Reduction of antimicrobial resistant pneumococci seven years after introduction of pneumococcal vaccine in Iceland

• Published in: PloS one Vol. 15; no. 3; p. e0230332
• Main Authors: Hjálmarsdóttir, Martha Á, Haraldsson, Gunnsteinn, Quirk, Sigríður Júlía, Haraldsson, Ásgeir, Erlendsdóttir, Helga, Kristinsson, Karl G
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 17.03.2020; Public Library of Science (PLoS)
• Subjects: Agglutination; Antibacterial agents; Antibiotics; Antiinfectives and antibacterials; Antimicrobial agents; Bioethics; Biology and Life Sciences; Ceftriaxone; Childhood; Children; Chloramphenicol; Chloromycetin; Clindamycin; Diseases; Drug dosages; Drug resistance; Drug therapy; Erythromycin; Fluids; Identification methods; Immunization; Laboratories; Latex; Latex agglutination; Medicine; Medicine and Health Sciences; Methods; Microbial drug resistance; Minimum inhibitory concentration; Nasopharynx; Otitis; Otitis media; Oxacillin; Patients; Penicillin; Penicillins; People and Places; Pharynx; Population; Serotypes; Serotyping; Streptococcus infections; Sulfamethoxazole; Tetracyclines; Time; Trimethoprim; Vaccination; Vaccines; Iceland
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0230332

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.