by Caleb Sooknanan

Pneumococcal disease is a bacterial infection caused by Streptococcus pneumoniae that occurs mainly among infants and young children. Invasive pneumococcal disease (IPD) is a more serious form of the infection that can cause meningitis, or bacterial infection in the blood, inflammation of the lungs, and other conditions. Bacterial infection, also known as sepsis, is especially common among patients who have undergone spleen removal, as it is the spleen’s macrophages that remove streptococcal bacteria from the blood stream. Dr. Thomas J. Marrie and his team of researchers from Dalhousie University in Canada performed a study to determine the relationship between asplenia, the lack of a spleen, and invasive pneumococcal disease in patients.

From 2000 to 2014, data was collected on all patients in Northern Alberta with IPD; each patient was asked whether they had undergone a splenectomy, and they were categorized based on their responses. The researchers studied conditions such as osteomyelitis, meningitis, septic arthritis, and acute kidney injury in asplenic patients. The researchers also performed serotyping, and the results were categorized according to the presence or absence of a spleen in the patient. Serotyping is a method used to determine the variant strains of microorganisms in a sample.

Of the 2435 patients studied, 37 were asplenic. These patients had more medical complications and were more likely to require treatment in an intensive care unit or with mechanical ventilation. The results also showed that asplenic patients had a higher occurrence of pneumococcal serotypes 23B and 22F. The researchers concluded that patients with IPD and asplenia were more likely to contract severe bacterial infections. However, the mortality rate among asplenic and non-asplenic patients did not differ significantly.

Given that the number of asplenic patients in the sample was very small, the data would be difficult to generalize. Another limitation of this study is that it did not focus on non-bacterial pneumococcal infections. More work is needed to study the serotypes that are prevalent in asplenic patients. Such research can help facilitate the development of future vaccinations for IPD.

References:

1. T. Marrie, et al., Asplenic patients and invasive pneumococcal disease—how bad is it these days?. International Journal of Infectious Diseases 51, 27-30 (2016). doi: 10.1016/j.ijid.2016.08.022
2. Image retrieved from: http://www.allhealthsite.com/wpcontent/uploads/2012/07/Asplenia.jpg