Antibacterial Activity Of Cyadox And The Therapeutic Effect On Swine Dysentery

Exploitation of new antimicrobial growth promoter is important to the aquaculture industry. Cyadox is a developing candidate of quinoxalines. Existing research demonstrated that cyadox has low toxicity, good safety, and has good prospects for development and application. Pharmacodynamic studies showed that cyadox can promote the growth of livestock, poultry and aquatic animals, reduce diarrhea frequencies, and be effective for prevention of E. coli infection in piglets and broilers. Some studies on antibacterial activity of cyadox in vitro have indicated that cyadox was active to many pathogens, especially Escherichia coli, Salmonella spp., Staphylococcus aureus, Pasteurella multocida, Erysipelothrix rhuriopathiae, Flavobacterim columnare, Edwardsiella tarda, Brachyspira hyodysenteriae and so on. The antibacterial activity of cyadox is similar to or stronger than olaquindox. However, the existing antibacterial data are lack of systematization, and the type and quantity of bacteria are limited, and the research on control disease is too little, so some new antibacterial activity and clinical value of cyadox need a further study. This antimicrobial susceptibility tests expanded the type and quantity of bacteria in vitro, built up the antimicrobial spectra of livestock, poultry and aquatic animals, and according to the result in vitro carried on approach II clinical study on the therapeutic effect of cyadox on swine dysentery, all of which will provide the scientific basis for the further application of this drug.1 In vitro antimicrobial activity of cyadoxThe minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of cyadox against 96 strains bacteria from35 species in 19 genus, isolated from pigs, poultry and fishes, were evaluated by twofold dilution methods recommended by Clinical and Laboratory Standards Institute (CLSI). The control drug including chlortetracycline, olaquindox, bacitracin zinc and sulfadimidine. Since it's an anaerobic or anoxic environment in vivo, the antimicrobial activity of facultative anaerobes in anaerobic condition was determined, too. The results showed that cyadox was a broad-spectrum antibacterial agent which has a good effect on gram-negative and gram-positive bacteria. The antibacterial activity of cyadox was stronger than or similar to that of olaquindox, stronger than that of bacitracin zinc and sulfadimidine, and weaker than that of chlortetracycline.The antimicrobial spectrum of cyadox against pathogens isolated from pigs were as follows. Under standard conditions, susceptible bacteria were Brachyspira hyodysenteria, Clostridium perfringen and Pasteurella multocida, the MICs and MBCs of former two were 0.031～1μg/mL, and the MlCc90 and MBC90 of Pasteurella multocida were 8μg/mL and 32μg/mL, respectively. Intermediate bacteria were Salmonella choleraesui, Escherichia coil, Erysipelothrix rhuriopathiae and Streptococcus, MICs were 8～128μg/mL and MBCs were 32～>128μg/mL, respectively. Under anaerobic conditions, the antibacterial activity were enhanced by 4-64 times on Escherichia coil, Pasteurella multocida, Salmonella choleraesui and Erysipelothrix. Susceptible bacteria were Pasteurella multocida, Escherichia coil, Salmonella choleraesui and Erysipelothrix, MICs were 0.125～4μg/mL, MBC were 0.5～64μg/mL. Intermediate bacteria was Streptococcus, MICs and MBCs were 16～64μg/m and 32～128μg/mL, respectively.The antimicrobial spectrum of cyadox against pathogens isolated from poultry were as follows. Under, standard conditions, susceptible bacteria were Campylobacter jejuni, Clostridium perfringen and Pasteurella multocida, MICs and MBCs of the former two were 0.25～1μg/mL and 1μg/mL, the MIC and MBC of Pasteurella multocida were 2-4μg/mL and 16～32μg/mL, respectively. Intermediate bacteria were Salmonella pullorum, Escherichia coil and Staphylococcus aureus, MICs were 8～32μg/mL, MBCs were 16～128μg/mL. Nonsusceptible bacteria were Enterococcu faecalis and Enterococcu faecium. Under anaerobic conditions, the antibacterial activity were enhanced by 8-16 times on Salmonella spp., Escherichia coil and Enterococcus spp.. Susceptible bacteria are Pasteurella multocida, Escherichia coil and Salmonella spp., MICs were 1～4μg/mL, MBCs were 4～32μg/mL. Intermediate bacteria were Enterococcu faecalis and Enterococcu faecium, MICs and MBCs were 8～16μg/mL and 64μg/mL, respectively.The antimicrobial spectrum of cyadox against common pathogens isolated from fishes were as follows. Under standard conditions, susceptible bacteria were Escherichia coil and Flavobacterim columnare, but there were no killing effect for Flavobacterim columnare. Intermediate bacteria were Yersinia ruckeri, Staphylococcus aureus, Streptococcus agalactiae and Mycobacterium tuberculosis, MICs were 2～32μug/mL, MBCs were 32～128μg/mL. Nonsusceptible bacteria were Pseudomonas fluorescent, Acinetobacter baumannii, Aeromonas spp. (including A. hydrophila, A. veronii, A. jandaei, A. caviae and A. sobria and A. punctata), Edwardsiell ictaluri and Vibrio fluvialis. Under anaerobic conditions, the antibacterial activity were enhanced by 8-256 times on Aeromonas spp. (exclude Aeromonas punctata), Vibrio fluvialis, Acinetobacter baumannii and Yersinia ruckeri. Susceptible bacteria were Aeromonas spp. (exclude A. punctata), Vibrio fluvialis, Yersinia ruckeri, Vibrio fluvialis and Streptococcus agalactiae, MICs were 0.5～8μg/mL, MBCs were 1～16μg/mL. Nonsusceptible bacteria were Pseudomonas fluorescent, Aeromonas punctata and Edwardsiell ictaluri.Antimicrobial susceptibility of cyadox against pathogenic bacteria isolated from others were as follows. Under standard conditions, susceptible bacteria were Salmonella typhimurium, MICs were 8μg/mL, MBCs were>128μg/mL. Intermediate bacteria are Yersinia enterocolitica and Proteus mirabilis, MICs and MBCs were 32μg/mL and 128μg/mL; Nonsusceptible bacteria is Pseudomonas pyocyanea. Under anaerobic conditions, the antibacterial activity were enhanced by 8 times on Proteus mirabilis. Susceptible bacteria is Salmonella typhimurium and Proteus mirabilis, MICs and MBCs were 4-8μg/mL and 32-64μg/mL, respectively. Intermediate bacteria were Yersinia enterocolitica, MIC and MBC were 16μg/mL and 64μg/mL, respectively; Nonsusceptible bacterium was Pseudomonas pyocyanea.2 Therapeutic effect of cyadox on swine dysenterySeventy crossbred piglets weighing～15kg were randomly divided into 7 treatments with ten replications (pens) each. Blank group, without artificial challenge nor administration. Negative control group, with artificial challenge, but not administration. Positive control groups, fed with olaquindox at 100 ppm and 200 ppm after the artificial challenge were successful. Experimental groups, fed with cyadox at 400 ppm,200 ppm and 100 ppm after the artificial challenge were successful. The average incubation period infection with B. hyodysenteriae is 7～13 days, when 7～9 piglets began to excrete with haemorrhagic diarrhoea, the treatment would begin as administration by fed, two times per day. Meanwhile, some those piglets did not eat any feed would be treated by oral medication, those with improved appetite or poor appetite still administration by fed. Stop administration when the groups had a 100% cure rate, and continued to observe two weeks. Evaluated the therapeutic effect with the clinical manifestation, cure rate, relapse rate, growth performance, blood biochemical indices and pathological examination.During administration, the appetite, mental status and fecal index of treatment group were gradually improved. Cyadox 400 ppm group had the shortest course of treatment, after 6 days of treatment the cure rate was 100%, and not relapse; Cyadox 200 ppm group had a good effect also, medication for 6 days also achieved more than 80% cure rate; Cyadox 100 ppm group had a long course of treatment for some dysentery repeat, and took two weeks to achieve more than 80% cure rate. Olaquindox 200 ppm group had an similar efficacy as cyadox 400 ppm group, better than cyadox 200 ppm group. Olaquindox 100 ppm group had a similar efficacy as cyadox 100 ppm group.Cyadox 400 ppm group had the highest Average Daily Gain (ADG) and Gain/Feed (G/F), the ADG and G/F were increased by 5.2% and 22.2% than blank group. Cyadox 200 ppm group was similar with blank group, while the ADG and G/F of olaquindox 200 ppm group were decreased to 25.4% and 30.6% of blank group. The ADG and G/F of cyadox 100 ppm group were decreased to 74.0% and 80.6% of blank group, olaquindox 100 ppm group were decreased to 55.6% and 58.3% of blank group. Negative growth was showed in negative group.The blood parameters and pathological examination indicated cyadox 400 ppm had a mild impact on water and salt metabolism and kidney, but there were no any clinical manifestations, and the growth performance had been significantly improved, so it could be considered no significant side effects. The 200 ppm olaquindox group suffered a moderate damage on kidney and adrenal and a mild negatively affected on water and salt metabolism and liver. The animals in this group would like drink ground water and urine of fellow, and had a decreased growth performance, so the side effects of 200 ppm olaquindox diet was obvious.In short, the therapeutic dose of cyadox recommended for swine dysentery is 200～400 ppm. We suggest taking 200～400 ppm cyadox for treatment by fed; 100 ppm dose for the prevention and metaphylaxis, or the process of consolidation after curing.In summary, this subject had referred the "Microbiological Data for Systemic Antibacterial Drug Products—Development, Analysis, and Presentation", "Developing Antimicrobial Drugs—General Considerations for Clinical Trials" formulated by Food and Drug Administration (FDA) and "Experimental Clinical Trial Technology Standard" issued by China Ministry of Agriculture, and established the antimicrobial spectra in a variety of animals, evaluate the phaseⅡclinical study of cyadox on the therapeutic effect on swine dysentery, and gave scientific guidance for the reasonable use of cyadox in livestock, poultry and aquatic animals. Cyadox will have a broad application prospect for it's good effect in animal production.