Haemophilus Species <ul><li>Group of small, gram-negative, pleomorphic bacteria that require enriched media, usually conta...
Haemophilus Species, cont.  <ul><li>Others are among the normal flora of mucous membranes and only occasionally causes dis...
Haemophilus Species, cont. <ul><li>Morphology and Identification </li></ul><ul><li>In specimens, short (1.5  µm) coccoid b...
Haemophilus Species, cont. <ul><li>Organisms in young cultures (6-18 hrs) on enriched medium have a definite capsule </li>...
Haemophilus Species, cont. <ul><li>Satellite phenomenon </li></ul><ul><li>H. influenzae  does not grow on sheep BA except ...
Haemophilus Species, cont. <ul><li>H. haemolyticus  and  H. parahemolyticus  are hemolytic variants of  H. influenzae  and...
Haemophilus Species, cont. <ul><li>Factor X acts physiologically as hemin </li></ul><ul><li>Factor V can be replaced by ni...
Haemophilus Species, cont. <ul><li>Species X V Hemolysis </li></ul><ul><li>H. influenzae + + - </li></ul><ul><li>(H. aegyp...
Haemophilus Species, cont. <ul><li>H. influenzae has a marked tendency to lose its capsule and the associated specificity ...
Haemophilus Species, cont. <ul><li>Antigenic structure </li></ul><ul><li>Encapsulated  H. influenzae  contains capsular po...
Haemophilus Species, cont. <ul><li>Most  H. influenzae  in the normal flora of the URT are not encapsulated </li></ul><ul>...
Haemophilus Species, cont. <ul><li>Pathogenesis </li></ul><ul><li>H. influenzae  produces no exotoxin </li></ul><ul><li>Ca...
Haemophilus Species, cont. <ul><li>Carrier rate in the URT for  H. influenzae  is 2-4% </li></ul><ul><ul><li>For nontypeab...
Haemophilus Species, cont. <ul><li>Nontypeable tends to cause chronic bronchitis, otitis media, sinusitis, and conjuctivit...
Haemophilus Species, cont. <ul><li>Clinical Findings </li></ul><ul><li>H. influenzae  type b enters by way of the respirat...
Haemophilus Species, cont. <ul><li>May reach blood bloodstream and be carried to the meninges or, less frequently may esta...
Haemophilus Species, cont. <ul><li>Diagnostic Laboratory Tests </li></ul><ul><li>Specimens </li></ul><ul><li>Nasopharyngea...
Haemophilus Species
Haemophilus Species, cont. <ul><li>Direct Identification </li></ul><ul><li>H. influenzae antigens in spinal fluid </li></u...
Haemophilus Species, cont. <ul><li>Tests for X and V factor requirements </li></ul><ul><li>A better test for X factor requ...
Haemophilus Species, cont. <ul><li>Organisms that do not require X factor synthesize porphobilinogen, porphyrins,protoporp...
Haemophilus Species, cont. <ul><li>Species that synthesize porphyrins (and thus heme) are not H. influenzae </li></ul><ul>...
Haemophilus Species, cont. <ul><li>Satellite phenomenon test </li></ul><ul><li>A capsule swelling test with specific antis...
Haemophilus Species, cont. <ul><li>Immunity </li></ul><ul><li>Infants< age 3 months may have serum antibodies from mother ...
Haemophilus Species, cont. <ul><li>By age 3-5 yrs, many unimmunized children have naturally acquired anti-PRP antibodies <...
Haemophilus Species, cont. <ul><li>Treatment </li></ul><ul><li>Mortality of untreated meningitis up to 90% </li></ul><ul><...
Haemophilus Species, cont. <ul><li>Cefotaxime IV may give excellent results </li></ul><ul><li>Prompt diagnosis and antimic...
Haemophilus Species, cont. <ul><li>Late complication - development of a localized subdural accumulation of fluid that requ...
Haemophilus Species, cont. <ul><li>Disease can be prevented by administration of haemophilus b conjugate vaccine to childr...
Haemophilus Species, cont. <ul><li>Children aged 15 months or older can receive vaccine conjugated with diphtheria toxoid ...
Haemophilus Species, cont. <ul><li>H. ducreyi </li></ul><ul><li>Causes chancroid (soft chancre), a sexually transmitted di...
Haemophilus Species, cont.
Haemophilus Species, cont. <ul><li>Disease must be differentiated from syphilis, herpes simplex infection and lymphogranul...
Haemophilus Species, cont. <ul><li>Grown best from scrapings of the ulcer base on CA containing 1% IsoVitalex and vancomyc...
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Haemophilus species

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Haemophilus species

  1. 1. Haemophilus Species <ul><li>Group of small, gram-negative, pleomorphic bacteria that require enriched media, usually containing blood or its derivatives, for isolation </li></ul><ul><li>H. influenzae type b is an important human pathogen </li></ul><ul><li>H. ducreyi, a sexually transmitted pathogen, causes chancroid </li></ul>
  2. 2. Haemophilus Species, cont. <ul><li>Others are among the normal flora of mucous membranes and only occasionally causes disease </li></ul><ul><li>Haemophilus influenzae </li></ul><ul><li>Found on the mucous membranes of the URT humans </li></ul><ul><li>Important cause of meningitis in children and occasionally respiratory tract infections in children and adults. </li></ul>
  3. 3. Haemophilus Species, cont. <ul><li>Morphology and Identification </li></ul><ul><li>In specimens, short (1.5 µm) coccoid bacilli, sometimes in pairs or chains </li></ul><ul><li>At 6-8 hrs in rich medium, small coccobacillary forms predominate </li></ul><ul><li>Later, longer rods, lysed bacteria, and very pleomorphic forms </li></ul>
  4. 4. Haemophilus Species, cont. <ul><li>Organisms in young cultures (6-18 hrs) on enriched medium have a definite capsule </li></ul><ul><li>Antigen used for typing H. influenzae </li></ul><ul><li>On CA, flat, grayish-brown colonies, 1-2 mm in diameter present after 24 hrs </li></ul><ul><li>IsoVitalex in media enhances growth </li></ul>
  5. 5. Haemophilus Species, cont. <ul><li>Satellite phenomenon </li></ul><ul><li>H. influenzae does not grow on sheep BA except around colonies of staphylococci </li></ul><ul><li>Colonies of staphylococci on sheep BA cause the release of NAD, yielding satellite growth phenomenon </li></ul>
  6. 6. Haemophilus Species, cont. <ul><li>H. haemolyticus and H. parahemolyticus are hemolytic variants of H. influenzae and H. parainfluenzae, respectively </li></ul><ul><li>Identification depends in part upon demonstrating the need for certain growth factors called X and V </li></ul>
  7. 7. Haemophilus Species, cont. <ul><li>Factor X acts physiologically as hemin </li></ul><ul><li>Factor V can be replaced by nicotinamide adenine nucleotide (NAD) or other coenzymes </li></ul><ul><li>Carbohydrates are fermented poorly and irregularly </li></ul>
  8. 8. Haemophilus Species, cont. <ul><li>Species X V Hemolysis </li></ul><ul><li>H. influenzae + + - </li></ul><ul><li>(H. aegyptius) </li></ul><ul><li>H. parainfluenzae - + - </li></ul><ul><li>H. ducreyi + - - </li></ul><ul><li>H. haemolyticus + + + </li></ul><ul><li>H. parahaemolyticus- + + </li></ul><ul><li>H. aphrophilus - - - </li></ul>
  9. 9. Haemophilus Species, cont. <ul><li>H. influenzae has a marked tendency to lose its capsule and the associated specificity </li></ul><ul><li>Resistance to ampicillin and chloramphenicol is controlled by genes on transmissible plasmids </li></ul>
  10. 10. Haemophilus Species, cont. <ul><li>Antigenic structure </li></ul><ul><li>Encapsulated H. influenzae contains capsular polysaccharides (MW>150,000) of one of 6 types a-f </li></ul><ul><li>The capsular antigen of type b is a polyribose-ribitol phosphate (PRP) </li></ul>
  11. 11. Haemophilus Species, cont. <ul><li>Most H. influenzae in the normal flora of the URT are not encapsulated </li></ul><ul><li>Somatic antigens consist of outer membrane proteins </li></ul><ul><li>Lipooligosaccharides (endotoxins) share many structures with those of neisseriae </li></ul>
  12. 12. Haemophilus Species, cont. <ul><li>Pathogenesis </li></ul><ul><li>H. influenzae produces no exotoxin </li></ul><ul><li>Capsule is antiphagocytic in the absence of specific anticapsular antibodies </li></ul><ul><li>Polyribose phosphate capsule of type b H. influenzae is the major virulence factor. </li></ul>
  13. 13. Haemophilus Species, cont. <ul><li>Carrier rate in the URT for H. influenzae is 2-4% </li></ul><ul><ul><li>For nontypeable H. influenzae is 50-80% or higher </li></ul></ul><ul><li>Causes meningitis, pneumonia and empyema, epiglottitis, cellulitis, septic arthritis </li></ul>
  14. 14. Haemophilus Species, cont. <ul><li>Nontypeable tends to cause chronic bronchitis, otitis media, sinusitis, and conjuctivitis following breakdown of normal host defense mechanisms </li></ul><ul><li>Carrier rate for encapsulated types a and c-f is 1-2% and rarely cause disease </li></ul>
  15. 15. Haemophilus Species, cont. <ul><li>Clinical Findings </li></ul><ul><li>H. influenzae type b enters by way of the respiratory tract </li></ul><ul><li>May be local extension with involvement of sinuses or middle ear </li></ul><ul><li>Type b and pneumococci are two of the most common etiologic agents of bacterial otitis media and acute sinusitis </li></ul>
  16. 16. Haemophilus Species, cont. <ul><li>May reach blood bloodstream and be carried to the meninges or, less frequently may establish themselves in the joints to produce septic arthritis </li></ul><ul><li>Pneumonitis and epiglottitis due to H. influenzae may follow URTI in small children and old or debilitated people </li></ul><ul><li>Adults may have bronchitis or pneumonia due to H. influenzae </li></ul>
  17. 17. Haemophilus Species, cont. <ul><li>Diagnostic Laboratory Tests </li></ul><ul><li>Specimens </li></ul><ul><li>Nasopharyngeal swabs, pus, blood and spinal fluid for smears and cultures </li></ul><ul><li>Microscopy </li></ul><ul><li>Gram negative coccobacilli, pleomorphic </li></ul>
  18. 18. Haemophilus Species
  19. 19. Haemophilus Species, cont. <ul><li>Direct Identification </li></ul><ul><li>H. influenzae antigens in spinal fluid </li></ul><ul><li>Generally not more sensitive than a Gram stain and not widely used. </li></ul><ul><li>Culture </li></ul><ul><li>IsoVitalex-enriched CA </li></ul><ul><li>Lack of hemolysis on BA </li></ul><ul><li>Antibiotic susceptibility testing </li></ul>
  20. 20. Haemophilus Species, cont. <ul><li>Tests for X and V factor requirements </li></ul><ul><li>A better test for X factor requirement is based on the ability of H. influenzae to synthesize heme from  -aminolevulinic acid </li></ul><ul><li>Inoculum is incubated with  -aminolevulinic acid </li></ul>
  21. 21. Haemophilus Species, cont. <ul><li>Organisms that do not require X factor synthesize porphobilinogen, porphyrins,protoporphyrins IX, and heme </li></ul><ul><li>Presence of red fluorescence under UV light indicates presence of porphyrins and a positive test </li></ul>
  22. 22. Haemophilus Species, cont. <ul><li>Species that synthesize porphyrins (and thus heme) are not H. influenzae </li></ul><ul><li>Encapsulated organisms can be typed by slide agglutination, coagglutination with staphylococci or agglutination of latex particles coated with type-specific antibodies </li></ul>
  23. 23. Haemophilus Species, cont. <ul><li>Satellite phenomenon test </li></ul><ul><li>A capsule swelling test with specific antiserum is analogous to quellung test for pneumococci </li></ul><ul><li>Typing can also be done by immunofuorescence </li></ul>
  24. 24. Haemophilus Species, cont. <ul><li>Immunity </li></ul><ul><li>Infants< age 3 months may have serum antibodies from mother </li></ul><ul><li>H. influenzae most common cause of bacterial meningitis in children from 5 months to 5 yrs </li></ul>
  25. 25. Haemophilus Species, cont. <ul><li>By age 3-5 yrs, many unimmunized children have naturally acquired anti-PRP antibodies </li></ul><ul><li>There is a correlation between the presence of bactericidal antibodies and resistance to major H. influenzae type b infections </li></ul>
  26. 26. Haemophilus Species, cont. <ul><li>Treatment </li></ul><ul><li>Mortality of untreated meningitis up to 90% </li></ul><ul><li>25% of strains produce beta lactamase under control of plasmids and are resistant </li></ul><ul><li>Essentially all strains are susceptible to newer cephalosporins </li></ul>
  27. 27. Haemophilus Species, cont. <ul><li>Cefotaxime IV may give excellent results </li></ul><ul><li>Prompt diagnosis and antimicrobial therapy are essential to minimize late neurologic and intellectual impairment </li></ul>
  28. 28. Haemophilus Species, cont. <ul><li>Late complication - development of a localized subdural accumulation of fluid that requires surgical drainage </li></ul><ul><li>Epidemiology, prevention and control </li></ul><ul><li>Encapsulated H. influenzae type b is transmitted from person to person by the respiratory tract </li></ul>
  29. 29. Haemophilus Species, cont. <ul><li>Disease can be prevented by administration of haemophilus b conjugate vaccine to children </li></ul><ul><li>Children aged 2 months or older can be immunized with vaccine conjugated with either HbOC with protein carrier CRM 197 mutant C. diphtheriae toxin protein or N. meningitidis outer membrane complex </li></ul>
  30. 30. Haemophilus Species, cont. <ul><li>Children aged 15 months or older can receive vaccine conjugated with diphtheria toxoid which is not immunogenic in younger children </li></ul><ul><li>Widespread use of vaccine reduced incidence of meningitis by over 95% </li></ul><ul><li>Prophylaxis is recommended for children who come in contacts with patients </li></ul>
  31. 31. Haemophilus Species, cont. <ul><li>H. ducreyi </li></ul><ul><li>Causes chancroid (soft chancre), a sexually transmitted disease </li></ul><ul><li>Chancroid consists of a rugged ulcer on the genitalia, with marked swelling and tenderness </li></ul><ul><li>Regional lymph nodes are enlarged and painful </li></ul>
  32. 32. Haemophilus Species, cont.
  33. 33. Haemophilus Species, cont. <ul><li>Disease must be differentiated from syphilis, herpes simplex infection and lymphogranuloma venereum </li></ul><ul><li>Occur in association with other pyogenic microorganism </li></ul><ul><li>Requires X but not V factor </li></ul>
  34. 34. Haemophilus Species, cont. <ul><li>Grown best from scrapings of the ulcer base on CA containing 1% IsoVitalex and vancomycin 3 ug/ml incubated in 10% carbon dioxide at 33 ° C </li></ul><ul><li>Treatment with IM ceftriaxone,oral trimethoprim-sulphamethoxazole, or oral erythromycin often results in healing in 2 weeks </li></ul>

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