Publications

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has recently emerged worldwide. The United States, in particular, is experiencing a serious epidemic of CA-MRSA that is almost entirely caused by an extraordinarily infectious strain named USA300. However, the molecular determinants underlying the pathogenic success of CA-MRSA are mostly unknown. To gain insight into the evolution of the exceptional potential of USA300 to cause disease, we compared the phylogeny and virulence of USA300 with that of closely related MRSA clones. We discovered that the sublineage from which USA300 evolved is characterized by a phenotype of high virulence that is clearly distinct from other MRSA strains. Namely, USA300 and its progenitor, USA500, had high virulence in animal infection models and the capacity to evade innate host defense mechanisms. Furthermore, our results indicate that increased virulence in the USA300/USA500 sublineage is attributable to differential expression of core genome-encoded virulence determinants, such as phenol-soluble modulins and alpha-toxin. Notably, the fact that the virulence phenotype of USA300 was already established in its progenitor indicates that acquisition of mobile genetic elements has played a limited role in the evolution of USA300 virulence and points to a possibly different role of those elements. Thus, our results highlight the importance of differential gene expression in the evolution of USA300 virulence. This finding calls for a profound revision of our notion about CA-MRSA pathogenesis at the molecular level and has important implications for design of therapeutics directed against CA-MRSA.

BACKGROUND

Nucleic acid amplification tests are sensitive and specific for identifying Mycobacterium tuberculosis in sputum smear-positive populations, but they are less sensitive in sputum smear-negative populations. Few studies have assessed their performance among patients infected with HIV, and no studies have assessed their performance with oral wash specimens, which may be easier to obtain than sputum samples.

METHODS

We performed a prospective study involving 127 adults from 2 populations who were undergoing evaluation for respiratory complaints at Mulago Hospital in Kampala, Uganda. We obtained and tested sputum samples for Mycobacterium tuberculosis, and we simultaneously obtained oral wash specimens to test for M. tuberculosis DNA by polymerase chain reaction (PCR) amplification of a novel locus, the secA1 gene. A positive mycobacterial culture of sputum was used to define cases of tuberculosis; we calculated the sensitivity and specificity of the PCR assay with sputum or oral wash specimens in reference to the standard of sputum culture results.

RESULTS

Tuberculosis (75 [59%] of 127 patients) and HIV infection (58 [46%] of 126 patients) were both common in the study population. PCR of sputum samples was highly sensitive (sensitivity, 99%; 95% confidence interval, 93%-100%) and specific (specificity, 88%; 95% confidence interval, 77%-96%) for detection of pulmonary tuberculosis and performed well among HIV-infected patients and among patients with negative sputum smear results. PCR of oral wash specimens was less sensitive (sensitivity, 73%; 95% confidence interval, 62%-83%) but also detected a substantial proportion of tuberculosis cases.

CONCLUSIONS

PCR targeting the secA1 gene was highly sensitive and specific for identifying M. tuberculosis in sputum samples, independent of smear or HIV infection status. Oral washes showed promise as an easily obtained respiratory specimen for tuberculosis diagnosis. PCR of sputum for detection of the secA1 gene could be a rapid, effective diagnostic tool for tuberculosis referral centers.

OBJECTIVE

To systematically develop a quality indicator (QI) set for systemic lupus erythematosus (SLE).

METHODS

We used a validated process that combined available scientific evidence and expert consensus to develop a QI set for SLE. We extracted 20 candidate indicators from a systematic literature review of clinical practice guidelines pertaining to SLE. An advisory panel revised and augmented these candidate indicators and, through 2 rounds of voting, arrived at 25 QIs. These QIs advanced to the next phase of the project, in which we employed a modification of the RAND/UCLA Appropriateness Method. A systematic review of the literature was performed for each QI, linking the proposed process of care to potential improved health outcomes. After reviewing this scientific evidence, a second interdisciplinary expert panel convened to discuss the evidence and provide final ratings on the validity and feasibility of each QI.

RESULTS

The final expert panel rated 20 QIs as both valid and feasible. Areas covered included diagnosis, general preventive strategies (e.g., vaccinations, sun avoidance counseling, and screening for cardiovascular disease), osteoporosis prevention and treatment, drug toxicity monitoring, renal disease, and reproductive health.

CONCLUSION

We employed a rigorous multistep approach with systematic literature reviews and 2 expert panels to develop QIs for SLE. This new set of indicators provides an opportunity to assess health care quality in patients with SLE and represents an initial step toward the important goal of improving care in this patient population.

BACKGROUND

Although antiretroviral therapy has the ability to fully restore a normal CD4(+) cell count (>500 cells/mm(3)) in most patients, it is not yet clear whether all patients can achieve normalization of their CD4(+) cell count, in part because no study has followed up patients for >7 years.

METHODS

Three hundred sixty-six patients from 5 clinical cohorts who maintained a plasma human immunodeficiency virus (HIV) RNA level 1000 copies/mL for at least 4 years after initiation of antiretroviral therapy were included. Changes in CD4(+) cell count were evaluated using mixed-effects modeling, spline-smoothing regression, and Kaplan-Meier techniques.

RESULTS

The majority (83%) of the patients were men. The median CD4(+) cell count at the time of therapy initiation was 201 cells/mm(3) (interquartile range, 72-344 cells/mm(3)), and the median age was 47 years. The median follow-up period was 7.5 years (interquartile range, 5.5-9.7 years). CD4(+) cell counts continued to increase throughout the follow-up period, albeit slowly after year 4. Although almost all patients (95%) who started therapy with a CD4(+) cell count 300 cells/mm(3) were able to attain a CD4(+) cell count 500 cells/mm(3), 44% of patients who started therapy with a CD4(+) cell count <100 cells/mm(3) and 25% of patients who started therapy with a CD4(+) cell count of 100-200 cells/mm(3) were unable to achieve a CD4(+) cell count >500 cells/mm(3) over a mean duration of follow-up of 7.5 years; many did not reach this threshold by year 10. Twenty-four percent of individuals with a CD4(+) cell count <500 cells/mm(3) at year 4 had evidence of a CD4(+) cell count plateau after year 4. The frequency of detectable viremia ("blips") after year 4 was not associated with the magnitude of the CD4(+) cell count change.

CONCLUSIONS

A substantial proportion of patients who delay therapy until their CD4(+) cell count decreases to <200 cells/mm(3) do not achieve a normal CD4(+) cell count, even after a decade of otherwise effective antiretroviral therapy. Although the majority of patients have evidence of slow increases in their CD4(+) cell count over time, many do not. These individuals may have an elevated risk of non-AIDS-related morbidity and mortality.

The use of antiretroviral therapy for HIV infection has extended the survival of individuals living with HIV. However, the effects of chronic HIV infection and aging are introducing another facet of HIV complications. HIV therapy can calm the immune system and lower viral replication to undetectable but the virus is still present. In the brain, amyloid beta (Abeta) increases during normal aging but Abeta accumulation appears to accelerate in HIV infection. HIV Tat protein inhibits the major Abeta-degrading enzyme neprilysin with the cysteine-rich domain of Tat being essential for this inhibition. In this minireview, we also include new data that the beta chemokine, CCL2/MCP-1, associated with HIV migration to the brain, also causes an increase in Abeta. These findings may explain the continued cognitive dysfunction found in HIV-infected individuals controlled on antiviral therapy.