This document provides information on the enteric bacilli Salmonella typhi. It describes S. typhi as a gram-negative facultative anaerobe that causes the systemic disease typhoid fever. The document outlines the clinical symptoms of typhoid fever such as sustained fever, headache and abdominal issues. It discusses the virulence factors that allow S. typhi to cause disease, including its ability to invade non-phagocytic cells and inhibit the immune response. Prevention is focused on proper sanitation and hygiene to avoid contamination of food and water from human feces carrying the bacteria.

1. What are Enteric Bacilli
• Gram negative facultative anaerobic rods
• Produce diseases in the Alimentary Tract of
warm-blooded animals
Oppurtunistic Pathogens
• Coliforms- Escherichia, Klebsiella, Enterobacter, Serratia,
Citrobacter, Proteus, Providencia, Morganella common causes of
pneumonia, meningitis, septicaemia, UTI, wound infections
Overt Pathogens-cause disease on GIT
• Salmonella, Shigella, Yersinia
• Found in man at a time of infection
• Transmitted via fecal-oral route except Y. pestis

2. BIOCHEMICAL AND MORPHOLOGICAL PROPERTIES
• Gram (-) Coccobacilli
• Oxidase (-)
• Grow well in McConkey Agar and EMB
• Ferment Glucose-Acid/Acid Gas
• Motile or Non-motile
• Do not form spores (Asporogenous)
• Catalase (+) except S. dysenteriae
• Reduce Nitrate to Nitrite except
Enterobacter and Yersinia

4. Escherichia coli

5. Escherichia coli
• Predominant in the large intestine of man-
part of normal flora
• Most strains are motile
• Lactose fermenter, aerogenic
• Non-sporeformers; form colonies with green
metallic sheen
• Most common cause of UTI, nosocomial
infections and Gram (-) bacteremia

6. Pathogenecity
Causes disease when
1. Intestinal wall become diseased
2. Lowered host resistance
3. Increased virulence of the organism
Pathology
ORGANISMS ABDOMINAL WALL BLOODSTREAM
causes peritonitis, meningitis, pyelonephritis, cystitis,
cholecystitis
Plays a part in the formation of Gallstones and UTI and
Infant Diarrhea

7. Strains which can cause serious GIT
infections
• Enterotoxigenic E. coli (ETEC)
• Enteroinvasive E. coli (EIEC)
• Enterohemorrhagic E. coli (EHEC)
• Enteropathogenic E.coli (EPEC)
• Enteroaggregative E. coli (EAEC)
– Transmitted by contaminated food and water

8. Prevention
1. Care on the preparation of infant formula
2. Sterilization of rubber nipples of feeding bottles
3. Drink pasteurized milk, juice and cider.
4. Wash raw produce thoroughly.
5. Control on septic procedures (instruments and equipment)
6. Precautions in keeping the urinary tract sterile
AVOID CROSS-CONTAMINATION
1. Wash utensils
2. Keep raw foods separate.
3. Wash your hands

9. Klebsiella pneumoniae

10. Klebsiella pneumoniae
• Gram-negative bacteria that can cause different types of
healthcare-associated infections, including primary
pneumonia, UTI, bloodstream infections, wound or surgical
site infections, bacteremia and meningitis.
• normally found in the human intestines (where they do not
cause disease
• Also found in human stool (feces)
• Friedlander’s Bacillus
• Capsulated, Non-motile, Urease (+)
• Lactose fermenter, aerogenic
• Large pink mucoid colonies

11. Pathogenecity
Causes disease when
1. enter the respiratory (breathing) tract to cause
pneumonia
2. blood to cause a bloodstream infection
Pathology
-spread through person-to-person contact
-contamination of the environment

12. Prevention
• Before preparing or eating food
• Before touching their eyes, nose, or mouth
• Before and after changing wound dressings or
bandages
• After using the restroom
• After blowing their nose, coughing, or
sneezing
• After touching hospital surfaces such as bed
rails, bedside tables, doorknobs, remote
controls, or the phone

13. Salmonella typhi

14. Salmonella sp
• Pathogenic for man and animals
• Do not ferment lactose nor sucrose
• Aerogenic except S. typhi and S. pollorium
Salmonella typhi
-facutaltively anaerobic
-glucose and mannose fermenters
-viable in fecal matter
-temp. range 4-40° optimum at 37°

15. Salmonellosis
• Fecal-oral route
• Has 3 general categories
1.) Gastroenteritis
*self-limiting lasts 2-5 days, affecting small and large
intestines, caused by S. typhimurium and S. enteritidis
(Gartner’s Bacillus); localized in GIT
*symptoms: nausea, vomiting, diarrhea 1-2 days after
ingestion of contaminated food
2.) Bacteremia, Septicemia and Extraintestinal Infections
*from GIT causative agent enters blood stream and
infects any tissue; caused by S. choleraesuis or S. dublin
*symptoms: fever, chills, anorexia and anemia

16. 3.) Enteric Fever
*life-threatening infection with prolonged fever and
multi-organ involvement: small intestines, lymph
nodes, liver and spleen (sometimes heart)
 Typhoid Fever
*most severe form of enteric fever
* man is the only known host
*transmitted by diseased persons or carriers will
recover but will still harbor disease
*incubation period: 2 weeks
*symptoms: headache, anorexia, abdominal pain,
weakness, rose spots, fever

17. Determinants of Pathogenecity
Enteroinvasive, Enterotoxins
-cytotoxins: gastroenteritis
S. typhi, paratyphoid bacilli, S. choleraesuis, etc.
-invade the bloodstream and release endotoxin
Some form Vi antigen
S. typhi grows intracellularly in monocytes

18. Pathology
1. Lethargy, Body Malaise, Fever
2. Skin eruptions, bowel disturbance
3. Profound toxemia; leukocytosis
4. Ingestion mouth---Intestinal wall---Regional Mesenteric
Lymph Nodes; Thoracic duct---Bloodstream; lysis---
Endotoxin released---after lysis proceeds to gall bladder
(Cholecytitis), bone marrow, spleen
5. Bacilli confined to intestinal wall
6. Immunity is permanent

19. Prevention
• Avoid risky foods and drinks.
• Get vaccinated against typhoid fever.
• Use only pasteurized milk
• Pure water supply
• Efficient sewage disposal
• Proper sanitary control
• Destruction of flies
• Detection and Isolation of carriers

20. Shigella dysenteriae

21. Shigella dysenteriae
• Bacillary dysentery- painful diarrhea with blood
mucus and pus in stool
• Man is the only known host
• Shigella infection is almost always limited to GIT
• Non-motile and Non-capsulated
• Facultatively anaerobic

22. • fecal-oral transmission
• ingestion of contaminated food or water
(untreated wading pools, interactive water
fountain)
• contact with a contaminated inanimate
object, and certain mode of sexual contact
• Vectors like the housefly can spread the
disease by physically transporting infected
feces
Pathogenecity

23. Pathology
• incubation period varies from 12 hours to 7 days but is
typically 2-4 days
• disease is communicable as long as an infected person
excretes the organism in the stool
• diarrhea and dysentery, along with frequent mucoid bloody
stools and abdominal cramps
• S. dysenteriae causes dysentery by invading the colonic
mucosa. The organism multiplies within colonic epithelial
cells, causing cell death, and spreads laterally to infect and kill
adjacent epithelial cells
• mucosal ulceration, inflammation and bleeding also
– CNS abnormalities

24. Prevention
• No vaccines are available for Shigella
• frequent handwashing and strict adherence to standard food
and water safety precautions
• Mother's milk is the safest food for young infants.
Breastfeeding prevents salmonellosis and many other health
problems.

25. Vibrio cholerae

26. Vibrio cholerae
• Motile with single polar flagellum
• Sensitive to acid; anaerogenic
• Multiply rapidly in the lumen of the small
bowel
• Rice-watery stool
• capable of both respiratory and fermentative
metabolism
• Asiatic Cholera affecting lower portion of the
small intestine

27. Pathogenecity-Pathogology
• Transmission to humans is by water or food.
• V. cholerae produces cholera toxin
• action on mucosal epithelium is responsible for the
characteristic diarrhea of the disease cholera
• sudden onset of massive diarrhea
• patient may lose gallons of protein-free fluid and associated
electrolytes, bicarbonates and ions within a day or two
• activity of the cholera enterotoxin which activates the
adenylate cyclase enzyme in the intestinal cells, converting
them into pumps which extract water and electrolytes from
blood and tissues and pump it into the lumen of the intestine

28. • loss of fluid leads to dehydration, anuria, acidosis and shock
• Vomiting, abdominal cramps and fever
• The watery diarrhea is speckled with flakes of mucus and
epithelial cells
• Suppression of urine, rapid collapse
• 70% Mortality Rate

29. • Drink only bottled, boiled, or chemically treated water and
bottled or canned carbonated beverages
• Wash your hands often with soap and clean water.
• Eat foods that are packaged or that are freshly cooked and
served hot.
• Dispose of feces in a sanitary manner to prevent
contamination of water and food sources
Prevention

30. Yersinia pestis

31. Yersinia pestis
• Causes human plague
• Transmitted via bite of an infected rat flea
Penetrate skin---macrophages of PMN---multiply---produce
protein and lipoprotein antigens (V and W)---less susceptible to
intracellular killing by other macrophages and PMN’s
• Ability to survive intracellularly

32. Mechanism of Pathogenicity
• 3 factors
-Bacteriocin
-Coagulase
-Fibrinolysin
• Envelope antigen

33. Forms of Plague in Man
• Bubonic- painful, swollen lymph nodes, fever
and bleeding under skin
• Septicemic-bloodstream and invade other
tissues
• Pneumonic-in the lungs; can be spread via
droplet spray

34. • Avoid contact with sick or dead animals,
especially rodents.
• Eliminate sources of food and nesting places
for rodents around homes, work places and
recreation areas
Prevention

35. Proteus vulgaris

36. Proteus vulgaris
• Motile
• Swarming growth on plated media with foul odor
• Inhabit the feces, water, soil and sewage
• Proteus vulgaris occurs naturally in the intestines of humans and a wide
variety of animals; also manure, soil and polluted waters
Pathogenecity
Infection depends on the interaction between the
infecting organism and the host defense
mechanisms. Various components of the
membrane interplay with the host to determine
virulence.
Causes UTI, polynephritis, mild diarrhea

37. • More than 80% of human urinary tract infections (UTI) are
due to the bacterium
• Bacterial production of urease has also been shown to
increase the risk of pyelonephritis in experimental animals.
Urease production, together with the presence of bacterial
motility and fimbriae, may favor the production of upper
urinary tract infections (UTIs) by organisms such as Proteus
Pathology

38. Case Study
A woman at the age of twenty applied to our clinic with
complaints of fever, headache and diarrhea with which she had
been suffering for five days.
On Physical Examination:
- She had a slight fever, with a body temperature of 38.6°C. Her
arterial blood pressure was 110/70 mm Hg and her heart rate
was 76 beats/minute.
- No other pathology was found apart from a slightly pale skin
and relative bradycardia.

39. Laboratory Analysis:
The patient's blood revealed a white blood cell (WBC) count of
6200/mm3 [70% polymorphonuclear leukocytes (PMNL), 30%
mononuclear leukocytes (MNL)], hemoglobin 13g/dL, hematocrit
38%, platelet count 103.000/mm3, erythrocyte sedimentation
rate (ESR) 34 mm/hour, C-reactive protein (CRP) 44.6 mg/L,
aspartate aminotransferase (AST) 35 U/L, alanine
aminotransferase (ALT) 21 U/L, alkaline phosphatase (ALP) 148
U/L, and direct/indirect bilirubin 1.6/0.2 mg/dL.
- Copious amounts of leucocytes were observed in feces by
microscopy.
- A fever-heart rate discordance was observed.

40. - From her blood culture, Salmonella typhi was isolated with
sensitivity to ciprofloxacin.
- On abdominal sonography, hepatomegaly (mid-clavicular and
in caudocranial 175 mm) was found.
Laboratory Diagnosis:
- Culture
- Polymerase Chain Reaction (PCR)
- Serologic Test

41. Salmonella typhi :
- Genus: Salmonella
- Family: Enterobacteriaceae
- rod-shaped bacteria
- Diameter: 0.7 - 1.5 microns; Length: 2-5 microns
- Gram-negative
- facultative anaerobes
- Do not form spores
- produce mainly the gastrointestinal tract of infected humans and
animals.
- They lead to the symptoms of typhoid fever (Salmonella typhi ,
Salmonella paratyphi ).
- Glucose and mannose fermenters viable in fecal matter

42. Common symptoms:
-Spiking fever, enlarged spleen, leukopenia, and hemorrhages of the
skin (rose spots)
Clinical Infection:
-Typhoid fever
incubation period: 7-14 days
Portal of Entry:
-Mouth
Transmission :
- Contaminated food and water; transmitted only by humans, no
animal reservoir

43. Antigenic structure
O or somatic antigen
-outer polysaccharide of the cell wall
H or flagellar antigen
- Species identification
- Change periodically protecting it from antibodies
Vi antigen
-polysaccharide capsule that surrounds the O antigen
-for detection of carriers

44. Typhoid/ Enteric Fever:
Infection of S. typhi leads to the development of typhoid, or
enteric fever. This disease is characterized by the sudden onset
of a sustained and systemic fever, severe headache, nausea, and
loss of appetite. Other symptoms include constipation or
diarrhea, enlargement of the spleen, possible development of
meningitis, and/or general malaise. Untreated typhoid fever
cases result in mortality rates ranging from 12-30% while treated
cases allow for 99% survival.

45. Virulence Factors:
S. typhi has a combination of characteristics that make it an
effective pathogen. This species contains an endotoxin typical of
Gram negative organisms, as well as the Vi antigen which is
thought to increase virulence. It also produces and excretes a
protein known as “invasin” that allows non-phagocytic cells to
take up the bacterium, where it is able to live intracellularly. It is
also able to inhibit the oxidative burst of leukocytes, making
innate immune response ineffective.

46. Prevention:
The key to avoiding infection by S. typhi is prevention of fecal
contamination in drinking water and food supplies. Since the
only source of this agent is infected humans, it is possible to
control transmission by proper hygiene, waste management,
water purification, and treatment of the sick.

47. END