Susceptibility and serotypes of Streptococcus pneumoniae isolates in invasive pneumococcal disease: a study from Kerala, South India.

Invasive pneumococcal disease (IPD) is a major burden causing significant mortality and morbidity. This study was conducted to ascertain the magnitude of the problem of drug resistance, the pneumococcal serotypes that are prevalent in our area, and whether current pneumococcal vaccines are able to cover the prevalent serotypes adequately. A retrospective study was done by reviewing the microbiology registry of our hospital. Details of patients whose blood, cerebrospinal fluid (CSF) or any other sterile fluid grew S. pneumoniae between the period January 1, 2016 and December 31, 2019 were collected. Identification and susceptibility testing were done by Vitek2 as per CLSI 2008 guidelines. Serotyping was attempted for 39 isolates. Fifty-five pneumococcal isolates in blood and CSF were identified over four years from 51 patients, of whom nine belonged to the paediatric age group. Among 55 isolates, 50 were isolated from blood, four had growth of pneumococci in both blood and CSF, and one had growth in CSF alone. Overall non-susceptibility to penicillin was noted in 11 isolates, and 10 isolates were non-susceptible to ceftriaxone. Common serotypes isolated were 9V, 19F, 23F and 6 B. The most common clinical presentation was pneumonia followed by sepsis and meningitis. Five of the 51 patients succumbed to the illness. Penicillin susceptibility among pneumococcal isolates in IPD was 80% and susceptibility to ceftriaxone was 82%. This observation reiterates the view that vancomycin must be added to the empiric therapy of suspected IPD. Most of the identified serotypes are covered by current pneumococcal vaccines, highlighting the pivotal role of pneumococcal vaccine in prevention of IPD.