Effects of chloramphenicol on Chlamydia trachomatis infection in neonatal conjunctivitis and in McCoy cell cultures.

It was found that 26 of 127 infants with chlamydial conjunctivitis had previously received chloramphenicol eye drops. This treatment had delayed the onset and reduced the degree of oedema, congestion and discharge compared with infected infants with no 'first-line' chemotherapy, but eye swabs remained positive in 22 (85%) of the chloramphenicol treated infants. The problems of designing laboratory tests which might accurately forecast the clinical value, or lack of value of antibiotics in chlamydial infections were investigated. The minimum inhibitory concentration (MIC) of chloramphenicol, against Chlamydia trachomatis in McCoy cell cultures varied widely according to the antibiotic preparation used, the timing and duration of its exhibition in relation to the single step growth cycle of C. trachomatis, and, in particular, the method of examination of infected tissue cultures for residual chlamydial growth after incubation with chloramphenicol.