Objective To analyze the differences of flora between the breastfeeding women with acute mastitis and yellow greasy tongue coating

and the healthy breastfeeding women with thin white coating

to provide idea for prevention and treatment of acute mastitis. Methods Twenty-four breastfeeding women with acute mastitis and having fever and yellow greasy tongue coating were included in the yellow-greasy group

while 17 healthy breastfeeding women who had thin white coating were set as control group（thin-white group）. MiSeq high-throughput sequencing technology in combination with Bayesian algorithm were used to analyze the flora composition of the tongue coating; the Student′s t test was used to compare the Alpha diversity of the tongue coating flora of the two groups including the Chao index

Shannoneven index and Shannon index; the partial least squares method（PLS-DA） was used to determine the similarity of the tongue coating flora structure between the two groups; Wilcoxon rank sum test and linear discriminant analysis effect size（LEfSe） on multi-level species were used to analyze the different species of the two groups. Results The yellow-greasy group had two unique bacteria phyla Deinococcota and Acidobacteriota and 34 unique bacteria genera

while the thin-white group had 16 unique bacterial genera

showing that the composition of microbiota in the tongue coating was significantly different between the two groups. The Shannoneven index and Shannon index of the yellow-greasy group were significantly higher than those of the thin-white group（P<0.05）. The content of Bacteroides in the yellow-greasy group was 29.68%

higher than 21.6% in the thin-white group; and the content of Proteobacteria was 9.43% in the yellow-greasy group

lower than 29.93% in the thin-white group（P<0.05）. In terms of bacterial genera

the content of Prevotella

Veronococcus and Prevotella in the yellow-greasy group was significantly higher than that in the thin-white group

while the content of Neisseria and Haemophilus in the thin-white fur group was significantly higher（P<0.05）. The main dominant bacteria in the yellow-greasy group were Veillonella

Macrococcus

Corynebacterium

Prevotella

Desmodium

Prevotella

and Solobacterium

while that of the thin-white group were Neisseria

Haemophilus and Streptomyces

with statistically significant differences between groups（P<0.05）. Conclusion The uniformity and diversity of the tongue coating is better in breastfeeding women with acute mastitis and yellow greasy coating than healthy women with thin white coating

and the species differences are mainly manifested in the higher degree of the richness of Prevotella

Prevotella and Veronococcus.