A blocking reagent (Abbott) was used to test 153 conjunctival and nasopharyngeal samples from children with signs of early trachoma and from neonates and adults with conjunctivitis caused by Chlamydia trachomatis in whom positive results had been obtained on at least one occasion in an enzyme immunoassay (EIA) (Abbott). EIA and cycloheximide-treated McCoy cell cultures of the eye sample were equally often positive in the non-trachoma cases (70 versus 71), the EIA results being confirmed by the blocking reagent test in these cases. The corresponding figures for the nasopharyngeal samples were 31 versus 25. There was full agreement between the results of the EIA and blocking reagent tests, except in two eye samples and one nasopharyngeal sample where the blocking reagent test was negative. Three EIA results were within the equivocal zone around the cutoff point, two of which were positive and one negative in the blocking test.

Saliva collected from adults with no antichlamydial antibodies in their serum or saliva, was tested for its capacity to inhibit the formation of inclusions of Chlamydia trachomatis in McCoy cell cultures. Pooled saliva, diluted in tissue culture medium and sterilized by filtration, was found to reduce the inclusion count by up to about 40%. However, the pretreatment of the chlamydial organisms for 2 hours with diluted saliva caused a 75% decrease in the number of inclusions. The inhibitory activity, which was concentration‐dependent, seems to affect the attachment of the chlamydial elementary body to the host cell by acting on both the chlamydiae and the McCoy cells. Saliva did not seem to affect the intracellular development of the chlamydiae. The inhibitory activity was not affected by trypsin treatment, while absorbtion with a gel of a chelating agent caused total loss of the antichlamydial effect. The purpose of our study was to test saliva for its possible antichlamydial activity and to partially characterize the active principle.

An enzyme linked immunosorbent assay (ELISA) and an immunofluorescence (IF) test were compared with culture for their value in the diagnosis of chlamydial infection in early trachoma. Conjunctival swabs and scrapings from 81 school children with active trachoma from Khartoum, Sudan, were tested. Fourteen (17.3%) of the children with signs of active trachoma were positive by isolation. The sensitivities of the ELISA and IF tests, compared to cultures, were 85.0% and 68.2%, while the specificities for the ELISA and IF tests were 99.2% and 99.3%, respectively. Chlamydial IgM and IgG antibodies reactive with serotypes A‐C and D‐K of Chlamydia trachomatis were detected in sera of 28 (71.2%) of the 39 children from whom serum was obtained. Only eight of the 14 isolation‐positive children were tested for chlamydial antibodies, and all of them had IgM and IgG antibodies at a titer of ≥ 1:16. An IgG antibody titer of 1:16 or greater was detected in 20 (65.0%) of the 31 isolation‐negative patients tested for chlamydial antibodies. The geometric mean titers of IgG antibodies to the antigen pools A‐C and D‐K were 132 and 42, respectively. Our study suggests that trachoma is prevalent in the child population studied. Clinical signs of active trachoma were found in 47.0% of the altogether 172 children investigated. ELISA can be recommended as a diagnostic tool in trachoma field surveys.

The relative value of culture, direct specimen antigen detection tests, i.e., enzyme‐linked immunosorbent assay (ELISA) and immunofluorescence (IF) tests in the diagnosis of Chlamydia trachomatis infection was studied in 125 newborns and 121 adults with signs of conjunctivitis. Eye and nasopharyngeal samples were tested by culture using cycloheximide‐treated or irradiated McCoy cells, ELISA (i.e., ChlamydiazymeTM, Abbott) and IF tests (i.e., ChlamysetTM, Orion and Micro TrakTM, Syva). Of the neonates, 70 (35 boys and 35 girls) and 54 (33 males and 21 females) of the adults were positive in one or both eyes in one or more tests: 191 (39%) in cultures, 173 (35%) in ELISA and 160 (33%), 176 (36%) in each of the IF tests. Using culture as standard reference, the sensitivities of ELISA and the IF tests were 88%, 81% and 87%, while the corresponding specificities were 99%, 98% and 97%, respectively. The predictive values for a negative test (PVN) were 93%, 89% and 92% and for a positive test (PVP) 98%, 96% and 94%. Of the 124 cases chlamydia‐positive in the eyes, 67 (54%), 76 (61%), 64 (52%) and 70 (57%) were positive in nasopharyngeal samples in one or more of culture, ELISA and the two IF tests, respectively. The sensitivities of ELISA and the IF tests in nasopharyngeal samples were 87%, 78% and 81%, while the corresponding specificities were 90%, 93% and 91%, respectively. The predictive values for a negative (PVN) test were 95%, 92% and 93%, and for a positive test (PVP) 76%, 81%, and 77%. Nasopharyngeal swabs were more often positive in cases with 2 or more weeks' duration of symptoms than in those with shorter duration.

A study of the effect of human breast milk, and components thereof, on the capacity of Chlamydia trachomatis to form inclusions in cycloheximide‐treated McCoy cells, was undertaken. Pooled whole milk collected during the first week of breast feeding caused a concentration‐dependent inhibition of the chlamydial inclusion‐formation. The activity resided in the fat and fat globule membrane (FGM) components of the milk. The active principle in the FGM fraction is heat‐stable and pronase‐sensitive, but resistant to both neuraminidase and periodate. Immunoglobulins was not responsible for the inhibition. Whey and casein fractions of milk increased the chlamydial inclusion‐formation. The activity of the whey was heat‐stable, dose‐related, and had a mol.wt. of 12,000. The casein fraction was still active after heat treatment. Whey samples collected up to 28 days after delivery varied slightly in their stimulatory activity, with an optimum between the 7th and 14th days. The present study demonstrated a multieffect of breast milk on chlamydial inclusion‐formation: an inhibitory activity due to a protein compound as well as another factor in the fat fraction and an enhancing effect due to a heat‐stable factor(s).