Page 195 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-20 Infectious Diseases

BACTERIAL MENINGITIS
Sources of infection
Basal skull fracture
Cribriform plate defect
Otitis media
Sinusitis (ethmoiditis)
Mastoiditis
Nasal furuncles

MENINGOCOCCEMIA (Continued) Nasopharyngitis

N. meningitidis infection. Culture of N. meningitidis Pneumonia
from blood, cerebral spinal fluid (CSF), or tissue is
diagnostic. The gram-negative diplococcal bacteria
grows on the chocolate agar plate and appears as small,
round, moist, gray colonies. Gram staining of CSF
shows intracellular gram-negative diplococcal bacteria. Dermal sinuses
This bacteria also grows well on the Thayer-Martin
agar plate. The bacteria is oxidase positive and is able Infection of leptomeninges is usually
to acidify certain sugars. These laboratory data can be hematogenous but may be direct
from paranasal sinuses, middle
used to help differentiate N. meningitidis from other ear, mastoid cells, or CSF leak due to
bacteria. CSF samples can be used for polymerase chain cribriform plate defect or via
reaction (PCR) testing for the bacteria, but this is not dermal sinuses.
routinely done in these cases. All cases of N. meningitidis
infection should be reported to state and national health
organizations.
Pathogenesis: Meningococcal infections, including Skin (furuncles)
septicemia and meningitis, are caused by the gram-
negative bacteria, N. meningitidis. This is a diplococcal
bacterium that requires an iron source for survival.
Because of this unique metabolic requirement, humans
are the only known host. The meningococcus bacteria
can be found as a transient colonizer in the oropharynx
of up to 10% of sampled individuals. These carriers
express no sequelae but serve as a potential reservoir for
meningococcal disease. The organisms are spread by
close contact and sharing of saliva. If the bacteria is able Inflammation and suppurative
to reproduce to such an extent as to cause bacteremia, process on surface of leptomeninges
it then becomes a potential pathogen. Bacteremia can of brain and spinal cord
quickly lead to septicemia (meningococcemia). This is
a severe, life-threatening disease that can kill quickly.
Meningeal involvement leads to neisserial meningitis.
The bacteria exhibit a neurotrophic behavior and attack
the lining of the central nervous system.
At least 13 serotypes of N. meningitidis are known,
9 of which have been conclusively shown to cause
human disease. Currently, a vaccine is available that
protects against the serotypes that most frequently
cause disease: serotypes A, C, Y, and W-135. The
remaining five serotypes can affect any individual Thrombophlebitis of superior
regardless of vaccination status. The bacteria expresses sagittal sinus and suppurative
a toxin (lipooligosaccharide) on its surface that causes ependymitis, with beginning
many of the systemic symptoms of disease. N. menin- hydrocephalus
gitidis is an encapsulated bacteria, and this helps protect
it from the host’s immune system.
Histology: Most skin biopsy specimens show evi-
dence of vasculitis with neutrophils, fibrinoid necrosis,
and extravasated red blood cells. Organisms can be
appreciated on tissue Gram stains. Embolism of capil- ceftriaxone, followed by penicillin or by chloram- confirmation can be the difference between life
laries and small venules is often seen, and necrosis and phenicol in penicillin-allergic patients. Patients with and death.
ulceration can be secondary findings. Waterhouse-Friderichsen syndrome need adrenal gland Immunization is helping to keep the disease inci-
Treatment: Treatment requires prompt recognition replacement therapy. dence low, and guidelines have been established for
of symptoms and immediate intravenous antibiotic Contacts should be treated with ciprofloxacin, which high-risk groups should get the vaccine and
therapy. Any close contacts of the patient should rifampin, or ceftriaxone. This prophylactic therapy, when. Although the vaccine protects against only 4
be screened for evidence of disease and given prophy- as well as intravenous therapy, should be started imme- of the 13 serotypes of N. meningitidis, it has the poten-
lactic oral therapy to decrease the potential of an epi- diately if clinical suspicion is high enough; delaying tial to decrease the incidence of this disease and save
demic. The main intravenous antibiotic of choice is therapy for even a few hours to wait for laboratory many lives.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 181