Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 14 5 2022 10 22 653 661 Bui Son Department of Pediatrics, Nghe An Obstetrics and Pediatrics Hospital, Nghe An, Vietnam Tang Hai Department of Pediatrics, Nghe An Obstetrics and Pediatrics Hospital, Nghe An, Vietnam Tran Cuong Department of Pediatrics, Nghe An Obstetrics and Pediatrics Hospital, Nghe An, Vietnam Duong Chinh Department of Neurology, Nghe An Friendship General Hospital, Nghe An, Vietnam Thi-Hong-Hanh Le Department of Respiratory Diseases, National Pediatrics Hospital, Hanoi, Vietnam Nguyen Dung Department of Scientific Management, 108 Military Centre Hospital, Hanoi, Vietnam Vu Dinh Department of Trauma and Orthopedic Surgery, 103 Military Hospital, Hanoi, Vietnam; Department of Laboratory Medicine, 103 Military Hospital, Hanoi, Vietnam Do Anh Department of Laboratory Medicine, 103 Military Hospital, Hanoi, Vietnam; Department of Medical Parasitology, Vietnam Military Medical University, Hanoi, Vietnam 2022 05 26 2022 07 13 Background and Objectives: Identification of pnemococcal serotypes and antimicrobial resistance provides helpful information for the use of suitable vaccines and antibiotics; however, very limited data is available on these issues in Vietnam. The present study aimed to find the serotype distribution and drug resistance patterns of Streptococcus pneumoniae isolated from unvaccinated children less than 5 years of age with pneumonia at a province in centre Vietnam. Materials and Methods: A total of 126 clinical pnemococcal strains isolated from unvaccinated children less than 5 years of age with pneumonia at the Nghe An province, Vietnam between Nov 2019 and Mar 2021. All strains were identified using conventional microbiological method, VITEK® 2 Compact system, specific PCR and sequencing. The serotypes and antimicrobial resistance patterns of pnemococcal strains were determined using the multiplex PCR assays and VITEK® 2 Compact system. Results: The results showed that, eight different pneumococcal serotypes were identified. The most common serotypes were 19F (67.46%), followed by 23F (10.32%), 19A (9.52%), 6A/B (3.17%), 15A (2.38%), 9V (3.17%), 11A (1.59%) and 14 (0.80%), respectively. More than half of the pneumococcal strains were non-susceptible to penicillin. The resistance rate to ceftriaxone and cefotaxime were 41.3% and 50.8%. The percentage of pneumococci strains resistant to clarithromycin, azithromycin, erythromycin, cotrimoxazole, tetracyclin, and clindamycin were more than 93% of all strains. All pneumococcal serotypes were highly resistant to clarithromycin, azithromycin, erythromycin, cotrimoxazole, and clindamycin. Conclusion: Our findings showed high antibiotic resistance rates of the strains causing pneumococcal pneumonia, mostly macrolide resistance, among unvaccinated children. https://ijm.tums.ac.ir/index.php/ijm/article/view/3745 https://ijm.tums.ac.ir/index.php/ijm/article/download/3745/1502