It was concluded that molecular characterization of ompP6 was unable to differentiate all strains of H. influenzae from H. haemolyticus (200). H. aegyptius was described by Pittman and Davis in 1950, as a species distinct from H. influenzae and with a particular propensity to cause conjunctivitis (71).
With the implementation of identification by matrix-assisted laser desorption ionization–time of flight mass spectrometry, the more rarely encountered species of Haemophilus and Aggregatibacter will increasingly be identified in clinical microbiology practice. In South America, this organism is the cause of Brazilian purpuric fever.17,18 Especially prominent in children younger than 10 years, this catastrophic illness typically begins as hyperacute conjunctivitis, which is followed by fever within 3 to 5 days. Such strains have been considered rare and of little clinical significance, and only a few isolates of this species were included in the influential phenotypic study of the Haemophilus genus by Kilian (28), with a reported phenotype as presented in Table 3. In the pre-Hib-vaccine era, H. influenzae meningitis and epiglottitis were caused predominantly by serotype b strains and mainly affected children of ≤5 years of age (220 Douglas R. Fredrick, in Principles and Practice of Pediatric Infectious Diseases (Fourth Edition), 2012. The technique is in an early stage, and identification algorithms and databases are continually being improved and refined.
All species ferment sucrose.
This is explained by the passive protection from maternal antibodies during the first months of life and the improving natural immunity after two years of age. For identification of H. influenzae, the hpd PCR performed with a high sensitivity (88% and 89% for the healthy and otitis-prone children, respectively).
Genetic relationships of Haemophilus and Aggregatibacter species, using Escherichia coli as an outgroup. (ii) Haemophilus intermedius.Based on DNA hybridization and selected phenotypic traits, the species Haemophilus intermedius was proposed in 1989 (35), but the species is not validly named and has no standing in nomenclature. 88), and it has been proposed that such strains be classified as H. haemolyticus (37, 86). These four traits can be determined by PCR on selected invasive isolates or for research purposes. DNA sequencing is increasingly used for identification and typing, and matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry holds promise for revolutionizing routine identification in the clinical microbiology laboratory. Housekeeping gene sequencing.Different protein-coding genes have been studied and compared for species of Haemophilus and Aggregatibacter (8, 98, 101, 154 However, some strains will exhibit a mixed genotype and must be identified finally by sequencing. Nonencapsulated or nontypeable H. influenzae (NTHi) lacks a polysaccharide capsule.
Most Haemophilus spp. MALDI-TOF mass spectrometry is likely to have a profound effect on the workflow and results of the clinical microbiology laboratory. In contrast, nonencapsulated H. influenzae, though present in 80% of healthy children, makes up less than 2% of the total pharyngeal flora.58 Aggregatibacter spp. The Hib conjugate vaccine, which consists of the polyribosylribitol phosphate (PRP) polysaccharide from the Hib capsule conjugated to a protein carrier, prevents invasive Hib disease and reduces naso-pharyngeal carriage. Phenotypic characteristics can be determined by conventional testing in single tubes (15, 28, 48, 130) or by a number of semi- or fully automated systems (129, 131 Fortnum H, Davis A. 157). Detecting the formation of porphyrins from δ-aminolevulinic acid performs better than growth-based testing methods and has become the standard method to document independence of X factor (27, 128, 129). In the original report, Haemophilus spp. Few species of Pasteurellaceae other than Haemophilus and Aggregatibacter species exhibit host specificity for humans. Demonstration of X factor dependence using growth tests may carry a high rate of misinterpretations due to trace amounts of heme present in the medium or to heme inadvertently carried over with the inoculum (26, 48).
Haemophilus spp. Colonies on chocolate agar are small, with a diameter of ≤0.5 mm after 24 h, but their diameter may exceed 1 to 2 mm after 48 h. On primary isolation, the colonies are rough and adherent and demonstrate an opaque pattern described as star-like or like “crossed cigars” (111). The family increased from 3 genera in 1995 to 18 genera in 2012, but most of these genera will not be found in clinical specimens unless they are incidentally introduced by animal bites or licks. Additionally, 8 of 163 isolates had variations in the OMP P6 translated amino acid sequence at sites outside the four key residues; 2 of these isolates were subjected to MLST and finally identified as H. influenzae and H. haemolyticus.
Another study characterized 60 selected strains from healthy and otitis-prone children by partial sequencing of 16S rRNA (598 nt) and recA (543 nt) genes and by seven separate PCR assays, including assays of fucK, hpd, iga, and lgtC (173). – The proportion of H. haemolyticus and related organisms among invasive strains (195) thus exceeded the reported proportion cultured from unselected clinical samples (199).
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