Case Study
Pathogenic Bacteriology
2009
Case # 42
Mamadou Diallo
Anne Roberts
Case Summary
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19 year old male student with normal health
went to bed with a fever/headache
Fever of 40˚c
Neck was supple
Purpuric rash on legs, trunk and wrists
CSF glucose, protein and white blood cell were
normal. Blood culture grew the organism.
Key Information Pointing to Diagnosis
PHYSICAL EXAMINATION
 19 years old, student
 Purpuric rash on legs, wrist, trunk
 Supple neck
LABORATORY EXAMINATION
 CSF glucose, protein, and white blood cell was normal
(indicates no bacteria in the CSF fluid)
 Organism was cultured from blood – Gram Negative Diplococci
 Low platelet count – indicates the intravascular coagulation
The Diagnosis for Case #42
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The patient was diagnosed with bacterial meningitis. The causative
agent of this infection was Neisseria meningitidis.
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The purpuric rash, and Gram stain results were key in the diagnosis of
the patient.
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The finding of a normal CSF profile without evidence of meningitis is
atypical. Usually a culture of this fluid will indicate the presence of
bacteria.
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This meant that the organism had disseminated to the blood, where it
was cultured.
Classification,Gram Stain Results, and Microscopic
Appearance of N. meningitidis
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Family – Neisseriaceae
Genus – Neisseria
Species – meningitidis
Gram Negative Diplococci
Can be NF of oropharynx in 40%
of adults. These carriers demonstrate
no symptoms of meningitis and are
primary source of spread through
aerosols, exchange of saliva, etc .
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Diseases and Pathogenesis Caused by Neisseria
meningitidis
Pathogenesis:
 N. meningitidis will attach to epithelial cells of nasopharynx and invade
mucous membranes.
 Bacteria enter blood stream, travel through body where Type IV pili will
allow organism to attach to meninges in brain
 Invasion of the blood stream occurs with individuals deficient in
complement component (C5- C8)
 Lipooligosaccharide (LOS) damages host tissue - hemorrhaging of
blood into skin and mucous membranes (purpuric rash)
 Activity of LOS elicits host inflammatory response
Diseases:
 Endemic and epidemic cerebral meningitis
 Waterhouse Friderichen syndrome – hemorrhaging into adrenal glands
 Meningiococcal pneumonia
 Capsular antigens A, B, C, Y, W135 are cause of illness.
Diagnosis/Isolation/Identification of Neisseria
meningitidis
Diagnosis:
Neck pain, purpuric rash
Gram stain of the blood culture
Gram stain from skin lesions
Isolation:
Growth on chocolate agar with 5 - 10% CO2
MTM agar
Identification:
Oxidase – Negative
Catalase - Positive
Nitrate Reduction – Positive
Growth on MTM
Carbohydrate utilization tests - Glucose and Maltose positive
Therapy, Prevention and Prognosis of Patient Infected
with N. meningitidis
Prophylactic strategies in large populations:
 Administer the tetravalent vaccine to capsular antigens A, C, Y, W135 (
group B vaccine not available in U.S)
 This is recommended to individuals living in colleges and military
settings
Prophylactic Strategies to exposed individuals:
 Isolate infected individuals
 Antimicrobial therapy imperative – fatal if individual goes untreated
 Penicillin, Chloramphenicol, erythromycin
 Prophylaxis with rifampin, ciprofloxacin or ceftriaxone for household
and others with close contacts.
Primary Research Article : Neisseria meningitidis
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Zarantonelli, Maria, et al. 2006. Differential Role of LOS of N. meningitidis in
Virulence & Inflammatory Response During Respiratory Infection in Mice, Infection
and Immunity, OCT: 5506-5512.
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Experimental:
Two mutant strains: double knock out and a single of the gene expressing the LOS from ( N.
meningitidis serogroupB)
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Mutant and wild type strain injected in a mouse model to observe the effect of LOS alteration
in meningococcal virulence and its role in inducing an inflammatory response.
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What did they find?
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Mutant devoid of LOS unable to invade / persist in the bloodstream
Lack of LOS makes N. meningitidis more susceptible to complement mediated bacteriolysis
and opsonophagocytosis – mechanisms of early innate defense.
The mutant devoid of LOS was also unable to induce an inflammatory response
Primary Research Article : Neisseria
meningitidis
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In conclusion
Take Home Message
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This type of meningitis involves N. meningitidis
Typical symptoms: Purpuric rash, supple neck, fever
Pathogen can: Disseminate into the blood stream,
causing serious complications
Diagnostics: Gram stain of CSF/blood culture/skin
lesions
Therapy is based: Penicillin, Chloramphenicol
Prognosis is: Fatal without antimicrobial therapy
Prevention: Get Tetravalent vaccine!!!!
Transmission: Aerosols, exchange of saliva, etc.
Threat: Endemic and epidemic threat among large
populations, mental retardation, loss of limbs
References
Mahon, Connie, Donald Lehman, George Manuselis. Textbook of
Diagnostic Microbiology. 3rd Edition. Saunders-Elsevier, St. Louis,
Missouri, 2007.
Zarantonelli, Maria, et al. 2006. Differential Role of LOS of N. meningitidis
in Virulence & Inflammatory Response During Respiratory Infection in
Mice, Infection and Immunity, OCT: 5506-5512.