Tuberculosis contact investigation in a rural state.

The investigation of contacts of tuberculosis (TB) cases is an essential part of Mississippi's comprehensive TB program. A case interview is initiated within 24 hours, and the concentric circle method is used to identify and evaluate contacts. High-risk contacts of pulmonary cases are located and evaluated within 10 days. A follow-up evaluation is conducted by a TB consultant to determine the need for additional tests. All pulmonary contacts receive a 12-week follow-up tuberculin skin test (TST) if the initial test is negative. Directly observed treatment for latent TB infection (LTBI) is offered to all children aged <15 years, human immunodeficiency virus positive persons and others deemed at high risk for developing active disease. Mississippi contact investigations in 1990-1998 identified 212 (0.7%) cases of TB, and 5608 (17.5%) contacts with LTBI. In that period, the proportion of cases with contacts identified averaged 99%, with a mean number of contacts per case of 15.4. At the same time, 95% of contacts completed an evaluation for active TB and LTBI. Among contacts <15 years of age, >96% have completed LTBI treatment annually since 1992. Cases and case rates in Mississippi have decreased annually during this period. Effective TB contact investigation yields immediate results by identifying other sources of TB transmission and preventing future transmission through appropriate treatment of contacts with LTBI.

Localization of the K(+)-Cl(-) cotransporter, KCC3, in the central and peripheral nervous systems: expression in the choroid plexus, large neurons and white matter tracts.

Na(+)-independent K(+)-Cl(-) cotransporters function in the regulation of cell volume, control of CNS excitability and epithelial ion transport. Several K(+)-Cl(-) cotransporter isoforms are expressed in the nervous system, and KCC3 in particular is expressed at significant levels in both the brain and spinal cord. The cellular localization of this transporter has, however, not been determined. In this study, we generated a polyclonal antibody against the KCC3 cotransporter in order to characterize and localize this protein in the brain. Western blot analysis of mouse kidney and brain demonstrated KCC3 proteins of different size, 150 and 170kDa, respectively; this disparity remained after deglycosylation. Northern blot confirmed the presence of two distinct forms of KCC3, KCC3a and KCC3b, generated by the inclusion of different first coding exons. KCC3a predominates in the brain, whereas KCC3b is more abundant in the kidney. Western blots with membrane protein from dissected mouse brain revealed abundant expression in all brain regions examined: the cerebral cortex, hippocampus, diencephalon, brainstem and cerebellum. The spinal cord showed the highest levels of KCC3 expression, whereas peripheral nerves did not contain immunoreactive KCC3 protein. Western blot analysis of whole brain from rats of various ages indicated increasing expression in the postnatal period, concurrent with CNS maturation and myelination. Immunofluorescence studies demonstrated strong signal in myelinated tracts of the spinal cord, consistent with individual myelin sheaths. Brain sections also showed white matter enhancement, but also cellular signal consistent with pyramidal neurons and Purkinje cells. The base of the choroid plexus epithelium was also strongly labeled. These data demonstrate the specificity and diversity of KCC3 expression in the mouse CNS.

Cadmium-regulated gene fusions in Pseudomonas fluorescens.

To study the mechanisms soil bacteria use to cope with elevated concentrations of heavy metals in the environment, a mutagenesis with the lacZ-based reporter gene transposon Tn5B20 was performed. Random gene fusions in the genome of the common soil bacterium Pseudomonas fluorescens strain ATCC 13525 were used to create a bank of 5,000 P. fluorescens mutants. This mutant bank was screened for differential gene expression in the presence of the toxic metal cadmium. Fourteen mutants were identified that responded with increased or reduced gene expression to the presence of cadmium. The mutants were characterized with respect to their metal-dependent gene expression and their metal tolerance. Half the identified mutants reacted with differential gene expression specifically to the metal cadmium, whereas some of the other mutants also responded to elevated concentrations of copper and zinc ions. One of the mutants, strain C8, also showed increased gene expression in the presence of the solvent ethanol, but otherwise no overlap between cadmium-induced gene expression and general stress response was detected. Molecular analysis of the corresponding genetic loci was performed using arbitrary polymerase chain reaction (PCR), DNA sequencing and comparison of the deduced protein products with sequences deposited in genetic databases. Some of the genetic loci targeted by the transposon did not show any similarities to any known genes; thus, they may represent 'novel' loci. The hypothesis that genes that are differentially expressed in the presence of heavy metals play a role in metal tolerance was verified for one of the mutants. This mutant, strain C11, was hypersensitive to cadmium and zinc ions. In mutant C11, the transposon had inserted into a genetic region displaying similarity to genes encoding the sensor/regulator protein pairs of two-component systems that regulate gene expression in metal-resistant bacteria, including czcRS of Ralstonia eutropha, czrRS of Pseudomonas aeruginosa and copRS of Pseudomonas syringae. Although the P. fluorescens strain used in this study had not been isolated from a metal-rich environment, it nevertheless contained at least one genetic region enabling it to cope with elevated concentrations of heavy metals.