Evaluation of Novel Quorum Sensing Inhibitors Targeting Auto-Inducer 2 (AI-2) for the Control of Avian Pathogenic Escherichia coli Infections in Chickens.

Avian pathogenic Escherichia coli (APEC) associated with colibacillosis results in high morbidity and mortality, and severe economic losses to the poultry industry. APEC is a zoonotic pathogen and can infect humans through contaminated poultry products. Vaccination and antibiotic treatment are currently used to control APEC infections; however, the limited effect of vaccines and the emergence of antibiotic-resistant strains have necessitated the development of novel therapeutics. Here, we evaluated seven quorum sensing inhibitors (QSI) identified in our previous study, in APEC-infected chickens. QSIs were administered orally (~92 to 120 µg/bird) and chickens were challenged subcutaneously with APEC. Among them, QSI-5 conferred the best protection (100% reduction in mortality, 82% to 93% reduction in lesions [airsacculitis, perihepatitis, lung congestion, pericarditis] severity, and 5.2 to 6.1 logs reduction in APEC load). QSI-5 was further tested in chickens raised on built-up floor litter using an optimized dose (1 mg/L) in drinking water. QSI-5 reduced the mortality (88.4%), lesion severity (72.2%), and APEC load (2.8 logs) in chickens, which was better than the reduction observed with currently used antibiotic sulfadimethoxine (SDM; mortality 35.9%; lesion severity up to 36.9%; and APEC load up to 2.4 logs). QSI-5 was detected in chicken's blood after 0.5 h with no residues in muscle, liver, and kidney. QSI-5 increased the body weight gain with no effect on the feed conversion ratio and cecal microbiota of the chickens. Metabolomic studies revealed reduced levels of 5'-methylthioadenosine in QSI-5-treated chicken serum. In conclusion, QSI-5 displayed promising effects in chickens and thus, represents a novel anti-APEC therapeutic. IMPORTANCE Avian pathogenic Escherichia coli (APEC), a subgroup of ExPEC, is a zoonotic pathogen with public health importance. Quorum sensing is a mechanism that regulates virulence, biofilm formation, and pathogenesis in bacteria. Here, we identified a novel quorum sensing autoinducer-2 inhibitor, QSI-5, which showed higher anti-APEC efficacy in chickens compared to the currently used antibiotic, sulfadimethoxine at a much lower dose (up to 4,500 times). QSI-5 is readily absorbed with no residues in the tissues. QSI-5 also increased the chicken's body weight gain and did not impact the cecal microbiota composition. Overall, QSI-5 represents a promising lead compound for developing novel anti-virulence therapies with significant implications for treating APEC infections in chickens as well as other ExPEC associated infections in humans. Further identification of its target(s) and understanding the mechanism of action of QSI-5 in APEC will add to the future novel drug development efforts that can overcome the antimicrobial resistance problem.

Chronic intermittent diarrhea in a 14-month-old Abyssinian cat.

A 14-month-old intact, female Abyssinian cat was presented for chronic intermittent diarrhea and bilateral enlargement of the mammary glands. Gastrointestinal coccidiosis was diagnosed; therapy with sulfadi-methoxine was unsuccessful in the elimination of Isospora felis and clinical signs. Infection with Tritrichomonas foetus was diagnosed by fecal polymerase chain reaction (PCR) and successfully treated with ronidazole and dietary modification.

Nephrotic syndrome associated with administration of sulfadimethoxine/ormetoprim in a dobermann.

This case report describes sulphonamide-induced nephrotic syndrome in a young dobermann dog. The clinical signs and laboratory abnormalities resolved shortly after discontinuation of the sulphonamide antibiotic and with generalised supportive care. Since nephrotic syndrome typically carries a guarded prognosis in veterinary medicine and is poorly responsive to therapy, a thorough drug history should be an important part of the investigation of any animal with a protein-losing nephropathy.

Evaluating new antimalarial drugs against trophozoite induced Plasmodium cynomolgi malaria in rhesus monkeys.

An antimalarial drug testing system is described which utilizes trophozoite induced Plasmodium cynomolgi malaria in rhesus monkeys. The schizonticidal activity of standard antimalarial drugs in this system is reported. The system accurately predicted antimalarial activity in man of 8 of 9 compounds selected for clinical trials.

Evaluation of two avirulent vaccines for preventing experimental fowl cholera in turkeys, and use of one vaccine in the field.

The Clemson University (CU) strain of live cholera vaccine administered in water (LCVW) was effective in immunizing turkeys against the pulmonary, arthritic, and cranial forms of fowl cholera. The Missouri strain of LCVW immunized turkeys against the pulmonary and septicemic forms of fowl cholera. Pasteurella multocida was isolated from the orifice of the auditory tube of 5% of the turkeys vaccinated with the CU strain 2 weeks postvaccination, but not 4 weeks after challenge. Mortality was not increased by administering the CU strain of LCVW at 5, 10, 20, and 40 x the standard dose of 4 x 10(8) P. multocida. A low concentration of Rofenaid (providing 0.01% potentiated sulfadimethoxine) had no perceptible effect on the development of immunity with the CU vaccine.

Rofenaid in the control of Pasteurella anatipestifer and Escherichia coli infections in ducklings.

In a series of controlled battery trials, Rofenaid (at doses ranging from 0.02 to 0.12% active drug in feed) was administered to ducklings infected experimentally with Pasteurella anatipestifer and Escherichia coli strains. Against P. anatipestifer, Rofenaid at 0.02 to 0.12% levels in feed either prevented or reduced mortality, gross lesions, and bacterial isolations. Furthermore, the weight gain and feed conversion of infected Rofenaid-medicated ducklings were superior to those of uninfected unmedicated controls in two out of three trials. Against E. coli, Rofenaid at 0.02 to 0.08% levels in feed either prevented or reduced mortality, gross lesions, and bacterial isolations. Weight gain and feed conversion of infected Rofenaid-medicated ducklings were also superior to those of uninfected unmedicated controls in two out of three trials. It appears that Rofenaid, at a 0.02-0.08% level, controls infections in ducklings caused by P. anatipestifer and E. coli strains sensitive to this compound.

Comparison of low-level rofenaid, low-level chlortetracycline, and vaccination with commercial bacterin for preventing pulmonary form of fowl cholera in turkeys.

The pulmonary form of experimentally induced fowl cholera was controlled effectively either by Rofenaid, a potentiated sulfadimethoxine, at 0.01% in feed, chlortetracycline at 0.0055% in feed, vaccination with a commercial fowl cholera bacterin and a combination of Rofenaid and vaccination. The medicated or/and vaccinated turkeys had a significantly (P less than 0.05) better livability than the unmedicated or unvaccinated exposed turkeys. Turkeys were exposed by contact with carriers and administration of Pasteurella multocida in drinking water. Transmission from carriers to recipients through the water was demonstrated. P. multocida was isolated from the mouths of recipient turkeys receiving low-level medication one week after carriers were introduced.

Comparative efficacy of enrofloxacin, oxytetracycline, and sulfadimethoxine for the control of morbidity and mortality caused by Escherichia coli in broiler chickens.

The purpose of the present study was to compare the ability of enrofloxacin, oxytetracycline, and sulfadimethoxine to reduce morbidity and mortality caused by Escherichia coli (colibacillosis) in broiler chickens. The chickens were raised in 80 pens (20 birds per pen) with 20 pens representing each treatment group under simulated commercial conditions that produced a colibacillosis challenge scenario. Each group of 20 randomized pens (replicates) was given one of four water treatments. Chickens that received enrofloxacin had significantly less mortality (P < 0.01), lower average gross pathology (colibacillosis) scores (P < 0.01), and better feed-conversion ratios (P < 0.05) than did chickens that received either oxytetracycline or no medication. Chickens that received enrofloxacin had significantly less mortality and lower pathology scores than those that received sulfadimethoxine and numerically lower feed conversion than the sulfadimethoxine group. Results from the present study show that enrofloxacin is superior to oxytetracycline and sulfadimethoxine for the control of morbidity and mortality caused by E. coli in broiler chickens. Our findings will help veterinarians choose and prescribe the most efficacious antimicrobial when treating colibacillosis.

Prophylactic and therapeutic activity of Rofenaid-40A in an experimental Escherichia coli airsac infection in chickens.

Rofenaid at a 0.02% dose level in feed was effective prophylactically and therapeutically against an experimentally induced Escherichia coli airsac infection in chickens. The activity of Rofenaid compared very favorably with that of the approved dose level of NF-180. Furthermore, the prophylactic use of Rofenaid did not interfere with the therapeutic efficacy of NF-180.

Influence of rofenaid-40 feed medication on an experimental Salmonella infection in chickens.

Rofenaid-40 administered at 0.02% in feed to chickens experimentally infected with Salmonella typhimurium resulted in less colonization and shedding of S. typhimurium than in unmedicated chickens. The antibacterial sensitivity pattern of S. typhimurium isolated from infected birds had not changed after exposure to Rofenaid for 56 days.

Anticryptosporidial activity is associated with specific sulfonamides in immunosuppressed rats.

Dexamethasone-immunosuppressed rats infected with Cryptosporidium parvum were used to assess 23 sulfonamides for anticryptosporidial activity. Five of the compounds administered before the animals were inoculated with C. parvum oocysts reduced the severity of cryptosporidial infections in the rat model. Two of the 5 agents with prophylactic activity, sulfadimethoxine and sulfamethazine, were effective also against an established infection, indicating that some sulfonamides may have therapeutic value in immunosuppressed patients with cryptosporidiosis. The findings also suggest that sulfonamide treatment of cryptosporidiosis in the immunocompromised host may not be successful unless the compound is administered continuously or over several weeks.

Activity of sulfadimethoxine against cryptosporidiosis in dairy calves.

Of 13 neonatal calves inoculated orally with 1.5 x 10(6) oocysts of Cryptosporidium parvum, 7 in group A were fed 5-g boluses of sulfadimethoxine for 21 consecutive days beginning 1 day before infection, and 6 calves in group B were untreated controls. Calves in group A had diarrhea for 6-18 days (mean = 11 days); those in group B had diarrhea for 4-14 days (mean = 8.7 days). The severity of diarrhea, based on a daily numerical scoring system, was similar for both groups. Calves in group A shed an average of 18 x 10(6) oocysts/ml of feces for 3.9 days; those in group B shed an average of 2.4 x 10(6) oocysts/ml of feces for 5.3 days. By 28 days of age, calves in group A vs. group B gained an average of 8.9 kg vs. 15.7 kg. These findings indicate that sulfadimethoxine did not significantly reduce the number of days or severity of diarrhea, or the number of oocysts or patent period, nor did it improve weight gains.

Chemotherapy and chemoprophylaxis of hepatic coccidiosis with sulphadimethoxine and pyrimethamine.

The activity of a mixture of sulphadimethoxine and pyrimethamine (10:3) as prophylactic medication and prophylactic and therapeutic medication was studied in rabbits experimentally infected with Eimeria stiedai. The haematocrit index (packed cell volume) and haemoglobin levels were studied for assessment of drug toxicity. The activity in serum of aspartate aminotransferase (AST) and alanine aminotransferase, alkaline phosphatase and gamma-glutamyltranspeptidase were studied as indicators of hepatic lesions. Parasite development was followed on the basis of the presence of oocysts; other parameters were analysed in order to monitor the performance of infected animals. All the parameters studied showed that the chemoprophylactic medication provided efficient control of the infection and of the hepatic lesions. Serum AST activity was seen to be a good indicator of the effect of the drugs on the liver.

Mass medication in reducing shipping fever-bovine respiratory disease complex in highly stressed calves.

One thousand and eighty-five newly received, stressed calves were used in studies to determine the effectiveness of certain mass medication procedures for reducing morbidity from shipping fever-bovine respiratory disease complex. In two experiments, im injections of oxytetracycline at 11 mg/kg body wt for 3 successive days reduced treatment days/calf purchased 21 (P less then .05) and 31% (P less than .05). Oral administration of 150 mg of sulfadimethoxine/kg body wt reduced treatment days/calf purchased 20 (P less than .05) and 54% (P less than .05) in the same two experiments. When sulfadimethoxine followed oxytetracycline on the third injection day an 81% reduction in treatment days/calf purchased was obtained, indicating an additive effect of the two drugs. The use of long acting oxytetracycline and sustained release sulfadimethoxine at the time of processing resulted in a 90% reduction in treatment days/calf purchased (P less than .01) and required only one handling of the calves for mass medication purposes.

Comparison of four methods for the determination of sulphonamide concentrations in human plasma.

Analysis of sulphadimethoxine in plasma from patients treated with this drug was performed with four chemical methods: Rieder's modification of the Bratton-Marshall technique and author's modification of the Morris technique, which are supposed to measure "potentially active fraction of sulphonamides", i.e., mainly unchanged sulphonamide; the Bratton-Marshall method, which enables the determination of "free sulphonamide", i.e., the sum of unchanged sulphonamide and glucuronide conjugate; and high performance liquid chromatography which made possible the determination of unchanged sulphadimethoxine. The spectrophotometric methods based upon Bratton-Marshall reaction gave very few higher results as compared with liquid chromatography. The differences between spectrophotometric and chromatographic methods were small; therefore, all four methods can be used for determination of sulphonamide concentrations in plasma during monitored treatment with these drugs.

Prevention of coccidiosis in domestic dogs and captive coyotes (Canis latrans) with sulfadimethoxine-ormetoprim combination.

Sulfadimethoxine-ormetoprim combination was evaluated as a coccidiostat against experimentally induced coccidiosis in young dogs and coyotes (Canis latrans). The animals were experimentally inoculated with 50,000 or 100,000 sporulated oocysts of Isospora ohiohensis (98%) and Isospora canis (2%). In experiment 1, daily treatment for 13 to 23 days with a combination of 27.5 mg of sulfadimethoxine/kg of body weight (BW) and 5.5 mg of ormetoprim/kg of BW admixed to the feed resulted in no significant (P greater than 0.05) difference in fecal oocyst counts between treated and nontreated groups of dogs or coyotes. In experiment 2, treatment with a combination of 55 mg of sulfadimethoxine/kg of BW and 11 mg of ormetoprim/kg of BW for 23 days was 99.8% effective against Isospora spp infections in dogs. Significantly (P less than 0.05) fewer oocysts were present in feces of treated dogs than were present in feces of nontreated dogs from first passage of oocysts at day 4 to the end of the patent period at days 19 to 21. After the 2nd week of treatment, BW of treated dogs were significantly greater (P less than 0.05) than BW of nontreated dogs. Evidence of drug toxicity was not observed clinically or by serum chemical analyses.

Effect of sulfadimethoxine-ormetoprim in the treatment of calves with induced Pasteurella pneumonia.

The efficacy of sulfadimethoxine (SDM)-ormetoprim (OMP) was evaluated in calves with induced Pasteurella pneumonia. A dose-titration study comparing 3 doses of SDM-OMP was performed to determine the optimal dose. Treatments included: group 1--nontreated controls; group 2--33 mg of SDM-OMP/kg of body weight, orally on day 1 and 17 mg/kg on days 2 to 5; group 3--66 mg of SDM-OMP/kg, orally on day 1 and 33 mg/kg on days 2 to 5; group 4--99 mg of SDM-OMP/kg, orally on day 1 and 50 mg/kg on days 2 to 5; and group 5--11 mg of oxytetracycline/kg, IV daily for 4 days. Group-2 calves responded to treatment as well as did group-5 calves. Group-4 calves responded the same as did group-3 calves. However, group-2 calves did not respond as well as did groups 3, 4, and 5 calves.

Haptoglobin response to clinical respiratory tract disease in feedlot cattle.

OBJECTIVE: To quantify haptoglobin response to respiratory tract disease in feedlot cattle, and to investigate its ability to predict disease outcome and response to antibiotic treatment. DESIGN: Randomized clinical trial. ANIMALS: 60 feedlot calves with clinical respiratory tract disease. PROCEDURE: Calves were randomly assigned to receive a standard antibiotic treatment regimen (TRT), or to observation pens without antibiotic treatment. Serum haptoglobin concentration was measured at initial and final examinations. Calves were examined for presence of gross pulmonary lesions at slaughter. RESULTS: Mean +/- SD serum haptoglobin concentration at initial examination was 67 +/- 108 mg/dl, with range of 0 to 508 mg/dl. Haptoglobin concentration at initial examination was similar for the TRT group and the group that did not receive antibiotic treatment, but at final examination, TRT-group calves had lower (P < 0.01) mean values. Calves receiving antibiotic treatment had haptoglobin concentration at or near zero at final examination. Calves not receiving antibiotic treatment had only slightly lower mean haptoglobin concentration at final examination, compared with initial examination. Within treatment groups, haptoglobin concentration was similar for cases with different outcomes. Calves with gross pulmonary lesions at slaughter had numerically higher, although statistically similar, haptoglobin concentrations at initial examination, compared with calves without lesions. CONCLUSIONS: Feedlot cattle with clinical respiratory tract disease have a large and variable haptoglobin response. Antibiotic treatment resulted in lower serum haptoglobin values, although low values were not required for full clinical recovery. CLINICAL RELEVANCE: Serum haptoglobin concentration may be an indicator of response to antibiotic therapy, although it appears to be unrelated to case severity or need for treatment.

Effects of various treatments on induced chronic aflatoxicosis in rabbits.

Male New Zealand White rabbits were orally given 0.05 mg of aflatoxin B1 (AFB1)/kg of body weight daily for 10 days and were treated with glutathione-precursors and depletor, antibacterial agents, or sodium thiosulfate. The drug administered, the mortality, and the mean survival time were as follows: corn-oil controls (0), euthanatized at 25 days; AFB1-controls (2), 21 days; AFB1 and saline controls (2), 22 days; cysteine and AFB1 (5), 13 days; methionine and AFB1 (5), 12 days; sodium thiosulfate and AFB1 (2), 21 days; sulfadimethoxine and AFB1 (1), 24 days; oxytetracycline and AFB1 (0), euthanatized at 25 days; and ethyl maleate and AFB1 (3), 21 days. Clinical signs of toxicosis included decreased feed consumption during AFB1 administration, loss of body weight or failure to gain, and death. Clinicopathologic changes included increases in serum bilirubin concentration and alanine aminotransferase and aspartate aminotransferase activities. Prothrombin and activated partial thromboplastin times were lengthened. Plasma fibrinogen concentration was decreased. Changes in PCV, hemoglobin concentration, and serum alkaline phosphatase were unremarkable. Oxytetracycline had protective effects against chronic aflatoxicosis in rabbits. Cysteine and methionine enhanced chronic aflatoxicosis.