Abstract
Penicillin non-susceptible (PNSP) and multi-resistant pneumococci have been prevalent in Iceland since early nineties, mainly causing problems in treatment of acute otitis media. The 10-valent protein conjugated pneumococcal vaccine (PHiD-CV) was introduced into the childhood vaccination program in 2011. The aim of the study was to investigate the changes in antimicrobial susceptibility and serotype distribution of penicillin non-susceptible pneumococci (PNSP) in Iceland 2011-2017. All pneumococcal isolates identified at the Landspítali University Hospital in 2011-2017, excluding isolates from the nasopharynx and throat were studied. Susceptibility testing was done according to the EUCAST guidelines using disk diffusion with chloramphenicol, erythromycin, clindamycin, tetracycline, trimethoprim/sulfamethoxazole and oxacillin for PNSP screening. Penicillin and ceftriaxone minimum inhibitory concentrations (MIC) were measured for oxacillin resistant isolates using the E-test. Serotyping was done using latex agglutination and/or multiplex PCR. The total number of pneumococcal isolates that met the study criteria was 1,706, of which 516 (30.2%) were PNSP, and declining with time. PNSP isolates of PHiD-CV vaccine serotypes (VT) were 362/516 (70.2%) declining with time, 132/143 (92.3%) in 2011 and 17/54 (31.5%) in 2017. PNSP were most commonly of serotype 19F, 317/516 isolates declining with time, 124/143 in 2011 and 15/54 in 2017. Their number decreased in all age groups, but mainly in the youngest children. PNSP isolates of non PHiD-CV vaccine serotypes (NVT) were 154/516, increasing with time, 11/14, in 2011 and 37/54 in 2017. The most common emerging NVTs in 2011 and 2017 were 6C, 1/143 and 10/54 respectively. PNSP of VTs have virtually disappeared from children with pneumococcal diseases after the initiation of pneumococcal vaccination in Iceland and a clear herd effect was observed. This was mainly driven by a decrease of PNSP isolates belonging to a serotype 19F multi-resistant lineage. However, emerging multi-resistant NVT isolates are of concern.
Highlights
Streptococcus pneumoniae are a common cause of relatively mild localized infections such as otitis media but can cause more severe infections like pneumonia and live threatening invasive diseases
Penicillin non-susceptible (PNSP) and multi-resistant pneumococci have been prevalent in Iceland since early nineties, mainly causing problems in treatment of acute otitis media
penicillin non-susceptible pneumococci (PNSP) of vaccine serotypes (VT) have virtually disappeared from children with pneumococcal diseases after the initiation of pneumococcal vaccination in Iceland and a clear herd effect was observed
Summary
Streptococcus pneumoniae are a common cause of relatively mild localized infections such as otitis media but can cause more severe infections like pneumonia and live threatening invasive diseases. The epidemiology of penicillin non-susceptible pneumococci (PNSP) in Iceland has been studied intensively from 1988–2010 with emphasis on pneumococcal serotypes and antimicrobial susceptibility [8, 9]. Two PNSP epidemics have been described in the country prior to implementation of the 10-valent protein conjugate pneumococcal vaccine (PHiD-CV) into the country’s childhood vaccination program in 2011. Both were caused by known multi-resistant international pneumococcal lineages, CC90, Spain6B-2 CC236/270/320, single and double locus variants of Taiwan19F-14. Penicillin non-susceptible (PNSP) and multi-resistant pneumococci have been prevalent in Iceland since early nineties, mainly causing problems in treatment of acute otitis media. The aim of the study was to investigate the changes in antimicrobial susceptibility and serotype distribution of penicillin non-susceptible pneumococci (PNSP) in Iceland 2011–2017
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