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.

1. SALMONELLA
PRAKASH DHAKAL
Public Health Microbiology
Tribhuvan University, Nepal

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.

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.

16. CLINICAL DISEASES
 Enteric fever
 Septicaemia
 Gastroenteritis
 Enteric fever :
This includes both Typhphoid fever and Paratyphoid
fever caused by S Typhi and S Paratyphi.

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

22. TREATMENT
 Chloramphenicol
 Ampicillin or Trimethoprim Sulfamethoxazole
 Ciprofloxcin and Norfloxacin

23. THANK YOU