
1. Flagellar antigen H
2. Somatic antigen O
3. Surface antigen Vi
H ANTIGEN
•
•
•
•
Heat labile protein
Strongly immunogenic
When mixed with antisera H
suspensions agglutinate rapidly
producing large, loose, fluffy clumps
Dual in nature
O ANTIGEN
•
•
•
•
•
Phospholipid-protien-polysaccharide
complex
Identical with endotoxin
Unaffected by boiling
When mixed with antisera O antigen
suspensions form compact, chalky,
granular clumps
Less immunogenic
VI ANTIGEN
•
•
•
•
Heat labile
Many strains fails to agglutinate with the
O antiserum, due to the presence of a
surface polysaccharide antigen
Acts as a virulence factor by inhibiting
phagocytosis
Poorly immunogenic
ANTIGENIC VARIATIONS
•
•
H-O VARIATIONS:- These variations is
associated with the loss of flagella
When salmonella are grown on the agar
containing phenol, flagella inhibited
Flagella reappears when the strain is sub
cultured on the media without phenol
INOCULATION
SUBCULTURE
PHASE VARIATION:•
•
•
Phase1 antigen are either specific for a
species or shared by a few species only so
called as specific phase. Designated as
a,b,c….z, z1 etc
Phase2 antigen are widely shared and
hence also called as non specific or group
phase. Designated as 1,2,….
Stains that possess both phases are called
diphasic
V-W variations:-
V form
• W form
• VW form
S-R variations :- The smooth to rough
variation is associated with the change in
the colony morphology and loss of O
antigen
•
CLASSFICATION &
NOMENCLATUREKAUFFMANN-WHITE SCHEME
SERO
SEROTYPE
GROUPS
ANTIGEN O ANTIGEN H
2-A
S paratyphi A
4-B
S paratyphi B 1,4,5,12
S typhimurium 1,4,5,12
S Chester
4,5,12
b
i
e, h
1,2
1,2
e,n,x
S paratyphi C 6,7(Vi)
S cholerae-suis 6,7
c
C
1,5
1,5
7-C1
1,2,12
Phase 1 Phase 2
a
-
8-C2
S muenchen
9-D
S typhi
9,12(Vi)
S enteritidis 1,9,12
S gallinarum 1,9,12
10-E1 S anatum
6,8
3,10
d
1,2
d
g, m
-
-
e, h
1,6
SALMONELLA GASTROENTERITIS:-
Also called food poisoning group.
Most common S typhimurium.Others S
enteritidis, S haldar, S newport etc
SALMONELLA SEPTICEMIA:•
S choleraesuis
FOOD POISONING