Antigenic Variation Explains the Natural History of Syphilis Infection
Syphilis occurs in several clinical stages and is increasing in incidence in parts of the world. The natural history of syphilis and the ability of Treponema pallidum to survive for decades in immunocompetent hosts have long puzzled scientists. New evidence reported by Reid et al. (p. 4959–4967) supports the role of antigenic variation of an outer membrane protein, TprK, in T. pallidum's ability to survive immune clearance during the primary stage to seed the lesions of secondary syphilis. This implicates TprK as a key antigen whose variability enables T. pallidum to cause this chronic multistage infection.
Novel Rodent Urinary Catheter Model Provides a Tool for Dissection of Fungal Biofilm Pathogenesis
Over 1 million patients yearly in the United States suffer catheter-associated urinary tract infections. Few models exist to examine the pathogenesis of device-associated biofilms in this unique environment. Nett et al. (p. 4931–4940) developed a rat indwelling urinary catheter biofilm model for Candida albicans, the most common fungal pathogen. This experimental model closely mimics the clinical scenario with regard to anatomic location, device material, and flow characteristics. The authors examine biofilm architecture, quantitative burden, biofilm gene expression, drug treatment, and host response. This model should be useful for future investigations of Candida biofilms in the urinary tract.
Mycoplasma gallisepticum Hydrogen Peroxide-Induced Cytotoxicity and Virulence: Lack of Correlation in the Natural Host
Hydrogen peroxide produced by mycoplasmas is reported to induce cytotoxicity of cells in vitro in the presence of glycerol and is considered to be a virulence factor. However, the correlative effect on virulence during infection has not been demonstrated. Szczepanek et al. (p. 4915–4920) report that hydrogen peroxide produced by Mycoplasma gallisepticum results in cytotoxicity of cells in vitro. However, when M. gallisepticum glycerol metabolism mutants were inoculated into the tracheas of chickens, their virulence was not attenuated. Hence, there appears to be no correlation between in vitro cytotoxicity and virulence during infection with regard to hydrogen peroxide production of this pathogen.
Emergence of Superinfecting Pathogen Strains with Distinct Genomic Backgrounds
Shifts in pathogen strain structure, characterized by emergence of unique strains and loss of others, result in changing patterns of disease. Immunity within a host population against a predominant strain provides strong selection for a genotypically and antigenically distinct strain to emerge within the host population (strain superinfection). Studying naturally occurring infections in populations with differing levels of infection prevalence and immunity, Vallejo Esquerra et al. (p. 5286–5292) show that the superinfecting strains have unique genomic backgrounds, indicating that the source of the emergent strain is exogenous rather than being derived endogenously from the predominant strain by allelic recombination and mutation.
Lactate Dehydrogenase Has a Central Role in Pneumococcal Pyruvate Metabolism and Survival in Blood
Streptococcus pneumoniae causes important human diseases such as pneumonia, bacteremia, otitis media, and meningitis. How pneumococcus maintains its survival in different tissues during infection is unknown. To address this fundamental question, Gaspar et al. (p. 5099–5109) determined the role of lactate dehydrogenase (LDH), an essential enzyme for redox balance that converts pyruvate to lactate, in pneumococcal central metabolism and virulence. Loss of LDH leads to a dramatic reduction in the growth rate and the virulence of the microbe.
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- Antigenic Variation Explains the Natural History of Syphilis Infection
- Novel Rodent Urinary Catheter Model Provides a Tool for Dissection of Fungal Biofilm Pathogenesis
- Mycoplasma gallisepticum Hydrogen Peroxide-Induced Cytotoxicity and Virulence: Lack of Correlation in the Natural Host
- Emergence of Superinfecting Pathogen Strains with Distinct Genomic Backgrounds
- Lactate Dehydrogenase Has a Central Role in Pneumococcal Pyruvate Metabolism and Survival in Blood
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