Mind the membrane

Community-acquired bacterial meningitis that spreads among people through the upper airway can be fatal, warn Dr Anup R Warrier, Dr Arun Wilson & Dr Sneha R

Meningitis can be caused by a multitude of infectious organisms from viruses to parasites and affect any age group, from newborn babies to the elderly. The common causes of community-acquired acute meningitis are bacteria like Streptococcus pneumoniae, Neisseria Meningitidis and Listeria monocytogenes. Most of these bacteria are spread among people through the upper airway. They can be harmless in many and seldom cause disease in humans. Overcrowding, smoking, alcoholism, diabetes, head injury, individuals with lower immunity due to various reasons and unvaccinated individuals, particularly concerning Hemophilus influenzae meningitis are some of the risk factors that can predispose a person to these infections. Streptococcus pneumoniae, with the nickname, pneumococci, is a common cause of pneumonia, especially in the elderly. Uncontrolled diabetics and
alcoholics are also at risk for acquiring this infection and the bacteria can spread from the lungs to the blood and further, to the brain causing one of the highly fatal meningitides. The second commonest cause of bacterial meningitis worldwide, Neisseria Meningitidis, is spread from one human to another in close contact, mainly among family members or hostel mates, or in overcrowded places and large outbreaks are seasonal as in Africa, during the dry seasons. This was one of the infections that spread from the endemic areas of the world to industrialised nations during World War II, spreading conveniently within military camps. Smoking is also another habit that can facilitate the bacteria leading to meningitis. Listeria infections are distinctive from the other common organisms causing acute bacterial meningitis in the manner that it spreads through contaminated food, predominantly processed and refrigerated items, such as cheese or canned food.

This is due to the bacteria’s ability to survive the disinfection used by food processing industries and cold temperatures. Food industries undergo testing that detects the organism as a quality screening process before distribution. One of the more commonly heard old-world infections of our country, tuberculosis, can also less commonly infect the meninges apart from the lungs or lymph nodes. Spreading through cough from an actively infected person, especially in crowded settings, most of our population has been infected by these bacilli. But it is a set of host factors that includes immunity and time that decides when and how this will lead to active disease. The type of meningitis that Mycobacterium tuberculosis causes are unlike the forms discussed till now as this leads to a more chronic or milder presentation than the rest. The treatment is distinct with a different set of drugs and longer duration. Infections of the brain or its covering, the meninges often presenting as fever along with headache, vomiting and sometimes with alteration of behaviour or seizures are medical emergencies with an emergent need for prompt diagnosis and targeted therapy which if delayed can cause irreversible debilitating states or even mortality to the person. This is why vaccinations are a key element in the management of these severe infections, especially in those who are at risk of getting the infection. At-risk populations are identified by not just those with dysfunctional immune systems either by a medical condition like malignancy or even uncontrolled diabetes or those taking immunosuppressive therapy such as post-transplant patients. Extremely effective and safe vaccinations against invasive infections caused by streptococcus pneumococci, Neisseria meningitides and Hemophilus influenza are currently available and have been included as routine as well as special population-based recommendations. The BCG vaccine against TB also offers considerable protection against TB meningitis. Apart from vaccinations, post-exposure prophylaxis, ie medications to be taken after a person has been inadvertently exposed to a pathogen also is a key step in the prevention of meningococcal meningitis.

(Dr Anup R Warrier is the head of infectious diseases & infection control, Dr Arun Wilson is a senior specialist in infectious diseases while Dr Sneha R is a Fellow in infectious diseases at a leading chain of hospitals in Bengaluru.)