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36 Cards in this Set

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  • Back
Define meningitis
An inflammation of the meninges with the exudative response present in the CSF. There are many infectious and some non-infectious causes of meningitis. The infectious agents that cause meningitis include bacteria, viruses and fungi
What are some host conditions that predispose patients to bacterial meningitis
Age, Immunocompromised state, Basilar skull fracture, Head trauma: postneurosurgery, Cerebrospinal fluid shunt
What is critical to the management of bacterial meningitis
Early recognition and institution of appropriate therapy. The disease is life-threatening and sequelae are common
The majority of meningitis cases in the US are caused by what microorganisms
Streptococcus pneumoniae, group B streptococci, and Neisseria meningitidis. Less than 16 years ago, Haemophilus influenzae was the most common cause in children less than 5
What bacteria cause meningitis in those less than one month old
group B streptococci (70%)
Listeria monocytogenes (25%)
Streptococcus pneumoniae (5%)
Also E. coli K-1, Klebsiella, and other gram negative enterics
What bacteria cause meningitis in those ages 1-23 months
Streptococcus pneumoniae (50%)
Neisseria meningitidis (30%)
group B streptococci (15%)
Haemophilus influenzae type b (5%)
What bacteria cause meningitis in those age 2-18 years
Neisseria meningitidis (60%)
Streptococcus pneumoniae (25%)
Haemophilus influenzae type b (9%)
group B streptococci (3%)
Listeria monocytogenes (3%)
What bacteria cause meningitis in those age 19-59 years
Streptococcus pneumoniae (60%)
Neisseria meningitidis (18%)
Haemophilus influenzae type b (12%)
Listeria monocytogenes (8%)
group B streptococci (2%)
What bacteria cause meningitis in those age 60 and up
Streptococcus pneumoniae (70%)
Listeria monocytogenes (24%)
Neisseria meningitidis (2%)
Haemophilus influenzae type b (2%)
group B streptococci (2%)
What are the general steps in development of meningitis
Nasopharyngeal colonization; Local invasion; Bacteremia; Meningeal invasion; Bacterial replication in the subarachnoid space; Release of bacterial components; Decreased cerebral blood flow and loss of cerebrovascular autoregulation
How do patients with meningitis present
With symptoms and signs related to their systemic illness, the initial focus of infection, and the CNS.
Symptoms and neurological signs in bacterial meningitis include headache, fever, meningismus, altered sensorium, Kernig's sign, Grudzinski's sign, vomiting, seizure, focal findings, and papilledema
What is the single most important laboratory test in patients with meningitis
Examination of the CSF
How should meningitis caused by Neisseria meningitidis be treated
Penicillin G or ampicillin
What is the mortality rate from community acquired bacterial meningitis
5-20%, even with antimicrobial therapy
What are the general characteristics of Neisseria
Gram negative diplococci; Occur in pairs; Non-motile; Non spore forming
All are aerobic but will multiply under microaerophilic conditions
Oxidase positive-have cytochrome C oxidase as measured by reduction of the dye N,N-dimethylp-p-phenylene diamine
How is pathogenic Neisseriae differentiated from non-pathogenic Neisseriae
Pathogenic will not grow at 22 C, will not grow on agar without blood, but does require 5-10% CO2 in atmosphere for optimal growth
What three antigens are used to classify Neisseria meningitidis
Polysaccharide capsule- 12 serogroups. Meningococcal capsular antigens are present in blood and CSF in severe infections. Antibodies to type B capsule cross-react with E.coli K-1 capsule
Lipo-oligosaccharide (LOS)- not LPS, because has short sugar chains rather than multiple repeating units
Outer membrane proteins- antibodies against serotype antigens are bactericidal in the presence of complement
What are the characteristics of the Asymptomatic pharyngeal carrier of Neisseria
5-25% of population are carriers at any one time
Rates increase in closed population
Carrier state enhances immunity of the host
Low incidence of disseminated disease after colonization in adults, though higher incidence in children
Define meningococcemia
Meningococci in the blood
What are some characteristics of meningococcemia
Cutaneous manifestations such as petechiae or purpura
Waterhouse-Friderichsen syndrome, manifests as shock, disseminated intravascular coagulation with bilateral destruction of the adrenal glands. Usually fatal
Meningitis is a common form of meningococcal disease
What bacterial disease is associated with C' deficiency (C6, C7, or C8)
Chronic recurring meningococcal disease
What are the virulence factors of Neisseria meningitidis
Capsules are antiphagocytic by interfering with complement deposition and preventing C3b-mediated uptake of the meningococci by phagocytes. Major virulence determinants
Protease which cleaves sIgA (LAMP1)
LOS-a hyperproducer of endotoxin-containing blebs
Capacity to acquire iron in vivo. Neisseria don't have siderophores
Can meningococci survive within PMNs
No, they are obligate extracellular parasites. Although meningococci often are seen on gram stains within PMNs, the bacteria are dead
What bacteria produce a protease that cleaves sIgA
Streptococcus pneumoniae
Neisseria meningitidis
Neisseria gonorrhoeae
Haemophilus influenzae
What does recovery from Neisseria meningitidis in untreated cases correlate with
Development of IgG bactericidal anti-capsular antibodies
What is the epidemiology of Neisseria meningitidis
Spread human to human. Asymptomatic carriers are the focus of infection
Highest attack rates in late winter, early spring
Greatest incidence between 6 months and 3 years
Which serogroup of Neisseria meningitidis typically causes epidemics in developed nations with attack rates of 50 to 100 per 100,000
Serogroup B
Where do Neisseria meningitidis serogroup C outbreaks occur
Developed and less developed countries. Attack rates can be as high as 500 per 100,000
Where does Neisseria meningitidis serogroup A cause epidemics
Less developed nations. Attack rates as high as 1000 per 100,000
How do patients with bacterial meningitis typically present
Headache, fever, and stiff neck. Vascular legions (petechiae and/or purpura) are commonly seen in patients with meningitis caused by Neisseria meningitidis. The CSF typically contains bacteria or polysaccharide capsules, PMNs, elevated levels of protein, and decreased amounts of glucose
What Neisseria species are pathogenic for humans
Neisseria gonorrhoeae (gonococcus)
Neisseria meningitidis (meningococcus)
The habitats of these organisms are mucosal surfaces. Pathogenic species are not normal flora but may be transient flora in the URT or genital tract without causing disease
Other members of the family Neisseriaceae that can cause disease include Eikenella corrodens and Kingella kingae
How is Neisseria meningitidis identified
Genera- gram negative diplococci, oxidase positive
Species- Sugar reactions
Serogroup- Agglutination reaction
How is Neisseria meningitidis treated
Penicillin G. Rifampin, ciprofloxacin, or ceftriaxone are sometimes used
How is Neisseria meningitidis immunity achieved
Acquired immunity as we get older
Vaccine that contains A,C,Y, and W-135 capsular polysaccharides. C not good for children under 2
Tetravalent conjugate vaccine (MCV4), contains capsular polysaccharide from A,C,Y, and W135 each conjugated to diphtheria toxoid. Vaccine for young adolescents, college freshmen in dormitories, microbiologists, military recruits, travelers, immunodeficiencies, and asplenia
Describe Eikenella corrodens
Family Neisseriaeaceae. Gram negative ROD, fastidious growth requirements, can pit or corrode agar. Normal flora in URT but cause subacute endocarditis in immunocompromised or oral cavity trauma. Can be part of polymicrobial infection
Describe Kingella kingae
Family Neisseriaeaceae, looks more like Neisseria (Gram negative coccobacilli). Resides in human oropharynx. Can cause septic arthritis in children, and subacute endocarditis in everyone