[Detection of Bordetella pertussis infection by culture, real-time polymerase chain reaction and serologic tests among children with prolonged cough].
Pertussis is a respiratory infection caused by Bordetella pertussis. It attacks all age groups. It has significantly higher mortality and morbidity among newborns and children. Adolescents and adults with symptomatic but unrecognized pertussis are often the source of the infection for pediatric cases. Therefore, it is suggested to perform laboratory diagnostic tests for B.pertussis infection in children and adolescents with prolonged cough of more than two weeks. In this study, it was aimed to identify B.pertussis infection by culture, real-time polymerase chain reaction (Rt-PCR) and serological methods among children with prolonged cough. Nasopharyngeal swab samples were obtained from 51 children (19 female, 32 male; age between 2 months-14 years; median age: 7.0), who attended the outpatient clinic of Ege University Medical Faculty Department of Pediatrics, Izmir, Turkey with prolonged cough (≥ 14 days) during December 2009-August 2010. While pertussis vaccination had been completed in 48 (94%) of the cases, three cases had not been vaccinated. Previous antibiotic treatment was reported for 38 (75%) of the cases. Cultivation was done by using 7% horse blood and charcoal containing Bordetella Agar (Becton Dickinson, Germany) and Rt-PCR targeting IS481 sequence (Roche Applied Science, Germany) was used to detect B.pertussis. In addition, in house ELISA was performed to detect titers of anti-pertussis toxin (anti-PT) IgG and anti-filamentous hemagglutinin (anti-FHA) IgG antibodies in paired sera collected in 2-4 week intervals. Fourfold titer increase of antibodies or anti-PT IgG levels of at least 100 EU/ml in one serum were evaluated as serological confirmation of B.pertussis infection. In our study, B.pertussis was isolated from one nasopharyngeal swab samples culture among the 51 patients, and IS481 Rt-PCR yielded positive results for B.pertussis in 6 (11.8%) samples. Nine (17.6%) patients were diagnosed as B.pertussis infection by serological tests. Totally 12 patients were evaluated as positive using at least one method. Among them only one had positive results with three of the tests used and two were positive with IS481 Rt-PCR assay and serologic tests. Three patients were found positive with only IS481 Rt-PCR and six were identified only with serologic diagnosis. In this study, 23.5% (12/51) of children with persistant cough were evaluated as having B.pertussis infection. The age range of these cases (5 female, 7 male) was 2 months-11 years and one case had not been vaccinated at all while four cases had not completed the vaccination schedule. It was concluded that since B.pertussis can be detected as the etiologic agent of persistant cough in a significant number of children by culture, PCR and serologic tests, diagnostic tests must be applied to evaluate B.pertussis infection. However, standardized serological methods and PCR protocols are needed for accurate and reliable diagnosis.
Ege University Faculty of Medicine, Department of Medical Microbiology, İzmir, Turkey. deryagursel@gmail.com
Derya
D
Gürsel
Aslı
A
Aslan
Cemile
C
Sönmez
Güldane
G
Koturoğlu
Nilay
N
Cöplü
Zafer
Z
Kurugöl
Söhret
S
Aydemir
D000293:Adolescent; D000907:Antibodies, Bacterial / Q000097:blood; D001886:Bordetella pertussis / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D002648:Child; D002675:Child, Preschool; D003371:Cough; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019085:Fluorescent Antibody Technique, Direct; D006388:Hemagglutinins / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D037342:Pertussis Toxin / Q000276:immunology; D060888:Real-Time Polymerase Chain Reaction; D013997:Time Factors; D014917:Whooping Cough / Q000175:diagnosis* / Q000382:microbiology
D000907:Antibodies, Bacterial; D004269:DNA, Bacterial; D006388:Hemagglutinins; D007074:Immunoglobulin G; D037342:Pertussis Toxin