This document discusses Salmonella, including its isolation, morphology, cultural characteristics, biochemical activities, epidemiology, virulence factors, pathogenesis, clinical diseases, laboratory diagnosis, and treatment. Salmonella was first isolated in 1885 and causes diseases like typhoid fever, paratyphoid fever, and foodborne illness in humans. It is a gram-negative rod found in the intestines of animals and can contaminate foods. Diagnosis involves culturing specimens from blood, feces, urine or vomit. Treatment includes antibiotics like chloramphenicol, ampicillin, and ciprofloxacin.
2. INTRODUCTION
Salmon and Smith in 1885 isolated for first time
Named after its discoverer Salmon
Wide spread pathogens of animal including man
belonging to Enterobacteriaceae
Found in the intestine of pigs ,cows ,goats , sheeps
,rodents ,hens , ducks and poultry
S Typhi and S Paratyphi found only in humans
Causes three types of diseases in human i.e enteric
fever, entercolitis and septicaemia
Two species of Salmonella i.e S enterica and S bongori.
There are six subspecies of S enterica , i.e enterica ,
salamae , arizonae ,diarizonae , houtenae,indica
No subspecies of S bongori
3. MORPHOLOGY
Gram negative rods with approximately size 2-4 X
0.6 µm
Non sporing, non capsulated, usually motile having
peritrichous flagella execption S gallinarium, S
pullorum
May posses fimbriae ( mannose sensitive,
hemagglutinating )
Non acid fast
4. CULTURAL CHARACTERISTICS
Grow over a wide temperature range from 7-48 °C,
optimum 37 °C at pH 4-8 and water activites 0.93
May be aerobic or facultatively anaerobic
Many strains are protrophic ( capable of growing on
a glucose - ammonium minimal medium ) while
some are auxotrophic ( require enrichment of some
amino acids and/ or vitamins on minimal medium) ,
most Typhi strains require Tryptophan
Grows on ordinary culture media
5. In NA and BA, colonies are moderately larger ( 2-3
mm) ,grey white, moist,circular disc with smooth
convex surface and entire edge
Colonies of Paratyphi A and Pullorum are relatively
small
Paratyphi B gives large mucoid colonies
In Peptone water and NB , most strains gives
abnormal growth with uniform turbidity . Thin
pellicle forms on prolonged incubation
In MA colonies are pale yellow , 1-3 mm diameter,
non lactose fermenting
Brilliant green MA : addition of brilliant green o.oo4
gm/ltr on MA.
inhibits E coli, Proteus and other commensal of
intestine.
colonies appear low convex , pale green translucent ,
1- 3 mm
6. In DCA, colonies are pale nearly colorless,shiny
and translucent. Sometime may have a black
center and sometime surrounded by a clear zone.
In XLD agar , H2S producing Salmonella produce
pink red colonies , having size 3-5 mm in diameter
with black center colonies . Salmonella that donot
produce H2S , most strains of Salmonella Paratyphi
A form pink red colonies without black center
colonies.
In SS agar colonies are colorless, S Typhi gives
black center colonies
7. In SM-ID agar colonies of both Typhi and
Paratyphi gives red colonies
Enirchment media :
Tetrathionate broth, Selenite F broth , Kauffman
Muller Tetrathionate broth with brilliant green ,
Rappaports Malacthite green magnesium cholride
broth
8. BIOCHEMICAL ACTIVITES
Lactose, Sucrose,Salicin or Adonitol non fermenter
but Glucose,Maltose,Manitol,
Arabinose,Dulcitol and Sorbitol fermenter.
Catalase +ve , Oxidase –ve
Gas production: gas produced from glucose
fermentation but S Typhi donot produce gas.
Indole –ve , MR +ve, VP –ve
Citrate positive , but S Typhi and S Paratyphi A
negative
H2S : S Typhi positive, S Paratyphi negative
TSIA: Alk/A , gas, H2S –ve = S Paratyphi
Alk/A, H2S+ve = S Typhi
9. Lysine decaboxyolase: positve, S Paratyphi A –ve
ONPG : negative
Gelatin liquefaction : negative
Nitrate reduction test : positive
KCN: capable to grow in KCN medium
10. EPIDEMIOLOGY
Salmonella are primarily intestinal parasites of
humans and many animals including wild birds,
domestic pets and rodents; they may be isolated
from thier blood and internal organs
Found frequently in sewage, rivers and other
waters and soil in which they do not multiply
significantly
Under suitable conditions they may survive in
waters and for years in soil
Have been isolated from many foods, vegetables
and fruit and are important contaminants of animal
protein –feed supplements
11. VIRULENCE FACTORS
Endotoxin ( O- Ag)
Invasions
Factors involved in reistance to phagocytosis i.e
catalase, superoxide dismutase, defensins
Acid tolerance response (ATR) gene protect
organism from stomach acid
Vi – antigen or virulence antigen
12. PATHOGENENSIS
S Typhi, S Paratyphi A and S Paratyphi B are of
great clinical and public health significance
Many infections due to ingestion of contaminated
food and also due to zoonotic and can be
transferred between humans and non humans
Infection occurs almost due to oral route.
13.
14. Small number of S Typhi can cause typhoid fever(
ID= 10 bacilli ) while for paratyphoid it needs large
dose
All virulent strains of Salmonella can survive gastric
acidity and penetrate intestinal mucosa and
submuocsa . Hence they are facultative intracellular
pathogens that enter cells via macopinosomes
Only S Typhi is principally systemic invasive.
These causes illness such as Typhoid fever,
Paratyphoid fever and food borne illness.
15.
16. CLINICAL DISEASES
Enteric fever
Septicaemia
Gastroenteritis
Enteric fever :
This includes both Typhphoid fever and Paratyphoid
fever caused by S Typhi and S Paratyphi.
17.
18.
19. Septicaemia
It is commonly caused by S Choleraesuis and S
Paratyphi C. Infection occurs through oral route and
incubation period is shorter.
Gastroenteritis
This is caused by ingestion of contaminated foods
like milk, eggs, meat etc with Salmonella . S
typhimurium is mostly isolated from food poisoning
cases.Besides S enterididuis, S newport , S dublin
may be involved.
20. LABORATORY DIAGNOSIS
Specimens
Blood : 1st ten days and during the 3rd weeks
Faeces: during 2nd and 3rd week
Urine : 2nd week
Vomit : food poisoning
In chronic Salmonellosis it may be bone marrow rather
than blood
Microscopy
Gm –ve rods, faecal specimens from patient with typhoid
usually contains macrophages and may contain blood
in late stage infection
Food poisoning samples may contain few pus cells and
red cells
21. Collection of sample
Sterile, screw capped bottle
Transportation
Should be processed as soon as possible, in case of delay
faeces should be transported in buffered Glycerol –Saline
transport medium.
Faecal and rectal swab in Stuart’s transport media.
Culture
Biochemical reactions
Serology
Perform Widal test