Meningitis pt.2 Flashcards
How prevalent is Haemophilus influenzae in the population? Which type is it?
- It can be found in the nasopharyngeal flora of 20% to 80% of healthy
persons, depending on age, season, and other factors - Most of these are NTHi (nonencapsulated, and thus nontypable), but encapsulated strains (including Hib) are not rare
How is Haemophilus influenzae spread? Which strains are envolved? What is the risk of serious infection?
- Spread is by respiratory droplets
- Most of the cases in immunized populations are now caused either by serotypes other than b or nonencapsulated strains
- The risk of serious
infection for unimmunized children younger than 4 years of age living with an index case is more than 500-fold than for unexposed children.
Describe the epidemiology of Haemophilus influenzae
- Before the introduction of effective vaccines, approximately 1 in every 200 children developed invasive disease by the age of 5 years; meningitis was the most common invasive
form and most often attacked those under 2 years of age - More than 90% of these cases were due to
a single serotype, Hib. - The introduction of universal immunization with the Hib protein conjugate vaccine has reduced invasive disease rates by 99%
- Most of the cases in immunized populations are now caused either by serotypes other than b or nonencapsulated strains
What is invasive Haemophilus influenzae disease usually caused by?
Invasive disease (systemic spread) is caused typically by encapsulated strains, mostly type b (Hib) (more than 90%)
What type of bacteria streptococcus pneumoniae?
Gram positive aerotolerant anaerobic diplococci
What are different serotypes of streptococcus pneumoniae based on?
- The distinguishing structural feature of the pneumococcus is its capsule
- All virulent strains have surface capsules
How many pneumococcus serotypes exist?
More than 90 serotypes
How prevalent is streptococcus pneumonia in the population?
Can be found in 5% to 40% of healthy persons depending on age, season, and other factors
What age group is pneumococcus meningeal disease most common in?
Most common in children (1 month to 4 years) but is also common in the elderly
Where does pneumococcus rank in frequency when it comes to bacterial meningitis?
One of the three leading causes of acute bacterial meningitis
Where does pneumococcus rank in mortality when it comes to bacterial meningitis?
30% of mortality cases due to bacterial meningitis are pneumococcal in etiology
Which vaccines are available against pneumococcus infection?
- Two pneumococcal vaccines prepared from capsular polysaccharide are now available
- The first pneumococcal polysaccharide vaccine (PPV) produced, contains purified polysaccharide extracted from the 23 serotypes of S pneumoniae most commonly isolated
from invasive disease - A 7-valent pneumococcal conjugate vaccine (PCV) was then introduced in which polysaccharide was
conjugated with protein - In 2010 the original 7-valent vaccine was replaced by
a 13-valent (PCV13) conjugate vaccine and is the standard for childhood immunization.
At which age can a person receive the pneumococcal vaccine?
- (PCV13) conjugate vaccine is the standard for childhood immunization and is effective
beginning at 2 months of age - Because of its broader coverage, the 23-valent PPV is recommended after age 2 except for immunocompromised children under 5, who should still receive PCV
Which are the most common causative agents of bacterial meningitis by age group?
- Neonate (1-28 days): Group B streptococci (Str. agalactiae) , E.Coli, L. Monocytogenes, and Klebsiella
- 1- 3 months: Str. pneumoniae, N.meningitidis, Group B streptococci
- Infant and child up to 12 years: N.meningitidis, Str. pneumoniae, H. Influenzae b
, Enterococcus - Adults: S. pneumoniae, N. meningitidis
- Elderly (above 50): S. pneumoniae, N. meningitidis, Listeria monocytogenes
Which listeria serotype is the common culprit of neonatal and new born infections?
Serotype 4B
