• Alyssa R Golden, Melanie R Baxter, Ross J Davidson, Irene Martin, Walter Demczuk, Michael R Mulvey, James A Karlowsky, Daryl J Hoban, George G Zhanel, Heather J Adam, and Canadian Antimicrobial Resistance Alliance (CARA) and CANWARD.
• Department of Medical Microbiology and Infectious Diseases, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Room 543-745 Bannatyne Avenue, Winnipeg, Manitoba, Canada.
• J. Antimicrob. Chemother. 2019 Aug 1; 74 (Suppl 4): iv39-iv47.

ObjectivesTo compare the epidemiology and antimicrobial susceptibility patterns of Streptococcus pneumoniae collected from respiratory and blood culture samples in Canada between 2007 and 2016.MethodsS. pneumoniae strains were obtained from Canadian hospitals as part of the ongoing national surveillance study, CANWARD. Isolates were serotyped using the Quellung method. Antimicrobial susceptibility testing was performed using the CLSI broth microdilution method. MDR and XDR were defined as resistance to three or more and five or more classes of antimicrobials, respectively.ResultsOf the 2581 S. pneumoniae isolates collected, 1685 (65.3%) and 896 (34.7%) were obtained from respiratory and blood samples, respectively. Respiratory isolates demonstrated lower rates of antimicrobial susceptibility than blood isolates to penicillin, ceftriaxone, clarithromycin, clindamycin, doxycycline and trimethoprim/sulfamethoxazole (P ≤ 0.03). From 2007 to 2016, invasive isolates demonstrated trends towards increasing penicillin susceptibility and decreasing clarithromycin susceptibility. MDR was significantly higher in respiratory S. pneumoniae compared with blood (9.1% versus 4.5%, P < 0.0001). Serotypes 11A, 16F, 19F, 23A/B/F, 34, 35B and non-typeable strains were more commonly isolated from respiratory specimens, while 4, 5, 7F, 8, 12F, 14 and 19A were more commonly invasive serotypes. Numerous serotypes, including 3 and 22F, were isolated frequently from both specimen sources.ConclusionsS. pneumoniae from respiratory samples demonstrated lower antimicrobial susceptibilities and higher MDR in a greater diversity of serotypes than isolates obtained from blood. Many serotypes were associated with one specific specimen source, while others were associated with both; genetic characterization is necessary to elucidate the specific factors influencing the ability of these serotypes to commonly cause both invasive and non-invasive disease.© The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.

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