Background: The presence of aerobic Gram-negative
bacilli (AGNB) in the oropharynx can be either temporary or persistent.
Prolonged colonization (ie, carriage) is distinguished
from transient presence (ie, acquisition), which often
occurs in healthy individuals but less frequently in those with
underlying disease. Prevalence rates of up to 61.1% quoted previously
for healthy individuals were obtained by using single sample surveys,
which fail to differentiate acquisition from carriage.
objectives: To illustrate the need to distinguish carriage from
acquisition in a healthy population at risk of acquisition of AGNB, and
to show that although differing groups of healthy individuals may
acquire oropharyngeal AGNB at differing frequencies, carriage is rare
in healthy individuals.
Participants: Two oral rinses
were obtained within a 2-day interval from 120 healthy individuals
comprising 40 nurses, 40 students, and 40 laboratory-associated
Design: Two hundred forty oral rinses were
quantitatively (1:10 dilution series) cultured for AGNB by using broth
Measurements and results: The rate of AGNB
carriage based on two consecutive samples positive for the same AGNB
was 6.6%; the rate of AGNB acquisition based on one positive
sample was 35.8%. The concentrations of all carried and acquired AGNB
were ≤ 103 cfu/mL. AGNB acquisition was significantly higher in
students (52.5%) compared to nurses (32.5%) and laboratory-associated
persons (22.5%; p < 0.05).
individuals rarely carry oropharyngeal AGNB, suggesting effective
oropharyngeal clearance in a healthy population predisposed to
acquisition. Apparently, the oropharyngeal mucosa in healthy
individuals is not receptive to adhesins of AGNB, resulting in rapid
elimination of these bacteria.
Abbreviations: AGNB = aerobic Gram-negative bacilli