Detection of Streptococcus pneumoniae carriage in adult patients and determination of serogroups

Streptococcus pneumoniae (pneumococcus) is an important cause of morbidity and mortality worldwide. With the widespread use of KPA13 (13-component conjugated pneumococcal vaccine) in the protection of pneumococcal diseases, shifts in the distribution of serotypes and an increase in non-vaccine strains have been observed. For this reason, continuing the surveillance and serotype monitoring of IPD (invasive pneumococcal disease) and pneumococcal carriage and determining the coverage of existing vaccines are very important in evaluating vaccine effectiveness. This study aimed to determine the Streptococcus pneumoniae carriage rate and risk factors affecting carriage in adult patients admitted to our hospital outpatient clinics, and to reveal the serogroup/serotype distribution of the detected strains,antibiotic resistance and vaccine coverage rates. Oropharyngeal swabs were taken from 1004 adult patients between the ages of 17 and 91 who applied to the outpatient clinics of Van Yüzüncü Yıl University Dursun Odabaş Medical Center between February 2022 and August 2022. Pneumococcus was identified from the samples taken by conventional methods. The pneumococcal carriage rate and risk factors for carriage were determined. Serogroups/serotypes of isolated pneumococci were determined using the latex agglutination method. Antibiotic resistance of isolated pneumococcal strains was determined using the Kirby-Bauer disc diffusion method and E-test method. Pneumococcus was isolated in 27 of 1004 people participating in the study and the pneumococcal carrier rate was calculated as 2.68%. No significant relationship could be established between the identified risk factors and pneumococcal carriage. A large proportion of non-vaccine serogroups/serotypes (56%) were detected. Serotypes 3, 20, 14 and serogroups 17, 11, 23, 15, 18 and 9 were the serogroups/serotypes detected. Serotype 3 was found to be the most frequently detected serotype. Although there is no clear information about the coverage rates of the vaccines for the detected serogroups/serotypes; The serotype coverage rates of KPA13 and KPA15 (15-component conjugated pneumococcal vaccine) are the same and range from 14.8-25.9%; The coverage rates of KPA20 (20-component pneumococcal conjugate vaccine) and PPA23 (23-component polysaccharide pneumococcal vaccine) were found to be between 14.8-37% and 18.5-44.4%, respectively. Resistance to penicillin (meningitis) was detected at a rate of 80.9%, trimethoprim-sulfamethoxazole 38%, tetracycline 38%, erythromycin 28.5%, clindamycin 28.5% and rifampin 4.7%. The highest resistance rates were seen in penicillin (meningitis), trimethoprimsulfamethoxazole and tetracycline. MDR (Multi Drug Resistance) rate was found to be 38%. cMLSB (constitutive Macrolide-Lincosamide Streptogramin B) phenotype was detected in 5 (23.8%) strains with macrolide resistance, M (Macrolide) phenotype resistance was detected in 1 strain (4.8%), and iMLSB (inducible MLSB) phenotype resistance was not detected. This study was conducted in a limited area, in a limited group, and may not represent the entire population. The pneumococcal carriage rate is consistent with the rates found in similar studies conducted in adults (1% - 10%). Although no significant relationship has been established with the risk factors identified in carriage, the predominance of non-vaccine serogroups/serotypes is an important finding. Our KPA13 vaccine coverage was found to be low, and this increase in non-vaccine strains and high antibiotic resistance rates reveal the need for new vaccines with wider strain coverage. In addition, our results showed that KPA20, one of the new vaccines not in use in our country, can provide wider coverage compared to KPA13. Key Words: Adult, Pneumococcal Vaccine, Serotype, Streptococcus pneumoniae, Carriage