Affiliation:
1. Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, Michigan
2. Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, Michigan
Abstract
ABSTRACT
Haemophilus influenzae
is an important cause of respiratory infections, including acute otitis media, sinusitis, and chronic bronchitis, which are preceded by asymptomatic
H. influenzae
colonization of the human pharynx. The aim of this study was to describe the dynamics of pharyngeal colonization by
H. influenzae
and an intimately related species,
Haemophilus haemolyticus
, in healthy adults. Throat specimens from four healthy adult carriers were screened for
Haemophilus
species; 860 isolates were identified as
H. influenzae
or
H. haemolyticus
based on the porphyrin test and on dependence on hemin and NAD for growth. Based on tests for hemolysis, for the presence of the 7F3 epitope of the P6 protein, and for the presence of
iga
in 412 of the isolates, 346 (84%) were
H. influenzae
, 47 (11%) were
H. haemolyticus
, 18 (4%) were nonhemolytic
H. haemolyticus
, and 1 was a variant strain. Carriers A and B were predominantly colonized with nontypeable
H. influenzae
, carrier C predominantly with b
−
H. influenzae
mutants, and carrier D with
H. haemolyticus
. A total of 358
H. influenzae
and
H. haemolyticus
isolates were genotyped by pulsed-field gel electrophoresis (PFGE) following SmaI or EagI digestion of their DNA, and the carriers displayed the following: carrier A had 11 unique PFGE genotypes, carrier B had 15, carrier C had 7, and carrier D had 10. Thus, adult
H. influenzae
and
H. haemolyticus
carriers are colonized with multiple unique genotypes, the colonizing strains exhibit genetic diversity, and we observed day-to-day and week-to-week variability of the genotypes. These results appear to reflect both evolutionary processes that occur among
H. influenzae
isolates during asymptomatic pharyngeal carriage and sample-to-sample collection bias from a large, variable population of colonizing bacteria.
Publisher
American Society for Microbiology
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