Microbiology
Summary
Neisseria meningitidis, the cause of meningococcal meningitis, is a gram-negative diplococcus that is oxidase positive and a glucose and maltose fermenter. It is the second-most common cause of acute bacterial meningitis. Key virulence factors of Neisseria meningitidis include its IgA protease and pili that demonstrate antigenic variation. This bacterium is able to colonize the nasopharynx, leading to asymptomatic carriage or spreading to the bloodstream and causing an invasive disease. To prevent phagocytosis, it has a protective capsule that can be shed to enter epithelial cells.
Neisseria meningitidis is a potent stimulator of the inflammatory system, primarily through lipooligosaccharide (LOS) molecules in its outer membrane. This can lead to septic shock and death. The bacterium spreads through respiratory droplets, causing it to spread easily in close quarters. The clinical presentation includes fever, malaise, headache, nausea, anorexia, and upper respiratory symptoms. As the bacteria causes bacteremia, meningococcemia, and sepsis, the rash progresses from petechial to purpuric, leading to disseminated intravascular coagulation (DIC). In some cases, Neisseria meningitidis can also cause acute bacterial meningitis, presenting with fever, headache, and neck stiffness. Effective treatment involves early diagnosis and administration of appropriate antibiotics like ceftriaxone and penicillin. Vaccines are available to prevent various serotypes of meningococcal infection, including serotype B.
Lesson Outline
Don't stop here!
Get access to 128 more Microbiology lessons & 13 more medical school learning courses with one subscription!
FAQs
Neisseria meningitidis and Streptococcus pneumoniae are both bacterial pathogens that can cause meningitis. Neisseria meningitidis, also known as meningococcus, is more often associated with meningococcal meningitis, whereas Streptococcus pneumoniae, also known as pneumococcus, is the most common cause of bacterial meningitis in children and adults. Both pathogens can enter the bloodstream and cross the blood-brain barrier, but meningococcus has unique virulence factors, such as IgA protease and pili antigenic variation, which contribute to a rapid onset and severe presentation of the disease.
Nasopharyngeal colonization refers to the presence of bacteria in the nasopharynx of an individual without causing disease. N. meningitidis are often found in the nasopharynx of asymptomatic carriers. These carriers can transmit the bacteria to other individuals through respiratory droplets when coughing, sneezing, or sharing respiratory secretions. Nasopharyngeal colonization is critical for the transmission of meningococcal meningitis. When the bacteria enter the bloodstream, they can cross the blood-brain barrier and cause inflammation of the meninges, leading to meningitis.
Maltose fermentation is a biochemical test that is used to differentiate between Neisseria species. N. meningitidis can ferment maltose, whereas N. gonorrhoeae, another pathogenic Neisseria species, cannot. The ability to ferment maltose is an important characteristic that aids in the identification of Neisseria meningitidis in laboratory settings. It helps confirm the presence of meningococcus in clinical samples, enabling appropriate treatment and prevention measures to be implemented for patients with suspected meningococcal meningitis.
Pili antigenic variation refers to the ability of N. meningitidis to alter the surface proteins (antigens) on its pili. This allows the bacteria to evade the host immune system, making it difficult for the immune system to recognize and eliminate the pathogen. Antigenic variation contributes to the persistence of meningococcus in the nasopharynx, increasing the likelihood of transmission to other individuals. Moreover, it makes the development of a vaccine against N. meningitidis more challenging, as the constantly changing antigens make it difficult to target the bacterium effectively.
Meningococcal meningitis and meningococcemia are both caused by Neisseria meningitidis, but they manifest differently. Meningococcal meningitis refers to inflammation of the meninges, the protective membranes covering the brain and spinal cord. Common symptoms include headache, fever, and stiff neck. Meningococcemia, on the other hand, is characterized by the presence of N. meningitidis in the bloodstream, which can lead to septicemia. Symptoms of meningococcemia include fever, chills, rapid breathing, rapid heart rate, and a characteristic rash. While both conditions are serious and require prompt medical attention, meningococcemia is often more severe and can lead to life-threatening complications such as septic shock or disseminated intravascular coagulation.
