Investigation of nasopharyngeal pneumococcal carriage and determination of serotype distribution in adults with risk factors for streptococcus pneumoniae infection

Introduction: The incidence and mortality of invasive pneumococcal disease is much higher in people over 65 years old compared to the general population. The most effective way to prevent disease is vaccination. The incidence of the disease and the distribution of serotypes changed with the widespread of childhood conjugate pneumococcal vaccines and the use of vaccines in the adult age group. Nasopharyngeal carriage is the first and most important step in the pathogenesis of the infection. In this study, we aimed to determine the pneumococcal carriage rate and serotype distribution in adults aged ≥ 65 years with risk for pneumococcal infection living in a nursing home. Method: To investigate pneumococcal carriage, nasopharyngeal swabs were taken from ≥ 65 years old people living in Narlıdede Nursing Home. The specimens were cultured and pneumococci were identified according to colony appearance, optochin susceptibility and solubility in bile salts. The pneumococcal carriage rate and risk factors for carriage were determined. Pneumococcal serotypes were identified using the capsule swelling reaction. Results: Pneumococcus was isolated in 10 of 341 subjects who participated in the study and the pneumococcal carriage rate was calculated as 2.9%. Risk factors for pneumococcal colonization were advanced age, immunocompromising conditions and chronic renal failure. Serotypes of isolated pneumococci were identified as 7F, 23F, 10, 11, 15, 17, 20 and 33. The coverage of 13 valent conjugated pneumococcal vaccine was 20%. Conclusion: Although this study was conducted in a limited group and the rate of pneumococcal carriage was low, it is an important finding that the serotypes other than conjugate pneumococcal vaccine are predominant in carriage. Furthermore, advanced age and immunocompromising conditions were found to be risk factors in terms of pneumococcal carriage. Similar studies to assess pneumococcal vaccine coverage in different adult populations at risk are required to be repeated at regular intervals in order to monitor serotype replacement. Keywords: Streptococcus pneumoniae, carriage, adult, serotype, pneumococcal vaccine