title: Increase in pertussis cases along with high prevalence of two emerging genotypes of Bordetella pertussis in Perú, 2012.
abstract: As has occurred in many regions worldwide, in 2012 the incidence of pertussis increased in Perú. This epidemiologic situation has been associated with a waning vaccine-induced immunity and the adaptation of Bordetella pertussis to vaccine-induced immunity along with improved diagnostic methods.
  
  
  
  The study comprised a total of 840 pertussis-suspected cases reported in Perú during 2012. We summarize here the distribution of pertussis cases according to age and immunization status along with the immunization-coverage rate. Laboratory diagnosis was performed by culture test and real-time polymerase-chain reaction (PCR). B. pertussis bacteria recovered from infected patients were characterized by pulsed-field gel electrophoresis (PFGE), and the DNA sequencing of the pertussis-toxin (promoter and subunit A), pertactin, and fimbriae (fim2 and fim3) genes.
  
  
  
  From the total pertussis-suspected cases, 191 (22.7 %) infections were confirmed by real-time PCR and 18 through cultivation of B. pertussis (2.1 %), while one infection of B. parapertussis (0.11 %) was also detected by culture. Pertussis was significantly higher in patients that had had 0-3 vaccine doses (pentavalent vaccine alone) than in those who had had 4-5 vaccine doses (pentavalent plus DwPT boosters) at 94.3 vs. 5.7 %, respectively (p < 0.00001). The relative risk (RR) for patients with 4-5 doses compared to those with fewer than 4 doses or no dose was 0.23 (95 % Confidence Interval: 0.11-0.44), while the vaccine effectiveness was 77 % and coverage 50.5 %. Genetic analysis of B. pertussis isolates from different Peruvian regions detected two clonal groups as identified by PFGE. Those two groups corresponded to the B. pertussis genotypes emerging worldwide ptxP3-ptxA1-prn2 or 9-fim3-1 and ptxP3-ptxA1-prn2 or 9-fim3-2.
  
  
  
  Two emerging B. pertussis genotypes similar to isolates involved in worldwide epidemics were detected in Perú. Low vaccine coverage (<50 %) and genetic divergence between the vaccine-producing strain and the local isolates could contribute to this pertussal epidemic.
authors.affiliation: Laboratorio de Biotecnología y Biología Molecular, Centro Nacional de Salud Pública, Instituto Nacional de Salud, Ministerio de Salud, Lima, Peru. henribailon@gmail.com.
authors.forename: H
authors.initials: H
authors.lastname: Bailon
authors.affiliation: Laboratorio de Biotecnología y Biología Molecular, Centro Nacional de Salud Pública, Instituto Nacional de Salud, Ministerio de Salud, Lima, Peru.
authors.forename: N
authors.initials: N
authors.lastname: León-Janampa
authors.affiliation: Laboratorio de Biotecnología y Biología Molecular, Centro Nacional de Salud Pública, Instituto Nacional de Salud, Ministerio de Salud, Lima, Peru.
authors.forename: C
authors.initials: C
authors.lastname: Padilla
authors.affiliation: Departamento de Ciencias Biológicas, Laboratorio VacSal del Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas Universidad Nacional de La Plata, CONICET, La Plata, Argentina.
authors.forename: D
authors.initials: D
authors.lastname: Hozbor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001886:Bordetella pertussis / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005838:Genotype; D006801:Humans; D007114:Immunization / Q000706:statistics & numerical data; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D037342:Pertussis Toxin / Q000235:genetics; D010567:Pertussis Vaccine / Q000008:administration & dosage; D010568:Peru / Q000453:epidemiology; D060888:Real-Time Polymerase Chain Reaction; D014611:Vaccination / Q000706:statistics & numerical data; D010566:Virulence Factors, Bordetella / Q000235:genetics; D014917:Whooping Cough / Q000453:epidemiology* / Q000276:immunology / Q000382:microbiology*; D055815:Young Adult
chemical_list: D001425:Bacterial Outer Membrane Proteins; D010567:Pertussis Vaccine; D010566:Virulence Factors, Bordetella; C068929:pertactin; D037342:Pertussis Toxin
keywords: Bordetella pertussis; Genotype; Pertussis; Perú; Pulsed-field gel electrophoresis