title: Trends of invasive serotype 6C pneumococci in Spain: emergence of a new lineage.
abstract: OBJECTIVE
  To analyse the epidemiology of isolates of serotype 6C among invasive pneumococci isolated from children and adults in Spain between 1997 and 2009, and to characterize serotype 6C clones and macrolide and quinolone resistance mechanisms.
  
  
  METHODS
  Antimicrobial susceptibility was determined following CLSI guidelines. Phenotypic characterization of macrolide-resistant isolates was performed by the double disc diffusion method. Genes associated with resistance to erythromycin and tetracycline were sought by PCR, while quinolone resistance was analysed by restriction fragment length polymorphism of the quinolone resistance-determining region. Isolates were typed by multilocus sequence typing.
  
  
  RESULTS
  Seven hundred and eighty-nine of 866 serotype 6A pneumococci collected from 1997 to 2009 were available. Of these, 213 (27.0%) were serotype 6C; 16/163 (9.8%) in the 1997-2001 (pre-PCV7) period, 37/322 (11.5%) in the 2002-05 (early-PCV7) period and 160/381 (42.0%) in the 2006-09 (late-PCV7) period. The overall proportions of serotype 6C increased from 0.1% (pre-PCV7) to 1% (late-PCV7) for paediatric isolates and from 0.3% to 1.7% among adult isolates. A major serotype 6C lineage (ST224/ST1150/ST4821), accounting for 66.7% of the isolates, was identified across the whole period. In the late-PCV7 period the antimicrobial non-susceptibility of serotype 6C increased in association with the emergence of the ST386/ST4310/ST4825 lineage, which carried a Tn6002 transposon [erm(B) and tet(M) genes].
  
  
  CONCLUSIONS
  Serotype 6C pneumococci were identified in Spain during the period 1997-2009. The increase in serotype 6C in the late-PCV7 period was associated with the spread of the ST224/ST1150/ST4821 lineage and the emergence of the ST386/ST4310/ST4825 lineage.
authors.affiliation: Microbiology Department, IDIBELL, Hospital Universitari de Bellvitge, Universitat de Barcelona, Feixa Llarga s/n, 08907 L'Hospitalet de Llobregat, Barcelona, Spain.
authors.forename: Dora
authors.initials: D
authors.lastname: Rolo
authors.forename: Asunción
authors.initials: A
authors.lastname: Fenoll
authors.forename: Carmen
authors.initials: C
authors.lastname: Ardanuy
authors.forename: Laura
authors.initials: L
authors.lastname: Calatayud
authors.forename: Meritxell
authors.initials: M
authors.lastname: Cubero
authors.forename: Adela G
authors.initials: AG
authors.lastname: de la Campa
authors.forename: Josefina
authors.initials: J
authors.lastname: Liñares
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents; D002648:Child; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018942:Macrolides / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology; D012150:Polymorphism, Restriction Fragment Length; D015363:Quinolones / Q000494:pharmacology; D012703:Serotyping; D013030:Spain / Q000453:epidemiology; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D013752:Tetracycline / Q000494:pharmacology; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D018942:Macrolides; D022242:Pneumococcal Vaccines; D015363:Quinolones; D013752:Tetracycline