Distribution of serotypes and antimicrobial sensitivity of invasive Streptococcus pneumoniae infections in two district general hospitals in South-East England

Abstract

Background: Invasive pneumococcal infections (IPIs), such as bacteremia, pneumonia, and meningitis, pose a significant risk to children <2 years and adults >65 years. The prevalence of serotypes causing IPIs varies over time and geographically. The increased use of pneumococcal polysaccharide (PPV)-23 for >65 years and pneumococcal conjugate vaccine (PCV)-13 for <2 years has led to the rise in non-vaccine serotypes in the world. The choice of antibiotics to treat IPIs has become a real challenge due to antimicrobial resistance. Aim: This study aimed to check the coverage of the vaccines and the effectiveness of locally recommended antibiotics for IPIs. Methods: This retrospective study was performed in East Sussex Healthcare Trust from January 2006 to December 2018. Results: A total of 523 invasive pneumococcal isolates were recovered from sterile samples from 491 patients. Of these, 498 were from blood cultures, and 16, 5, and 4 each were from cerebrospinal fluid (CSF), joint fluid, and pleural fluid, respectively. More than one specimen yielded Streptococcus Pneumoniae (S. pneumoniae): 12 of 491 patients had both CSF and blood culture, 2 had blood culture and joint fluid, and 1 had blood culture and pleural fluid. All 523 isolates were subjected to Quellung serotyping and antimicrobial susceptibility testing. Forty-nine different serotypes were observed; 68% (357/523) of these serotypes come under pneumococcal vaccine coverage. The prevalent serotypes were 12F (9%), 8 (9%), 19A (7%), 3 (6%), 7F (5%), 9N (5%), and 22F (4%), while 32 isolates were undetermined. Serotype 23B was isolated from 5 patients. The vaccine serotype coverage of PCV13 and PPV23 against serotypes causing IPIs was 34% and 68%, respectively. Among patients aged <2 years, 35% of isolates belonged to serotypes covered by PCV13, while among patients aged >2 years, 68% of isolates belonged to serotypes covered by PPV23. Antimicrobial susceptibility results showed that more than 93% of S. pneumoniae were sensitive to penicillin, amoxicillin, and cefuroxime, while <1% were resistant to penicillin. Conclusion: Locally recommended antibiotics are effective against IPIs. Inclusion of 15A and 23B in the vaccine would improve the PCV-13 and PPV-23 performance in IPI prevention. Continuous surveillance of serotype distribution and antimicrobial susceptibility is important for appropriate use of antimicrobials to avoid antimicrobial resistance, plus serves as important data for vaccinologists.