Laura E. Welsh

In vitro evaluation of activities of azithromycin, erythromycin, and tetracycline against Chlamydia trachomatis and Chlamydia pneumoniae.

The in vitro activities of azithromycin (CP-62,993; Pfizer), erythromycin, and tetracycline were evaluated by inhibiting Chlamydia trachomatis and Chlamydia pneumoniae, formerly TWAR, propagation in vitro in McCoy cells, HeLa cells, and HL cells. Eleven clinical isolates of C. trachomatis (serovars D, E, F, J, K, and L2) and four strains of C. pneumoniae were tested with an inoculum of 10(3) inclusion-forming units in a 96-well microtiter plate. The MIC ranges of these antimicrobial agents against C. trachomatis were as follows: azithromycin, 0.125 to 0.5 microgram/ml; erythromycin, 0.25 to 0.1 microgram/ml; and tetracycline, 0.0625 to 1.0 microgram/ml. The MBC ranges, calculated from passage into antibiotic-free medium, were as follows: azithromycin, 0.125 to 4.0 micrograms/ml; erythromycin, 0.5 to 8.0 micrograms/ml; and tetracycline, 0.0625 to 4.0 micrograms/ml. The MIC ranges for C. pneumoniae in both HeLa and HL cells were as follows: azithromycin, 0.125 to 1.0 micrograms/ml; erythromycin, 0.0625 to 1.0 microgram/ml; and tetracycline, 0.125 to 1.0 microgram/ml. The MBC ranges were as follows: azithromycin, 0.25 to 1.0 microgram/ml; erythromycin, 0.25 to 1.0 microgram/ml; and tetracycline, 0.125 to 4.0 micrograms/ml. From the results of this in vitro study, azithromycin appears to be an effective antibiotic comparable to tetracycline and erythromycin for use in the treatment of both C. trachomatis and C. pneumoniae infections.

Macrophage Migration Inhibitory Factor Governs Endothelial Cell Sensitivity to LPS-Induced Apoptosis

Human endothelial cells (EC) are typically resistant to the apoptotic effects of stimuli associated with lung disease. The determinants of this resistance remain incompletely understood. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by human pulmonary artery EC (HPAEC). Its expression increases in response to various death-inducing stimuli, including lipopolysaccharide (LPS). We show here that silencing MIF expression by RNA interference (MIF siRNA) dramatically reduces MIF mRNA expression and the LPS-induced increase in MIF protein levels, thereby sensitizing HPAECs to LPS-induced cell death. Addition of recombinant human MIF (rhMIF) protein prevents the death-sensitizing effect of MIF siRNA. A common mediator of apoptosis resistance in ECs is the death effector domain (DED)-containing protein, FLIP (FLICE-like inhibitory protein). We show that LPS induces a transcription-independent increase in the short isoform of FLIP (FLIP(s)). This increase is blocked by MIF siRNA but restored with the addition of recombinant MIF protein (rHMIF). While FLIP(s) siRNA also sensitizes HPAECs to LPS-induced death, the addition of rhMIF does not affect this sensitization, placing MIF upstream of FLIP(s) in preventing HPAEC death. These studies demonstrate that MIF is an endogenous pro-survival factor in HPAECs and identify a novel mechanism for its role in apoptosis resistance through the regulation of FLIP(s). These results show that MIF can protect vascular endothelial cells from inflammation-associated cell damage.

Urine as a diagnostic specimen for the detection of Chlamydia trachomatis in Malaysia by ligase chain reaction

Background and Objectives: Noninvasive urine screening for Chlamydia trachomatis infections offers a valuable public health tool, which could be of vast importance in chlamydial control programs. The authors evaluated a new DNA amplification method, ligase chain reaction (LCR). Goals: The goal was to ascertain whether urine testing could be used as screening method to detect C. trachomatis infections in commercial sex workers, patients at sexually transmitted diseases clinic, and asymptomatic patients in Kuala Lumpur, Malaysia. Methods: First‐void urine specimens from 300 men and 300 women were tested by LCR, as well as by a commercially available enzyme immunoassay. The LCR assay amplifies specific sequences within the chlamydial plasmid with ligand‐labeled probes, and the resultant amplicons are detected by an automated immunoassay. Specimens with discrepant results were confirmed by another LCR of the specimen that targeted the gene for the major outer membrane protein (OMP1). Results: There were 31 LCR‐positive male urine and 37 LCR‐positive female urine specimens. The resolved sensitivity and specificity for the LCR of the male urine specimens were 100% and 99.6%, respectively, whereas for female urine specimens, the sensitivity and specificity were 100% and 98.5%, respectively. After resolution of discrepant test results by OMP1 LCR, the prevalence was 10% for men and 11% for women. The urine enzyme immunoassay was not useful in diagnosing C. trachomatis infections in either men or women, as the resolved sensitivities were 10% and 15.2%, respectively. The specificities were 99.6% for men and 98.9% for women. Conclusions: Testing first‐void urine specimens by LCR is a highly sensitive and specific method to diagnose C. trachomatis infections in men and women, providing health care workers and public health officials with a new molecular amplification assay that uses noninvasive urine specimens for population‐based screening purposes.