Immunological diagnosis of common infections

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Immunological diagnosis of common
infections causing prolonged fever in Egypt
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Introduction
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• Prolonged fever is defined as fever more than 2
  weeks duration greater than 38.3?C (101?F) on
  several occasions. The causes of prolonged fever
  are classified in to 4 major groups
  
• infections (most common cause).
• non-infectious inflammatory diseases (NIID).
• malignancies.
• miscellaneous conditions.

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• Infection is the most common diagnosis in most
  cases of prolonged fever especially in developing
  countries which include
• Bacterial (salmonellosis , tuberculosis
  ,brucellosis, and abdominal or pelvic abscesses
  ,osteomyelitis, infective endocarditis,
  Pyelonephritis and tuberculous meningitis ).
• Viral (CMV, EBV, Herpes viruses , and HIV).
• Rickettsial (Q fever).
• Parasitic infections.

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• The common infections in Egypt causing
  prolonged fever that we will study in this essay
  as regard the diagnosis especially the serology
  are
• salmonellosis ,
• tuberculosis(TB) ,
• brucellosis,
• Q fever,
• Epstein-Barr virus (EBV),
• chronic meningitis.

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Common infections causing prolonged fever in Egypt
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Mal-treated typhoid fever

-Typhoid fever (enteric fever) is caused by the
Gram-negative bacterium Salmonella enterica
serotype typhi. -Estimates for the year 2000
suggest there are approximately 21.5 million
infections and 200,000 deaths from typhoid fever
globally each year . -The clinical
manifestations of typhoid fever are usually
nonspecific, and include prolonged fever and
gastrointestinal symptoms.

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• Typhoid fever in Egypt

-In Bilbeis district (population 664,000) in
Lower Egypt the estimated incidence of typhoid
fever was calculated to be 13 cases per 100,000
persons per year . -Also the results of
population-based surveillance in Fayoum governate
indicate that incidence of typhoid fever was 59
cases per 100,000 persons per year.
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Brucellosis
-The causative agent is Brucella spp., (
Gram-negative intracellular coccobacillus
discovered by David Bruce in 1887). -Brucellosis
is a relatively common condition and may present
with prolonged fever without a focus, however due
its wide spectrum of clinical symptoms it remains
an important diagnostic challenge. -It is a
zoonotic disease found worldwide, with a high
morbidity rate.
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• Brucellosis in Egypt

-Brucellosis is endemic in the middle East. -In
Egypt 11 of the population had serological
evidence of infection with Brucella spp., while
in acute febrile illnesses 3 of all bacteraemias
were caused by the organism . -Although
brucellosis is recognized as a common cause of
fever in various parts of Egypt, it is often
misdiagnosed and mistreated. -More than half of
all brucellosis cases were misdiagnosed as
typhoid, and only a quarter of them received
treatment with more than one antibiotic.
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Tuberculosis
-Tuberculosis is caused by Mycobacterium
tuberculosis complex (MTBC). -Tuberculosis may
involve every organ in the body but the most
common clinical presentation is pulmonary
disease. -In 2006, 9.2 million new active
disease cases (4.1 million being sputum
smear-positive) corresponding to an estimated
incidence of 139 per 100,000 population occurred
throughout the world. -The highest incidence
rate was recorded for the African region , mainly
due to high prevalence of HIV infection.
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• Tuberculosis in Egypt
• According to a 1997 report from the Egyptian
  National Tuberculosis Program, revealed that the
  incidence of smear-positive cases in Egypt is 16
  per 100,000 population, This report concluded
  that TB and especially drug-resistant strains of
  Mycobacterium tuberculosis pose serious public
  health problems and that multiple drug resistance
  and low cure rates are the most important
  problems facing TB control efforts in Egypt .

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Qfever
Q fever is a widespread zoonotic disease,
caused by Coxiella burnetii (C. burnetii). Wild
and domestic animals are the reservoir of C.
burnetii, It is a zoonosis occurring worldwide.
Q fever is associated with a wide spectrum of
clinical manifestations. In most cases, this
illness has a self-limiting febrile course, but
it may also manifest with a variety of
non-specific symptoms. As with most other
rickettsioses, Q fever is infrequently suspected
and remain unrecognized .
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Infectious mononucleosis
The clinical triad of pharyngitis, fever, and
lymphadenopathy was first described as glandular
fever,. IM is caused by the Epstein Barr virus
(EBV), which infects more than 98 of the worlds
adult population . The overall clinical
incidence is 45/100 000 and it is particularly
common in adolescence. IM is a clinical
syndrome characterized by fever, fatigue,
malaise, lymphadenopathy and sore throat.

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Chronic meningitis
-Chronic meningitis is defined by persistent or
clinically progressive signs and symptoms of
meningitis, such as headache, fever, stiff neck,
nausea, vomiting, lethargy, and confusion
associated with cerebrospinal fluid (CSF) changes
lasting for a duration of at least 4 weeks
without improvement.
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• -Chronic meningitis is caused by a wide
  variety of infectious and noninfectious pathogens
  that remain difficult to diagnose. In Egypt,
  Tuberculous meningitis (TBM) being one of the
  most common causes of bacterial meningitis and
  being associated with a high mortality (47) and
  it continues to be a significant public health
  problem .

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Non-immunological diagnosis of common infections
causing prolonged fever
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Typhoid fever diagnosis
Although the mainstay of diagnosing typhoid
fever is a positive blood culture it is
time-consuming and takes at least 2 to 5 days
until the identification of the organism. PCR
is a better alternative because it is sensitive
and rapid method. PCR-based diagnoses are
superior to the classical serological method,
Widal test, and blood culture test in terms of
their specificity and sensitivity . Nested PCR
had higher efficacy in detecting typhoid fever
than Widal test, blood and urine cultures .
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Brucella diagnosis
Isolation of brucella from blood, bone marrow,
lymph nodes or cerebrospinal fluids remains the
gold-standard for diagnosis of brucellosis in
humans. Despite its high specificity, brucella
culture has several drawbacks such as slow growth
and poor sensitivity. PCR proved to be a very
useful tool not only for the diagnosis of acute
brucellosis but also as a predictive marker for
the course of the disease and the post treatment
follow-up, which is valuable for the early
detection of relapses .

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Tuberculosis (TB) diagnosis

• Microscopy is still the backbone of laboratory
  diagnostics in TB. Many nucleic acid
  amplification methods are much more sensitive
  than sputum microscopy, and results can be
  available within several hours.
• The cost and complexity of existing nucleic acid
  amplification methods has limited their
  application in resource-poor settings.
• Transrenal DNA provides a challenging new target
  for molecular tuberculosis diagnosis in all
  groups of patients.

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Q Fever diagnosis
The isolation of the Q fever pathogen is a
reliable diagnostic method, but it remains
time-consuming and hazardous and requires
biosafety. The PCR assays performed are better
tests than pathogen isolation for the rapid and
reliable diagnosis of Q fever.
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Infectious mononucleosis diagnosis

Quantitative Epstein bar virus (EBV) DNA
measurement is essential for differentiating the
low-level infection of healthy carriers from the
high levels characteristic of EBV-related
disease. Real-time PCR is the principal
technology used for modern EBV viral load
measurement.

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Chronic meningitis
The identification of meningitis etiology is
primarily based on the examination of CSF and
other tissues, which includes direct stain,
cultures on aerobic, anaerobic media. However,
even with the use of modern techniques, the
etiology of chronic meningitis remains unknown in
a substantial percentage of patients. The CSF
polymerase chain reaction (PCR) assay represents
a significant advance in the diagnosis of TBM.
The results of PCR studies in the CSF have shown
a 94100 specificity but sensitivities ranging
from 75 to 100. CT and MRI are used in the
evaluation of TBM and to identify complications.

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Immunological diagnosis of common infections
causing prolonged fever
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Maltreated Typhoid fever
The most widely used serologic test is the
Widal test, However, false-positive results are
common because of antigenic cross sharing with
other salmonella serotypes . Several new
serologic tests for typhoid fever have been
introduced which detect IgM or IgG antibodies to
various purified antigens of S. Typhi. The assay
methods used include enzyme-linked immunosorbent
assay (ELISA), dot-blot ELISA, immunochromatograph
y and a novel particle separation method used in
TUBEX. The TUBEX test is simple and rapid to use
not only in hospitals but also for outpatients as
well. It is good alternative for widal test .

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Typhidot-M is a dot enzyme immunoassay for the
detection of specific IgM to Salmonella typhi .
Typhidot-M was positive in 97 of cases who
presented with fever of lt7 days among blood
culture positives as compared to Widal, which was
positive in 24.2. It is a dot-Enzyme
Immunoassay (EIA), a new serologic test based
upon the presence of specific IgM antibodies to a
specific 50 kDa outer membrane protein (OMP)
antigen on Salmonella typhi. The test become
positive as early as in the first week of the
fever, the results can interpreted visually and
available within one hour
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Brucellosis
Serological testing often is used for the
confirmation of brucellosis. The agglutination
tests in tubes, e.g serum agglutination test
(SAT), or on slides (Rose Bengal) continue to be
the mainstay of laboratory diagnosis . .
However, SAT and the other formats of direct
agglutination tests suffer from high false
negative rates in complicated and chronic cases
ELISA is one method that has been incorporated
into serologic diagnosis of brucellosis. Among
its advantages are speed and automatization.
ELISA also allows detection of antibodies against
different bacterial antigenic structures such as
corpuscular antigen, S-LPS or protein antigens .


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Tuberculosis
The detection of circulating mycobacterium
antigens using specific monoclonal antibodies
(mAbs) has been shown to be a promising approach
to the detection of active infection. Recently,
developed a simple and rapid dot- ELISA test
based on IgG monoclonal antibody (TB-55 mAb)
specific for a 55-kDa mycobacterial antigen and
had been evaluated in the diagnosis of pulmonary
as well as extrapulmonary TB .
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The gold-standard screening method for LTBI is
the tuberculin skin test (TST). The TST has
several limitations, including the need for
repeat visits and trained staff in addition to
limited validity of the results. T-cellbased
interferon-? release assay are whole-blood
enzyme-linked immunosorbentassay (ELISA) and
enzyme linked immunospot assay(ELISpot). The
whole blood ELISA is available commercially as
QuantiFERON-TB Gold and an in-tube variant,
QuantiFERON-TB Gold In-tube . This T-cell-based
assay for diagnosing tuberculosis infection gave
promising results .
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Q fever
Human Q fever is currently diagnosed by
clinical presentation and supporting serological
responses against fixed, whole-cell phase I and
phase II forms of the C. burnetii. The
serological testing include immunofluorescence,
complement fixation, enzyme- linked immunosorbent
assay (ELISA) and microagglutination.Q fever IgG
ELISA is a specific alternative method for
prevaccination testing and the diagnosis of Q
fever. Worldwide, the most common method used in
human diagnosis of Q fever is the indirect
immunofluorescence antibody (IFA).
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• Infectious mononucleosis

Detection of IgM antibody against the virus
capsid antigen (VCA) is the best approach for the
identification of primary EBV infection. Indirect
immunofluorescence assay (IFA) of anti-VCA IgM
and IgG antibody has been regarded as the golden
standard for the serological diagnosis of EBV
infection, and other methods, such as
enzyme-linked immunosorbent assays (ELISA) and
chemiluminescent immunoassay (CLIA), were
developed to improve the assay procedure.
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Tuberculous meningitis
Immunological methods such as
antibody-capture enzyme-linked immunosorbant
assay (ELISA) have been previously used for
diagnosing TBM . The cell ELISA method allows
further confirmation of the results obtained by
antibody-capture ELISA. The presence of a 30-kD
protein antigen in CSF of TBM patients indicates
that this protein carries the candidate marker
antigen which is specific to M. tuberculosis.
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Common causes of prolonged fever in Mansoura
fever hospital
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Statistical comparisons for cases of typhoid
from2003 to2008 admitted in Mansoura fever
hospital
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Statistical comparisons for cases of
brucella from 2003 to2008 admitted in Mansoura
fever hospital
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Statistical comparisons for cases of
tuberculosis from 2003 to2008 admitted in
Mansoura fever hospital
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Statistical comparisons for cases of meningitis
from 2003 to2008 admitted in Mansoura fever
hospital
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