Haemophilus.ppt
- 1. Haemophilus Buga Rudolf HTC LECTURE SERIES
- 2. Introduction Family Pasteurallaceae (Pasteurella and Actinobacillus) Also known as Parvobacteria Species: H.influenzae, H.parainfluenzae, H.ducreyi, H.aegptius, H.haemolyticus,H.parahaemolyticus, H.segnis, H.aphrophilus and H.paraphraphrophilus. H.influenzae the commonest of medical importance.
- 3. Introduction… Haemophilus – ‘’ haem lover’’ Require complex media and growth factors for growth. Growth factors: X factor (haematin) and V factor ( NAD and NADP/Co-enzyme I and II) Best growth on Choc agar than BA Growth atm:Opt TO 35 – 370 C; pH – 7.6 and ambient air plus 5-10 % CO2 Glycolytic and respiratory growths using nitrate as final electron acceptor is possible
- 4. H. influenzae Microscopy: Gm positive cocco-bacilli Encapsulated strains (CSF), coccobacilli, 0.2-0.3µm by 0.5 – 0.8µm. Non-encapsulated strains (sputum) are pleomorphic and at times filamentous Appears gram negative if not properly Gram stained Some elongated forms (sputum) may show bipolar staining, leading to erroneous diagnosis as Streptococcus pneumoniae
- 5. Habitat Adapted to human hosts Occur in the nasopharynx of about 75% of healthy children and adults Non encapsulated forms normally occur as normal flora Intermittent occurrence of encapsulated Hib is found in the URT of 3-7% of healthy people Pharyngeal carriage is important in the transmission of Hib.
- 6. Diagnosis 1. Direct detection: Capsular Ags in CSF 2. Culture: Sputum and CSF culture on Choc and BA, done promptly since the organisms are fragile Colonies are small on BA than Choc (24- 48hrs) Incubation atmosphere: O2 + 5-10% CO2 Blood culture positive in meningitis
- 7. Diagnosis… 3. Identification: •Gram stain •Sateletism •X and V factors
- 8. Pathogenesis Hib colonizes the nasopharynx Penetrate the epithelium and capillary endothelium to cause bacteremia Meningitis result from direct spread via lymphatic drainage or from haematogeneous spread Capsules resist phagocytosis and complement mediated lysis in non immune host Non encapsulated strains are less invasive but can induce inflammatory response that can cause disease Outbreaks of Hib may occur in nurseries and childcare centers
- 9. Virulence factors •Lipopolysaccharides (LPS) •Neuraminidase •IgA protease •Fimbriae
- 10. Host defenses •Serum antibodies to oCapsular antigens (Hib) or oSomatic antigens •Abs are bactericidal and promote phagocytosis
- 11. Diseases caused Hib: meningitis, epiglottitis, bacteremia, cellulitis, osteomyelitis, septic arthritis, pericarditis or endocarditis Non typable Hin: Otitis media, sinusitis, tracheobronchitis and pneumonia Other species: H. parainfluenzae- pneumonia and endocarditis; H. ducreyi- chancroid; H. aegyptius- conjunctivitis
- 12. Epidemiology Hib is widely spread in human population First isolated by Pfeiffer during the influenza pandemic of 1890 Hin colonizes healthy children and adults but the rate is more for non typable strains Spread is by direct contact, secretions and aerosols NB: H.ducreyi is spread by venereal contact No animal reservoirs for these organisms
- 13. Antibiotics/Control •Ampicillin (for non beta-lactamase producers) •3rd Generation Cephalosporins (Cefotaxime, Ceftriaxone, Ceftazidime), Chloramphenicol, Amoxycillin/Clavulanic acid, Tetracycline •Hib –vaccine