title: Oropharyngeal Gram-negative bacillary carriage: a survey of 120 healthy individuals.
abstract: 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.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  Two oral rinses were obtained within a 2-day interval from 120 healthy individuals comprising 40 nurses, 40 students, and 40 laboratory-associated persons.
  
  
  METHODS
  Two hundred forty oral rinses were quantitatively (1:10 dilution series) cultured for AGNB by using broth enrichment.
  
  
  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 < or = 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).
  
  
  CONCLUSIONS
  Healthy 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.
authors.affiliation: Department of Genetics and Microbiology, University of Liverpool, UK. K.J.Mobbs@liv.ac.uk
authors.forename: K J
authors.initials: KJ
authors.lastname: Mobbs
authors.forename: H K
authors.initials: HK
authors.lastname: van Saene
authors.forename: D
authors.initials: D
authors.lastname: Sunderland
authors.forename: P D
authors.initials: PD
authors.lastname: Davies
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001420:Bacteria, Aerobic / Q000254:growth & development / Q000302:isolation & purification*; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D015169:Colony Count, Microbial; D004739:England / Q000453:epidemiology; D005260:Female; D006090:Gram-Negative Bacteria / Q000254:growth & development / Q000302:isolation & purification*; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009960:Oropharynx / Q000382:microbiology*; D011159:Population Surveillance; D015995:Prevalence; D012016:Reference Values