[Clinical research of Bordetella pertussis infection in infants with prolonged cough].

Objective: To explore the prevalence of Bordetella pertussis (B. pertussis) infection in unvaccinated or incomplete vaccinated infants with cough for a prolonged duration.
Methods: The serum samples and nasopharyngeal secretions were collected from 176 patients with cough for a prolonged duration ( ≥ 2 weeks) from 2011 to 2012 at Children's Hospital Affiliated to Capital Institute of Pediatrics. Multiplex PCR of nasopharyngeal secretion was employed to identify B.pertussis. And enzyme-linked immunosorbent assay(ELISA) was used to detect antibody to pertussis toxin(PT-IgG). Total bacterial DNA was enacted from nasopharyngeal secretion and two-target IS481/PT of B.pertussis was detected by PCR. The sera and nasopharyngeal secretions were also collected from household contacts with cough for a prolonged duration. Their clinical characteristic and epidemiological profiles were collected and analyzed.
Results: B.Pertussis infection was demonstrated in 51 cases (29.0%). The patients ages were from 23 days to 4 years. Among them, 46 cases (90.2%) were aged under 12 months and 5 cases (9.8%) over 12 months. And 40 cases were unvaccinated (31 cases <3 months old, 4 cases 3-12 months old, 5 cases >5 years old) and 11 cases incompletely vaccinated. There were 31 males and 20 females. More patients were found in spring and summer than those in autumn and winter. Nine infant cases had 12 household contacts. Among 12 household contacts, 3 were PCR positive and 12 PT-IgG positive. Pertussis was remarkably critical in infants. Serious complications included failure to thrive, pneumonia, respiratory failure and seizures.
Conclusions: B.pertussis infection is an important cause in unvaccinated or incomplete vaccinated infants with prolonged cough. Peak seasons of pertussis are spring and summer. Undiagnosed adolescents and adults with pertussis may be a significant source for transmission of B.pertussis to other susceptible children. Infants aged under 1 year are at risk for severe pertussis and life-threatening complications. As a rapid and sensitive method of detecting B.pertussis, PCR may be used in early phase.