Molecular diagnosis of Neisseria gonorrhoeae infection in the United States.

BACKGROUND: Gonorrhea, with its Neisseria gonorrhoeae etiology, is the second most common bacterial sexually transmitted infection in the United States and is most often transmitted through asymptomatic individuals. N. gonorrhoeae is a fastidious organism and can be susceptible to killing during transport to the laboratory; hence, diagnostic methods that do not require organism viability are becoming more commonplace in the clinical setting. OBJECTIVE: This review summarizes traditional and molecular-based diagnostic modalities specific to N. gonorrhoeae. Several commercially available, FDA-approved molecular methods to diagnose N. gonorrhoeae infection include nucleic acid hybridization, signal amplification, polymerase chain reaction, strand displacement amplification and transcription-mediated amplification. RESULTS/CONCLUSION: Molecular-based methods are rapid, reliable and effective genital specimen screening measures, especially when applied to areas of high disease prevalence. However, clinical and analytical sensitivity for some commercial systems decreases dramatically when testing urine samples. Moreover, crossreactivity to non-pathogenic Neisseria species has been documented for selected methods. Therapeutic decisions may increasingly become compromised owing to a lack of cultured N. gonorrhoeae for antimicrobial susceptibility testing. In vitro experiments suggest that transcription-mediated amplification has greater analytical sensitivity than the other molecular-based methods now available. The development of future molecular testing could address conundrums associated with confirmatory testing, medicolegal testing, testing for cure and detection of antimicrobial-resistant strains.

Low concentrations of nitric oxide exert a hormetic effect on Mycobacterium tuberculosis in vitro.

Susceptibilities of 12 clinical Mycobacterium tuberculosis isolates to acidified sodium nitrite (ASN) were compared. The results demonstrate that 8 of the 12 isolates exhibited enhanced survival levels in 1.5 mM ASN compared to levels in medium alone, suggesting that low concentrations of reactive nitrogen intermediates have a hormetic effect on M. tuberculosis in vitro.

Molecular diagnostic techniques for use in response to bioterrorism.

The use of micro-organisms as agents of biological warfare is considered inevitable for several reasons, including ease of production and dispersion, delayed onset of symptoms, ability to cause high rates of morbidity and mortality and difficulty in diagnosis. Therefore, the clinical presentation and pathogenesis of the organisms posing the highest threat (variola major, Bacillus anthracis, Yersinia pestis, Clostridium botulinum toxin, Francisella tularensis, filoviruses, arenaviruses and Brucella species), as well as the available diagnostic techniques and treatments for such infections, will be reviewed in this article. Due to the necessity of rapid identification and diagnosis, molecular techniques have been the ongoing focus of current research. Consequently, the molecular diagnostic techniques that have recently been developed for the diseases associated with these agents will be emphasized.

Reactive nitrogen intermediates have a bacteriostatic effect on Mycobacterium tuberculosis in vitro.

Susceptibility of six isolates of Mycobacterium tuberculosis (CB3.3, CDC1551, RJ2E, C.C.13, H37Rv, and H37Ra) and two isolates of Mycobacterium bovis (Ravenel and BCG) to reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) was determined by standard in vitro survival assays. After 21 days of incubation, the survival of most strains exposed to either acidified sodium nitrite (ASN) or hydrogen peroxide (H(2)O(2)) was significantly lower than the same strains unexposed to these RNI or ROI products. However, after 50 days of incubation, these differences in susceptibility became less apparent for strains exposed to ASN but not for strains exposed to H(2)O(2). The recovery of these strains after exposure to RNI suggests that the effect of RNI on M. tuberculosis is bacteriostatic. The in vitro concentrations of ROI and RNI used in these assays were higher than those expected in vivo. These observations suggest that, in vivo, RNI expression at physiologically achievable concentrations may keep M. tuberculosis from proliferating but that removal of RNI may allow the organisms to proliferate. Furthermore, the ability of some M. tuberculosis strains to cause rapidly progressive disease may relate to their intrinsic levels of RNI and ROI resistance.

Mycobacterium tuberculosis CDC1551 is resistant to reactive nitrogen and oxygen intermediates in vitro.

Resistance to reactive oxygen intermediates and reactive nitrogen intermediates in vitro of a clinical isolate of Mycobacterium tuberculosis (CDC1551) that caused a large outbreak of tuberculosis was compared to that of M. tuberculosis strains CB3.3, H37Rv, H37Ra, Erdman, RJ2E, C.C. 13, and C.C. 22 as well as M. bovis strains Ravenel and BCG. CDC1551 and CB3.3 were significantly more resistant to both hydrogen peroxide (H(2)O(2)) and acidified sodium nitrite than were the other strains tested. This biological phenotype may serve as an in vitro marker for clinical strains of M. tuberculosis likely to cause a large outbreak of tuberculosis.