Quantifying the Feeding Periods Required by Corn Flea Beetles to Acquire and Transmit Pantoea stewartii.

The feeding periods required by corn flea beetles to acquire and transmit Pantoea stewartii were investigated in the Stewart's disease of corn pathosystem. To quantify the effect of acquisition feeding period on percentage of acquisition, field-collected corn beetles were allowed to feed for 6, 12, 24 36, 48, and 72 h on corn seedlings previously inoculated with a rifampicin- and nalidixic acid-restraint strain of P. stewartii. Acquisition of P. stewartii by corn flea beetles was considered positive if the rifampicin- and nalidixic acid-marked strain was recovered on selective media. To quantity the effect of transmission feeding period on percent transmission of P. stewartii by corn flea beetles, P. stewartii- infested corn flea beetles were allowed to feed on healthy corn seedlings for periods of 3, 6, 12, 24, 36, 48, and 72 h. After the appropriate transmission feeding period, leaf tissues surrounding the sites of feeding scars were cultured for the presence of the P. stewartii-marked strain. Transmission of P. stewartii was considered positive if the marked strain was recovered on selective media. Acquisition of P. stewartii occurred within 6 h and the percentage of corn flea beetles that had acquired P. stewartii after 72 h ranged from 68 to 94%. The change in P. stewartii acquisition by corn flea beetles (Y) with respect to acquisition feeding period (X) was best described by the Gompertz model, with R2 values ranging from 91 to 99%. The mean time for acquisition by 50% of the corn flea beetles was 36.5 ± 11.6 h. The minimum transmission feeding time required for corn flea beetles to transmit P. stewartii following a 48-h acquisition feeding period was less than 3 h. The percent transmission of P. stewartii by corn flea beetles was nearly 100% after a 48-h transmission feeding period and was 100% by 72 h. Among population growth models evaluated, the monomolecular model best described the relationship between percent transmission (Y) and transmission feeding periods (X), with R 2 values of up to 84%. However, a nonlinear form of the monomolecular model better quantified the relationship between percent transmission and transmission feeding period, because pseudo-R2 values ranged between 98.1 and 99.5%. The predicted transmission feeding time required for 50% of P. stewartii-infested corn flea beetles to transmit the pathogen was 7.6 ± 0.87 h. These results suggest that the corn flea beetle is a highly efficient vector that can quickly acquire and transmit P. stewartii, thereby requiring insecticide seed treatments and foliar insecticides that act quickly to prevent corn flea beetles from acquiring and transmitting P. stewartii to corn plants.

Ability of an ELISA-Based Seed Health Test to Detect Erwinia stewartii in Maize Seed Treated with Fungicides and Insecticides.

Two sets of experiments were done to examine whether seed-treatment chemicals affected the ability of an enzyme-linked immunosorbent assay (ELISA)-based seed health test to detect Erwinia stewartii. The chemicals evaluated included Actellic, Apron, Captan, Cruiser, Gaucho, Maxim, Poncho, Thiram, and Vitavax in 11 seed-treatment combinations. In one experiment, seed-treatment chemicals were evaluated quantitatively in a critical region of ELISA absorbance values near 0.5 using maize seed that were spiked with uniform quantities of a liquid suspension of E. stewartii. The number of bacteria in each sample was estimated from ELISA absorbance values using standard curves. Log CFU of E. stewartii per sample were not significantly different among the untreated control and the 11 seed treatments compared with Tukey's Studentized Range Test (P = 0.05). Means of log CFU/ml for all treatments were tightly clustered around 5.70 which corresponded to an absorbance value of 0.440 and a bacterial population of about 500,000 CFU/ml. In a second set of experiments, seed treatment chemicals were evaluated based on qualitative decisions that resulted from the ELISA-based seed health test of seed lots of Jubilee and A632 infected with E. stewartii. The number of negative samples was not substantially greater than expected based on binomial probabilities except for samples of Captan/Vitavax-treated A632, which we considered to be a type I error. The mean absorbance values of positive samples ranged from 1.42 to 1.72 for A632 and from 1.51 to 1.91 for Jubilee and did not differ significantly among the seed treatments. There was no consistent evidence from these experiments that fungicide or insecticide seed treatments interfered with the sensitivity of the ELISA or altered low (e.g., 0.5) or high (e.g. 1.4 to 1.9) absorbance values. The ability of the ELISA-based seed health test to detect E. stewartii in maize seed was not affected by these seed treatments.

Assessing suspected spinal cord compression: a multidisciplinary outcomes analysis of 342 episodes.

The object of this work was to evaluate the assessment and document the outcomes of cancer patients with suspected spinal cord compression (SCC). In a retrospective cohort study of 342 episodes of suspected SCC in cancer patients evaluated by computed tomography (CT) of the spine, a multidisciplinary team of neurologists, radiologists, and oncologists assessed the impact of varying the anatomical criterion for SCC and including new SCC diagnosed shortly after definitive radiographical imaging. We developed a logistic regression model to identify independent clinical predictors of SCC, including the natural history of the underlying cancer as well as neurological and radiological risk factors. Management of suspected SCC infrequently involved neurology consultation (21% of episodes). The frequency of SCC increased more than four-fold when the definition was expanded to include epidural cancer rather than spinal cord displacement only (36% vs. 8%), and 90-day clinical follow-up identified few new lesions not evident on definitive imaging studies. Clinical information about the course of cancer (documentation and duration of metastatic cancer) added independent predictive information to that yielded by neurological assessment and prior imaging studies in a multiple regression model. The a priori predicted risk of SCC, which ranged from 4% to 87% in this study, may vary enough to affect treatment strategies, although our population may have excluded very-low-risk patients. Consistent anatomical definitions of SCC, clinical follow-up of definitive imaging studies and the addition of information on the natural history of cancer to traditional neurological and radiographical evaluation may all improve clinical assessment of suspected SCC in cancer patients.

Relationship Between Late-Season Severity of Stewart's Bacterial Wilt and Seed Infection in Maize.

The relationship between the amount of foliar disease on maize plants and seed contamination by the causal bacterium, Pantoea stewartii, was studied by comparing disease severity on adult plants with results from laboratory seed tests. Seventy-seven naturally infected maize lines (25 in 1990 and 52 in 1992) were selected and assigned to one of six disease severity classes based on the percentage of ear leaf tissue killed by Stewart's wilt: trace to 2%, 6 to 14%, 25 to 34%, 35 to 49%, 50 to 74%, and 75 to 100%. Ears were harvested from 10 to 20 plants representative of the disease class for each maize line, and seeds were tested by enzyme-linked immunosorbent assay (ELISA) of bulk-seed samples. Seed infection percentages were estimated from the bulk-test results by using statistical equations for group testing. The accuracy of the bulk-seed method for estimating seed infection was validated by comparison with 300-kernel single-seed tests. Infected seed was detected only from seed of plants with ≥25% disease severity; however, 45 of 63 such seed lots had no infection. Three seed lots had >5% infected seeds, all from plants with >50% disease severity. The results suggest a possible threshold level between 15 and 25% disease severity for Stewart's wilt on leaves before bacteria are detected in seed. This study describes a relatively simple method for estimating the incidence of infected seeds in a seed lot and contributes additional evidence to indicate that the chance of spreading P. stewartii from U.S.-produced maize seeds is low.

Suspected spinal cord compression in breast cancer patients: a multidisciplinary risk assessment.

Breast cancer is the most common cause of metastatic epidural spinal cord compression (SCC) in women, and this condition results in significant neurologic dysfunction and morbidity. Prior studies of patients with suspected SCC did not employ multivariate analysis techniques, often included persons with a wide variety of malignancies, and generally focused on identifying associated neurologic and radiologic features. We therefore conducted a study examining a more comprehensive set of potential clinical risk factors in breast cancer patients with suspected SCC. We retrospectively analysed 123 episodes of suspected SCC among 93 breast cancer patients evaluated by spine computed tomography (CT) scanning. Multiple logistic regression analysis was employed to identify independent predictors of SCC. Clinically significant metastatic epidural cancer was defined as thecal sac compression (TSC), which occurred in 33 episodes (27%). Four independent predictors of TSC were identified and included oncologic features (known bone metastases > or = 2 years, metastatic disease at initial diagnosis) in addition to neurologic and radiologic features (objective weakness, vertebral compression fracture on spine radiograph). These four predictors stratified episodes into subgroups with widely varying risks of TSC, ranging from 12% (0 risk factors) to 85% (> or = 3 risk factors). These results suggest that the evaluation of breast cancer patients with suspected SCC should include clinical information about their disease course in addition to neurologic examination and prior imaging studies. If confirmed, these predictors may help clinicians assess risk in this patient population.

Seed Transmission of Pantoea stewartii in Field and Sweet Corn.

Seed transmission of Pantoea stewartii was evaluated by assays of more than 76,000 plants in greenhouse and field grow-out trials. Fourteen P. stewartii-infected seed lots were obtained from two dent corn inbreds and two sweet corn cultivars that were inoculated with either a rifampicin and nalidixic acid-resistant strain (rif-9A) or a wild-type strain (SS104) of P. stewartii. Four additional seed lots were collected from naturally infected inbreds. Percentages of infected kernels ranged from 0.8 to 72%, as determined by agar plating or by individual-kernel enzyme-linked immunosorbent assay (ELISA). Plants grown from this seed were assayed by a stem-printing technique that consisted of cutting and pressing a cross-section of each stem onto agar media. Prints were examined for development of P. stewartii colonies after 24 and 48 h. The transmission rate from seed produced on the inoculated plants was 0.066% (28 of 42,206 plants), based on all seedlings assayed. Transmission was estimated to be 0.14% from infected kernels. The transmission rate from seed produced on naturally infected plants was 0.0029% (1 of 34,924 plants), based on all seedlings, and 0.022% from infected kernels. Seed transmission occurred significantly less often (P = 0.034) from seed produced on naturally infected plants than from seed produced on inoculated plants, probably due to greater kernel damage caused by ear shank inoculation. The rarity of seed transmission of P. stewartii from heavily infected seed lots that would ordinarily be rejected due to poor germination suggests that the likelihood of seed transmission from good quality commercial seed corn is virtually nonexistent.

Development of Lhermitte's sign after bone marrow transplantation.

The authors observed Lhermitte's sign in four patients after bone marrow transplantation (BMT) for hematologic malignancies. Three patients had acute myelogenous leukemia (AML), and one had chronic myelogenous leukemia. Before BMT, the patients with AML received daunorubicin, cytosine arabinoside and etoposide, whereas the patient with chronic myelogenous leukemia received hydroxyurea. One patient with AML received MY-9 antibody-depleted autologous BMT. The other patients received human lymphocyte antigen-identical, allogeneic BMT. Preparative therapy for BMT was cytosine arabinoside, cyclophosphamide, and total body exposure to radiation for two patients, and busulfan, cyclophosphamide, and no exposure to radiation in two other patients. Lhermitte's sign appeared 4 to 8 months after BMT and resolved spontaneously after 2 to 5 months. Neurologic sequelae had developed in none of the patients 16 to 34 months after BMT. No unifying etiologic factor could be identified in these patients. The development of Lhermitte's sign after BMT appears to be a benign, self-limited phenomenon that requires no specific treatment.

Immune-mediated cytopenia following bone marrow transplantation. Case reports and review of the literature.

We describe 3 cases of immune-mediated cytopenia occurring after bone marrow transplantation (BMT). In 1 case, only the platelet line was affected, whereas in the other 2 cases more than 1 cell lineage was involved simultaneously. Two of the cases presented with falling peripheral blood counts following apparently normal early engraftment, while in 1 of the cases the affected lineage failed to appear in the peripheral blood despite normal engraftment of the other lineages. In all 3 cases the cytopenia improved following the initiation of treatment with systemic corticosteroids. Immune-mediated cytopenia following bone marrow transplantation may occur via alloimmune or autoimmune mechanisms. Alloimmune cytopenias have arisen in the context of major or minor mismatches in the ABO system, but cases related to mismatches in the Rh system and other erythroid and non-erythroid alloantigen systems may also occur. Alloimmune cytopenias have been reported primarily in the setting of allogeneic BMT, whereas autoimmune cytopenias have been reported following both allogeneic and autologous BMT. Immune-mediated cytopenia may present as early as the day of transplant, or as late as many months afterward. The possibility of immune-mediated cytopenia should always be considered when unexpected peripheral blood cytopenia is present, or when unexpected hemolysis develops, following bone marrow transplantation. The diagnosis is supported by a normal appearance of the affected lineage or lineages in the bone marrow, the absence of other apparent causes for the cytopenia, and the presence of the relevant auto- or allo-antibodies in the serum. However, any of these features may be absent in individual cases. The importance of these syndromes lies in the fact that they may be life-threatening, yet they often respond well to steroids or other standard immunosuppressive measures. It is important to be aware that effective prophylactic measures are available for patients receiving ABO- or Rh-incompatible marrow.