ABSTRACT
The hypothesis that host cell surface heparan sulfate is required to promote chlamydial infection was tested using a cell line (CHO-18.4) containing a single retroviral insertion and the concomitant loss of heparan sulfate biosynthesis. Tests of chlamydial infectivity of heparan sulfate-deficient CHO-18.4 cells and parental cells, CHO-22, demonstrated that both were equally sensitive to infection by Chlamydia trachomatis serovars L2 and D. These data do not support the hypothesis and demonstrate that host cell surface heparan sulfate does not serve an essential functional role in chlamydial infectivity.
Subject(s)
CHO Cells/metabolism , Chlamydia trachomatis/metabolism , Glycosaminoglycans/metabolism , Heparitin Sulfate/metabolism , Animals , Chlamydia trachomatis/pathogenicity , Cricetinae , Glycosaminoglycans/physiology , Heparitin Sulfate/physiologyABSTRACT
PURPOSE: To describe the relationship between the clinical exam for trachoma and the polymerase chain reaction (PCR) for ocular chlamydia. METHODS: One hundred children in a trachoma-endemic area of Ethiopia were examined three times and swabbed twice for PCR analysis. The assays were compared, and an analysis of the variance between exam and PCR was performed. RESULTS: Inter-examiner agreement was 0.57 (Cohen's kappa), inter-PCR agreement 0.98, and agreement between examiner and PCR, 0.26-0.34. The positive predictive value of the exam in identifying infection was 66%. Inter-examiner variance accounted for 30% of the total variance between the exam and PCR, with the remainder presumably due to an underlying difference in what the exam and PCR measure. CONCLUSIONS: Despite modest inter-grader reliability and correlation with evidence of infection, the clinical exam is widely used due to its convenience and low cost. Efforts to make laboratory tests for ocular Chlamydia trachomatis more affordable would be useful.
Subject(s)
Chlamydia trachomatis/isolation & purification , DNA, Bacterial/analysis , Trachoma/diagnosis , Child , Child, Preschool , Chlamydia trachomatis/genetics , Ethiopia/epidemiology , Humans , Infant , Observer Variation , Physical Examination , Polymerase Chain Reaction , Predictive Value of Tests , Reproducibility of Results , Sensitivity and Specificity , Trachoma/epidemiology , Trachoma/microbiologyABSTRACT
BACKGROUND: Considerable variation in the outer membrane protein (ompA) of Chlamydia trachomatis has been uncovered by immunotyping and, more recently, by genotyping. This diversity may assist Chlamydia in evading the human immune system; organisms may have a competitive advantage if they infect a host who has previously been infected only by other strains. If so, a diverse set of strains may attain a higher prevalence in a community than a single strain. We determined the predominant strains of ocular C. trachomatis in trachoma-endemic villages of Nepal and tested the hypothesis that strain diversity is associated with the prevalence of infection. METHODS: Major outer membrane protein gene sequences of chlamydial isolates were determined from ligase chain reaction-positive eye swab samples collected from 10 villages. The diversity of genovars was determined for each village, using Simpson's index. RESULTS: Two genovar families (Ba and C) and nine genovars were detected, with a single genovar (C1) comprising more than one-half of the samples. The prevalence of clinically active trachoma was significantly associated with the genetic diversity in a village, controlling for village size and number of samples taken in a village. CONCLUSION: Genetic diversity of C. trachomatis is associated with the prevalence of infection in a community, consistent with the hypothesis that diversity may be necessary to attain a high prevalence in a community.
Subject(s)
Chlamydia trachomatis/genetics , Genes, Bacterial , Genetic Variation , Trachoma/microbiology , Base Sequence , Child , Child, Preschool , Chlamydia trachomatis/isolation & purification , Female , Genotype , Humans , Infant , Linear Models , Male , Nepal/epidemiology , Polymerase Chain Reaction , Prevalence , Trachoma/epidemiologyABSTRACT
Distinct morphological changes associated with the complex development cycle of the obligate intracellular bacterial pathogen Chlamydia trachomatis have been historically well characterized by microscopy. A number of temporally regulated genes have been characterized previously, suggesting that the chlamydial developmental cycle is regulated at the transcriptional level. This hypothesis was tested by microarray analysis in which the entire C. trachomatis genome was analyzed, providing a comprehensive assessment of global gene regulation throughout the chlamydial developmental cycle. Seven temporally cohesive gene clusters were identified, with 22% (189 genes) of the genome differentially expressed during the developmental cycle. The correlation of these gene clusters with hallmark morphological events of the chlamydial developmental cycle suggests three global stage-specific networks of gene regulation.
Subject(s)
Chlamydia trachomatis/growth & development , Chlamydia trachomatis/genetics , Gene Expression Regulation, Bacterial , Multigene Family , Oligonucleotide Array Sequence Analysis , Reproducibility of Results , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
The lytic outcome of natural infection by Chlamydia trachomatis was exploited to select CHO (Chinese hamster ovary) cells, following chemical mutagenesis, that were deficient in their ability to sustain productive chlamydial infection. Four distinct mutant cell phenotypes with defects in either attachment or postattachment mechanisms that are required for infection by C. trachomatis and Chlamydia pneumoniae were characterized.
