No abstract

The presence of KatG(S315T), a mutation frequently detected in clinical isolates of Mycobacterium tuberculosis, has been associated with loss of catalase-peroxidase activity and resistance to isoniazid therapy. Wild-type KatG and KatG(S315T) were expressed in a heterologous host (Escherichia coli) and purified to homogeneity, and enzymatic activity was measured. The catalase activity for KatG(S315T) was reduced 6-fold, and its peroxidase activity was decreased <2-fold, compared with the activities for wild-type KatG. Pyridine hemochrome analysis demonstrated 1.1 +/- 0.1 hemes/subunit for wild-type KatG and 0.9 +/- 0.1 hemes/subunit for KatG(S315T), indicating that the difference in enzymatic activity is not the result of incomplete heme cofactor incorporation in KatG(S315T). High-performance liquid chromatography analysis showed that wild-type KatG was more efficient than KatG(S315T) at converting isoniazid to isonicotinic acid. These results demonstrate that KatG(S315T), as expressed in E. coli, is a competent catalase-peroxidase that exhibits a reduced ability to metabolize isoniazid.

The speed with which the LC-PCR procedure can be performed offers significant advantages over both culture-based methods and conventional PCR techniques. In contrast, for the methods evaluated, culture was the best for detecting multiple Legionella species in lung tissue. WS staining, Legionella genus LC-PCR, and L. pneumophila species-specific ISH were useful as rapid tests with lung tissue.

During surveillance for various tickborne pathogens in the upper Midwest during the summer and early fall of 1995, a Bartonella-like agent was detected in the blood of mice that were concurrently infected with Borrelia burgdorferi or Babesia microti (or both). The organism was isolated in pure culture after inoculation of blood from wild-caught mice into C.B-17 scid/scid mice. Phylogenetic analysis of the 16S rRNA and the citrate synthase genes showed that the novel Bartonella species and a Bartonella isolate from a mouse captured on Martha's Vineyard, Massachusetts, were closely related to each other and secondarily related to Bartonella grahamii and Bartonella vinsonii. [11] has been reported granulocytic ehrlichiosis (HGE), has also been described [1, 2]. All three pathogens are transmitted by the deer tick; acquisiand could account for the occurrence of some coinfected vector ticks. However, coinfection of mice with B. burgdorferi and tion of infection in ticks probably occurs via feeding of immature stages of the tick on the white-footed mouse (Peromyscus Ehrlichia species has not been described. The original intention of this study was to describe the prevaleucopus), which appears to be an important reservoir of infection with all of these agents. Consistent with their overlapping lence of infection with B. burgdorferi, B. microti, and Ehrlichia species in P. leucopus mice, wild-caught in Minnesota and transmission cycles, coinfection with these agents in some human cases has been described, with possible effect on disease Wisconsin. Unexpectedly, instead of detecting Ehrlichia species in the blood of P. leucopus, we detected a novel Bartonella duration and severity [3]. Indeed, coinfection with other tickborne pathogens may be a confounding variable in investigaspecies. Herein we describe the outcome of these surveillance studies and the isolation and initial characterization of the ortions of the biologic variation of Lyme disease [4]. Animal experiments were conducted using a protocol approved by the Mayo delein, IL), identified to species, weighed, sexed, and examined for and 1000 mg of fosfomycin/mL as previously described [14]. The were placed in 10 mM HCl and were dipped in 95% ethanol and