title: Oral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci in irradiated, dentate, xerostomic individuals.
abstract: This study aimed at investigating the oral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci in head- and neck-irradiated, dentate, xerostomic individuals. Subjects were recruited from a nasopharyngeal carcinoma clinic and were segregated into group A: <60 years (n=25, 48+/-6 years, 5+/-5 years post-irradiation) and group B: >or=60 years (n=8, 67+/-4 years, 2+/-2 years post-irradiation) and were compared with age- and sex-matched normal individuals, group C: <60 years (n=20, 44+/-12 years) and group D: >or=60 years (n=10, 70+/-3 years). Selective culture of the oral rinse samples was carried out to isolate, quantify and speciate (using API 20E kit) aerobic and facultatively anaerobic gram-negative rods and cocci recovery. All test subjects were put under comprehensive oral and preventive care for 3 months, and 12 group A and 5 group B subjects were recalled for reassessment of aerobic and facultatively anaerobic gram-negative rods and cocci colonization. All identical isolates, pre- and post-hygienic care, were phenotypically (Vitek, Hazelwood, MA and antibiogram profile) and genotypically (pulsed-field gel electrophoresis) evaluated. The aerobic and facultatively anaerobic gram-negative rods and cocci isolated from the first round oral rinse samples included: Acinetobacter, Neisseria, Chryseomonas, Flavimonas, Pseudomonas, Citrobacter, Enterobacter, Escherichia, Klebsiella, Flavobacterium and Weeksella species. The aerobic and facultatively anaerobic gram-negative rods and cocci isolation rate was high for irradiated individuals, and they were 64/25% and 100/80% for groups A/C and B/D, respectively. Recovery of aerobic and facultatively anaerobic gram-negative rods and cocci and Klebsiella pneumoniae subsp. pneumoniae in oral rinse samples were found to be significantly more prevalent in the irradiated subjects (groups A and B). Enterobacteriaceae were more frequently isolated from oral rinse samples of aged irradiated subjects (group B vs D, P<0.05), where the quantity of Citrobacter freundii (colony-forming units/ml oral rinse) was also significantly elevated. The isolation rate of aerobic and facultatively anaerobic gram-negative rods and cocci after hygienic care remained unchanged; 3 of 12 and 3 of 5 of the recalled subjects from groups A and B, respectively, harbored same aerobic and facultatively anaerobic gram-negative rods and cocci species. However, only two pairs of K. pneumoniae subsp. pneumoniae, sequentially isolated from same patients in group B, were found to be identical by pulsed-field gel electrophoresis. This may be due to reinfection of the microbes from the same source or permanent colonization. In conclusion, irradiation-induced xerostomia seems to favor frequent, repeated, transient intraoral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci.
authors.affiliation: Faculty of Dentistry, Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China.
authors.forename: W K
authors.initials: WK
authors.lastname: Leung
authors.forename: L J
authors.initials: LJ
authors.lastname: Jin
authors.forename: W C
authors.initials: WC
authors.lastname: Yam
authors.forename: L P
authors.initials: LP
authors.lastname: Samaranayake
mesh_terms: D000150:Acinetobacter / Q000145:classification; D000328:Adult; D000367:Age Factors; D000368:Aged; D015373:Bacterial Typing Techniques; D002277:Carcinoma / Q000532:radiotherapy*; D016022:Case-Control Studies; D002954:Citrobacter / Q000145:classification; D015331:Cohort Studies; D004269:DNA, Bacterial / Q000032:analysis; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004754:Enterobacter / Q000145:classification; D004925:Escherichia / Q000145:classification; D005417:Flavobacterium / Q000145:classification; D005500:Follow-Up Studies; D005838:Genotype; D016946:Gram-Negative Aerobic Rods and Cocci / Q000145:classification*; D006092:Gram-Negative Facultatively Anaerobic Rods / Q000145:classification*; D006801:Humans; D007709:Klebsiella / Q000145:classification; D007711:Klebsiella pneumoniae / Q000145:classification; D008875:Middle Aged; D009055:Mouth / Q000382:microbiology* / Q000528:radiation effects; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D009343:Neisseria / Q000145:classification; D009910:Oral Hygiene; D010641:Phenotype; D011549:Pseudomonas / Q000145:classification; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D014987:Xerostomia / Q000209:etiology / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial