Development of a New Semiselective Medium for Isolating Xanthomonas campestris pv. manihotis from Plant Material and Soil

ABSTRACT An effective control for bacterial blight of cassava (Manihot esculenta), caused by Xanthomonas campestris pv. manihotis, requires the use of non-contaminated cuttings and seeds. Using classical agar plating techniques for screening planting material for contamination has not been very successful because of the lack of a reliable semiselective agar medium. The pathogen grows slowly on general plating media and is easily overgrown by saprophytic bacteria during isolation from diseased plants. In an effort to develop a semiselective medium, the utilization of several carbon and nitrogen sources was studied. Results of these tests provided information used to design a basal medium allowing good growth of the target organism while suppressing growth of several common saprophytes. Additional selectivity was achieved by incorporating three antibiotics into the basal medium. The new semiselective agar medium, designated cefazolin trehalose agar (CTA) medium, contained (per liter) 3.0 g of K(2)HPO(4), 1.0 g of NaH(2)PO(4), 0.3 g of MgSO(4).7H(2)O, 1.0 g of NH(4)Cl, 9.0 g of D(+)-trehalose, 1.0 D(+)-glucose, 1.0 g of yeast extract, 0.025 g of cefazolin, 0.0012 g of lincomycin, 0.0025 g of phosphomycin, 0.25 g of cycloheximide, and 14.0 g of agar. In comparison to a starch-based semiselective medium (SXM), plating efficiencies using pure cultures of 10 strains of X. campestris pv. manihotis were significantly higher on CTA, with an average of 85 and 50%, respectively. Likewise, isolation and recovery of X. campestris pv. manihotis from infected cassava leaves and contaminated soil were much higher on CTA than on SXM agar. When X. campestris pv. manihotis occurs in high concentrations in diseased tissue, the standard yeast trehalose glucose agar medium supplemented with 250 mug of cycloheximide per ml appears to be satisfactory. The newly developed CTA medium should prove useful for control strategies to identify and remove infected planting material of cassava, as well as for basic ecological studies of the pathogen.     

Alterations in the jejunum of young goats caused by feeding soy protein‐based diets

This study was designed to investigate whether soy protein or soy protein supplemented with indispensable amino acids (AA) change the protein expression pattern and utilization of pre‐cursors for RNA biosynthesis in jejunal mucosa in relation to casein and whether these changes affect mucosal cell growth. Kids were fed comparable diets based on cow`s milk, of which 50% of crude protein were replaced by either casein (CAS), soy protein (SP) or soy protein supplemented with indispensible AA (SPA) for 34 days (n = 4/group). Jejunal tissue was collected 5 h after adding a single dose of ¹⁵N‐RNA to the diet, in order to determine morphology, protein repertoire by two‐dimensional gel electrophoresis and matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry, and RNA biosynthesis by isotope ratio‐mass spectrometry. In mid‐jejunum, morphological alterations induced by partial replacement of casein with soy protein were accompanied by changes in mucosal proteins related to generation of the cytoskeleton and in pathways for mucosal RNA biosynthesis, resulting in a smaller re‐utilization of dietary RNA pre‐cursors and in an increased activity of enzymes involved in nucleic acid breakdown. Soy protein supplemented with indispensible aminoacids tended to revise mucosal growth retardation with no impact on salvage of dietary RNA pre‐cursors for mucosal RNA biosynthesis, but changes in cytoskeleton generation. Feeding soy protein with supplementation of indispensible AA does not ameliorate soy protein effects on mucosal morphology and RNA metabolism in the jejunum in a significant manner.     

Identification of a highly virulent strain of <Emphasis Type="Italic">Xanthomonas axonopodis</Emphasis> pv. <Emphasis Type="Italic">malvacearum</Emphasis>

A highly virulent strain (HVS) of Xanthomonas axonopodis pv. malvacearum (Xam) was first reported in Africa in 1983, infecting all commercial cultivars of cotton including the immune cv. ‘101–102B’. The HVS was considered to be a new race of pathovar malvacearum (race 20). Here we studied a HVS (GSPB 2388) isolated in Sudan, which causes symptoms that clearly differed from the typical angular water-soaked spots of bacterial bright of cotton. Our investigations showed that extracellular cellulase activity of this HVS was higher than that of the control strain GSPB 1386 (race 18). Additionally, SDS-PAGE indicated that the HVS cell wall contained short LPS molecules with fewer O-chain repeating units, lacking in GSPB 1386. The higher cellulase activity and the distinct lipopolysaccharide of HVS are correlated with the higher virulence and deviating symptom formation. Rep-PCR fingerprinting showed that the HVS was very closely related to other strains of Xam.     

Recent advances in the management of bovine tuberculosis in free-ranging wildlife

Established foci of Mycobacterium bovis (the causative agent of bovine tuberculosis [bTB]) in free-ranging wildlife are currently under various stages of management on three continents (Africa, Europe and North America) and in New Zealand. Other, as yet undiagnosed, foci seem likely to exist elsewhere. The complex roles that these wildlife foci play in the ecology of bTB remain among the greatest challenges facing bTB control globally. Conceptually, management of bTB in free-ranging wildlife can be thought of as progressing from the discovery of an outbreak through frequently overlapping stages of epidemiological characterization, initial control, simulation and forecasting, focused control, and verification of eradication. Surveillance in its various forms remains a critical component of assessment throughout. Since the Fourth International M. bovis Conference in 2005, research on management of bTB in free-ranging wildlife has encompassed such areas as the human dimensions of wildlife management, mitigation of bTB risks from wildlife on cattle farms, vaccine biology, and epidemiology, with a major contribution from simulation modeling. In order to advance the actual field management of bTB, however, research must be sufficiently grounded to aid development of practical, affordable and politically defensible management interventions which stand a reasonable chance of being implemented. The current management of two wildlife reservoirs of bTB, brushtail possums (Trichosurus vulpecula) in New Zealand, and white-tailed deer (Odocoileus virginianus) in Michigan, USA, serve as contrasting examples of different wildlife management strategies aimed at achieving a common goal. In New Zealand, the importance of agricultural export markets and the status of the possum as a non-native pest have facilitated direct, aggressive management of the disease reservoir, resulting in considerable progress towards bTB freedom since 1994. In Michigan, the relative importance of the hunting economy and of whitetails as a game animal have made such aggressive culling politically untenable. This has forced reliance upon publicly supported, and implemented, management tools, and so provided impetus to better understand social support for wildlife management policy, its limitations, and ways to employ it in disease control policy development.     

A new selective medium for isolation of Clavibacter michiganensis subsp. michiganensis from tomato plants and seed

A new selective and highly sensitive medium was developed for isolation of Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of bacterial canker of tomato, from seed and latently infected plants. The new medium (BCT) proved to be superior to all published semiselective media for Cmm and is denoted as selective medium because of (i) its mean plating efficiency, amounting to ≤89% within 7 days for all 30 Cmm strains from different sources tested; (ii) the high selectivity, because accompanying bacterial species occurring on tomato plants and seed or bacteria obtained from culture collections were inhibited to an extent of 98 to 100%; and (iii) the remarkable detection sensitivity. Thus, 8 CFU of Cmm in field plant homogenates containing 12,750 CFU of accompanying saprophytes were detected on BCT. Under these extreme conditions, all of the published semiselective media (D2, KBT, D2ANX, SCM, mSCM, CMM1, mCNS, and EPPO) gave false-negative results. Either some media were rather toxic and Cmm growth was also inhibited or the other, less toxic media allowed growth of high numbers of saprophytes, so that Cmm growth was suppressed. Exclusively, BCT also supported growth of the closely related C. michiganensis subsp. insidiosus, nebraskensis, and tessellarius. The new medium is recommended for Cmm detection in tomato seed, and in symptomless tomato plantlets, to improve disease control of bacterial canker of tomato.     

The effects of ephedrine on intramuscular blood flow and other cardiopulmonary parameters in halothane-anesthetized ponies

Objective To evaluate the effect of ephedrine on intramuscular blood flow and hemodynamic parameters during equine anesthesia. Study design Prospective experimental study. Animals Six healthy adult Welsh Mountain ponies (five males, one female, mean weight: 267 kg, range: 213–347 kg). Methods Halothane‐anesthetized ponies received an IV bolus of ephedrine (0.1 mg kg^?1), followed 30 minutes later by a second IV ephedrine injection (0.2 mg kg^?1). Changes in intramuscular blood flows (IMBF) in upper and lower triceps brachii were measured by laser Doppler flowmetry. Cardiopulmonary measurements were made at intervals for 30 minutes following each injection. Results were compared with values from a control group, similarly anesthetized but given saline in an earlier study. Results Ephedrine at either dose increased heart rate, arterial blood pressure (AP), cardiac index (CI) and intramuscular blood flow (IMBF), the effects on these parameters being significant and long‐lasting following the higher dose. Systemic vascular resistance remained unchanged, and was significantly lower than in the control saline group. PaO₂ decreased significantly immediately following the first injection of ephedrine, then remained unchanged for the remainder of the experiment. PaCO₂ increased slowly throughout the anesthetic period. One pony developed supraventricular premature complexes following the second injection. No other side effects were seen. Conclusion Ephedrine at dose rates of 0.2 mg kg^?1 IV consistently increased in CI, AP, and IMBF in both forelimbs. Clinical relevance Ephedrine may be of use to improve AP, CI and IMBF during halothane anesthesia, although the occurrence of an arrhythmia in one pony is of concern.     

A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging

ObjectiveTo compare the recovery after anaesthesia with isoflurane, sevoflurane and desflurane in dogs undergoing magnetic resonance imaging (MRI) of the brain.Study designProspective, randomized clinical trial.AnimalsThirty‐eight dogs weighing 23.7 ± 12.6 kg.MethodsFollowing pre‐medication with meperidine, 3 mg kg^?1 administered intramuscularly, anaesthesia was induced intravenously with propofol (mean dose 4.26 ± 1.3 mg kg^?1), the trachea was intubated, and an inhalational anaesthetic agent was administered in oxygen. The dogs were randomly allocated to one of three groups: group I (n = 13) received isoflurane, group S (n = 12) received sevoflurane and group D (n = 13) received desflurane. Parameters recorded included cardiopulmonary data, body temperature, end‐tidal anaesthetic concentration, duration of anaesthesia, and recovery times and quality. Qualitative data were compared using chi‐squared and Fisher's exact tests and quantitative data with anova and Kruskal–Wallis test. Post‐hoc comparisons for quantitative data were undertaken with the Mann–Whitney U‐test.ResultsThe duration of anaesthesia [mean and standard deviation (SD)] in group I was: 105.3 (27.48) minutes, group S: 120.67 (19.4) minutes, and group D: 113.69 (26.68) minutes (p = 0.32). Times to extubation [group I: 8 minutes, (interquartile range 6–9.5), group S: 7 minutes (IQR 5–7), group D: 5 minutes (IQR 3.5–7), p = 0.017] and to sternal recumbency [group I: 11 minutes (IQR 9.5–13.5), group S: 9.5 minutes (IQR 7.25–11.75), group D: 7 minutes (range 3.5–11.5), p = 0.048] were significantly different, as were times to standing. One dog, following sevoflurane, had an unacceptable quality of recovery, but most other recoveries were calm, with no significant difference between groups.Conclusions and clinical relevanceAll three agents appeared suitable for use. Dogs’ tracheas were extubated and the dogs recovered to sternal recumbency most rapidly after desflurane. This may be advantageous for animals with some neurological diseases and for day case procedures.