Modeling in vivo pharmacokinetics and pharmacodynamics of moxifloxacin therapy for Mycobacterium tuberculosis infection by using a novel cartridge system.

To study the efficacy of moxifloxacin treatment for tuberculosis, we utilized a novel cartridge system to simulate in vivo pharmacokinetics. We found this system to be a robust method for modeling in vivo pharmacokinetics and present data supporting the utility of intermittent moxifloxacin treatment as a component of antituberculosis chemotherapy.

The Mycobacterium tuberculosis SigD sigma factor controls the expression of ribosome-associated gene products in stationary phase and is required for full virulence.

During infection Mycobacterium tuberculosis is exposed to several environmental conditions depending on the stage and severity of the disease. To survive, M. tuberculosis uses alternate sigma factors to regulate its gene expression in response to the changing host environment.

Evidence that the Streptomyces developmental protein WhiD, a member of the WhiB family, binds a [4Fe-4S] cluster.

WhiD is required for the late stages of sporulation in the Gram-positive bacterium Streptomyces coelicolor. WhiD is a member of the WhiB-like family of putative transcription factors that are present throughout the actinomycetes but absent from other organisms. This family of proteins has four near-invariant cysteines, suggesting that these residues might act as ligands for a metal cofactor.

Dormancy phenotype displayed by extracellular Mycobacterium tuberculosis within artificial granulomas in mice.

Mycobacterium tuberculosis residing within pulmonary granulomas and cavities represents an important reservoir of persistent organisms during human latent tuberculosis infection. We present a novel in vivo model of tuberculosis involving the encapsulation of bacilli in semidiffusible hollow fibers that are implanted subcutaneously into mice. Granulomatous lesions develop around these hollow fibers, and in this microenvironment, the organisms demonstrate an altered physiologic state characterized by stationary-state colony-forming unit counts and decreased metabolic activity.

Moxifloxacin-containing regimens of reduced duration produce a stable cure in murine tuberculosis.

In a recent experimental study using the mouse model of tuberculosis, treatment with a combination of rifampin, moxifloxacin, and pyrazinamide was able to shorten the time to negative lung cultures by up to 2 months compared with the standard regimen of rifampin, isoniazid, and pyrazinamide. To confirm that this substitution of moxifloxacin for isoniazid permits a shorter duration of treatment, a second study was performed in which mice were assessed for relapse after treatment with combination therapy for 3, 4, 5, or 6 months. Although no relapse was observed among mice treated for at least 4 months with rifampin, moxifloxacin, and pyrazinamide, mice treated with rifampin, isoniazid, and pyrazinamide required 6 months of treatment before no relapse could be detected.

A review of clinical failures associated with macrolide-resistant Streptococcus pneumoniae.

The emerging reports of clinical failures using macrolides and their associations with macrolide-resistant Streptococcus pneumoniae prompted us to review the literature describing these cases. Thirty-three cases reporting macrolide treatment failure during treatment of pneumococcal infections were available for review. The most prevalent diagnosis (24/27 or 88.

Antibiotic resistance in Streptococcus pneumoniae: what does the future hold?

The recent emergence of strains of drug-resistant Streptococcus pneumoniae (DRSP) is a serious clinical and public health problem. Several interventions have been proposed to limit the further emergence and spread of DRSP, including campaigns for appropriate antibiotic use and the introduction of pneumococcal conjugate vaccines. Whether the current epidemic of drug resistance in S.

Mycobacterium tuberculosis ECF sigma factor sigC is required for lethality in mice and for the conditional expression of a defined gene set.

Bacterial alternative RNA polymerase sigma factors are key global adaptive response regulators with a likely role in Mycobacterium tuberculosis pathogenesis. We constructed a mutant lacking the sigma factor gene, sigC, by allelic exchange, in the virulent CDC1551 strain of M. tuberculosis and compared the resulting mutant with the isogenic wild-type strain and complemented mutant strain.

Short report: modulation of Mycobacterium tuberculosis infection by Plasmodium in the murine model.

A large proportion of people with latent tuberculosis live in malaria-endemic areas, so co-infection with these two organisms is likely to be common. To determine whether there might be a biologic interaction between these two pathogens in vivo, we infected mice with Mycobacterium tuberculosis and then with a non-lethal strain of Plasmodium yoelii eight weeks later. Mice chronically infected with M.

Risk factors for relapse and acquired rifamycin resistance after directly observed tuberculosis treatment: a comparison by HIV serostatus and rifamycin use.

We sought to determine the risk of acquired rifamycin resistant (ARR) tuberculosis associated with rifampin- versus rifabutin-based directly observed therapy and to assess the risk factors for relapse of tuberculosis. This observational cohort study included patients with culture-confirmed rifamycin-susceptible tuberculosis reported to the Baltimore City Health Department (Baltimore, MD) during the period of January 1993 through December 2001. Of the 407 patients, 108 (27%) were human immunodeficiency virus (HIV) seropositive, 161 (40%) were HIV seronegative, and 138 (34%) had an unknown serostatus.

Attenuation of late-stage disease in mice infected by the Mycobacterium tuberculosis mutant lacking the SigF alternate sigma factor and identification of SigF-dependent genes by microarray analysis.

The Mycobacterium tuberculosis alternate sigma factor, SigF, is expressed during stationary growth phase and under stress conditions in vitro. To better understand the function of SigF we studied the phenotype of the M. tuberculosis DeltasigF mutant in vivo during mouse infection, tested the mutant as a vaccine in rabbits, and evaluated the mutant's microarray expression profile in comparison with the wild type.

Susceptibility to tuberculosis: clues from studies with inbred and outbred New Zealand White rabbits.

The rabbit model of tuberculosis (TB) is important because rabbits develop a disease that is similar to TB in humans, namely, granulomas with caseous necrosis, liquefaction, and cavities. We describe here a comparison of inbred and outbred New Zealand White rabbits infected by aerosol with either Mycobacterium tuberculosis Erdman or H37Rv strain. Five weeks after infection with either bacillary strain, the inbred rabbits had significantly larger pulmonary tubercles than did outbred rabbits (2.

Method to integrate multiple plasmids into the mycobacterial chromosome.

In order to create a system in which two independent plasmids can be integrated into a mycobacterial chromosome, a mycobacterial plasmid was constructed containing the phage attachment site attP from the mycobacteriophage L5 genome and additionally containing the bacterial attachment site, attB. This plasmid will integrate into the mycobacterial chromosome via recombination of the plasmid-borne attP site with the chromosomal attB site in the presence of a mycobacterial vector carrying the L5 integrase (int) gene. The integrated plasmid has a plasmid-borne attB site that is preserved and will accept the integration of additional mycobacterial plasmids containing the L5 attP site.

The clinical significance of macrolide-resistant Streptococcus pneumoniae: it's all relative.

Macrolides are currently recommended as first-line agents for the empirical treatment of community-acquired pneumonia. Heavy use of these agents for a variety of indications has resulted in an increasing incidence of macrolide resistance among pneumococcal isolates. Although several case reports and small case series have suggested that in vitro macrolide resistance is associated with treatment failure in cases of pneumococcal pneumonia, other observational data suggest that drug susceptibility testing may not correlate with treatment failure.

Deletion of Mycobacterium tuberculosis sigma factor E results in delayed time to death with bacterial persistence in the lungs of aerosol-infected mice.

The stress-induced extracytoplasmic sigma factor E (SigE) of Mycobacterium tuberculosis shows increased expression after heat shock, sodium dodecyl sulfate treatment, and oxidative stress, as well as after phagocytosis in macrophages. We report that deletion of sigE results in delayed lethality in mice without a significant reduction of bacterial numbers in lungs.

Fluoroquinolone resistance in patients with newly diagnosed tuberculosis.

Fluoroquinolones are widely used for the treatment of bacterial infections and are also second-line therapy for tuberculosis. However, fluoroquinolone resistance in patients with newly diagnosed cases of tuberculosis is not routinely assessed. We performed in vitro susceptibility testing of Mycobacterium tuberculosis to fluoroquinolones for all culture-confirmed tuberculosis cases in adults that were diagnosed at Johns Hopkins Hospital (Baltimore) between January 1998 and March 2002.

Moxifloxacin-containing regimen greatly reduces time to culture conversion in murine tuberculosis.

Tuberculosis continues to be a major cause of morbidity and mortality in the world. The expansion of tuberculosis control programs has been limited by the lengthy and cumbersome nature of current chemotherapeutic regimens. A new drug that improves the sterilizing activity of current regimens would reduce the duration of therapy without sacrificing efficacy, thereby enhancing treatment completion rates and preserving precious public health resources.

Different strains of Mycobacterium tuberculosis cause various spectrums of disease in the rabbit model of tuberculosis.

The rabbit model of tuberculosis has been used historically to differentiate between Mycobacterium tuberculosis and Mycobacterium bovis based on their relative virulence in this animal host. M. tuberculosis infection in market rabbits is cleared over time, whereas infection with M.

Fluoroquinolones, tuberculosis, and resistance.

Although the fluoroquinolones are presently used to treat tuberculosis primarily in cases involving resistance or intolerance to first-line antituberculosis therapy, these drugs are potential first-line agents and are under study for this indication. However, there is concern about the development of fluoroquinolone resistance in Mycobacterium tuberculosis, particularly when administered as monotherapy or as the only active agent in a failing multidrug regimen. Treatment failures as well as relapses have been documented under such conditions.

A postgenomic method for predicting essential genes at subsaturation levels of mutagenesis: application to Mycobacterium tuberculosis.

We describe a postgenomic in silico approach for identifying genes that are likely to be essential and estimate their proportion in haploid genomes. With the knowledge of all sites eligible for mutagenesis and an experimentally determined partial list of nonessential genes from genome mutagenesis, a Bayesian statistical method provides reasonable predictions of essential genes with a subsaturation level of random mutagenesis. For mutagenesis, a transposon such as Himar1 is suitable as it inserts randomly into TA sites.

Characterization of the role of the divalent metal ion-dependent transcriptional repressor MntR in the virulence of Staphylococcus aureus.

DtxR-type metal ion-dependent repressors, present in many bacterial pathogens, may regulate expression of virulence genes such as that encoding diphtheria toxin. SirR, a DtxR homologue initially identified in Staphylococcus epidermidis, governs the expression of the adjacent sitABC operon encoding a putative metal ion ABC transporter system. We identified a sirR homologue, mntR, in Staphylococcus aureus and demonstrated by gel shift assay that the corynebacterial repressor DtxR binds to the S.