draditithegreat
Credits:
1247950
My Scrapbook
|
|
01.01.06 (2 years ago)
#4
|
|
yup it is bone marrow only!!! 
Lab Studies:
Most patients are
* moderately anemic,
*have an elevated erythrocyte sedimentation rate,
*thrombocytopenia, and
*relative lymphopenia.
Most also have a
*slightly elevated prothrombin time (PT) and activated partial thromboplastin time,
*decreased fibrinogen levels, and circulating fibrin degradation products.
*Liver transaminase values are usually elevated to twice the reference range, as is serum bilirubin.
*Mild hyponatremia and hypokalemia are common.
Clinical diagnosis is suggested by assays that identify Salmonella antibodies, antigens, or DNA and is then confirmed by isolation of the organism.
Isolation of the organism is as follows:
Definitive diagnosis of typhoid fever requires isolation of the organism from blood or bone marrow. With culture-positive rates of approximately 90%, the most sensitive method of isolating S typhi is obtaining a bone marrow aspirate (BMA) culture.
S typhi can be isolated from BMA even if patients have been taking antibiotics for several days, regardless of how long they have been ill. This test may be indicated in patients whose initial blood culture results are negative, presumably because of prior antibiotic therapy.
If BMA cannot be performed, blood, intestinal secretions, and stool culture findings are usually positive in approximately 85-90% of patients with typhoid fever during the first week, declining to 20-30% later in the course of the disease.
These conventional culture techniques usually take 48-72 hours from acquisition until the organism is identified. A sensitivity of 63% has also been reported from culturing skin snips of rose spots.
A single rectal swab culture at hospital admission can be expected to detect S typhi in 30-40% of patients.
BMA and blood are cultured in a selective medium, such as 10% aqueous oxgall, or a nutritious medium, such as tryptic soy broth, and are incubated at 37°C for at least 7 days. Subcultures are made daily to one selective medium, such as MacConkey agar, and one inhibitory medium, such as Salmonella-Shigella agar.
S typhi has been isolated from the cerebrospinal fluid, peritoneal fluid, mesenteric lymph nodes, resected intestine, pharynx, tonsils, abscess, bone, and urine, among others.
Serology is as follows:
The Widal test is the traditional serologic test used for the diagnosis of typhoid fever. The test measures agglutinating antibodies against flagellar (H) and somatic (O) antigens of S typhi.
In acute infection, O antibody appears first, rising progressively, later falling, and often disappearing within a few months. H antibody appears slightly later but persists longer.
Rising or high O antibody titers generally indicate acute infection, whereas elevations of H antibody help to identify the type of enteric fever.
Numerous studies have shown that the sensitivity, specificity, and predictive values of this test vary dramatically among laboratories, rendering the test's value to the clinician questionable.
This wide variation is caused by differences in patient population, antigens, and techniques.
The Widal reaction is indicative of typhoid fever in only 40-60% of patients at the time of admission.
Indirect hemagglutination, indirect fluorescent Vi antibody, and indirect enzyme-linked immunosorbent assay for immunoglobulin M (IgM) and immunoglobulin G antibodies to S typhi polysaccharide are available.
Monoclonal antibodies against S typhi flagellin and DNA probes are promising developments.
DNA probes and polymerase chain reaction are described as follows;
Although not commercially available, DNA probes have been developed for identifying S typhi from bacterial culture isolates and directly from blood.
Recently, a nested polymerase chain reaction–based test of blood was shown to detect 11 of 12 culture-confirmed and 4 culture-negative clinically suggestive typhoid cases.
Procedures:
The most sensitive method of isolating S typhi is obtaining a BMA culture
Histologic Findings: The hallmark histologic finding in typhoid fever is infiltration of tissues by macrophages (typhoid cells) containing bacteria, erythrocytes, and degenerated lymphocytes.
Aggregates of these macrophages are called typhoid nodules, which are found most commonly in the intestine, mesenteric lymph nodes, spleen, liver, and bone marrow but may be found in the kidneys, testes, and parotid glands.
In the intestines, 4 classic pathologic stages occur in the course of infection:
(1) hyperplastic changes,
(2) necrosis of the intestinal mucosa,
(3) sloughing of the mucosa, and
(4) the development of ulcers.
The ulcers may perforate into the peritoneal cavity.
In the mesenteric lymph nodes, the sinusoids are enlarged and distended by large collections of macrophages and reticuloendothelial cells.
The spleen is enlarged, red, soft, and congested; its serosal surface may have a fibrinous exudate. Microscopically, the red pulp is congested and contains typhoid nodules.
The gallbladder is hyperemic and may show evidence of cholecystitis.
A liver biopsy specimen from a person with typhoid often shows cloudy swelling, balloon degeneration with vacuolation of hepatocytes, moderate fatty change, and focal typhoid nodules.
Intact typhoid bacilli can be observed at these sites.
|
|
|
Topic Tags: 
