pneumonia

EuroPneumo Special Issue / pneumonia 2015 Oct 21;7:I–72
of this collection. From a total of 1661 isolates, a random sample of at least 50% of the isolates from each serotype was
chosen for multilocus sequence typing (MLST) and goeBURST analysis (n = 872). We detected a diverse clonal composition
with 205 different sequence types (STs) (SID = 0.972 [95% CI 0.967–0.976]) organised in 82 different clonal complexes
(CCs) (SID = 0.948 [95% CI 0.942–0.953). Although there was high genetic diversity half of the isolates arranged in only
6 CCs: CC156 (11.6%), CC191 (10.1%), CC180 (8.0%), CC306 (7.8%), CC62 (7.7%), CC230 (5.4%). The major clone was
mostly composed of PCV7 serotypes (89%) although these only accounted for 18.1% of the isolates analysed by MLST.
The additional serotypes found in PCV13 (42.0% of the genotyped isolates) were the major constituents of 4 of these
6 major clones (CC191, CC180, CC306, and CC230) while PPV23 additional serotypes (20.0%) were the most frequent
in CC62. The clonal frequency was greatly influenced by serotype fluctuations, especially of the CC306, represented by
serotype 1, which significantly declined from 12.8% (2008) to 2.8% (2011). A few possible capsular switches between
vaccine and non-vaccine types were identified. For instance, isolates of ST1201 presented serotypes 19A and 7C, ST230
had serotypes 19A and 24F, ST42 was from serotypes 23A or 6A, and ST241 had both 19A and 18A capsular types.
Antimicrobial resistance was more strongly associated with ST than with serotype, with different STs of the resistant
serotypes 19A and 14 behaving differently. Since the most important clones causing adult IPD are mainly composed of
PCV13 serotypes, major changes in the clonal composition of pneumococci are expected with continued vaccine use.
P2.24
The identification of pneumococci by lytA-based identification methods
may retrieve false results
Débora A. Tavares 1 , Alexandra S. Simões 1 , Hermínia de Lencastre 2, 3 , Raquel Sá-Leão 1
1
Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de
Lisboa, Oeiras, Portugal; 2 Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa,
Oeiras, Portugal; 3 Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, NY, USA
In recent years, molecular strategies targeting lytA (coding for the major pneumococcal autolysin), have been proposed
to identify pneumococcus. In the clinical setting, the identification of pneumococci based on the amplification of lytA by
real-time PCR is increasingly used particularly when doing direct detection in clinical samples. In research laboratories,
the distinction between atypical pneumococci and closely related species has often been based on the assignment of
specific lytA-BsaAI-RFLP signatures and/or MLST and multilocus sequence analysis (MLSA) strategies. In our collection,
we detected 11 strains displaying conflicting or novel results when identified by lytA-BsaAI-RFLP and MLST. Here we
report further characterisation of these strains and discuss the utility of using lytA-real-time PCR in these cases. MLSA
for viridans streptococci divided the 11 strains in 4 pneumococci 2 lineages), 5 Streptococcus mitis (5 lineages), and 2
S. pseudopneumoniae (1 lineage). Three novel lytA-BsaAI-RFLP signatures were found. In addition, 1 pneumococcus
displayed the atypical lytA-BsaAI-RFLP signature characteristic of non-pneumococci and 2 S. pseudopneumoniae
displayed the typical lytA-BsaAI-RFLP pattern characteristic of pneumococci. lytA-real-time PCR misidentified these 3
isolates. DNA sequencing of lytA confirmed these observations. Although rare, lytA-based identification methods may
lead to false results.
P2.25
Characterisation of the blp locus of co-colonising pneumococci and its
impact on co-colonisation
Carina Valente 1 , Suzanne Dawid 2, 3 , Hermínia de Lencastre 4, 5 , Raquel Sá-Leão 1
1
Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras,
Portugal; 2 Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, Michigan, USA; 3 Department of Microbiology
and Immunology, University of Michigan, Ann Arbor, Michigan, USA; 4 Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica,
Universidade Nova de Lisboa, Oeiras, Portugal; 5 Laboratory of Microbiology, The Rockefeller University, New York, New York, USA
Pneumococcal co-colonisation of the nasopharynx is frequent and is important for pneumococcal biology by promoting
both evolution and competition. The bacteriocin-like peptides (blp) locus has been implicated in intra-species competition
but the effect of bacteriocin secretion on co-colonisation remains to be assessed. We aimed to evaluate the impact
of the blp locus and bacteriocin production on pneumococcal co-existence in the nasopharynx. A collection of 135
co-colonised nasopharyngeal samples from healthy children was used. The inhibitory activity of all strains (n = 285)
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