haemophilus species

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1 Haemophilus Species Haemophilus Species Group of small, gram-negative, Group of small, gram-negative, pleomorphic bacteria that pleomorphic bacteria that require enriched media, usually require enriched media, usually containing blood or its containing blood or its derivatives, for isolation derivatives, for isolation H. influenzae H. influenzae type b is an type b is an important human pathogen important human pathogen H. ducreyi, H. ducreyi, a sexually transmitted a sexually transmitted pathogen, causes chancroid pathogen, causes chancroid

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Page 1: Haemophilus species

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Haemophilus SpeciesHaemophilus Species

►Group of small, gram-negative, Group of small, gram-negative, pleomorphic bacteria that require pleomorphic bacteria that require enriched media, usually enriched media, usually containing blood or its containing blood or its derivatives, for isolationderivatives, for isolation

►H. influenzaeH. influenzae type b is an type b is an important human pathogenimportant human pathogen

►H. ducreyi,H. ducreyi, a sexually transmitted a sexually transmitted pathogen, causes chancroidpathogen, causes chancroid

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►Others are among the normal flora Others are among the normal flora of mucous membranes and only of mucous membranes and only occasionally causes diseaseoccasionally causes disease

Haemophilus influenzaeHaemophilus influenzae►Found on the mucous membranes Found on the mucous membranes

of the URT humansof the URT humans►Important cause of meningitis in Important cause of meningitis in

children and occasionally children and occasionally respiratory tract infections in respiratory tract infections in children and adults.children and adults.

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Morphology and IdentificationMorphology and Identification►In specimens, short (1.5 In specimens, short (1.5 µm) µm)

coccoid bacilli, sometimes in coccoid bacilli, sometimes in pairs or chainspairs or chains

►At 6-8 hrs in rich medium, small At 6-8 hrs in rich medium, small coccobacillary forms coccobacillary forms predominatepredominate

►Later, longer rods, lysed bacteria, Later, longer rods, lysed bacteria, and very pleomorphic formsand very pleomorphic forms

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►Organisms in young cultures (6-18 Organisms in young cultures (6-18 hrs) on enriched medium have a hrs) on enriched medium have a definite capsuledefinite capsule

►Antigen used for typing Antigen used for typing H. H. influenzaeinfluenzae

►On CA, flat, grayish-brown colonies, On CA, flat, grayish-brown colonies, 1-2 mm in diameter present after 24 1-2 mm in diameter present after 24 hrshrs

►IsoVitalex in media enhances growthIsoVitalex in media enhances growth

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Satellite phenomenonSatellite phenomenon►H. influenzaeH. influenzae does not grow on does not grow on

sheep BA except around sheep BA except around colonies of staphylococcicolonies of staphylococci

►Colonies of staphylococci on Colonies of staphylococci on sheep BA cause the release of sheep BA cause the release of NAD, yielding satellite growth NAD, yielding satellite growth phenomenonphenomenon

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►H. haemolyticusH. haemolyticus and and H. H. parahemolyticusparahemolyticus are hemolytic are hemolytic variants of variants of H. influenzae H. influenzae and and H. H. parainfluenzae,parainfluenzae, respectively respectively

►Identification depends in part Identification depends in part upon demonstrating the need upon demonstrating the need for certain growth factors for certain growth factors called X and Vcalled X and V

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►Factor X acts physiologically as Factor X acts physiologically as heminhemin

►Factor V can be replaced by Factor V can be replaced by nicotinamide adenine nucleotide nicotinamide adenine nucleotide (NAD) or other coenzymes(NAD) or other coenzymes

►Carbohydrates are fermented Carbohydrates are fermented poorly and irregularlypoorly and irregularly

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SpeciesSpecies XX VVHemolysisHemolysis

►H. influenzaeH. influenzae ++ ++ --

(H. aegyptius)(H. aegyptius)►H. parainfluenzaeH. parainfluenzae -- ++ --►H. ducreyiH. ducreyi ++ -- --►H. haemolyticusH. haemolyticus ++ ++ ++►H. parahaemolyticus-H. parahaemolyticus- ++ ++►H. aphrophilusH. aphrophilus -- -- --

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►H. influenzae has a marked H. influenzae has a marked tendency to lose its capsule tendency to lose its capsule and the associated specificityand the associated specificity

►Resistance to ampicillin and Resistance to ampicillin and chloramphenicol is controlled chloramphenicol is controlled by genes on transmissible by genes on transmissible plasmidsplasmids

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Antigenic structureAntigenic structure►Encapsulated Encapsulated H. influenzae H. influenzae

contains capsular contains capsular polysaccharides (MW>150,000) polysaccharides (MW>150,000) of one of 6 types a-fof one of 6 types a-f

►The capsular antigen of type b is The capsular antigen of type b is a polyribose-ribitol phosphate a polyribose-ribitol phosphate (PRP) (PRP)

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►Most Most H. influenzaeH. influenzae in the in the normal flora of the URT are not normal flora of the URT are not encapsulatedencapsulated

►Somatic antigens consist of outer Somatic antigens consist of outer membrane proteinsmembrane proteins

►Lipooligosaccharides (endotoxins) Lipooligosaccharides (endotoxins) share many structures with those share many structures with those of neisseriaeof neisseriae

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PathogenesisPathogenesis►H. influenzaeH. influenzae produces no produces no

exotoxinexotoxin►Capsule is antiphagocytic in the Capsule is antiphagocytic in the

absence of specific anticapsular absence of specific anticapsular antibodiesantibodies

►Polyribose phosphate capsule of Polyribose phosphate capsule of type b type b H. influenzae H. influenzae is the major is the major virulence factor.virulence factor.

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►Carrier rate in the URT for Carrier rate in the URT for H. H. influenzaeinfluenzae is 2-4% is 2-4% For nontypeable For nontypeable H. H.

influenzaeinfluenzae is 50-80% or is 50-80% or higherhigher

►Causes meningitis, pneumonia Causes meningitis, pneumonia and empyema, epiglottitis, and empyema, epiglottitis, cellulitis, septic arthritiscellulitis, septic arthritis

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►Nontypeable tends to cause Nontypeable tends to cause chronic bronchitis, otitis media, chronic bronchitis, otitis media, sinusitis, and conjuctivitis sinusitis, and conjuctivitis following breakdown of normal following breakdown of normal host defense mechanismshost defense mechanisms

►Carrier rate for encapsulated Carrier rate for encapsulated types a and c-f is 1-2% and types a and c-f is 1-2% and rarely cause diseaserarely cause disease

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Clinical FindingsClinical Findings►H. influenzaeH. influenzae type b enters by way type b enters by way

of the respiratory tractof the respiratory tract►May be local extension with May be local extension with

involvement of sinuses or middle earinvolvement of sinuses or middle ear►Type b and pneumococci are two of Type b and pneumococci are two of

the most common etiologic agents the most common etiologic agents of bacterial otitis media and acute of bacterial otitis media and acute sinusitissinusitis

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►May reach blood bloodstream and be May reach blood bloodstream and be carried to the meninges or, less carried to the meninges or, less frequently may establish themselves frequently may establish themselves in the joints to produce septic in the joints to produce septic arthritisarthritis

►Pneumonitis and epiglottitis due to Pneumonitis and epiglottitis due to H. influenzaeH. influenzae may follow URTI in may follow URTI in small children and old or debilitated small children and old or debilitated peoplepeople

►Adults may have bronchitis or Adults may have bronchitis or pneumonia due to pneumonia due to H. influenzaeH. influenzae

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Diagnostic Laboratory TestsDiagnostic Laboratory Tests

SpecimensSpecimens►Nasopharyngeal swabs, pus, Nasopharyngeal swabs, pus,

blood and spinal fluid for blood and spinal fluid for smears and culturessmears and cultures

MicroscopyMicroscopy►Gram negative coccobacilli, Gram negative coccobacilli,

pleomorphicpleomorphic

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Haemophilus SpeciesHaemophilus Species

H influenzae: gram stain

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Direct IdentificationDirect Identification►H. influenzae antigens in spinal H. influenzae antigens in spinal

fluidfluid►Generally not more sensitive than Generally not more sensitive than

a Gram stain and not widely used.a Gram stain and not widely used.CultureCulture►IsoVitalex-enriched CAIsoVitalex-enriched CA►Lack of hemolysis on BALack of hemolysis on BA►Antibiotic susceptibility testingAntibiotic susceptibility testing

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►Tests for X and V factor Tests for X and V factor requirementsrequirements

►A better test for X factor A better test for X factor requirement is based on the requirement is based on the ability of H. influenzae to ability of H. influenzae to synthesize heme from synthesize heme from --aminolevulinic acidaminolevulinic acid

►Inoculum is incubated with Inoculum is incubated with --aminolevulinic acid aminolevulinic acid

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►Organisms that do not require X Organisms that do not require X factor synthesize factor synthesize porphobilinogen, porphobilinogen, porphyrins,protoporphyrins IX, porphyrins,protoporphyrins IX, and hemeand heme

►Presence of red fluorescence Presence of red fluorescence under UV light indicates under UV light indicates presence of porphyrins and a presence of porphyrins and a positive testpositive test

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►Species that synthesize Species that synthesize porphyrins (and thus heme) are porphyrins (and thus heme) are not H. influenzaenot H. influenzae

►Encapsulated organisms can be Encapsulated organisms can be typed by slide agglutination, typed by slide agglutination, coagglutination with coagglutination with staphylococci or agglutination of staphylococci or agglutination of latex particles coated with type-latex particles coated with type-specific antibodiesspecific antibodies

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►Satellite phenomenon testSatellite phenomenon test►A capsule swelling test with A capsule swelling test with

specific antiserum is analogous specific antiserum is analogous to quellung test for to quellung test for pneumococcipneumococci

►Typing can also be done by Typing can also be done by immunofuorescenceimmunofuorescence

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ImmunityImmunity

►Infants< age 3 months may Infants< age 3 months may have serum antibodies from have serum antibodies from mothermother

►H. influenzae most common H. influenzae most common cause of bacterial meningitis in cause of bacterial meningitis in children from 5 months to 5 yrschildren from 5 months to 5 yrs

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►By age 3-5 yrs, many By age 3-5 yrs, many unimmunized children have unimmunized children have naturally acquired anti-PRP naturally acquired anti-PRP antibodiesantibodies

►There is a correlation between There is a correlation between the presence of bactericidal the presence of bactericidal antibodies and resistance to antibodies and resistance to major major H. influenzaeH. influenzae type b type b infectionsinfections

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TreatmentTreatment►Mortality of untreated meningitis Mortality of untreated meningitis

up to 90%up to 90%►25% of strains produce beta 25% of strains produce beta

lactamase under control of lactamase under control of plasmids and are resistantplasmids and are resistant

►Essentially all strains are Essentially all strains are susceptible to newer susceptible to newer cephalosporinscephalosporins

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►Cefotaxime IV may give Cefotaxime IV may give excellent resultsexcellent results

►Prompt diagnosis and Prompt diagnosis and antimicrobial therapy are antimicrobial therapy are essential to minimize late essential to minimize late neurologic and intellectual neurologic and intellectual impairmentimpairment

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►Late complication - development Late complication - development of a localized subdural of a localized subdural accumulation of fluid that accumulation of fluid that requires surgical drainagerequires surgical drainage

Epidemiology, prevention and Epidemiology, prevention and controlcontrol

►Encapsulated H. influenzae type b Encapsulated H. influenzae type b is transmitted from person to is transmitted from person to person by the respiratory tractperson by the respiratory tract

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►Disease can be prevented by Disease can be prevented by administration of haemophilus b administration of haemophilus b conjugate vaccine to childrenconjugate vaccine to children

►Children aged 2 months or older Children aged 2 months or older can be immunized with vaccine can be immunized with vaccine conjugated with either HbOC with conjugated with either HbOC with protein carrier CRMprotein carrier CRM197197 mutant C. mutant C. diphtheriae toxin protein or N. diphtheriae toxin protein or N. meningitidis outer membrane meningitidis outer membrane complexcomplex

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►Children aged 15 months or older Children aged 15 months or older can receive vaccine conjugated can receive vaccine conjugated with diphtheria toxoid which is not with diphtheria toxoid which is not immunogenic in younger childrenimmunogenic in younger children

►Widespread use of vaccine Widespread use of vaccine reduced incidence of meningitis reduced incidence of meningitis by over 95%by over 95%

►Prophylaxis is recommended for Prophylaxis is recommended for children who come in contacts children who come in contacts with patientswith patients

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H. ducreyiH. ducreyi►Causes chancroid (soft chancre), Causes chancroid (soft chancre),

a sexually transmitted diseasea sexually transmitted disease►Chancroid consists of a rugged Chancroid consists of a rugged

ulcer on the genitalia, with ulcer on the genitalia, with marked swelling and tendernessmarked swelling and tenderness

►Regional lymph nodes are Regional lymph nodes are enlarged and painfulenlarged and painful

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H ducreyi – gram apperance

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►Disease must be differentiated Disease must be differentiated from syphilis, herpes simplex from syphilis, herpes simplex infection and lymphogranuloma infection and lymphogranuloma venereumvenereum

►Occur in association with other Occur in association with other pyogenic microorganismpyogenic microorganism

►Requires X but not V factorRequires X but not V factor

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►Grown best from scrapings of the Grown best from scrapings of the ulcer base on CA containing 1% ulcer base on CA containing 1% IsoVitalex and vancomycin 3 ug/ml IsoVitalex and vancomycin 3 ug/ml incubated in 10% carbon dioxide at incubated in 10% carbon dioxide at 33 33 °°CC

►Treatment with IM ceftriaxone,oral Treatment with IM ceftriaxone,oral trimethoprim-sulphamethoxazole, trimethoprim-sulphamethoxazole, or oral erythromycin often results or oral erythromycin often results in healing in 2 weeksin healing in 2 weeks