Objective       To investigate the difference of main pathogenic bacteria in subgingival plaque of periodontitis rabbits under normal oxygen and simulated high altitude hypoxia conditions.       Methods       A total of 40 rabbits were randomly divided into 4 groups including a normal oxygen periodontitis group

a normal control group

a hypoxia periodontitis group and a hypoxia control group (n=10). Rabbits of the periodontitis groups were given ligation of anterior teeth by steel wire and high-carbohydrate diet

while rabbits of the hypoxia groups were raised in a low pressure oxygen cabin simulating high altitude hypoxia condition (5 000 m)

23 h/day for 8 weeks. Genomic DNA in subgingival plaque was extracted after 8 weeks treatment and 16S rDNA gene fragments were amplified by polymerase chain reaction (PCR) to test 6 periodontits pathogenic bacteria

including Porphyromonas gingivalis (Pg)

Bacteroides forsythus (Bf)

Actinobacillus actinomycetemcomitans (Aa)

Prevotella intermedia (Pi)

Fusobacterium nucleatum (Fn) and Treponema denticola (Td).       Results       Gingival bleeding index

plaque index and periodontal pocket depth in the hypoxia periodontitis group were significantly different from those in the normal oxygen periodontitis group (P0.05). Putative periodontal pathogens

including Pg

Bf

Aa

Pi

Fn and Td

were detected both in the hypoxia periodontitis group and normal oxygen periodontitis group. The positive rate of Fn in the hypoxia periodontitis group (80%) was higher that in the normal oxygen periodontitis group (20%) (P0.05)

while the positive rate of Pi was higher in the normal oxygen periodontitis group (70%) than that in the hypoxia periodontitis group (15%) (P0.05).       Conclusion       High altitude hypoxia is the main reason of periodontitis aggravation

which is also associated with Fn.