Dr.T.V.Rao MD

WEIL – FELIX TEST

DR.T.V.RAO MD 1

• Gram-negative, obligate intracellular coccobacilli bacteria that infect mammals and arthropods

• Rickettsia are transmitted in the arthropods, which serves as both vector and reservoir

• Contain Both DNA and RNAIs sensitive to antibiotics.

RICKETTSIA

GENERAL INTRODUCTION

DR.T.V.RAO MD 2

CATEGORY OF RICKETTSIA

• Genus

Rickettsia, Coxiella ,Orientia,Ehrlichia Bartonella

• Species

Rickettsia prowazekii (epidemic typhus), Rickettsia

typhi (endemic typhus), Rickettsia rickettsii

(spotted fever), Rochalimaea Quintana (trench

fever), Coxiella burnetii (Q fever)

DR.T.V.RAO MD 3

RICKETTSIA AND SEROLOGY

• Rickettsiae is a genus of motile, Gram-negative, non-spore forming, highly pleomorphic bacteria that can present as cocci (0.1 μm in diameter), rods (1–4 μm long) or thread-like (10 μm long). Obligate intracellular parasites

• Because of this, Rickettsiae cannot live in artificial nutrient environments and are grown either in tissue or embryo cultures (typically, chicken embryos are used).

• Still we have to dependent on Weil Felix test DR.T.V.RAO MD 4

• The agglutination reactions, based on antigens common to both organisms, determine the presence and type of rickettsial infection

• Because Rickettsia are both fastidious and hazardous, few laboratories undertake their isolation and diagnostic identification

• Weil-Felix test that is based on the cross-reactive antigens of OX-19 and OX-2 strains of Proteus vulgaris.

WEIL-FELIX A HETEROPHILE

AGGLUTINATION TEST

DR.T.V.RAO MD 5

• In 1915, Weil and Felix

showed that serum of

patients infected with any

member of the typhus

group of diseases contains

agglutinins for one or more

strains of O X Proteus. In

cases of typhus fever the

reaction usually appears

before the sixth day and

reaches its height in the

second week.

WEIL AND FELIX

CONTRIBUTE FOR TESTING

DR.T.V.RAO MD 6

BASIS OF THE WEIL-FELIX TEST • The basis of the test is the presence of antigenic

cross-reactivity between Rickettsia spp. and certain

serotypes of non-motile Proteus spp., a

phenomenon first published by Edmund Weil and

Arthur Felix in 1916. The serum of patients diagnosed

with epidemic typhus was found to agglutinate in the

presence of bacteria known as Proteus vulgaris.

Ensuing work elucidated that it was in fact the somatic

(O) antigen that cross-reacted with anti-rickettsial

antibodies, and furthermore, that different Proteus O

antigens would cross-react with different species of

Rickettsia. DR.T.V.RAO MD 7

WEIL-FELIX TEST

INDICATED IN WHEN PATIENTS PRESENT WITH

RASHES

• Test for diagnosis of typhus and certain other rickettsial diseases. The blood serum of a patient with suspected rickettsial disease is tested against certain strains of (OX-2, OX-19, OX-K)..

DR.T.V.RAO MD 8

WEIL-FELIX REACTION –

A HETEROPHILE AGGLUTINATION TEST

• A Weil-Felix reaction is a type of

agglutination test in which patients serum is

tested for agglutinins to O antigen of

certain non-motile Proteus and rickettsial

strains (OX19, OX2, OXK)

• OX19, OX2 are strains of Proteus vulgaris.

OXK is the strain of Proteus mirabilis.

DR.T.V.RAO MD 9

• The Weil-Felix Test

can be done as

either a slide or a

tube test. The

antigens necessary

(OX2, OX19, and

OXK) can be

obtained

commercially.

PROCEDURE OF WEIL -FELIX TEST

DR.T.V.RAO MD 10

• On a solid surface (glass slide,

tile, card), a small amount (50-

100 μL) of the patient’s serum is

placed. A single drop of the

desired antigen is added, and the

resulting suspension is mixed

and then rotated for one minute.

Visible agglutination is indicative

of a positive result, and

corresponds roughly to a titre of

1:20. Positive results can be

further titrated using the tube

method, which is more labour-

intensive.

SLIDE METHOD

DR.T.V.RAO MD 11

TUBE METHOD

• Using 0.25% phenol saline as a diluent, a series of

tubes containing twofold dilutions of patient serum are

made with a final volume of 1 mL. A drop of antigen

suspension is added to each tube, and the mixture is

incubated at 50-55 °C for 4-6 hours. A positive tube

would show visible flocculation or granulation, which is

accentuated when the tube is gently agitated. The titre

corresponds to the most dilute tube in the series that

still shows positivity. Generally, a titre of ≥1:320 is

considered diagnostic.

DR.T.V.RAO MD 12

INTERPRETATIONS IN WEIL-FELIX

REACTION

• Sera from endemic typhus agglutinate OX19, OX2. Tick borne spotted fever agglutinate OX19, OX2.

• Scrub Typhus agglutinate OXK strain

• Test is negative in rickettsialpox, trench fever and Q-fever. False positive reaction may occur in urinary or other Proteus infections Test may be negative in 50 percent scrub typhus

DR.T.V.RAO MD 13

DR.T.V.RAO MD 14

WEIL FELIX TEST AND

CONCENTRATION CAMPS

DR.T.V.RAO MD 15

WEIL-FELIX TEST POSITIVITY

SAVES FROM NAZIS • In Poland, during World War II, where a pair of

quick-thinking doctors used a little-known organism to keep the Nazis at bay. The microorganisms is Proteus OX19. . Its one remarkable feature is that human antibodies for Proteus OX19 cross-react with the antibodies for Rickettsia – the bacterium responsible for the deadly disease typhus. Blood from a patient infected with Proteus Ox19 will give a false-positive in the most common typhus screening method, the Weil-Felix test.

DR.T.V.RAO MD 16

• While the Polish doctors

could, and did, inject a

number of other people

with Proteus to induce

positive Weil-Felix results,

an on-site Nazi medical

team could well have

proved their undoing.

Fortunately, ingenuity and a

good dose of hospitality

and alcohol prevented them

from being uncovered. ( From the British Medical

Journal)

HOW THEY MADE

WEIL-FELIX TEST POSITIVE

DR.T.V.RAO MD 17

LIMITATION OF WEIL-FELIX TEST

• The Weil-Felix test suffers from poor sensitivity and

specificity, with a recent study showing an overall

sensitivity as low as 33% and specificity of 46%.[ Other

studies have had similar findings. As a result, it has

largely been supplanted by other methods of serology,

including indirect immunofluorescence antibody

(IFA) testing, which is the gold standard. However, in

resource-limited settings, it still remains an important

tool in the diagnosis and identification of public health

concerns, such as outbreaks of epidemic typhus.

DR.T.V.RAO MD 18

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

and Paramedical Students in the

Developing World

• Email

• doctortvrao@gmail.com

DR.T.V.RAO MD 19