Bacterial isolates and in vitro antimicrobial susceptibility in blepharitis

Blepharitis is an induce factor for multiple ocular surface diseases. Research showed that bacteria play an important role in the pathogenesis of blepharitis. To make sure the pathogenic bacteria and effective antimicrobial agents are of clinical significance for the prevention and treatment of blepharitis.

The purpose of this study was to investigate the bacterial isolates of conjunctival sac secretion and meibomian secretion in the patients with blepharitis and study their in vitro antimicrobial susceptibility.

Forty-five patients with anterior blepharitis and 45 cases with posterior blepharitis were included in Beijing Chaoyang Hospital from December 2006 to December 2012, and 45 patients for laser in situ keratomileusis were enrolled in the same period as control group. The secretions of the conjunctival sac and meibomian were collected with sterile cotton swab, and bacterial isolates were cultured in bouillon culture-medium. The number of eyes with different bacteria was examined and calculated. Then the bacteria were switched to blood agar plates, and antimicrobial susceptibility test to erythromycin, gentamicin, tobramycin, rifampin, levofloxacin were performed by Mueller Hinton (M-H) medium paper method.

The total germiculture positive rates were 81.1%, 76.1% and 65.0% in the anterior blepharitis group, posterior blepharitis group and the control group, showing a significant difference among them (χ²=12.80, P=0.00). The germiculture positive rates in meibomian secretion were 84.4% and 78.8% in the anterior blepharitis group and the posterior blepharitis group, which were significantly higher than 67.8% in the control group (χ²=7.30, P=0.03). There was no statistically significant difference in the germiculture positive rate of conjunctival sac section among the three groups (77.8%, 73.3% and 62.2%) (χ²=5.60, P=0.06). The main bacteria in conjunctival sac secretion and meibomian secretion were staphylococcus epidermidis, staphylococcus aureus and corynebacterium in all the subjects, but streptococcus pneumoniae and gram-negative bacillus were not detected in the control group. Staphylococcus showed the highest susceptibility to gentamicin, tobramycin and rifampicin, with the sensitive rate >70%. Corynebacterium was susceptible to various drugs. Streptococcus pneumoniae had susceptibility to erythromycin and tobramycin. However, Gram-negative bacillus was not susceptible to all the drugs above.

Bacteria participate in the pathogenesis of blepharitis, but the germiculture positive rate, bacterial species and drug susceptibility of bacteria are obviously different between patients with blepharitis and normal population. Reasonable application of antimicrobial agents is important to blepharitis.