A whole-genome single nucleotide polymorphism-based approach to trace and identify outbreaks linked to a common Salmonella enterica subsp. enterica serovar Montevideo pulsed-field gel electrophoresis type

In this study, we report a whole-genome single nucleotide polymorphism (SNP)-based evolutionary approach to study the epidemiology of a multistate outbreak of Salmonella enterica subsp. enterica serovar Montevideo. This outbreak included 272 cases that occurred in 44 states between July 2009 and April 2010. A case-control study linked the consumption of salami made with contaminated black and red pepper to the outbreak. We sequenced, on the SOLiD System, 47 isolates with XbaI PFGE pattern JIXX01.0011, a common pulsed-field gel electrophoresis (PFGE) pattern associated with isolates from the outbreak. These isolates represented 20 isolates collected from human sources during the period of the outbreak and 27 control isolates collected from human, food, animal, and environmental sources before the outbreak. Based on 253 high-confidence SNPs, we were able to reconstruct a tip-dated molecular clock phylogeny of the isolates and to assign four human isolates to the actual outbreak. We developed an SNP typing assay to rapidly discriminate between outbreak-related cases and non-outbreak-related cases and tested this assay on an extended panel of 112 isolates. These results suggest that only a very small percentage of the human isolates with the outbreak PFGE pattern and obtained during the outbreak period could be attributed to the actual pepper-related outbreak (20%), while the majority (80%) of the putative cases represented background cases. This study demonstrates that next-generation-based SNP typing provides the resolution and accuracy needed for outbreak investigations of food-borne pathogens that cannot be distinguished by currently used subtyping methods.     

Catalytic cooperativity induced by SH1 labeling of myosin filaments

Modifications of SH1 groups on isolated myosin subfragment 1 (S-1) and myosin in muscle fibers affect differently the acto-S-1 ATPase and the fiber properties. Consistent with the findings of earlier work on fibers, the modification of SH1 groups in relaxed myofibrils with phenylmaleimide caused a loss of their shortening. This loss paralleled the decrease in the Vmax of extracted myosin but was not linear with the extent of SH1 labeling. Strikingly, the decrease in Vmax of S-1 prepared from the modified myofibrils was directly proportional to the extent of SH1 labeling. The specificity of SH1 labeling in myofibrils was verified by ATPase activities, thiol titrations, radiolabeling experiments, and comparisons to myosin labeled on SH1 in solution. To test for intermolecular interactions in the myosin filaments and their contribution to the differences between S-1 and myosin, the catalytic properties of copolymers of myosin were examined. Copolymers of myosin and rod minifilaments were formed in 5 mM citrate-Tris (pH 8.0) buffer, and their homogeneity was verified by sedimentation velocity analysis. The inhibition of actomyosin ATPase by rod particles was related to the decrease in the Km value. When rod particles were replaced in these minifilaments by SH1-modified myosin, the ATPase of the copolymers was increased over that of the combined ATPases of the individual filaments. The actomyosin ATP turnover rates on the unmodified heads were increased severalfold by the modified heads.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enhanced killing of penicillin-treated gram-positive cocci by human granulocytes: role of bacterial autolysins, catalase, and granulocyte oxidative pathways

Staphylococci pretreated with subminimal inhibitory concentrations (subMIC) of cell-wall active antibiotics exhibit increased susceptibility to killing by human polymorphonuclear leukocytes (PMNs), even when phagosome information is impaired by the mold metabolite, cytochalasin B. To investigate the role of specific bacterial factors in the process, studies were carried out with organisms lacking catalase (streptococci) or cell-wall autolytic enzymes and compared to findings with Staphylococcus aureus 502A. Neutrophil factors were studied using inhibitors, oxygen radical scavengers, myeloperoxidase (MPO)-deficient PMNs, or PMNs from a patient with chronic granulomatous disease (CGD). Documentation of the enhanced susceptibility of the streptococcal strains to killing by PMNs following subMIC penicillin pretreatment required the use of cytochalasin B. Enhancement of killing occurred independent of the presence or absence of bacterial autolysins or catalase. SubMIC penicillin pretreatment of S. pneumoniae R36A specifically promoted the susceptibility of these organisms to killing by myeloperoxidase (MPO)-mediated mechanisms (enhancement lost using MPO-deficient or azide-treated cells). Factors other than MPO or toxic oxygen products generated by the PMN respiratory burst are responsible for enhanced killing of penicillin-pretreated S. aureus 502A (enhancement preserved using MPO-deficient, azide-treated, or chronic granulomatous disease patient cells). These studies define methods to study the interaction of antimicrobial agents and PMNs in the killing of microorganisms. They also demonstrate that penicillin treatment can change the susceptibility of gram-positive cocci to the action of specific PMN microbicidal mechanisms. The mechanism of the enhancement appears to be bacterial strain-dependent and not predictable by bacterial autolysin or catalase activity.     

Seasonal bulk xylem pressure in temperate broadleaf eudicot trees: a case study for sugar long-distance transport and signaling

Sugars regulate growth, development, and defense in trees. Sugars are also important signaling molecules and are transported over long distances via xylem and phloem. Sucrose loading to tracheids and vessels is associated with bulk xylem pressure and occurs seasonally in temperate broadleaf eudicot trees. Following restoration of xylem hydraulic conductivity in spring, sugars are unloaded from xylem sap at apical branches and deposited as starch before growth of shoot apical meristems. Growth of cambia and shoot apical meristems leads to starch catabolism that yields hexose-phosphates to fuel cell growth and regulate other signal networks. The contrast between cell molecular biology of Arabidopsis and physiology of temperate broadleaf eudicot trees indicates the importance of phosphorylation in long-distance sugar signaling. Hexokinase, acting as a hub for signal and hormone networks, is likely an important regulator of sugar signaling in response to stimuli such as energy status, sugar status, and environmental conditions. The comparative analysis suggested here could help bridge physiology and detailed molecular mechanisms regarding physiology of trees.     

Cervical cancer screening: are the 1989 recommendations still valid? National Workshop on Screening for Cancer of the Cervix.

Although screening for cervical cancer has been shown to be effective in reducing the morbidity and mortality associated with this disease, and despite many attempts to encourage the development of provincial programs, as of 1995 no province had a comprehensive screening program for cervical cancer. Participants at the Interchange ''95 workshop, held in Ottawa in November 1995, reviewed the recommendations of the 1989 National Workshop on Screening for Cancer of the Cervix and identified factors that have impeded their implementation. Participants discussed the need for comprehensive information systems, quality control and strategies to increase recruitment of unscreened and underscreened women. They concluded that the formation of a Cervical Cancer Prevention Network involving key stakeholders will facilitate the development and implementation of provincial programs to ensure optimal screening. They agreed that, in the interim, recommendations for practising physicians should remain as they were following the 1989 workshop.     

Abrupt shortening of bird W chromosomes in ancestral Neognathae

As a result of suppressed recombination, heterogametic sex chromosomes (either Y or W) are usually assumed to gradually shorten over evolutionary time as a way to remove accumulated mutations. However, suppressed recombination removes the most obvious mechanism for excising portions of sex chromosomes. We examined ratios of W/Z chromosome size across 224 bird species from 146 genera. Much of the data were obtained from a previous study (Rutkowska et al. 2012. Biology Letters 8 : 636–638), who, similar to ourselves, found no gradual decrease in W chromosome length over evolutionary time. However, we show an abrupt decrease in W chromosome length at or just after the phylogenetic split between the two extant bird superorders, Paleognathae and Neognathae, indicating that the key to understanding sex chromosome evolution may have little to do with gradual suppression of recombination.     

Yersinia enterocolitica and related species isolated from wildlife in New York State.

Fecal specimens for Yersinia screening were obtained from a variety of wild mammals, birds, reptiles, fish, and invertebrates throughout New York State. One specimen from each of 1,426 animals was examined. A total of 148 isolates of Yersinia enterocolitica and related species were obtained from 133 (9.3%) of the animals. Y. enterocolitica was isolated from 100 (7%) of the animals tested, including 81 (10%) of 812 mammals and 19 (3.3%) of 573 birds. Y. intermedia, Y. frederiksenii, and Y. kristensenii were isolated from 39 (2.7%), 5 (0.35%), and 4 (0.28%) animals, respectively. The 81 Y. enterocolitica isolates from mammals belonged to 15 serogroups and included three pathogens: two isolates of typical serogroup 0:8, the "American strain," one from a gray fox (Urocyon cinereoargenteus) and one from a porcupine (Erethizon dorsatum); and one isolate of serogroup 0:3, bacteriophage type IXb, the "Canadian strain," from a gray fox. The most prevalent serogroups recovered from mammals were 0:6,31 (16 isolates) and 0:5,27 (6 isolates). The 19 isolates of Y. enterocolitica from birds belonged to nine serogroups and included one serogroup 0:6,31 isolate from a common grackle (Quiscalus quiscula) and two serogroup 0:5,27 isolates from great horned owls (Bubo virginianus).