SALMONELLA

Pathogenesis..

PATHOGENICITY OF SALMONELLAE

Clinical syndromes caused by Salmonellae in human beings:

A. Enteric fever B. Gastroenteritis (food poisoning)

C. Salmonella septicemia

ENTERIC FEVER The term ENTERIC FEVER includes

1. TYPHOID FEVER – caused by S typhi

2. PARATYPHOID FEVER – caused by S paratyphi A, B & C

CONTD..

Enteric fever is endemic in all over India.

With a proportion of TYPHOID to PARATYPHOID A about 10 : 1.

Paratyphoid B is rare andParatyphoid C is very rare.

TYPHOID FEVER

Typhoid fever, also known as typhoid

Other names: abdominal typhus,  infantile remittant fever,  slow fever,  nervous fever,  pythogenic fever, etc.

CONTD..

Typhos in Greek means, smoke and typhus fever got its name from smoke that was believed to cause it.

Typhoid means typhus-like and thus the name given to this disease.

The term Typhoid was given by Louis (1829) to distinguish it from typhus fever.

Eberth described the typhoid bacillus in spleen sections and mesenteric lymph nodes from a patient who died from typhoid and Gaffky isolated it in pure cultures.

SALMONELLAElectron microscopy

EPIDEMIOLOGY

Epidemiological types

Endemic Epidemic

WORLD WIDE DISTRIBUTION

CONTD..

Source : Case of Typhoid or carriers in frequent.

Infective material : Contaminated food or water.

Route of infection : Ingestion of contaminated food or water.

CARRIER STATE..

CARRIERS are more important in the transmission of the disease.

Types of carriers: 1. Convalescent carriers 2. Temporary carriers 3. Chronic carriers

Convalescent carriers shed bacilli in feces for 3 WEEKS to 3 MONTHS after clinical cure.

Temporary carriers shed bacilli for more than 3 MONTHS but less than A YEAR.

Chronic carriers shed bacilli for over A YEAR.

CONTD..

2-4 % of patients become Chronic carriers, esp. women over 40yrs.

Food handlers or cooks that become carriers are particularly dangerous.

The best known example was Mary Mallon, named for nick as TYPHOID MARY.

She caused at least 7 outbreaks in 15 yrs affecting over 200 people.

MARY MALLON

in a 1909 newspaper illustration

BACILLI PERSIST IN GALL BLADDER OR KIDNEY ARE SHRED OUT

Carriers

Fecal(Gall bladder)

Urinary(Kidney)

PATHOGENESIS

Median Infective Dose (ID50) is about 1 000 to 1 000 000 bacilli in human volunteers.

The course of organism in the body is as follows.

BACILLI MICRO VILLI OF ILEUM

PENETRATION

PHAGOCYTOSIS

MESENTERIC LYMPHNODES

THORACIC DUCT

(Multiplication)

BLOOD STREAM (Transient

Bacteremia)

LIVER, G.B., SPLEEN, B.M., L.N., LUNGS.

MASSIVE BACTEREMIA

CLINICAL COURSE..

Incubation period is usually 7-14 days, but may range 3-56 days according to dose of infection.

Clinical course:

From Mild Undifferentiated Pyrexia (AMBULANT TYPHOID)

Rapidly fatal disease

CLINICAL FEATURES..

Gradual Onset of head ache malaise anorexia

Typical features: Step ladder pyrexia Relative bradycardia Toxemia

CONTD..

A soft, palpable spleen is a constant finding

Hepatomegaly is also common

Rose spots that fade on pressure appear on skin during 2nd or 3rd week.

ROSE SPOTS

Bile is a good culture medium for the bacillus, it multiplies

abundantly in GALL BLADDER

INTESTINES involves the PAYERS PATCHES LYMPHOID FOLLICLES

INFLAMMED PAYERS PATCHES

NECROSIS

SLOUGH OFF

TYPHOID ULCERS

ULCERATION OFBOWEL

PERFORATION

HEMORRHAGE

CAUSATION

Ingestion of organisms

Colonization of lower intestine

Mucosal invasion

Acute inflammation

Activation of Adenyl cyclase

Fluid production

Diarrhea

COMPLICATIONS OF THE DISEASE

Intestinal perforation Hemorrhage Circulatory collapse

Bronchitis or Bronchopneumonia is always found.

Psychoses Meningitis Cholecystitis Arthritis Abscesses

CONTD..

Periostitis Nephritis Hemolytic anemia Venous thromboses Peripheral neuritis

Osteomyelitis is rare sequel.

CONVALESCENCE & RELAPSE

Convalescence is slow

In 5-10% of cases relapse occurs during convalscence

Relapse rate is higher in patients treated early with Chloramphenicol.

PARATYPHOID FEVER

Resembles typhoid fever but is generally milder

Caused by S. paratyphi A and B, rarely by S. paratyphi C which is often associated with frank septicemia in supporative complications.

SALMONELLA GASTROENTERITIS

Food poisoning. Zoonotic disease. Caused by any Salmonella except S. typhi.

Pathogenic Species: 1. S typhimurium (most

common) 2. S enteritidis

PATHOGENESIS

Source: Poultry, Meat, Milk and its products, esp., Eggs and its products (as the bacteria can enter through the shell if eggs are contaminated and grow inside), uncooked vegetables.

Route: Ingestion

Gastroenteritis may occur without food poisoning as in cross infection in hospitals.

CLINICALLY..

Short incubation period of 24hrs or less.

Featured by Diarrhea, Vomiting, Abdominal pain, Fever.

Diarrhea: May vary from one or more loose stools to an acute Cholera like

Usually subsides in 2-4 days resembles and dysentery.

SALMONELLA SEPTICEMIA

Caused by: S choleraesuis

Focal supporative lesions:

Osteomyelitiss, Deep abscesses, Endocarditis, Pneumonia, Meningitis.