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Category: Clinical Microbiology
Haemophilus, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap34-1.gif /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap34-2.gifAbstract:
While the number of Haemophilus species described greatly exceeds the number of human pathogens, eight species affecting humans currently included in this genus are H. influenzae, H. aegyptius, H. ducreyi, H. pittmaniae, H. parainfluenzae, H. haemolyticus, H. parahaemolyticus, and H. paraphrohaemolyticus. Aggregatibacter aphrophilus, Aggregatibacter paraphrophilus, and Aggregatibacter segnis were formerly included in the genus Haemophilus but have recently been reclassified into the genus Aggregatibacter (formerly Actinobacillus) based on molecular taxonomy. In the absence of the recently reclassified species, significant genetic diversity still exists in the Haemophilus genus. Haemophilus influenzae may be found as part of the commensal bacterial flora of the mucosal surfaces of the upper respiratory tracts (URT) of many healthy individuals. Several molecular methods, including 16S rRNA gene sequencing, polymerase chain reaction (PCR), and fluorescence in-site hybridization have been described in the literature as being effective tools for the species identification of Haemophilus when performed on organisms recovered in culture. Other molecular methods for typing have also been applied to Haemophilusspecies. In one study evaluating the performance of intergenic dyad sequence (IDS)-PCR with 69 NTHi isolates, the assay demonstrated 65 different banding patterns that were epidemiologically classified as fingerprints similar to those obtained by pulsed-field gel electrophoresis (PFGE).
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Electron micrographs depicting an encapsulated type b strain (left) and a nonencapsulated, nontypeable strain (right) of Haemophilus influenzae.
Electron micrographs depicting an encapsulated type b strain (left) and a nonencapsulated, nontypeable strain (right) of Haemophilus influenzae.
Gram stain of Haemophilus influenzae present in CSF.
Gram stain of Haemophilus influenzae present in CSF.
Colony morphologies of type b encapsulated (left) and nonencapsulated (right) strains of Haemophilus influenzae when propagated on enriched chocolate agar.
Colony morphologies of type b encapsulated (left) and nonencapsulated (right) strains of Haemophilus influenzae when propagated on enriched chocolate agar.
Colony morphologies of type b encapsulated (left and right) and nonencapsulated (center) strains of Haemophilus influenzae when propagated on Levinthal's agar. Note the conspicuous iridescence apparent with the encapsulated strain.
Colony morphologies of type b encapsulated (left and right) and nonencapsulated (center) strains of Haemophilus influenzae when propagated on Levinthal's agar. Note the conspicuous iridescence apparent with the encapsulated strain.
Colony growth from an expectorated-sputum specimen containing Haemophilus influenzae from a patient with cystic fibrosis propagated on enriched chocolate agar (left) and enriched chocolate agar
Colony growth from an expectorated-sputum specimen containing Haemophilus influenzae from a patient with cystic fibrosis propagated on enriched chocolate agar (left) and enriched chocolate agar
Satellite phenomenon observed when Haemophilus influenzae is propagated next to a streak of Staphylococcus aureus on a 5% sheep blood agar plate.
Satellite phenomenon observed when Haemophilus influenzae is propagated next to a streak of Staphylococcus aureus on a 5% sheep blood agar plate.
Use of X and V factor disks and strips in determining the growth factor requirements of Haemophilus influenzae (left disks) and H. parainfluenzae (right disks).
Use of X and V factor disks and strips in determining the growth factor requirements of Haemophilus influenzae (left disks) and H. parainfluenzae (right disks).
Positive (top) and negative (bottom) porphyrin tests.
Positive (top) and negative (bottom) porphyrin tests.
Conventional biochemicals depicting positive and negative reactions for indole, urease, and ornithine decarboxylase production (left to right) by Haemophilus spp.
Conventional biochemicals depicting positive and negative reactions for indole, urease, and ornithine decarboxylase production (left to right) by Haemophilus spp.
Differential characteristics of Haemophilus species e
a Indole, urease, and ornithine decarboxylase production are the basis for biotyping schemes with H. influenzae and H. parainfluenzae as depicted in Table 2 .
b A delayed positivereaction occurs in more than 90% of strains.
c Delayed development of hemolysis occurs in 11 to 89% of strains.
d Elevated concentrations of CO2 of ≥10% enhance growth.
e +, positive; –, negative; v, variable reaction; w, weak reaction; uk, unknown.
Differential characteristics of Haemophilus species e
a Indole, urease, and ornithine decarboxylase production are the basis for biotyping schemes with H. influenzae and H. parainfluenzae as depicted in Table 2 .
b A delayed positivereaction occurs in more than 90% of strains.
c Delayed development of hemolysis occurs in 11 to 89% of strains.
d Elevated concentrations of CO2 of ≥10% enhance growth.
e +, positive; –, negative; v, variable reaction; w, weak reaction; uk, unknown.
Biotypes of Haemophilus influenzae and H. parainfluenzae
Biotypes of Haemophilus influenzae and H. parainfluenzae