Streptococcus pneumoniae colonization in the nasopharynx (NP) of elderly reflects transmission in the community and disease risk. Few studies measured pneumococcal carriage among adults. However in developing countries, the data is scare. To address this, we conducted cross-sectional studies during October 2014-February 2015 and July-September 2015. As PCV-10 introduced in Bangladesh on March 2015, both periods are considered baseline data.
In Mirzapur, a rural area in Bangladesh, 1408 NP swabs were collected from healthy adults (age, 45-95 years) identified during demographic surveillance system household visits. Swabs were cultured for pneumococci and serotyped using quellung reaction.
Pneumococcal colonization rates during the two time periods were 10% (80/762) and 9% (61/646), respectively. Fifty-one different serotypes were detected. Only 13% (19/141) of isolates were PCV-10 serotypes, 22% (31/141) were PCV-13, 33% (46/141) were PCV-20, and 34% (48/141) were 23-valent polysaccharide vaccine serotypes. The most predominant serotypes were 13 (8%), 34 (8%), 3 (6%), 39 (6%), 35B (4%), 18C (4%) and 19F (4%).
Our findings indicate that a diverse set of serotypes cause pneumococcal carriage among older adults in Bangladesh, with 4 of the 7 most predominant not found in existing or forthcoming conjugate vaccine formulations.