Microbiology Case Study: A Preteen Boy with Cold and Cough

Case History

A preteen boy presented to primary care office with a complaint of flu-like symptoms for the past five weeks. His symptoms improved after 2-3 weeks but noted acute worsening of symptoms in the last two weeks, including sore throat, head congestion, and cough. The physical exam was unremarkable except for nasal congestion, mucosal edema, and some drainage. A chest X-ray was taken, which was normal. Results were negative for a Streptococcal infection, SARS-CoV-2, Bordetella pertussis, and influenza. Bordetella parapertussis was detected by PCR (Image 1).

Discussion

Bordetella is a small, non-fermentative, gram negative coccobacilli. The genus Bordetella has 15 species, and B. pertussis & B. parapertussis are most commonly found in human infections causing pertussis. B. parapertussis usually cause milder disease, but reports of outbreaks of B. parapertussis have increased in recent literature. The epidemic cycles for pertussis occur at 3–4 years intervals² and pertussis vaccination does not prevent B. parapertussis infection. B. parapertussis generally occurs in a younger age group than disease caused by B. pertussis.⁴ Cherry et al. indicated that B. parapertussis infections contribute significantly to the disease burden, which was previously thought to be vaccine failure in children.²

Pertussis is primarily a toxin-mediated disease; the bacteria attach to the cilia of the respiratory epithelial cells and produce toxins that paralyze the cilia and cause inflammation of the respiratory tract, which interferes with the clearing of pulmonary secretions.¹ B. pertussis and B. parapertussis are almost identical at the DNA level and produce many similar virulence factors like as filamentous hemagglutinin (FHA), pertactin, tracheal cytotoxin, dermonecrotic toxin, and adenylate cyclase-hemolysin. An essential difference between the two is that B. parapertussis does not secrete pertussis toxin.^3,5-9 Despite the high degree of homology shown by the amino acid sequences of the main antigens, the two species differ in respect to several protective epitopes.¹⁰

Pertussis (whooping cough) can cause serious illness in babies. Symptoms of pertussis usually develop within 5-10 days of exposure. Early non-specific symptoms, including runny nose, low-grade fever, and occasional cough, can last for 1 to 2 weeks. After 1 to 2 weeks, as the disease progresses, paroxysms occur, which are many, rapid coughs followed by a high-pitched “whoop” sound. Vomiting or exhaustion develops at this stage. Recovery from pertussis is slow, the cough becomes milder and less common, but coughing fits can return with other respiratory infections for many months after the pertussis infection started. The “whoop” is often absent or mild in less severe disease. The illness is generally milder in teens and adults, especially those who have gotten the pertussis vaccine. The cough can be minimal or absent in babies, but they might get apnea, which is most dangerous.¹

Bordetella is a fastidious organism as it requires special media, prolonged incubation, timely transport, and rapid plating for recovery of the organism. Regan low and Bordet Gengou are the special media used for culture of B. parapertussis and B. pertussis. Unlike B. pertussis, B. parapertussis can grow on blood and chocolate agar. Colonies may appear like mercury drop and produce beta hemolysis on prolonged incubation. Culture has the highest recovery if a nasopharyngeal swab is collected within two weeks of symptom onset. Sensitivity can be as high as 56% in early disease and decrease over time, while specificity is 100%.¹ Serological assay are not clinically validated and do not help differentiate between recent or remote infection or vaccination. PCR is the most sensitive methodology and should be performed from a nasopharyngeal swab taken within three weeks of symptom onset; after the fourth week of cough, the amount of bacterial DNA rapidly diminishes, which increases the risk of obtaining falsely-negative results. PCR-detectable B. pertussis DNA in some pertussis vaccines and the contamination of the clinic environment by those vaccines increases the risk of false-positive PCR. As per CDC guidelines, PCR in asymptomatic persons, asymptomatic close contacts of a confirmed case, and after five days of antibiotic use is unlikely to benefit and is generally not recommended because of the risk of false positivity. In our lab, we use the DiaSorin Simplexa Bordetella direct assay system – RT PCR which targets IS481 and IS1001 for pertussis PCR (other PCR may use different targets). B. pertussis contains ∼238 copies of IS481 and no copies of IS1001, multiple copies of IS481 are responsible for the high sensitivity of PCR and increased risk of false-positive. B. parapertussis has ∼22 copies of IS1001 and no copies of IS481; false-positive identification of IS1001 seems unlikely, as IS1001 is not present in vaccines and its copy numbers are low.²

The recommended antimicrobial agents for treatment or chemoprophylaxis is azithromycin. Antibiotic susceptibility data indicate that the same antibiotics recommended for treating and preventing B. pertussis might help treat and prevent B. parapertussis.^11,12 CDC recommends vaccinating young children, preteens, pregnant women, and adults, but pertussis vaccine immunity is short-lived and wanes after 7- 10 years. Immunized children become susceptible after that and can transmit B. pertussis to their very young infant siblings or get B. parapertussis as the vaccine does not protect against it. The average age of patients with B. parapertussis is much younger than those with B. pertussis, and some literature suggest B. parapertussis should be considered when developing new pertussis vaccines.¹³

References

1. https://www.cdc.gov/pertussis/index.htmlJames D. Cherry, Brent L. Seaton, Patterns of Bordetella parapertussis Respiratory Illnesses: 2008–2010, Clinical Infectious Diseases, Volume 54, Issue 4, 15 February 2012, Pages 534–537, https://doi-org.proxy.uchicago.edu/10.1093/cid/cir860
2. Arico B, Rappuoli R. Bordetella parapertussis and Bordetella bronchiseptica contain transcriptionally silent pertussis toxin genes. J Bacteriol.1987;169:2847-2853.
3. https://www.mayocliniclabs.com/test-catalog/overview/80910#Clinical-and-Interpretive
4. Blom J., Hansen G. A., and Poulsen F. M.Morphology of cells and hemagglutinogens of Bordetella species: resolution of substructural units in fimbriae of Bordetella pertussis.Infect. Immun.421983308317 Crossref. PubMed.
5. Cookson B. T. and Goldman W. E.Tracheal cytotoxin: a conserved virulence determinant of all Bordetella species.J. Cell. Biochem.11B1987124
6. Endoh M., Takezawa T., and Nakase Y.Adenylate cyclase activity of Bordetella organisms. Its production in liquid medium.Microbiol. Immunol.24198095104 PubMed.
7. Li L. J., Dougan P., Novotny P., and Charles I. G.P70 pertactin, an outer membrane protein from Bordetella parapertussis: cloning, nucleotide sequence and surface expression in Escherichia coli.Mol. Microbiol.51991409417 PubMed.
8. Mooi F. R., van der Heide H. G. J., TerAvest A. R., Welinder K. G., Livey I., van der Zeisj B. M. A., and Gaastra W.Characterization of fimbrial subunits from Bordetella species.Microb. Pathog.3198718 PubMed.
9. He Q, Viljanen MK, Arvilommi H, Aittanen B, Mertsola J. Whooping Cough Caused by Bordetella pertussis and Bordetella parapertussis in an Immunized Population. JAMA. 1998;280(7):635–637. doi:10.1001/jama.280.7.635
10. Hoppe JE, Bryskier A. In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to two ketolides (HMR 3004 and HMR 3647), four macrolides (azithromycin, clarithromycin, erythromycin A, and roxithromycin), and two ansamycins (rifampin and rifapentine). Antimicrob Agents Chemother. 1998 Apr;42(4):965-6. doi: 10.1128/AAC.42.4.965. PMID: 9559823; PMCID: PMC105582.
11. Mortensen JE, Rodgers GL. In vitro activity of gemifloxacin and other antimicrobial agents against isolates of Bordetella pertussis and Bordetella parapertussis. J Antimicrob Chemother. 2000 Apr;45 Suppl 1:47-9. doi: 10.1093/jac/45.suppl_3.47. PMID: 10824032
12. Karalius VP, Rucinski SL, Mandrekar JN, Patel R. Bordetella parapertussis outbreak in Southeastern Minnesota and the United States, 2014. Medicine (Baltimore). 2017 May;96(20):e6730. doi: 10.1097/MD.0000000000006730. PMID: 28514288; PMCID: PMC5440125.
13. Karalius VP, Rucinski SL, Mandrekar JN, Patel R. Bordetella parapertussis outbreak in Southeastern Minnesota and the United States, 2014. Medicine (Baltimore). 2017 May;96(20):e6730. doi: 10.1097/MD.0000000000006730. PMID: 28514288; PMCID: PMC5440125.

-Payu Raval, MD is a 1st year anatomic and clinical pathology resident at University of Chicago (NorthShore). Her academic interests include hematology, molecular, and surgical pathology.

-Paige M.K. Larkin, PhD, D(ABMM), M(ASCP)^CM is the Director of Molecular Microbiology and Associate Director of Clinical Microbiology at NorthShore University HealthSystem in Evanston, IL. Her interests include mycology, mycobacteriology, point-of-care testing, and molecular diagnostics, especially next generation sequencing.