A child presented with chronic coughing.On culture from Nasopharyngeal Secretions,the following picture was seen.Regarding this condition,which of the following statement is true?
Incubation period is 7-14 days.
Infectivity is maximum in catarrhal stage
Azithromycin is given in treatment.
All of the above.
Ans:D.)All of the above.
- The patient is suffering from Pertusis.
- Mercury drop like colony appearance is seen in the culture,suggestive of Bordatella Pertusis.
- It is a Gram-negative, aerobic, pathogenic, encapsulated coccobacillus of the genus Bordetella.
- Its virulence factors include pertussis toxin, filamentous hæmagglutinin, pertactin, fimbria, and tracheal cytotoxin.
- Pertusis toxin
- Pertussis toxin is an exotoxin that has A and B subunits.
- B subunit binds to the target cells whereas A subunit acts on the target.
- First, the pertussis toxin itself gets activated by glutathione and ATP.
- Once the toxin gets activated it activates cell membrane bound G proteins.
- Pertussis toxin catalyzes the ADP ribosylation of the G proteins and activates them.
- The activated G protein in turn activates adenylate cyclase, this results in an outpouring of cAMP which activates protein kinase and other intracellular messangers.
- Pertusis toxin
- Most of the cases of whooping cough is caused by B. pertussis.
- In a small percentage of cases (< 5%), it is caused by B. parapertussis.
- There is no cross immunity of B. pertussis with B. parapertussis —> antibodies against B. Pertussis do not protect against B. parapertussis.
- In prevaccine era, and in countries where immunization is limited the peak incidence of pertussis is in children 1-5 years of age
- The bacterium is spread by airborne droplets; its incubation period is to human whooping cough in average 7-17 days..
- Stage 1 – Catarrhal phase
- Initially, symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough.
- Infectivity is maximum in catarrhal stage
- Stage 2 – Paroxysmal phase
- Severe coughing fits. Following a fit of coughing, a high-pitched whoop sound or gasp may occur as the person breathes in.
- The coughing may last for 10 or more weeks, hence the phrase “100-day cough”.
- A person may cough so hard that they vomit, break ribs, or become very tired from the effort.
- The cough from pertussis has been documented to cause subconjunctival hemorrhages, rib fractures, urinary incontinence, hernias, and vertebral artery dissection.
- Stage 3 – Convalescent phase
- Chronic cough lasting for weeks.
- A nasopharyngeal or an oropharynx swab is sent to the bacteriology laboratory for Gram stain (Gram-negative, coccobacilli, diplococci arrangement), growth on Bordet-Gengou agar or BCYE plate with added cephalosporin to select for the organism, which shows mercury drop-like colonies.
- Prevention is mainly by vaccination with the pertussis vaccine.
- Initial immunization is recommended between six and eight weeks of age, with four doses to be given in the first two years of life.
- Treatment :Antibiotics ;erythromycin, azithromycin, clarithromycin, or trimethoprim/sulfamethoxazole.