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Updated: Jun 7, 2026

Conjunctival Commensal Isolation and Identification in Mice
Published on: May 1, 2021
[Normal conjunctival flora in healthy infants aged from 1 to 4 months]
Ning Hua1, Wen-jiang Ma, Jian-tao Wang
1Tianjin Medical University Eye Center, Tianjin, China.
Insights
The normal conjunctival bacterial flora in healthy infants is established early, with Diphthamide bacillus and Staphylococcus epidermidis being the most common. Factors like feeding method or gender did not significantly correlate with flora presence.
Area of Science:
- Ophthalmology
- Microbiology
- Neonatal Health
Context:
- The conjunctival bacterial flora plays a crucial role in ocular health, particularly in neonates.
- Understanding the normal flora in infants is essential for diagnosing and managing eye infections.
Purpose:
- To investigate the typical conjunctival bacterial flora in healthy infants aged 1 to 4 months.
- To identify common bacterial species and analyze factors potentially correlated with their presence.
Summary:
- A cross-sectional study of 109 healthy infants (1-4 months) found that 23.9% had positive conjunctival cultures.
- The most prevalent bacteria were Diphthamide bacillus (38.6%) and Staphylococcus epidermidis (36.4%).
- No significant correlation was found between the presence of conjunctival flora and infant factors such as feeding method, gender, birth weight, or gestational age.
Impact:
- This study provides baseline data on the normal conjunctival flora in early infancy.
- It suggests that conjunctival flora may establish within the first few months of life.
- Further research is recommended to explore potential correlations with other factors not examined in this study.
Objective:
To investigate the normal conjunctival bacterial flora isolated from healthy infants aged from 1 to 4 months and to analyze its correlated factors.
Methods:
This was a cross-sectional study. From January to March 2009, 109 cases of healthy babies aged from 1 to 4 months were selected through simple random sampling when they accepted health examination provided by Tianjin Medical University Eye Center and Tianjin Women and Children's Health Center. Conjunctival swabs were taken from both eyes and inoculated onto blood agar plates. The isolated bacteria were classified professionally. The distribution of different bacteria was investigated as well as the possible correlated factors by using t-test, χ(2) test and binary logistic regression of SPSS 11.5.
Results:
26 cases of healthy babies (23.9%) got positive culture results which consisted 44 strains of ocular bacterial isolates. 25 strains were gram-positive cocci, while 18 strains gram-positive bacilli, and 1 strain gram-negative bacillus. The first three isolated bacteria were Diphthamide bacillus (17/44, 38.6%), Staphylococcus epidermidis (16/44, 36.4%), and Staphylococcus aureus (6/44, 13.6%). The two subtypes of Staphylococci coexisted with Diphthamide bacillus in 8 eyes of 36 eyes from which bacteria were isolated. The bacterial isolation rate through every month age group had no significant difference (χ(2) = 0.351, P > 0.05). There was no significant difference in the group of positive isolation (26 cases, 36 eyes) or negative isolation (83 cases, 166 eyes) through breast, formula or mixed feeding (χ(2) = 1.182, P > 0.05). The gender had no influence on the detection of bacteria (χ(2) = 0.001, P > 0.05). The birth weight, gestational age or examined age between the two groups had no significant difference (t = 0.078, t = 0.940, t = 0.686, P > 0.05). The gender, age, birth weight, gestational age and the way of feeding had no correlation with existence of conjunctival flora in these healthy infants (Wald χ(2) = 0.001, Wald χ(2) = 0.003, Wald χ(2) = 0.117, Wald χ(2) = 1.307, Wald χ(2) = 1.490, P > 0.05).
Conclusions:
The normal conjunctival flora might establish during the initial months of little babies. Staphylococcus epidermidis and Diphthamide bacillus are the most common bacteria. Future studies should be conducted to make sure whether there would be some factors correlated with the culture results.
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