Streptococcus pneumoniae, or pneumococcus, is a widespread spherical, Gram-positive bacterium. While a common inhabitant of the human body, it can also cause various illnesses, from mild to severe.
Its Home in the Human Body
Streptococcus pneumoniae frequently resides in the upper respiratory tract of healthy individuals without causing symptoms. Its primary reservoir is the nasopharynx, the area behind the nose and above the throat. This asymptomatic presence is known as carriage.
Carriage of Streptococcus pneumoniae can be temporary or long-term. It is particularly common in young children, with colonization rates in preschool students fluctuating between 25% to 65%. While less common in adults, healthy adults can also frequently acquire and carry the bacterium, sometimes for several months.
Locations of Infection
When Streptococcus pneumoniae causes disease, it can spread from its usual habitat to other parts of the body, leading to various infections. One of the most common and serious infections is pneumonia, where the bacteria infect the lungs. Pneumococcal pneumonia can cause symptoms such as fever, cough, shortness of breath, and chest pain.
The bacterium can also cause infections in areas adjacent to the nasopharynx. This includes the middle ear, leading to otitis media, and the sinuses, resulting in sinusitis. Symptoms of otitis media often involve ear pain and hearing loss, while sinusitis can cause facial aching and a blocked nose.
In more severe cases, Streptococcus pneumoniae can invade the bloodstream, causing bacteremia. This can lead to sepsis, a dangerous inflammatory response throughout the body. The bacteria can also reach the central nervous system, infecting the membranes surrounding the brain and spinal cord, which results in meningitis. Pneumococcal meningitis is a serious condition that can cause severe headaches, stiff neck, and confusion.
How It Spreads
Streptococcus pneumoniae primarily spreads from person to person through respiratory droplets. These droplets are released into the air when an infected individual coughs, sneezes, or even talks. Close contact with someone carrying the bacteria or who is actively ill facilitates this transmission.
The bacteria can also spread through indirect contact, such as touching surfaces contaminated with respiratory secretions and then touching one’s nose or mouth. Transmission is highly efficient, often occurring from asymptomatic carriers. Children in group childcare settings are at increased risk due to frequent close contact and sharing of objects.
Factors Influencing Its Presence
Several factors influence the likelihood of Streptococcus pneumoniae being present in an individual, either as a harmless carrier or as a cause of infection. Young children, particularly those under five years old, have higher rates of carriage and are more susceptible to infections due to their developing immune systems. Adults over 65 years of age are also at increased risk for severe pneumococcal disease.
Individuals with weakened immune systems, such as those with HIV or undergoing chemotherapy, are more vulnerable to pneumococcal infections. Certain chronic health conditions also increase susceptibility, including chronic heart, lung (like asthma or COPD), kidney disease, and diabetes. Crowded living conditions can further increase the prevalence and spread of Streptococcus pneumoniae within a community.