Evaluation of the cytocentrifuge Gram stain as a screening test for bacteriuria in specimens from specific patient populations.

To assess the usefulness of the cytocentrifuge Gram stain as a urine screening test in the clinical microbiology laboratory for the elimination of culture for screen-negative specimens, we compared the results of the cytocentrifuge Gram stain to the results of culture for 1,171 urine specimens. The data were analyzed separately for specimens from males (inpatients) and females (inpatients and outpatients), as well as for catheterized and voided specimens. Overall, the cytocentrifuge Gram stain had excellent negative predictive value (97.7%) and sensitivity (92.3%) at a culture threshold of 10(5) colony-forming units per milliliter or more. The negative predictive value and sensitivity decreased at lower culture thresholds in all populations. The negative predictive value decreased most markedly for female outpatients. Because of low positive predictive value and specificity, this test is not reliable as a sole indicator for presumptive therapy in many cases with positive results. If its limitations are recognized, the cytocentrifuge Gram stain is a useful screening test for the rapid exclusion of bacteriuria.

Molecular and biochemical comparison of the 70-kDa heat shock proteins of Trypanosoma cruzi.

An analysis of the genetic organization, regulated expression and biochemical properties of the cytoplasmic/nuclear (hsp70) and mitochondrial (mtp70) 70-kDa heat shock proteins of Trypanosoma cruzi is presented. The two proteins are encoded by tandemly arranged gene families that are located on different chromosomes. Both are mildly heat-inducible but have different optimal temperatures for expression. During the switch from proliferation to differentiation that occurs during the growth of T. cruzi in culture, the hsp70 level decreases dramatically while the mtp70 level falls only slightly. The subcellular locations of the two proteins differ during heat shock. While mtp70 remains associated with the kinetoplast at all temperatures, hsp70 becomes more concentrated in the nucleus at higher temperatures. Biochemical analysis of hsp70 and mtp70 revealed both to be potent ATPases. Each protein binds ATP with a Km of about 70 microM and hydrolyzes ATP with a kcat of about 100 min-1, 100 times greater than the kcat of human hsp70. The high ATPase activities of hsp70 and mtp70 are further stimulated by incubation with peptides, suggesting that these trypanosome heat shock proteins have protein chaperone activity. Finally, mtp70, but not hsp70, was found to possess autophosphorylation activity in vitro, a property that it shares with prokaryotic hsp70. These findings demonstrate unique cellular and biochemical characteristics of T. cruzi mtp70 and hsp70 that suggest that they play distinct physiologic roles in the biology of the cell.