Invasive pneumococcal disease caused by ceftriaxone-resistant Streptococcus pneumoniae in Taiwan

Background: Invasive pneumococcal disease (IPD) was associated with mortality, but the risk factors associated with mortality remains controversial. Methods: A retrospective cohort study was designed. All patients with IPD from 2011 to 2013 admitted in a medical center were screened and collected for their clinical presentations and laboratory characteristics. Results: Approximately half of the 134 IPD isolates derived from these patients belonged to three major serotypes (19A, 6A and 3), which are included in 13-valent pneumococcal conjugate vaccine (PCV13), but not in 7-valent pneumococcal conjugate vaccine (PCV7). Ceftriaxone resistance according to non-meningitis criteria was identified in 38% of the IPD isolates, and was the major independent risk factor associated with inappropriate initial therapy that subsequently contributed to mortality of the patients. Infection by serotype 6A, 15B, 19A, 19F, or 23F was the major independent risk factor associated with ceftriaxone resistance (non-meningitis criteria). 77.6% of these isolates belonged to additional PCV13 serotypes, with more than 40% expressing resistance to ceftriaxone. In terms of serotype coverage, PCV13 covered 94.1% of the IPD isolates with ceftriaxone resistance, in comparison to 21.6% only by PCV7. Conclusions: The increase of ceftriaxone resistance in pneumococci in part driven by PCV7 vaccination in Taiwan is worrisome. The use of PCV13 in children as well as in the elderly population is likely to offer protection from the infection caused by ceftriaxone-resistant pneumococci. It is important to give an effective drug such as penicillin, fluoroquinolones or vancomycin in 2 days for improving outcome of IPD patients. Copyright (C) 2017, Taiwan Society of Microbiology. Published by Elsevier Taiwan LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).