BORDETELLA General Features • • • • Highly fastidious, gram-negative coccobacillus, Bordetella pertussis: causes whooping cough in children B. parapertussis: causes milder form of whooping cough B. bronchiseptica: causes kennel cough in dogs, atrophic rhinitis and pneumonia in pigs, and pneumonia in cats • B. Avium: causes respiratory disease in turkeys • B. hinzii and B. holmesii: cause bacteremia in immunocompromised people. Virulence Factors • - Toxins: Tracheal cytotoxin: damage to respiratory epithelial cilia Pertussis toxin Adenylate cyclase toxin: activates cyclic AMP - impairs the host immune function - Dermonecrotic toxin: respiratory mucosal damage - Endotoxin: similar to LPS - Adhesins: Filamentous hemagglutinin (FHA), Pertactin, Fimbriae or pili or agglutinogens, BrkA (Bordetella resistance to killing) protein Pertussis Toxin (PT) • Mechanism: structurally similar to cholera toxin B subunit: binding to target cells - - A subunit: active subunit - activates adenylyl cyclase  leading to ↑ concentrations of cAMP  biologic effects: • T cell mitogenicity, Hemagglutination • Adhesion to respiratory ciliated cells • Inhibition of neutrophil oxidative burst, monocyte migration, histamine release from mast cells, Induction of leukocytosis • Enhancement of insulin secretion leading tohypoglycemia. Clinical Manifestations • • • • Incubation period 7–10 days. Catarrhal phase: 1–2 weeks Common cold like nonspecific symptoms Highly infectious stage, Both smear and cultures - positive Paroxysmal phase: Less infectious, Smear and culture may become negative Specific symptoms – whooping cough and post-tussive vomiting Convalescent stage: Frequency and severity of coughing gradually decreaseEsss.e Whooping Cough Paroxysm • Bursts of 5–10 repetitive violent spasmodic coughs in a single expiration -endswith an audible sound or whoop. • Whoop occurs due to rapidinspiration against a closed glottis at the end of the paroxysm Whooping Cough Paroxysm • Paroxysms precipitated - noise, eating or physical contact • Frequency of paroxysms - variable - several per hour to 5–10 per day. Worse at night During a spasm - Visible neck vein distension, bulging • of eyes, tongue protrusion and cyanosis • Fever is uncommon Complications • More common among infants than older children or adults. • Pressure effects during the violent spasms of coughing - Subconjunctival hemorrhage, hernias, pneumothorax, rib fracture and petechiae on the faceand body. • Pneumonia - secondary infection • Neurological complications - convulsions, encephalopathy & coma Epidemiology • Exclusively human disease. No animal reservoir. • Source: Early cases (catarrhal stage) main source. There is no carrier state • Age: Below 5 years - Maternal antibodies are not protective, infants remain the most vulnerable group • Shift of median age: from infants to older children and adolescence with high vaccination coverage. Immunizations or natural infection do not provide lifelong immunity • Mode of transmission: inhalation of droplets Epidemiology • Worldwide incidence of pertussis is declining • Global vaccine coverage 86% in 2016 • India: marked decline of disease after launch of the vaccine under universal immunization programme • There is no cross protection to B. parapertussis infection Laboratory Diagnosis • • • • Specimen collection Nasopharyngeal secretions - best specimens Throat and/or sputum specimens are unacceptable Nasopharyngeal aspiration or Pernasal swab Type of swabs used: For culture, alginate/dacron swabs. For PCR – dacron/rayon swabs. Fatty acids in cotton swab inhibit growth. Charcoal-impregnated cotton swabs (Stuart’s) useful • Collect six swabs, at 1–2 days intervals to achieve maximum yield Laboratory Diagnosis • Transport : - To be processed immediately - Charcoal-based transport medium (Amies Regan-Lowe, JonesKendrick transport media) • Direct detection: - Direct immunofluorescence test using fluorescein labelled polyclonal or monoclonal antibodies. - Poor sensitivity (18-75%) and specificity (65-99%) - Not widely used Laboratory Diagnosis...Culture • • • - Nasopharyngeal csecretions ulture - gold standard Strict aerobe, fastidious Regan and Lowe medium Charcoal agar supplemented with 10% horse blood and cephalexin. Currently the medium of choice Bordet-Gengou glycerine-potato-blood agar • • Jones Kendrick agar • Stainer- Scholte synthetic medium Laboratory Diagnosis...Culture • Colony – mercury drops or bisected pearls appearance • Culture remains positive only during the first three weeks of infection (i.e. mainly in catarrhal stage) • where the symptoms are nonspecific Laboratory Diagnosis • • • • - Molecular methods: PCR – Higher sensitivity, specificity and quicker Targeted genes - IS481 & PT promoter region genes Typing of B. Pertussis Important during outbreak Serotyping: based on two fimbrial antigens (type 2 and 3) and one lipooligosaccharide antigen (type 1) - four recognized serotypes (1,2,3; 1,2; 1,3; and 1) - Genotyping: by gene sequencing & PFGE Laboratory Diagnosis • Culture smear: - Gram negative coccobacilli thumb print appearance - Capsules may be demonstrated in fresh cultures - Bipolar metachromatic granules - toluidine blue • Detection of serum antibodies Treatment • As pertussis is mainly toxin mediated, antibiotics are less useful once the infection is established. However, they play a vital role to eliminate the bacteria from nasopharynx. Macrolides - DOC-(azithromycin for 5 days or • erythromycin for 7–14 days) • Cotrimoxazole - alternative in macrolide resistance. • Isolation in a quiet environment may inhibit the stimulation of paroxysms. Cough suppressants are not much effective • Prevention • Chemoprophylaxis • Erythromycin is widely recommended as chemoprophylaxis • for household contacts of pertussis cases. Immunoprophylaxis • • • • • - Whole-cell Pertussis Vaccine - Efficacy 85% Given as DPT vaccine under national immunization programme Doses – Primary 6, 10 and 14 wk two boosters at 1yr, 5 yr Pertussis component acts as an adjuvant Adverse effects: Common: Fever, injection-site pain, erythema, swelling Uncommon: Encephalitogenic Bordetella pertussis component (encephalitis, prolonged convulsion) & hypotonic hyporesponsive syndrome Immunoprophylaxis • Contraindication: - Children more than 5–6 years age ,Previous Hypersensitivity - Any progressive neurological conditions & strong family history of epilepsy • Acellular Pertussis Vaccine • Pertussis toxoid + 2 or more bacterial components such as FHA, pertactin or fimbriae • Efficacy is same as WC vaccine with fewer side effects • Can be safely given after 5–6 years Essentials ofwith Medicaldiphtheria Microbiology © 2018, Jaypee and tetanus toxoid). • Available as DapT (along