Charles E. Davis

Mycobacterium bovis infections in San Diego: a clinicoepidemiologic study of 73 patients and a historical review of a forgotten pathogen.

We have presented 73 patients (48 adults and 25 children) with microbiologically documented M. bovis infections identified over the 12-year period from 1980 through 1991. Epidemiologic investigation of these patients revealed that the majority (80%) were of Hispanic origin. The non-Hispanic patients either had traveled extensively outside the United States, were born in the United States during its endemic period or in other countries with endemic bovine tuberculosis, or were exposed to a close relative with a positive PPD and known exposure to M. bovis. For Hispanic patients, the presence of reactivation disease in adults and primary disease in children indicate that this mycobacterium remains endemic in Mexican beef and dairy herds, a position supported by United States monitoring of Mexican cattle transferred across the border. Our review of the historical and contemporary efforts to eradicate this animal and human pathogen from the livestock industry in the United States and abroad shows that the implementation of similar methods could be effective in Mexico. The detailed presentations of selected patients and summaries of the clinical manifestations in the remainder of our 73 patients reveal striking similarities to historical accounts and to more contemporary studies of reactivated disease in England. Although M. bovis infections are still expressed predominantly in extrapulmonary sites (cervical and mesenteric nodes, the peritoneum, and the GU tract), as many as 50% of adult patients will present only with pulmonary disease. Underlying immunosuppressive disorders were particularly prominent in adults with extrapulmonary disease. For example, HIV positive patients accounted for 12 of 48 adults and 1 adolescent patient in our series. Overall, M. bovis infections accounted for almost 3% of all tuberculous disease reported in San Diego County during the study period. The intrinsic resistance of M. bovis to PZA could threaten the response of patients with bovine tuberculosis to the short-course chemotherapeutic regimens now recommended by the CDC and the American Thoracic Society. We strongly recommend continued surveillance for this forgotten pathogen because the importation of Mexican cattle, the migration of Hispanic immigrants from border areas to the United States interior, and the persistence of extrapulmonary disease in immunocompetent and HIV-infected United States citizens assure its persistence in this country.

Rapid Identification of Candida albicans Septicemia in Man by Gas-Liquid Chromatography

Gas-liquid chromatography (GLC) was used to study normal serum and serum from patients with septicemia caused by a variety of bacteria and by Candida albicans. The gas chromatograms of seven sera from six patients with septicemia due to C. albicans were found to be significantly and reproducibly different from those of normal sera. Chromatograms of serum from 19 bacteremic patients were indistinguishable from normals. The major peaks present in chromatograms of normal sera were identified by GLC and mass spectroscopy as the methyl esters of palmitic, oleic, linoleic, and stearic acids. In addition to these peaks, serum from patients with candidemia contained abnormal peaks that were also present in cultures of C. albicans grown in normal serum and in washed C. albicans harvested from cultures in yeast nitrogen base broth. Chromatograms from 11 cases of mucosal candidates differed little from normal and were easily distinguished from those of fungemia patients. Chromatograms of serum from two of four patients with deep-invasive candidiasis were indistinguishable from those of fungemia and reverted to normal after infections were eradicated.

Effect of Deutetrabenazine on Chorea Among Patients With Huntington Disease: A Randomized Clinical Trial

IMPORTANCE Deutetrabenazine is a novel molecule containing deuterium, which attenuates CYP2D6 metabolism and increases active metabolite half-lives and may therefore lead to stable systemic exposure while preserving key pharmacological activity. OBJECTIVE To evaluate efficacy and safety of deutetrabenazine treatment to control chorea associated with Huntington disease. DESIGN, SETTING, AND PARTICIPANTS Ninety ambulatory adults diagnosed with manifest Huntington disease and a baseline total maximal chorea score of 8 or higher (range, 0-28; lower score indicates less chorea) were enrolled from August 2013 to August 2014 and randomized to receive deutetrabenazine (n = 45) or placebo (n = 45) in a double-blind fashion at 34 Huntington Study Group sites. INTERVENTIONS Deutetrabenazine or placebo was titrated to optimal dose level over 8 weeks and maintained for 4 weeks, followed by a 1-week washout. MAIN OUTCOMES AND MEASURES Primary end point was the total maximal chorea score change from baseline (the average of values from the screening and day-0 visits) to maintenance therapy (the average of values from the week 9 and 12 visits) obtained by in-person visits. This study was designed to detect a 2.7-unit treatment difference in scores. The secondary end points, assessed hierarchically, were the proportion of patients who achieved treatment success on the Patient Global Impression of Change (PGIC) and on the Clinical Global Impression of Change (CGIC), the change in 36-Item Short Form- physical functioning subscale score (SF-36), and the change in the Berg Balance Test. RESULTS Ninety patients with Huntington disease (mean age, 53.7 years; 40 women [44.4%]) were enrolled. In the deutetrabenazine group, the mean total maximal chorea scores improved from 12.1 (95% CI, 11.2-12.9) to 7.7 (95% CI, 6.5-8.9), whereas in the placebo group, scores improved from 13.2 (95% CI, 12.2-14.3) to 11.3 (95% CI, 10.0-12.5); the mean between-group difference was -2.5 units (95% CI, -3.7 to -1.3) (P < .001). Treatment success, as measured by the PGIC, occurred in 23 patients (51%) in the deutetrabenazine group vs 9 (20%) in the placebo group (P = .002). As measured by the CGIC, treatment success occurred in 19 patients (42%) in the deutetrabenazine group vs 6 (13%) in the placebo group (P = .002). In the deutetrabenazine group, the mean SF-36 physical functioning subscale scores decreased from 47.5 (95% CI, 44.3-50.8) to 47.4 (44.3-50.5), whereas in the placebo group, scores decreased from 43.2 (95% CI, 40.2-46.3) to 39.9 (95% CI, 36.2-43.6), for a treatment benefit of 4.3 (95% CI, 0.4 to 8.3) (P = .03). There was no difference between groups (mean difference of 1.0 unit; 95% CI, -0.3 to 2.3; P = .14), for improvement in the Berg Balance Test, which improved by 2.2 units (95% CI, 1.3-3.1) in the deutetrabenazine group and by 1.3 units (95% CI, 0.4-2.2) in the placebo group. Adverse event rates were similar for deutetrabenazine and placebo, including depression, anxiety, and akathisia. CONCLUSIONS AND RELEVANCE Among patients with chorea associated with Huntington disease, the use of deutetrabenazine compared with placebo resulted in improved motor signs at 12 weeks. Further research is needed to assess the clinical importance of the effect size and to determine longer-term efficacy and safety. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01795859.

Identification of a developmentally regulated cysteine protease of Trypanosoma brucei

Trypanosoma brucei undergoes dramatic metabolic changes during differentiation from the mammalian bloodstream form into the procyclic form of the insect midgut. Because modulation of protein degradation is likely to be important during this process we studied T. brucei for life cycle mediated proteolysis. We detected an increase in the activity of a 28 kDa protease as pleomorphic GUTat 3.1 trypanosomes differentiate in the mammalian bloodstream from long slenders into short stumpies. Short stumpy trypanosomes hydrolyse z-Phe-Arg-AMC 12 fold more actively than either long slenders or procyclics. The 28 kDa protease is activated by dithiothreitol and is inhibited by trans-epoxysuccinyl-L-leucyl-amido(4-guanidino) butane (E-64), indicating that it is a cysteine protease. The proteolytic activity of monomorphic ILTat 1.4 trypanosomes does not increase during mammalian parasitemia. If monomorphic ILTat 1.4 trypanosomes are induced to differentiate into short stumpies by exposure to difluoromethylornithine, however, the activity of the 28 kDa cysteine protease increases 8 fold. This suggests that polyamine depletion induces the 28 kDa cysteine protease and that its expression may be regulated by mechanism not previously described in protozoa.

Brucellosis in San Diego: Epidemiology and Species-related Differences in Acute Clinical Presentations

Abstract: Although aggressive public health measures have greatly reduced the number of brucellosis cases in the United States, there is a resurgence of interest in this worldwide zoonosis because of its potential as a bioweapon and its 8-fold higher incidence in California, Texas, and the other borderlands between the United States and Mexico compared with the national rate. Accordingly, we reviewed the clinical records of 28 patients diagnosed at a university hospital in San Diego, CA, between 1979 and 2002 to look for new epidemiologic trends and to test the hypothesis that there are species-specific differences in clinical presentations. In contrast to the latest California-wide study completed in 1992, Brucella abortus infections were more common (73%) than Brucella melitensis after 1992, and women were more commonly infected (77% compared with 39%) than men. Major risk factors remained Hispanic ethnicity, travel to Mexico, and ingestion of nonpasteurized dairy products. Analysis of diagnostic procedures suggested that the traditional practice of prolonged incubation of blood cultures increased their sensitivity for Brucella, even in automated radiometric systems. Direct comparison of the clinical manifestations of infections with B. abortus and B. melitensis strongly supported differences in acute presentations. B. melitensis presented more acutely as fevers of unknown origin with statistically significant higher rates of abdominal tenderness, hepatomegaly, splenomegaly, thrombocytopenia, pancytopenia, and hepatic dysfunction. These results suggest that the epidemiology of brucellosis in California may be evolving, and they show, to our knowledge for the first time in a single series, that species-specific differences in presentations may account for some of the protean manifestations of brucellosis. Familiarity with manifestations of brucellosis and the optimal laboratory techniques for its diagnosis could help physicians protect the public against this reemerging, under-recognized zoonosis. Abbreviations: FUO = fever of unknown origin, SAT = slide agglutination test.

Expression in Escherichia coli of cryptic tetracycline resistance genes from Bacteroides R plasmids

The putative clindamycin resistance region of the Bacteroides fragilis R plasmid pBF4 was cloned in the vector R300B in Escherichia coli. This 3.8-kb EcoRI D fragment from pBF4 expressed noninducible tetracycline resistance in E. coli under aerobic but not anaerobic growth conditions. The fragment does not express tetracycline resistance in Bacteroides, a strict anaerobe. The separate tetracycline resistance transfer system in the Bacteroides host strain V479-1 has no homology to the cryptic determinant on pBF4. In addition, this aerobic tetracycline resistance determinant is not homologous to the three major plasmid mediated tetracycline resistance regions found in facultative gram-negative bacteria, represented by R100, RK2, and pBR322. A similar cryptic tetracycline resistance fragment was cloned from pCP1, a separate clindamycin resistance plasmid from Bacteroides that shares homology with the EcoRI D fragment of pBF4. This study identifies cryptic drug resistance determinants in Bacteroides that are expressed when inserted into an aerobically growing organism.

Thrombocytopenia in experimental trypanosomiasis.

The effect of experimental trypanosomiasis on coagulation was studied because a patient in this hospital with Rhodesian trypanosomiasis developed thrombocytopenia with disseminated intravascular coagulation. Rats injected intraperitoneally with this strain of Trypanosoma rhodesiense consistently developed trypanosomiasis and severe thrombocytopenia without changes in hematocrit or concentration of fibrinogen or fibrin split products. At the time of 50% mortality (4-5 days) mean platelet counts per cubic millimeter of infected rats were 18,000+/-9,000 (+/-2 SEM) compared to 1,091,000+/-128,000 in uninfected controls. In vitro, concentrated trypanosomes and trypanosomefree supernates of disrupted organisms added to normal rat, rabbit, or human blood produced platelet aggregation within 30 min. This platelet aggregation was not blocked by inhibitors of ADP, kinins, or early or late components of complement. In vivo thrombocytopenia also occurred in infected rabbits congenitally deficient in C6 and in infected, splenectomized rats. Although the aggregating substance obtained from disrupted trypanosomes is heat-labile, it is active in the presence of complement inhibitors, suggesting that this trypanosomal product may be a protein enzyme or toxin. Since the phenomenon is independent of immune complexes, complement, ADP, and kinins, it appears to represent a new mechanism of microbial injury of platelets and the induction of thrombocytopenia.

Repeated Immunization with Recombinant gp160 Human Immunodeficiency Virus (HIV) Envelope Protein in Early HIV-1 Infection: Evaluation of the T Cell Proliferative Response

This longitudinal study was designed to evaluate cellular immunity in early-stage, asymptomatic human immunodeficiency virus (HIV)-1-infected persons (CD4 cell count,>400/mm3; median, 625/mm3) who were immunized with either recombinant (r) gp160 or placebo every 2 months for 5 years. Proliferative responses were assessed against rgp160, rp24, and a panel of recall antigens and mitogens. Despite good reactivity to recall antigens, at baseline approximately 33% had proliferative responses to gp160, and approximately 42% showed p24 gag responses. There was no statistical difference between vaccine and placebo groups for antigens or mitogens. After 1 year, approximately 73% of the subjects in the vaccine arm had new or boosted responses to gp160, versus approximately 18% in the placebo arm. Statistical significance was maintained throughout the study. Recurrent vaccination with recombinant gp160 was proven to be persistently immunogenic, increasing significantly the ability of HIV-1-infected persons to mount new proliferative responses to the vaccine.

Major histocompatibility complex genotype is associated with disease progression and virus load levels in a cohort of human immunodeficiency virus type 1-infected caucasians and African Americans

To assess the influence of HLA on AIDS-free survival, human immunodeficiency virus load, and CD4 cell counts, 91 Caucasian and 48 African-American seroprevalent men were typed for HLA classes I and II and TAP alleles. HLA associations with these markers were assessed by assigning sum integer scores based on 7 class I allele-TAP variants (+1) and 13 class I-class II-TAP combinations (-1) with different AIDS-free survival times found in a prior study. Subjects in both racial groups and combined with positive sum scores were less likely to have CD4 cell decline (P=.0004), to have increased virus burden (P=.014), and to develop AIDS (P=.034) in the follow-up period than were Caucasians and African Americans with scores of 0 or -1. These results confirm the reported associations of specific major histocompatibility complex genes with AIDS-free survival time in Caucasians and specifically extend them to African Americans and to two established markers of disease progression.

An immunoassay for the detection and quantitative determination of mycothiol

Mycothiol (MSH) is a glycosylated derivative of N-acetylcysteine that may have antioxidant functions in mycobacteria and other actinomycetes. To develop a highly specific assay for MSH, we capitalized on the selective binding of thiols to a maleimide residue linked to bovine serum albumin and employed affinity-purified polyclonal antibody and an enzyme-linked secondary antibody for detection. The assay was shown to be specific and to detect MSH at levels as low as 0.1 pmol when conducted in the form of a microtiter plate-based ELISA. A similar, nitrocellulose membrane-based immunoassay was shown to be useful for qualitative detection of MSH-producing bacterial colonies.