Antibiotic resistance and serotype distribution of invasive pneumococcal diseases before and after introduction of pneumococcal conjugate vaccine in the Kingdom of Saudi Arabia (KSA).

Streptococcus pneumoniae is one of the most common bacterial causes of morbidity and mortality worldwide, causing life threatening infections such as meningitis, pneumonia and febrile bacteremia, particular among young children. The severity and frequency of S. pneumoniae infection and emergence of drug-resistant isolates have highlighted the need for prevention of invasive pneumococcal disease (IPD) as the best method for controlling disease; to better achieve this, more information is needed about serotype distribution and patterns of antibiotic resistance in children in the Kingdom of Saudi Arabia (KSA). Cases of pneumococcal infections in children aged <5 years, recorded in hospitals throughout KSA from 2005 to 2010 were reviewed for serotyping and for antibiotic susceptibility. This covers the time period just before limited introduction of 7-valent pneumococcal conjugate vaccine (PCV7) in 2006, to its introduction into the national immunization program in 2008, until right after a switch to PCV13 in 2010. Case definition required isolation of S. pneumoniae from blood, cerebrospinal fluid, or any sterile biological fluid. Isolates from 311 eligible cases were collected from different regions across KSA, 250 from blood and 61 from cerebrospinal fluid. The most frequently isolated IPD serotypes were 23F, 19F, 6B, 5 and 1. Over the course of the study, there was significant rise of serotype 19A (covered by PCV13 but not PCV7), which accounted for 20% of isolates of IPD in Western and 5% in Central regions in the last 2 years in KSA. There was a notable decrease in serotype 18C over this period, one of the PCV7 serotypes. Serotype coverage for PCV7, PCV10, PCV13 in children <5 years was 53%, 80%, and 91%, respectively across the Kingdom from 2005 to 2010. A total of 66% of IPD isolates were penicillin-resistant, and 62% were erythromycin-resistant. Continued surveillance is critical to measure the emerging of new serotypes and antibiotic resistance strain, and the potential impact of new PCVs. PCV13, recently introduced into the national immunization schedule in place of PCV7, provides the widest coverage among all IPD serotypes across KSA.