SX Wu, L Shen, GX Liu

In order to know the frequency of vertical transmission of Chlamydia trachomaris in Chongqing, we studied 278 pregnant women and their 79 infants using cell culture, the polymerase chain reaction (PCR) and DNA sequencing. 549 cervical samples were collected from the women and 258 nasopharyngeal and conjunctival samples were taken from their infants and from 45 cases of neonatal pneumonia.

C. trachomaris was isolated in mouse McCoy cells with one blind passage. DNA was extracted using a modified NaI method. Two sets of primers derived from C. trachomaris common plasmid and MOMP gene were used for PCR. After cloning, recombinant plasmids were used for sequence determination by the dideoxy chain termination method. 10.8% (30/278) of the cervical cultures were positive for C. trachomaris, while the positive rate by PCR was 14.0% (39/278). Conjunctival and nasopharyngeal samples of 59 infants born from mothers who had negative C. trachomaris cultures were all negative for C. trachomaris, whereas the samples of 11 infants born from 20 mothers with positive C. trachomaris cultures were positive (P < 0.005). The vertical transmission rate of C. trachomaris was 55% (11/20). The incidence of conjunctivitis and pneumonia in infants born from C. trachomaris positive mothers was 27.3% (3/11) and 18.2% (2/11), respectively. 17.7% (8/45) of nasopharyngeal cultures were positive, while the positive rate by PCR was 22.2% (10/45). The sequences amplified from a maternal-infant pair matched perfectly. They were identical with those of serovar E compared with the sequence data reported before. This is the first report of vertical transmission of C. trachomaris proved by DNA sequence analysis. It is important to know that vertical transmission of C. trachomaris and C. trachomaris pneumonia in neonates is not uncommon in China.