Microbiology - Bordetella Pertussis
Specimens for isolation of Bordetella pertussis and B. parapertussis in suspected cases of whooping cough are accepted from public and private health care providers. PCR screening is available for Bordetella pertussis only. Only symptomatic contacts of diagnosed cases of pertussis are recommended for Bordetella examination, since a carrier state in asymptomatic persons has not been demonstrated as an important source of transmission. Reference cultures are accepted for confirmation of Bordetella pertussis, B.parapertussis and B.bronchiseptica. Consultation and bench training are provided upon request.
Nasopharyngeal swabs should be collected as soon as possible after onset of symptoms, and prior to antibiotic treatment. There is a greater likelihood of positive cultures and/or PCR in the first two weeks of symptomatic infection than during later weeks of illness. However, PCR may detect organisms for a prolonged period of time regardless of viability.
A mailer containing materials and instructions necessary for collecting and shipping nasopharyngeal specimens is available from the Laboratory Mailroom by ordering online at https://slphreporting.ncpublichealth.com/labportal. Transport medium in the mailer has a shelf life of two months. Notify the unit before submitting large numbers of specimens. Regan-Lowe Transport Medium (RLTM) and 2ml microcentrifuge tube included in the mailer should be labeled with two patient identifiers and accompanied by a completed DHHS form 4121. Please do not place adhesive labels on the microcentrifuge tube. Unlabeled specimens will not be tested. Follow collection instructions included in the mailer. The following additional clinical information should be entered on the back of the form: nature of symptoms, date of onset, immunization history, contact with other cases of whooping cough, any antibiotic therapy prior to specimen collection and other pertinent information.
Note: Specimens received without submitter return address are subject to rejection!
Under certain circumstances: If the mailer is not available and culture is not attempted, nasopharyngeal swab specimens may be used for DFA. Swabs should be moistened lightly in a few drops of sterile distilled water or saline and spread thinly over the central area of a glass slide, re-wetting the swab for each slide. Allow smears to air dry and gently heat fix before packaging (see SHIPMENT OF SPECIMENS) with a completed DHHS form 4121. Preferably four smears should be submitted per patient.
Lab records are computerized and the following data are required: patient name, patient Social Security Number (or assigned number), date of birth, patient Medicaid number (if applicable), submitter Federal Tax Number (Employer Identification Number), submitter return address, specimen collection date and specimen source. Without these data, specimen records cannot be entered into the computer, nor can a report of results be printed. Other data are helpful for epidemiological follow-up and for statistical purposes.
Note: CLIA regulations require the following information on all test requisitions:
- Patient name or identifier
- Name and address of submitting agency
- Test requested
- Date specimen collected
Isolated organisms for identification should be subcultured to appropriate media and incubated until growth is apparent before shipping. Bordet-Gengou or Regan-Lowe Agar is recommended for B.pertussis; blood, chocolate or infusion agar is satisfactory for other bordetellae. Agar slants are preferred. Plates are discouraged, but if necessary may be used if they are taped closed, sealed in leak-proof bags and securely packaged in a crush-proof container. Growth from culture plates also may be suspended in RLTM for shipment or used to prepare smears for DFA confirmation staining.
Specimens should be shipped as soon as possible after collection. Clinical specimens for pertussis culture should be shipped refrigerated in cold RLTM using frozen cold packs provided in the insulated mailer. Nasopharyngeal swabs may be held, if necessary, in refrigerated RLTM up to three days before shipping. Friday shipments are not recommended as specimens should be kept cold.
It is essential for culture specimens to be kept cold after collection and during transit to the Laboratory. Another nasopharyngeal swab for PCR inside the microcentrifuge tube also should be returned in the mailer, along with the completed DHHS form 4121 form.
Reference cultures may be shipped in a microbiology reference mailer with a completed DHHS form 4121. Plates should be wrapped individually in absorbent cushioning material and securely packaged in a leak-proof, crush-proof container. Label "Pertussis" on the outside of the package. When shipping by U.S. mail, use first-class postage. Be sure to place return address on outside of container, regardless of shipping method.
Reporting Procedure and Interpretation
PCR tests are batched twice per week and positive results are telephoned to the submitter on the day of completion, usually within three to four days of sample receipt. Positive culture results will also be called to the submitter; negatives will be held for 7 days before reporting. Positive PCR and culture results are reported to the Epidemiology Section, Division of Public Health, for surveillance purposes. All results are available at https://slphreporting.ncpublichealth.com/lims/ClinicalLims/Login.aspx.
PCR results are reported as presumptive while culture is considered the gold standard and is used for confirmation. However, culture can be less sensitive than PCR, since PCR is not dependent on viability and may detect fewer organisms present. Discrepant PCR and culture reports may occur. Low numbers of organisms may be detected by PCR but may be overgrown by normal flora or non-viable in culture. This PCR has been known to cross-react with Bordetella holmesii.
Cultures indicating growth consistent with Bordetella, are stained with the DFA conjugate to confirm. A rare B. bronchiseptica may cross-react with the DFA conjugate.
Both culture and PCR may fail to detect B. pertussis. Positive PCR are valuable for early diagnosis of pertussis but should be accompanied by culture since culture is the recommended diagnostic method. As the disease process may continue for weeks or months after viable organisms no longer remain in the nasopharynx, a negative culture does not rule out infection, especially if specimens were collected late in the course of illness. Organisms present in low numbers may be difficult to detect by either method. Prior antibiotic therapy, overgrowth of contaminants or failure to keep specimens cold after collection and during transit may result in a negative culture. Cultures performed at the local level using commercial agar plates may be negative due to insufficient moisture in the medium. Accuracy in both tests is dependent on correctly collected specimens.
Reports are returned only to the submitting agency; the submitter is responsible for sending copies to any other agency. Copies of reports are retained at the NCSLPH. The submitting agency is responsible for maintaining reports in the patient's file.
- About Microbiology
- Bordetella Pertussis
- Enteric Bacteriology
- Foodborne Illness
- Neisseria Gonorrhoeae
- Special & Atypical Bacteriology
- Turnaround Times