enteric fever

Dr.T.V.Rao MD 1

ENTERIC FEVERDr.T.V.Rao MD

Salmonella A Very complex group Contains more > 2,000 spp Typed on the basis of Serotyping, and species typing Divided into two groups

1 Enteric fever group

2 Food poisoning group –

3 Septicemias

Dr.T.V.Rao MD 2

Salmonella can causeCauses Infections in Humans and

vertebrates,Enteric Fever ( Typhoid fever )GastroenteritisSepticemias,Carrier state a concernDr.T.V.Rao MD 3

Key points There are more than 2000 different

antigenic types of Salmonella; those pathogenic to man are serotypes of S. enterica.

Most serotypes of S. enterica cause food-borne gastroenteritis and have animal reservoirs.

S. enterica serotypes Typhi and Paratyphi cause typhoid fever.

Dr.T.V.Rao MD 4

Enteric FeverTyphoid Fever

Caused by Salmonella typhi, and other Groups called as Paratyphoid A, B, C

Salmonella typhi - Causes Typhoid Salmonella Paratyphi A,B,C Causes Paratyphoid fevers. Food Poison group Spread from Animals – Humans Causes Gastroenteritis – Septicemias, Localized Infection

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Dr.T.V.Rao MD 6

Typhoid fevers are prevalent in many regions in the World

Typhoid Mary Most Dangerous Woman in America

Dr.T.V.Rao MD 7

Typhoid MaryA famous example

is “Typhoid” Mary Mallon, who was a food handler responsible for infecting at least 78 people, killing 5. These highly infectious carriers pose a great risk to public health.

Dr.T.V.Rao MD 8

Morphology of Salmonella

Gram negative bacilli

1-3 / 0.5 microns,

Motile by peritrichous flagella Dr.T.V.Rao MD 9

Bacteriology –Typhoid fever

The Genus Salmonella belong to Enterobacteriaceae

Facultative anaerobeGram negative bacilliDistinguished from

other bacteria by Biochemical and

antigen structureDr.T.V.Rao MD 10

Cultural Characters Aerobic / Facultatively anaerobic Grows on simple media – Nutrient agar, Temp 15 – 41ºc / 37º c Colonies appear as large 2 -3 mm, circular,

low convex, On MacConkey medium appear

Colorless ( NLF )

Selective Medium - Wilson Blair Bismuth sulphide medium. Produce Jet black colonies

H2 S produced by Salmonella typhiDr.T.V.Rao MD 11

Enrichment MediumLiquid Medium

Selenite F mediumTetrathionate broth Above medium are used for

isolation of Salmonella from contaminated specimens

Particularly stool specimens..Dr.T.V.Rao MD 12

Identifying Enteric Organisms

Isolates which are Non lactose fermenting Motile, Indole negative Urease negative Ferment Glucose,Mannitol,Maltose Do not ferment Lactose, Sucrose Typhoid bacilli are anaerogenic Some of the Paratyphoid form acid and gas Further identification done by slide

agglutination testsDr.T.V.Rao MD 13

Biochemical Characters Glucose ,Mannitol ,Maltose produce A/G

Salmonella typhi do not produce gas Lactose/Salicin/sucrose not fermented. Indole – Methyl Red + V P - Citrate + Urea – H2S – produced by Salmonella typhi Paratyphi A do not produce H2S

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Resistance of Salmonella

55º c – 1 hour60º c – 15 MTBoiling ,Chlorination, Pasteurization Destroy the Bacilli.Dr.T.V.Rao MD 15

Pathogenicity Salmonella are definite parasites to

humans.Eg S.typhi. S.paratyphi A, B ,C Other groups Salmonella The important clinical syndromes

1. Enteric fever, Septicemias, gastroenteritis.Dr.T.V.Rao MD 16

Dr.T.V.Rao MD 17

Enteric Fever: S. typhi

Ileocecal penetration intraluminal multiplication mononuclear response (macrophages) Salmonella remains alive 2nd week - lymphoid hyperplasia

(mesenteric lymph nodes) back to bowel

Dr.T.V.Rao MD 18

Enteric FeverTyphoid

Typhoid – caused by S.typhi

Paratyphoid Caused by Paratyphi A,B,C

Typhoid --- Like TyphusInfective dose ID50 / 107,

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Dr.T.V.Rao MD 20

Fever All the events coincides with

Fever and other signs of clinical illness

From Gall bladder further invasion occurs in intestines

Involvement of peyr’s patches, gut lymphoid tissue

Lead to inflammatory reaction, and infiltration with monocular cells

Leads to Necrosis, Sloughing and formation of chacterstic typhoid ulcers

Rashes in Typhoid

May present with rash, rose spots 2 -4 mm in diameter raised discrete irregular blanching pink maculae's found in front of chest

Appear in crops of upto a dozen at a time

Fade after 3 – 4 days Dr.T.V.Rao MD 21

Pathology and Pathogenesis

Bacilli enter through ingestion,

Bacilli attach to Microvilli,ileal mucosa, penetrate to Lamina propria and sub mucosa

Phagocytosis by Polymorphs and Macrophages

Enters the mesenteric lymph nodes

Enter the thoracic duct – Blood streamDr.T.V.Rao MD 22


Bacteremia Spread to Liver, Gall bladder, Spleen, Bone marrow, Lymph nodes, Lungs, Multiply in kidneys

Once again spill into Blood stream

Causes clinical illness.Dr.T.V.Rao MD 23

Dr.T.V.Rao MD 24


Multiply abundantly in Gall bladder,Bile rich source of Bacteria Spill into Intestine, infects payers

patches, Lymph follicles Inflammation – Undergo necrosis,

Slough offTyphoid ulcersTyphoid ulcers can cause perforation

and hemorrhage Duration of Illness 3 – 4 weeks Incubation 7 -14, ( 3-56 days )

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S.typhi more seriousThe clinical features tend to be

more severe with S. Typhi (typhoid fever). After penetration of the ileal mucosa the organisms pass via the lymphatic's to the mesenteric lymph nodes, whence after a period of multiplication they invade the bloodstream via the thoracic duct.

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Progress in Enteric Fever

The liver, gall bladder, spleen, kidney and bone marrow become infected during this primary bacteraemic phase in the first 7-10 days of the incubation period. After multiplication in these organs, bacilli pass into the blood, causing a second and heavier bacteraemia, the onset of which approximately coincides with that of fever and other signs of clinical illness.

Dr.T.V.Rao MD 27

Progress in Enteric FeverFrom the gall bladder, a further invasion

of the intestine results. Peyer's patches and other gut lymphoid tissues become involved in an inflammatory reaction, and infiltration with mononuclear cells, followed by necrosis, sloughing and the formation of characteristic typhoid ulcers occurs.

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Immunity in Typhoid

Typhoid bacilli are Intracellular pathogens

Cell mediated immunity is crucial

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Clinical manifestations Head ache, malise,anorexia ,coated tongue Abdominal discomfort, Constipation / Diarrhea Step ladder type fever, Relative bradycardia, A soft palpable spleen Hepatomegaly Rose spots appear

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Complications of Enteric fever

Intestinal perforation,Hemorrhage,Circulatory collapse.Bronchitis Bronchopneumonia,Meningitis,Cholecystitis,Arthritis,Periostitis / Nephritis,Osteomyletis,Dr.T.V.Rao MD 31

Relapses in Typhoid Fever

Apparent recovery can be followed by relapse in 5-10% of untreated cases. Relapse is usually shorter and of milder character than the initial illness, but can be severe and may be fatal. Severe intestinal haemorrhage and intestinal perforation are serious complications that can occur at any stage of the illness.

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Other complications

Causes relapses in particular to patients treated with chloramphenicol.

S.paratyphi produce septicemias.

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Typhoid carriers Salmonella enterica causes

approximately 16 million cases of typhoid fever worldwide, killing around 500,000 per year. One in thirty of the survivors, however, become carriers. In carriers the bacteria remain hidden inside cells and the gall bladder, causing new infections as they are shed from an apparently healthy host.

Carrier Stage in Typhoid FeverMost people infected with salmonella

continue to excrete the organism in their stools for days or weeks after complete clinical recovery, but eventual clearance of the bacteria from the body is usual. A few patients continue to excrete the salmonellae for prolonged periods. The term chronic carrier is reserved for those who excrete salmonellae for a year or more. Dr.T.V.Rao MD 35

Carrier Stage in Typhoid Fever Chronic carriage can follow

symptomatic illness or may be the only manifestation of infection. It can occur with any serotype, but is a particularly important feature of enteric fever: up to 5% of convalescents from typhoid and a smaller number of those who have recovered from paratyphoid fever become chronic carriers, many for a lifetime.

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How we Diagnose Typhoid FeverDiagnosis is made by any blood, bone

marrow or stool cultures and with the Widal test (demonstration of salmonella antibodies against antigens O-somatic and H-flagellar ). In epidemics and less wealthy countries, after excluding malaria, dysentery or pneumonia, a therapeutic trial time with chloramphenicol is generally undertaken while awaiting the results of Widal test and cultures of the blood and stool.

Dr.T.V.Rao MD 37

Laboratory Diagnosis ofTyphoid Fever

1 Isolation of Bacilli. A Gold standard 2 Diagnosis for presence of Antibodies,Positive Blood culture – A gold standardIsolation from Feces and Urine ?Detection of Antibodies Inconclusive.Newer methods Detection of antigen in Blood and Urine

Dr.T.V.Rao MD 38

Blood Culture1 st week Positive in 90

%

2 nd week Positive in 75 %

3 rd week Positive in 60 %

> 3 weeks positive in 25 %

Draw 5 – 10 cc of Blood by venipuncture.

ADD to 50 -100 ml of Bile broth.

Incubate at 37 c /Subculture in MacConkey

At regular intervals

Dr.T.V.Rao MD 39

Blood Cultures in Typhoid Fevers

Bacteremia occurs early in the disease

Blood Cultures are positive in

1st week in 90%2nd week in 75%3rd week in 60%4th week and later in 25%

Dr.T.V.Rao MD 40

Castaneda’s method ofBlood Culture

Double medium used Solid/Liquid medium in the same Bottle.

Bottle contains Bile broth/agar slant,

For subculture the bottle is merely tilted.

A subculture into MacConkey at regular intervals,

Reduces the chances of contamination

Increases the chances of isolation.

Dr.T.V.Rao MD 41

Clot cultureClot cultures are more

productive in yielding better results in isolation.

A blood after clotting, the clot is lysed with Streptokinase ,but expensive to perform in developing countries.Dr.T.V.Rao MD 42

Bacteriological Diagnosis of Typhoid Fever

Selective media, such as Deoxycholate-citrate agar or xylose-lysine Deoxycholate agar, are used for the isolation of salmonella bacteria from faeces. Fluid enrichment media, such as Tetrathionate or selenite broth, are also useful to detect small numbers of salmonellae in faeces, foods or environmental samples.

Dr.T.V.Rao MD 43


Suspicious colonies from the culture plates are tested directly for the presence of Salmonella somatic (O) antigens by slide agglutination and subcultured to peptone water for the determination of flagellar (H) antigen structure and further biochemical analysis.

Dr.T.V.Rao MD 44

Slide agglutination tests In slide agglutination

tests a known serum and unknown culture isolate is mixed, clumping occurs within few minutes

Commercial sera are available for detection of A, B,C1,C2,D, and E.

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A presumptive diagnosis of salmonellosis can often be made within 24 h of the receipt of a specimen, although confirmation may take another day, and formal identification of the serotype takes several more days. A negative report must await the result of enrichment cultures - at least 48 h.

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Bactec and Radiometric based methods are in recent use

Bactek methods in isolation of Salmonella is a rapid and sensitive method in early diagnosis of Enteric fever.

Many Microbiology Diagnostic Laboratories are upgrading to Bactek methods

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Culturing other Specimens

Feces Enrichment in Tetrathionate broth and Selenite broth

Culturing in MacConkey/DCA/Wilson Blair medium – Large black colonies.

Urine Culture – positive in 25 % Other samples

Bone Marrow,Bile,CSF/Sputum

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Serology WIDAL Test – Tube

agglutination test.

Detects O and H antibodies

Diagnosis of Typhoid and Paratyphoid

Testing for H agglutinins in Dryers tubes, a narrow tube floccules at the bottom

Testing for O agglutinins in Felix tubes, Chalky

Incubated at 37º c overnight

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Diagnosis of Enteric FeverWidal test

Serum agglutinins raise abruptly during the 2nd or 3rd week

The Widal test detects antibodies against O and H antigens

Two serum specimens obtained at intervals of 7 – 10 days to read the raise of antibodies.

Serial dilutions on unknown sera are tested against the antigens for respective Salmonella

False positives and False negative limits the utility of the test

The interpretative criteria when single serum specimens are tested vary

Cross reactions limits the specificity

Widal Test Single test not diagnostic. Paired samples tests Diagnostic. O > 1 in 80 H > 1in 160H agglutinins appear firstFalse positives in

Unapparent infection, Immunization Previously infectedDr.T.V.Rao MD 51

Widal test

Anamnestic response previous infection and responding to unrelated infection

Other Diagnostic tests CIE and ELISADetection of Circulating antigensCo agglutination test.Dr.T.V.Rao MD 52

Limitation of Widal TestThe Widal test is time

consuming and often times when diagnosis is reached it is too late to start an antibiotic regimen.

In spite of several limitation many Physicians depend on Widal TestDr.T.V.Rao MD 53

False Positive and Negative Reactions with WIDAL Test

The Widal test should be interpreted in the light of baseline titers in a healthy local population. This is especially important when there is a high local prevalence of non-typhoid salmonellosis. The Widal test may be falsely positive in patients who have had previous vaccination or infection with S typhi.Dr.T.V.Rao MD 54

False Positive and Negative Reactions with WIDAL Test

Widal titers have also been reported in association with the dysgammaglobulinaemia of chronic active hepatitis and other autoimmune diseases.64 '8 '9 False negative results may be associated with early treatment, with "hidden organisms" in bone and joints, and with relapses of typhoid fever. Occasionally the infecting strains are poorly immunogenic.

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WIDAL A DELETED TEST IN MANY NATIONS

Widal test is Discontinued in all Developed countries,

However many in Developed countries still depend on

this test which lacks Sensitivity and Specificity

Diagnosis of Carriers and Environments

Fecal carriers by isolation from specimens. or Bile aspirated.

Sewer swabsBacteriophage

typingDr.T.V.Rao MD 57

Prophylaxis TAB vaccine S.typhi 1,000 millions S Paratyphi A,B 750 millions. Injected subcutaneously 0.5 ml at 4 – 6 weeks.Live Oral Vaccine Typhoral

Mutant S.typhi strain Ty 2 1a Lacking enzyme UDP galctose 4 epimerase 10 to9

Viable bacilliGiven orally 1 – 3 – 5 daysDr.T.V.Rao MD 58

Dr.T.V.Rao MD 59

PreventionVi Polysaccharide vaccine

Administered subcutaneously or intramuscular

Confers protection seven days after injection

Approximately 50% efficacy after three years

Ty 21 vaccine Live attenuated strain of S. typhi

Administered orally in capsule form

Also available in liquid form which can be taken by children as young as two years of age

Vaccines An Injectable vaccine Typhium

ViContains purified Vi

polysaccharide antigen from S.typhi strain Ty2

A single dose, subcutaneous route

Given to children > 5 yearsImmunity lasts for 2- 3 years.Follow a booster

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TreatmentChloramphenicol 1948 /1970

resistance.Other Important drugs Ampicillin Amoxicillin, Furazolidine Cotromoxazole Chloramphenical resistance /Mexico KeralaDr.T.V.Rao MD 61

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Antimicrobial Therapy in Typhoid With prompt antibiotic

therapy, more than 99% of the people with typhoid fever are cured, although convalescence may last several months. The antibiotic chloramphenicol Some Trade Names CHLOROMYCETINis used worldwide, but increasing resistance to it has prompted the use of other antibiotics BACTRIMSEPTRANor Ciprofloxacin

Other DrugsFluroquinolon

es

Ciprofloxacillin, Pefloxacillin Ofloxacillin

Ceftazidime Ceftriaxone / Cefotoxaime

Dr.T.V.Rao MD 63

EpidemiologyDeveloped countries - Controlled.Water supply/ Sanitation /Economically

poor.S.typhi and S.paratyphi are prevalent in

IndiaPreviously Typhi are more common

Paratyphoid A on raise.Age 5 – 20 years, Sanitation Dr.T.V.Rao MD 64

Epidemiology Sanitation has great role Source an active patient or a

Carrier shed the Bacilli. Who are carriers.

Convalescent carrier 3 weeks to 3 months

Temporary carrier 3 months to 1 year

Chronic carrier > 1 year,

Women attain more carrier stage

Dr.T.V.Rao MD 65

Epidemiology (Contd)

Bacilli persist in the Gall bladder and kidney Food handlers spread the infection Cooks great role S.typhi and S.paratyphi in humans S.para B in Animals, Typhoid spread through Water, Milk, FoodHIV patients potentially susceptible for Typhoid

disease.Dr.T.V.Rao MD 66

Dr.T.V.Rao MD 67

A Simple Hand washing has many reasons to prevent

Enteric fever

Dr.T.V.Rao MD 68

Programme Created by Dr.T.V.Rao MD for Medical

and Paramedical Students in the Developing World

[email protected]

enteric fever

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