Homeostasis of selenium (Se), a critical antioxidant incorporated into amino acids and enzymes, is disrupted by exposure to aryl hydrocarbon receptor (AhR) agonists. Here we examined the importance of dietary Se in preventing the toxicity of the most toxic polychlorinated biphenyl congener, 3,3',4,4',5-pentachlorobiphenyl (PCB 126), a potent AhR agonist. Male Sprague-Dawley rats were fed a modified AIN-93 diet with differing dietary Se levels (0.02, 0.2, and 2 ppm). Following 3 weeks of acclimatization, rats from each dietary group were given a single ip injection of corn oil (vehicle), 0.2, 1, or 5 μmol/kg body weight PCB 126, followed 2 weeks later by euthanasia. PCB exposure caused dose-dependent increases in liver weight and at the highest PCB 126 dose decreases in whole body weight gains. Hepatic cytochrome P-450 (CYP1A1) activity was significantly increased even at the lowest dose of PCB 126, indicating potent AhR activation. PCB exposure diminished hepatic Se levels in a dose-dependent manner, and this was accompanied by diminished Se-dependent glutathione peroxidase activity. Both these effects were partially mitigated by Se supplementation. Conversely, thioredoxin (Trx) reductase activity and Trx oxidation state, although significantly diminished in the lowest dietary Se groups, were not affected by PCB exposure. In addition, PCB 126-induced changes in hepatic copper, iron, manganese, and zinc were observed. These results demonstrate that supplemental dietary Se was not able to completely prevent the toxicity caused by PCB 126 but was able to increase moderately the levels of several key antioxidants, thereby maintaining them roughly at normal levels.

This manuscript describes an outbreak of fatal toxoplasmosis in wallabies. Ten adult red necked wallabies (Macropus rufogriseus) were imported from New Zealand to the Virginia Zoo. Agglutination testing upon admission into quarantine showed all animals to be negative for antibodies to Toxoplasma gondii. Nine of these wallabies died from acute toxoplasmosis within 59-565 (average 224) days after being moved onto exhibit. Clinical signs included lethargy, diarrhea, tachypnea, and ataxia that progressed rapidly; death without premonitory signs occurred in one case. Histopathologic examination revealed interstitial pneumonia, encephalomyelitis, myositis, enteritis, and myocarditis. The diagnosis was confirmed through serologic, histopathologic, and polymerase chain reaction (PCR) testing. Multilocus PCR-RFLP (restriction fragment length polymorphism) genotyping revealed that the first six animals were infected by a previously undiscovered Toxoplasma gondii genotype, designated as ToxoDB PCR-RFLP genotype No. 263. These six cases survived for an average of 118 days on exhibit before succumbing to toxoplasmosis. The other three wallabies were infected with a Toxoplasma gondii strain of ToxoDB PCR-RFLP genotype No. 4, which is a common strain type circulating in wild animals in North America. These three cases survived for an average of 435 days on exhibit before succumbing to toxoplasmosis. The outbreaks of toxoplasmosis in these wallabies are likely from two different sources. Furthermore, the results highlight Toxoplasma gondii PCR-RFLP genotyping in parasite diagnosis and understanding parasite transmission and potential mitigation procedures.

Pseudomonas aeruginosa is a major bacterial pathogen commonly associated with chronic lung infections in cystic fibrosis (CF). Previously, we have demonstrated that the type IV pilus (Tfp) of P. aeruginosa mediates resistance to antibacterial effects of pulmonary surfactant protein A (SP-A). Interestingly, P. aeruginosa strains with group I pilins are O-glycosylated through the TfpO glycosyltransferase with a single subunit of O-antigen (O-ag). Importantly, TfpO-mediated O-glycosylation is important for virulence in mouse lungs, exemplified by more frequent lung infection in CF with TfpO-expressing P. aeruginosa strains. However, the mechanism underlying the importance of Tfp glycosylation in P. aeruginosa pathogenesis is not fully understood. Here, we demonstrated one mechanism of increased fitness mediated by O-glycosylation of group 1 pilins on Tfp in the P. aeruginosa clinical isolate 1244. Using an acute pneumonia model in SP-A ؉/؉ versus SP-A ؊/؊ mice, the O-glycosylation-deficient ⌬tfpO mutant was found to be attenuated in lung infection. Both 1244 and ⌬tfpO strains showed equal levels of susceptibility to SP-Amediated membrane permeability. In contrast, the ⌬tfpO mutant was more susceptible to opsonization by SP-A and by other pulmonary and circulating opsonins, SP-D and mannose binding lectin 2, respectively. Importantly, the increased susceptibility to phagocytosis was abrogated in the absence of opsonins. These results indicate that O-glycosylation of Tfp with O-ag specifically confers resistance to opsonization during host-mediated phagocytosis.

A 13-year-old 480-kg mixed breed gelding was examined because of a 2-day history of anorexia, fever, mild colic, and icterus.Three days before the onset of clinical signs, the horse received vaccinations for rabies, tetanus, West Nile virus, Western equine encephalomyelitis, and Eastern equine encephalomyelitis.On examination the horse was quiet, alert, and responsive. Heart rate was 54 beats/min, respiration rate was 18 breaths/min, and temperature was 37.9°C. Mucous membranes and sclera of the eyes were markedly icteric and capillary refill time was 2 seconds. Heart, lung, and abdominal auscultation were within normal limits. Peripheral lymph nodes were not enlarged and no abnormalities were detected on the remainder of the physical examination.Naso-gastric intubation revealed no net gastric reflux. Abdominal ultrasonography revealed a small area of moderately thickened (0.8 cm) ventral colon. Thoracic ultrasound did not reveal abnormalities. Rectal examination revealed splenomegaly but was otherwise within normal limits. Abdominocentesis was attempted but peritoneal fluid was not obtained.Complete blood count (CBC) revealed anemia (PCV 16%; reference range 33-42%) and thrombocytopenia (26,000/lL [reference range 100,000-600,000/lL]). Total white blood cell count and differential were within normal limits. Cytological evaluation of peripheral blood revealed rare nucleated red blood cells but otherwise abnormalities were not detected. Serum biochemistry abnormalities were limited to hyperglycemia (135 mg/ dL; reference range 60-107 mg/dL) and hyperbilirubinemia (10.9 mg/dL; reference range 0.5-2.5 mg/ dL). Direct and indirect bilirubin values were not measured. Total protein (TP) was 6.1g/dL (reference range 5.5-7.5 g/dL). Hyperfibrinogenemia was detected (275 g/dL; reference range 125-262 g/dL). Venous blood gas analysis a identified hyperlactatemia (7.1 mmol/L; reference range <1 mmol/L) but was otherwise normal. Prothrombin time and partial thromboplastin time were normal. A direct Coombs test was negative.ELISA and agar gel immunodiffusion (Coggins test) for equine infectious anemia and ELISA for Anaplasma phagocytophilum were negative.Volume replacement included lactated Ringer's b (20 mL/kg bolus followed by 2 mL/kg/h IV maintenance). Urine specific gravity (USG) after the initial fluid bolus was 1.025 and dipstick analysis did not reveal any abnormalities. Following the fluid bolus, PCV was 13% and TP 5.6 g/dL. The horse was lethargic and tachycardic (66 beats/min). Commercial fresh frozen plasma c was administered (4 mL/kg IV). Cross matching was performed and 8 L whole blood was administered from a donor horse. Treatment included dexamethasone d (0.2 mg/kg, IV, q24h), trimethoprim sulfamethoxazole e (TMS) (30 mg/kg, PO, q12h), and sucralfate f (20 mg/kg, PO, q6h). Because of the history of colic, feed was withheld for the first 18 hours. No signs of colic or fever were noted. The day after initial examination the horse was brighter and vital parameters were within normal limits. PCV was 17% and blood l...

Pseudomonasaeruginosa(PA) is a Gram-negative bacterial pathogen commonly associated with chronic lung infections. Previously, we have identified several PA virulence factors that are important for resistance to the surfactant protein-A (SP-A), a pulmonary innate immunity protein that mediates bacterial opsonization and membrane permeabilization. In this study, we demonstrate that the type IV pilus (Tfp) is important in the resistance of PA to the antibacterial effects of SP-A. The Tfp-deficient mutant ΔpilA is severely attenuated in an acute pneumonia model of infection in the lungs of wild-type mice, but is virulent in the lungs of SP-A^-/- mice. The ΔpilA bacteria are more susceptible to SP-A-mediated aggregation and opsonization. In addition, the integrity of the outer membranes of ΔpilA bacteria is compromised, rendering them more susceptible to SP-A-mediated membrane permeabilization. By comparing Tfp extension and retraction mutants, we demonstrate that the increased susceptibility of ΔpilA to SP-A-mediated opsonization requires the total absence of Tfp from PA cells. Finally, we provide evidence of increased expression of nonpilus adhesin OprH that may serve as an SP-A ligand, resulting in increased phagocytosis and preferential pulmonary clearance of ΔpilA.