Bacterial infection and trachoma in the gambia: a case control study

Trachoma is the leading infectious cause of blindness worldwide. Conjunctival scarring is initiated by recurrent Chlamydia trachomatis infection. However, disease progression to trichiasis occurs even in regions where chlamydial prevalence is currently low, which suggests that other factors, for example other bacterial infection, may also drive inflammation and scarring, particularly in the late stages of trachoma. This study was undertaken to investigate whether trachomatous trichiasis or conjunctival scarring are associated with increased prevalence of bacterial infection.

Within a case-control study design, individuals with trichiasis or conjunctival scarring (without trichiasis) were compared with normal matched control subjects. Subjects were examined for signs of trachoma. Conjunctival swab samples were collected for bacteriologic culture and C. trachomatis PCR.

Recruited for the study were 121 trichiasis case-control pairs and 117 conjunctival scarring case-control pairs. Eyes with trichiasis were more frequently infected with bacteria (37%) than were normal control eyes (7%) (OR: 8.2; P < 0.001; 95% CI: 3.24-20.8). Bacterial infection was more common with increased trichiasis severity. In the conjunctival scarring case-control group, scarred eyes had slightly more bacterial infection (11%) than did normal control eyes (6%), although this was not significantly different (OR: 2.2; P = 0.144; 95% CI: 0.79-6.33).

Trichiasis is associated with increased risk of bacterial infection, and there may be a similar trend in eyes with conjunctival scarring. Bacterial infection of the conjunctiva is associated with inflammation, which may result in progressive scarring. Prospective studies are needed to determine the contribution of bacterial infection to disease progression. Bacterial infection probably also contributes to the development of corneal opacification.