Bordetella pertussis

Bordetella pertussis
File:Bordetella pertussis 01.jpg
Scientific classification
Kingdom: Bacteria Phylum: Proteobacteria Class: Beta Proteobacteria Order: Burkholderiales Family: Alcaligenaceae Genus: Bordetella Species: B. pertussis
Binomial name
Bordetella pertussis (Bergey et al. 1923) Moreno-López 1952

Bordetella pertussis is a Gram-negative bacterium of the genus Bordetella, and the causative agent of pertussis or whooping cough. Unlike B. bronchiseptica, B. pertussis is non-motile.

There does not appear to be a zoonotic reservoir for B. pertussis—humans are its only host.

The bacterium is spread by coughing and by nasal drops. The incubation period is 7-14 days.

Features

Whooping Cough, or Pertussis, is an infection of the respiratory system and characterized by a “whooping” sound when the person breathes in. In the US it killed 5,000 to 10,000 people per year before a vaccine was available. Vaccination has transformed this and between 1985-88 less than 100 children died from pertussis. Worldwide in 2000, according to the WHO, around 39 million people were infected annually and about 297,000 died. A graph is available showing the dramatic effect of introducing vaccination in England.

Whooping Cough occurs most with children under the age of one when they are immunized or children with faded immunity, normally around the age 11 through 18. The signs and symptoms are similar to a common cold: runny nose, sneezing, mild cough, and low-grade fever. After a spell, they might make a “whooping” sound when breathing in or vomit. Adults have milder symptoms, like prolonged coughing without the “whoop.” Pertussis is highly contagious and may become airborne when the person coughs, sneezes, or laughs. People infected by this disease are more contagious in the earliest stages of it, normally 2 weeks after the coughing begins. Whooping Cough can be prevented by the Pertussis Vaccine which is part of the DTaP (diphtheria, tetanus, acellular Pertussis) immunization. The paroxysmal cough precedes a crowing inspiratory sound characteristic of pertussis. (Infants less than 6 months may not have the typical whoop.) A coughing spell may last a minute or more, producing cyanosis, apnoea and seizures. A prolonged cough may be irritating and sometimes a disabling cough may go undiagnosed in adults for many months.

Bodetella pertussis also produces a lymphocytosis-promoting factor, which causes a decrease in the entry of lymphocytes into lymph nodes. This can lead to a condition known as lymphocytosis, with a complete lymphocyte count over of 4000/μL in adults or over 8000/μL in children.

Antimicrobial therapy

• 1. Whooping cough

• 1.1 Adults

• Preferred regimen (1): Azithromycin 500 mg PO single dose on day 1 THEN 250 mg PO qd on 2-5 days
• Preferred regimen (2): Erythromycin 2 g/day PO qid for 14 days
• Preferred regimen (3): Clarithromycin 1 g PO bid for 7 days.
• Alternative regimen (intolerant of macrolides): Trimethoprim 320 mg/day AND Sulfamethoxazole 1600 mg/day PO bid for 14 days

• 1.2 Infants <6 months of age

• 1.2.1 Infants <1 month

• Preferred regimen (1): Azithromycin 10 mg/kg PO qd for 5 days
• Preferred regimen (2) (if azithromycin unavailable): Erythromycin 40-50 mg/kg/day PO q6h for 14 days
• Note: TMP-SMX contraindicated for infants aged < 2 months

• 1.2.2 Infants of 1-5 months of age

• Preferred regimen (1): Azithromycin 10 mg/kg PO qd for 5 days
• Preferred regimen (2): Erythromycin 40-50 mg/kg/day PO qid for 14 days
• Preferred regimen (3): Clarithromycin 15 mg/kg PO bid for 7 days
• Alternative regimen: For infants aged ≥ 2 months TMP 8 mg/kg q24h AND SMX 40 mg/kg/day PO bid for 14 days

• 1.3 Infants ≥6 months of age-children

• Preferred regimen(1): Azithromycin 10 mg/kg single dose THEN 5 mg/kg (500 mg Maximum) qd for 2-5 days
• Preferred regimen(2): Erythromycin 40-50 mg/kg PO (2 g daily Maximum) qid for 14 days
• Preferred regimen(3): Clarithromycin 15 mg/kg PO (1 g daily Maximum) bid for 7 days
• Preferred regimen(4): TMP 8 mg/kg/day AND SMX 40 mg/kg/day bid for 14 days

• 2. Post exposure prophylaxis

• Preferred regimen: The antibiotic regimens for post exposure prophylaxis are similar to the regimens used for the treatment of pertussis
• Note (1): Post exposure prophylaxis to an asymptomatic contacts within 21 days of onset of cough in the index patient can potentially prevent symptomatic infection
• Note (2): Close contacts include persons who have direct contact with respiratory, oral or nasal secretions from a symptomatic patient (eg: cough, sneeze, sharing food, eating utensils, mouth to mouth resuscitation, or performing a medical examination of the mouth, nose, throat.
• Note (3): Some close contacts are at high risk for acquiring severe disease following exposure to pertussis. These contacts include infants aged < 1 year , persons with some immunodeficiency conditions, or other underlying medical conditions such as chronic lung disease, respiratory insufficiency and cystic fibrosis.

References

• Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.CS1 maint: Extra text: authors list (link) CS1 maint: Extra text (link)

External links

• Pertussis Information from the World Health Organisation

• Bordetella chapter in Baron's Medical Microbiology (online text at the NCBI bookshelf).

• Bordetella pertussis in ARUP Consult — The Physician's Guide to Laboratory Test Selection and Interpretation

• Pertussis United Kingdom Health Protection Agency.