Which of the following is a most common cause of pyogenic meningitis in older adults?

Appeared in: NORCET -4 , 2023

Explanation

Streptococcus pneumoniae is the leading cause of community-acquired bacterial meningitis in adults, particularly those over the age of 20, and is the most frequent pathogen in the elderly.
It accounts for about 50% of all bacterial meningitis cases in this population.
Older adults are more susceptible due to factors like waning immunity and a higher prevalence of predisposing conditions such as pneumonia, sinusitis, or otitis media.

Option A: Neisseria meningitidis is a primary cause of meningitis in adolescents and young adults, often associated with epidemics, but it is not the most common cause in older adults.
Option C: Beta-haemolytic streptococcus, specifically Group B Streptococcus, is the leading cause of meningitis in neonates (newborns).
Option D: The incidence of Haemophilus influenzae type B meningitis has been drastically reduced in all age groups due to the success of the Hib conjugate vaccine.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of bacterial meningitis in older adults as background academic context rather than a clinical decision trigger.
Knowing the most likely pathogen based on a patient's age is critical for initiating empiric antibiotic therapy immediately, even before CSF culture results are available. This rapid intervention significantly improves outcomes.
For an elderly patient presenting with meningitis symptoms, treatment protocols will almost always include antibiotics that cover S. pneumoniae and L. monocytogenes.
What if? If the patient was a 19-year-old college student instead of an older adult, the primary suspected pathogen would shift to Neisseria meningitidis, and public health measures to identify and treat close contacts would be a high priority.

How to Approach the Question

First, identify the key elements of the question: 'most common cause', 'pyogenic meningitis', and 'older adults'.
The question asks for factual recall about the epidemiology of an infectious disease.
Systematically review the options, mentally associating each bacterium with the age group it most commonly affects.
Recall that Streptococcus pneumoniae is a very common cause of community-acquired infections, including pneumonia and meningitis, in adults and the elderly.
Eliminate Neisseria meningitidis as it's primarily linked to younger adults and epidemics.
Eliminate Beta-haemolytic streptococcus (Group B) as it's the main cause in neonates.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 p. 1160-1162

Practise the full NORCET -4 , 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.