Page 170 - Concise Pathology for Exam Preparation ( PDFDrive )

7 Infections 155

TABLE 7.1. Clinical manifestations of typhoid

Disease period Signs and symptoms Pathology
First week Fever, chills, headache, abdominal tenderness Bacteraemia
Second week Rash, diarrhoea or constipation, hepatospleno- Hyperplasia of ileal Peyer’s patches and
megaly typhoid nodules in spleen and liver
Third week Complications of intestinal bleeding and Ulceration over Peyer’s patches, perfora-
perforation, shock, melena, ileus, coma tion with peritonitis, septicaemia
Fourth week Resolution of symptoms/relapse, cholecystitis, —
chronic faecal carriage of bacteria

Complications
• Bleeding from congested Peyer’s patches or eroded vessels in ulcer base
• Perforation in distal ileum is frequently fatal and may be followed by septicaemia and
peritonitis
• Metastatic abscesses in other organs
• Osteomyelitis, endocarditis, glomerulonephritis and infection of genitourinary tract or
meningitis
• S. typhi preferentially localizes in the gall bladder, where infection tends to become
chronic, especially in individuals with a pre-existing pathology
Morphology
• Ileum shows superficial, longitudinal mucosal ulcers aligned along Peyer’s patches.
• Intestinal wall shows chronic nonspecific inflammation with numerous macrophages
and prominent erythrophagocytosis.
• Draining lymph nodes show reactive hyperplasia and the liver may show focal hepato-
cytic necrosis with the replacement of the parenchyma by macrophage aggregates called
‘typhoid nodules’.
Diagnosis
• Peripheral blood shows leukopenia with relative lymphocytosis. Rarely thrombocytope-
nia may be seen.
• Salmonella species can be isolated from blood during the first week of fever and from
stool or urine in the second or third week.
• ‘Widal test’ is positive after the first week. It is a serological test which involves demonstra-
tion of agglutinating antibodies against O-somatic and H-flagellar antigens in the blood of
the affected individual. Cross-reactivity can be seen with antibodies formed against other
bacteria and this can result in a false-positive result. False positive results are also possible
in the event of typhoid vaccination, and general level of antibodies in endemic areas
(therefore rising titer is more important and a value .1:160 is convincing).
• ‘Typhidot’ is a rapid test used to diagnose typhoid fever, and is negative in the first week
and positive thereafter.
• Indirect haemagglutination test, indirect fluorescent antibody test, indirect enzyme-
linked immunosorbent assay (ELISA) for IgM and IgG antibodies to S. typhi polysac-
charide, and monoclonal antibodies against S. typhi flagella (STF) have variable success
rates as per existing literature.

Neisserial Infections
• Neisseria are Gram-negative diplococci with flattened adjacent sides giving the pair the
shape of a coffee bean. They are aerobic (grow best on enriched media such as lysed
sheep’s blood agar or ‘chocolate’ agar).

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