Dairy production practices and associated risks for bovine vaccinia exposure in cattle, Brazil

A cross-sectional serosurvey was performed to identify environmental features or practices of dairy farms associated with risk for exposure to vaccinia-like viruses in dairy cattle in Brazil. Sera from 103 cows from 18 farms in Minas Gerais state were examined for Orthopoxvirus-neutralizing antibodies. A database of 243 binary or multiple-selection categorical variables regarding the physical features and surrounding ecology of each property was obtained. Thirteen of 46 presumptive predictor variables were found to be significantly associated with Orthopoxvirus serostatus by univariate logistic regression methods. Use of teat sanitizer and having felids on the property were independently associated with virus exposure by multivariable analysis. Rodents have long been suspected of serving as maintenance reservoirs for vaccinia-like viruses in Brazil. Therefore, domestic felids are not only effective predators of small rodent pests, but also their urine can serve as a deterrent to rodent habitation in buildings such as stables and barns. These results corroborate previous evidence of the high significance of rodents in the Vaccinia virus transmission cycle, and they also raise questions regarding the common use of teat sanitizers in dairy production areas.

Acquired PTPN11 mutations occur rarely in adult patients with myelodysplastic syndromes and chronic myelomonocytic leukemia

Myelodysplastic syndromes (MDS) are comprised of a heterogeneous group of stem cell disorders characterized by ineffective hematopoiesis and susceptibility to transform to acute myeloid leukemia. The molecular pathways underlying disease initiation and evolution are still largely unknown. We recently demonstrated that acquired mutations in PTPN11 are a major event in JMML and occur with variable prevalence in children with other hematologic malignancies, including MDS. Here, we investigated contribution of PTPN11 mutations to adult MDS and CMML pathogenesis. Our results indicate that PTPN11 lesions might play a role in adult MDS/CMML pathogenesis but do not represent a major molecular event.

Mutations in PTPN11 implicate the SHP-2 phosphatase in leukemogenesis

The PTPN11 gene encodes SHP-2 (Src homology 2 domain-containing protein tyrosine Phosphatase), a nonreceptor tyrosine protein tyrosine phosphatase (PTPase) that relays signals from activated growth factor receptors to p21Ras (Ras) and other signaling molecules. Mutations in PTPN11 cause Noonan syndrome (NS), a developmental disorder characterized by cardiac and skeletal defects. NS is also associated with a spectrum of hematologic disorders, including juvenile myelomonocytic leukemia (JMML). To test the hypothesis that PTPN11 mutations might contribute to myeloid leukemogenesis, we screened the entire coding region for mutations in 51 JMML specimens and in selected exons from 60 patients with other myeloid malignancies. Missense mutations in PTPN11 were detected in 16 of 49 JMML specimens from patients without NS, but they were less common in other myeloid malignancies. RAS, NF1, and PTPN11 mutations are largely mutually exclusive in JMML, which suggests that mutant SHP-2 proteins deregulate myeloid growth through Ras. However, although Ba/F3 cells engineered to express leukemia-associated SHP-2 proteins cells showed enhanced growth factor-independent survival, biochemical analysis failed to demonstrate hyperactivation of the Ras effectors extracellular-regulated kinase (ERK) or Akt. We conclude that SHP-2 is an important cellular PTPase that is mutated in myeloid malignancies. Further investigation is required to clarify how these mutant proteins interact with Ras and other effectors to deregulate myeloid growth.

In vitro generation of novel pyrimethamine resistance mutations in the Toxoplasma gondii dihydrofolate reductase

Pyrimethamine is a potent inhibitor of dihydrofolate reductase and is widely used in the treatment of opportunistic infections caused by the protozoan parasite Toxoplasma gondii. In order to assess the potential role of dhfr sequence polymorphisms in drug treatment failures, we examined the dhfr-ts genes of representative isolates for T. gondii virulence types I, II, and III. These strains exhibit differences in their sensitivities to pyrimethamine but no differences in predicted dhfr-ts protein sequences. To assess the potential for pyrimethamine-resistant dhfr mutants to emerge, three drug-sensitive variants of the T. gondii dhfr-ts gene (the wild-type T. gondii sequence and two mutants engineered to reflect polymorphisms observed in drug-sensitive Plasmodium falciparum) were subjected to random mutagenesis and transfected into either wild-type T. gondii parasites or dhfr-deficient Saccharomyces cerevisiae under pyrimethamine selection. Three resistance mutations were identified, at amino acid residues 25 (Trp-->Arg), 98 (Leu-->Ser), and 134 (Leu-->His).

Compensatory evolution in rifampin-resistant Escherichia coli

This study examines the intrinsic fitness burden associated with RNA polymerase (rpoB) mutations conferring rifampin resistance in Escherichia coli K12 (MG1655) and explores the nature of adaptation to the costs of resistance. Among 28 independent Rif(r) mutants, the per-generation fitness burden (in the absence of rifampin) ranged from 0 to 28%, with a median of 6.4%. We detected no relationship between the magnitude of the cost and the level of resistance. Adaptation to the costs of rif resistance was studied by following serial transfer cultures for several Rif(r) mutants both in the presence of rifampin and in the absence. For cultures evolved in the absence of rifampin, single clones isolated after 200 generations were more fit than their ancestor; we saw no association between increased fitness and changes in the level of rifampin resistance; and in all cases, increased fitness was due to compensatory mutations, rather than to reversion to drug sensitivity. However, in the parallel evolution experiments in the presence of rifampin, overall levels of resistance increased as did relative fitness-for all strains save one that had an initially high level of resistance. Among the evolved clones tested, five (of seven) demonstrated increased transcription efficiency (assessed using a semiquantitative RT-PCR protocol). The implications of these results for our understanding of adaptive molecular evolution and the increasing clinical problem of antibiotic resistance are discussed.

Transport and trafficking: Toxoplasma as a model for Plasmodium

Like Plasmodium, the protozoan parasite Toxoplasma gondii is a member of the phylum Apicomplexa, and an obligate intracellular pathogen. Unlike Plasmodium, however, Toxoplasma is highly amenable to experimental manipulation in the laboratory. The development of molecular transformation protocols for T. gondii has provided both scientific precedent and practical selectable markers for Plasmodium. Beyond the feasibility of molecular biological experimentation now possible in both systems, the high frequency of stable transformation in Toxoplasma allows this parasite to be used for molecular genetic analysis. The ability to control homologous vs. non-homologous recombination in T. gondii permits gene knockouts/allelic replacements at previously cloned loci, and saturation insertional mutagenesis of the entire parasite genome (and cloning of the tagged loci). T. gondii also exhibits unusual ultrastructural clarity, facilitating cell biological analysis. The accessibility of Toxoplasma as an experimental system allows this parasite to be used as a surrogate for asking many questions that cannot easily be addressed in Plasmodium itself. T. gondii also serves as a model system for genetic exploration of parasite biology and host-parasite interactions. Success stories include: biochemical analysis of antifolate resistance mechanisms; pharmacological studies on the mechanisms of macrolide activity; genetic identification of nucleobase/nucleoside transporters and metabolic pathways; and cell biological characterization of the apicomplexan plastid. As with any model system, not all questions of interest to malariologists can be addressed in Toxoplasma; differentiating between sensible and foolish questions requires familiarity with the biological similarities and differences of these systems.

A biochemical and genetic model for parasite resistance to antifolates. Toxoplasma gondii provides insights into pyrimethamine and cycloguanil resistance in Plasmodium falciparum

We have exploited the experimental accessibility of the protozoan parasite Toxoplasma gondii and its similarity to Plasmodium falciparum to investigate the influence of specific dihydrofolate reductase polymorphisms known from field isolates of drug-resistant malaria. By engineering appropriate recombinant shuttle vectors, it is feasible to examine mutations by transient or stable transformation of T. gondii parasites, in bacterial and yeast complementation assays, and through biochemical analysis of purified enzyme. A series of mutant alleles that mirror P. falciparum variants reveals that the key mutation Asn-108 (Asn-83 in T. gondii) probably confers resistance to pyrimethamine by affecting critical interactions in the ternary complex. Mutations such as Arg-59 (T. gondii 36) have limited effect in isolation, but in combination with other mutations they enhance the competitive ability of folate by increasing the speed of product turnover. Val-16 (T. gondii 10) confers low level resistance to cycloguanil but hypersensitivity to pyrimethamine. This mutation precludes Asn-108, probably because compression of the folate binding pocket introduced by this combination is incompatible with enzyme function. These studies permit detailed biochemical, kinetic, and structural analysis of drug resistance mutations and reconstruction of the probable phylogeny of antifolate resistance in malaria.

Do dressings with increased permeability reduce the incidence of central venous catheter related sepsis?

The incidence of catheter-related sepsis associated-with the use of Tegaderm or Opsite IV3000 dressings on 100 critically ill patients with liver disease was studied. All the patients had central venous catheters in situ and they were randomly assigned to one of the two dressings. In this study the sites of insertion were assessed at each dressing change, together with any fluid under the dressing. No statistically significant difference between the two dressings was found in accumulation of fluid, skin microbial colonization, local infection or systemic infection of patients in our sample. There was no apparent advantage to using the more permeable Opsite IV3000 dressing.

Suprachoroidal hemorrhage. Clinical features and results of secondary surgical management

PURPOSE

The purposes of this study are to identify clinical features in eyes with suprachoroidal hemorrhage which portend a poor visual prognosis and to determine visual outcome in these eyes after secondary surgical management of suprachoroidal hemorrhage.

METHODS

This was a retrospective study of 106 patients with suprachoroidal hemorrhages occurring in association with trauma (35), cataract surgery (30), glaucoma surgery (17), penetrating keratoplasty (6), corneal perforation (5), secondary lens implantation (3), pars plana vitrectomy (3), and other causes (7).

RESULTS

Five (10%) of 49 eyes with a suprachoroidal hemorrhage and an initial retinal detachment had a visual outcome of 20/200 or better compared with 21 (43%) of 49 eyes without a retinal detachment. The presence or absence or a retinal detachment could not be determined in eight patients and all eight of these patients had a poor visual outcome. Sixteen (20%) of 82 eyes with a 360 degrees suprachoroidal hemorrhage had a visual outcome of 20/200 or better compared with 10 (47%) of 21 for those with suprachoroidal hemorrhage limited to one or two quadrants. The extent of the hemorrhage could not be determined in three eyes. Overall, 34% (14/41) of the patients with suprachoroidal hemorrhage who had a secondary surgical procedure achieved a visual outcome of 20/200 or better. Forty-three percent (6/14) who had a suprachoroidal hemorrhage during or after cataract surgery and who were treated with secondary surgical management achieved a visual outcome of 20/200 or greater.

CONCLUSION

Clinical features associated with a poorer visual outcome included initial or indeterminate retinal detachment and 360 degrees suprachoroidal hemorrhage. Limited suprachoroidal hemorrhage without initial retinal detachment usually has a good visual prognosis and does not usually require secondary surgical intervention. However, if the former complication is present, secondary surgical intervention should be considered.

Chiasmal compression from fat packing after transsphenoidal resection of intrasellar tumor in two patients

After transsphenoidal resection of a pituitary (or other) tumor, the remaining intrasellar cavity, and sphenoid sinus are usually packed with exogenous fat or muscle to prevent cerebrospinal leak and prolapse of the optic chiasm into an empty sella. We treated two patients in whom chiasmal compression occurred postoperatively because of packing of fat. In one patient, the expected visual improvement in the postoperative period was suboptimal. The subsequent removal of fat resulted in total visual recovery. In the other patient, chiasmal compression persisted from intrasellar fat and residual tumor. Iatrogenic compression of the optic nerves or chiasm should be considered in all patients in whom visual recovery is incomplete.

Treatment of infectious scleritis and keratoscleritis

We reviewed 28 cases of culture-proven infectious scleritis and keratoscleritis to clarify the role of an operation in this disorder. Surgical management in 11 patients with keratoscleritis included cryotherapy, five; penetrating corneal-scleral graft, two; lamellar corneoscleral graft, two; and tectonic penetrating keratoplasty, two; in addition to intensive fortified antibiotic eyedrops. Eight patients with keratoscleritis were treated medically only with intensive fortified frequent antibiotic eyedrops, one; intensive instilled plus intravenous antibiotics, three; and instilled, intravenous, and subconjunctival antibiotics, four. Seven of eight patients treated with antibiotics alone and two of 11 patients who received surgical intervention in addition to antibiotics eventually required evisceration or enucleation of the eye. These results suggest that cryotherapy, lamellar or penetrating corneoscleral graft, in addition to intensive antibiotic therapy, may improve the outcome of patients with infectious keratoscleritis. Five eyes with isolated scleritis without corneal involvement were treated with conjunctival recession and cryotherapy in addition to aggressive antibiotics, and four were treated with antibiotics alone. The infections of these nine patients resolved.