Streptococcus pneumoniae: prevalence in nasopharyngeal carriers of more than 50-years-old, in a Mexican rural community

Abstract

IntroductionStreptococcus pneumoniae (Sp) is the main cause of community-acquired pneumonia in the elderly, hence the importance to establish the prevalence of nasopharyngeal colonization by different Sp serotypes in adults. Methodsfrom December 2009 to June 2010, nasopharyngeal cultures were taken from adults living in rural communities in Mexico for the isolation and serotyping of Sp by the Quellung reaction. Penicillin and ceftriaxone susceptibility tests were performed by the microdilution method. Resultstwo hundred and thirty-six adults over 50 years old, were included. The prevalence of colonization by Sp was 21.6%. The most frequent serotypes were 19A (21%), 6A (13%), 6B and 11A (11%). All isolates were susceptible to ceftriaxone, and 52.8% of the isolates showed penicillin minimal inhibitory concentrations ≥0.12mg/L. Conclusionthis is the first study analyzing the nasopharyngeal colonization by Sp in adults in Mexico. Serotypes not included in any of the pneumococcal vaccines were frequently identified.