Influence of combined sulfachloropyridazine sodium and zinc on enzyme activities and biogas production during anaerobic digestion of swine manure.

In order to study the influence of different concentrations of zinc and sulfachloropyridazine sodium (SCPS) on anaerobic digestion (AD) during biogas production, we determined the levels of urease, dehydrogenase activity, and volatile fatty acids (VFAs) in batch tests. The experiments were conducted in small AD devices at a temperature of 37 °C using swine manure and wheat straw as raw materials. Four digestion trials were performed using different zinc and SCPS contents: control digestion with no additives (CK), SCPS at 630 mg kg-1 dry weight (S), SCPS at 630 mg kg-1 with zinc at 500 mg kg-1 dry weight (SL), and SCPS at 630 mg kg-1 with zinc at 5,000 mg kg-1 dry weight (SH). The biogas accumulation under S was 1.7 times that with CK, while SL and SH produced 78% and 35% of that under S, respectively. Correlation analysis showed that the accumulated biogas was significantly negatively correlated (p < 0.05) with VFAs, and the urease activity was significantly negatively correlated (p < 0.01) with zinc and significantly positively correlated with VFAs (p < 0.05). The dehydrogenase activity was strongly correlated (p < 0.01) with the biogas accumulated during the AD of swine manure.

Relationships between sulfachloropyridazine sodium, zinc, and sulfonamide resistance genes during the anaerobic digestion of swine manure.

In this study, swine manure containing sulfachloropyridazine sodium (SCPS) and zinc was subjected to mesophilic (37°C) anaerobic digestion (AD). The absolute abundances (AAs) of antibiotic resistance genes (ARGs) were evaluated, as well as intI1 and intI2, and the degradation of SCPS according to variation in the amount of bio-available zinc (bio-Zn). In digester that only contained SCPS, the concentrations of SCPS were lower than that digesters both contain SCPS and Zn. Compared with the control digester, the addition of SCPS increased the AAs of sul1, sul3, drfA1, and drfA7 by 1.3-13.1 times. However, compared with the digester with SCPS but no added Zn, the AAs of sul3, drfA1, and drfA7 were decreased by 21.4-70.3% in the presence of SCPS and Zn, whereas sul1 and sul2 increased 1.3-10.7 times. There were significant positive correlations (P<0.05) between the concentrations of SCPS with several ARGs and bio-Zn.

Effects of oxytetracycline and sulfachloropyridazine residues on the reductive activity of Shewanella decolorationis S12.

Effects of oxytetracycline (OTC) and sulfachloropyridazine (SCP), two of the widely used antibiotics in livestock production, on beneficial environmental microorganisms were studied. Shewanella decolorationis S12 was selected as the target bacteria for the role in reduction of Fe(III) and dye under anaerobic conditions. The results showed that the antibiotics significantly inhibited Fe(III) reduction and dye decoloration in the reduction system. The rates of Fe(II) formed (-r) were 3.6 and 0.2 mg/L/day for the OTC concentrations of 0-1 mg/L and 1-50 mg/L, respectively, with 1 mg/L as the turning point of the inhibition effect. The turning point of inhibition effect was much higher for SCP treatments, at 4 mg/L. The results also showed higher production values for adsorbed Fe(II) than soluble Fe(II) in OTC treatments, but the reverse occurred in the SCP treatments. The difference between the treatments could be due to higher sorption coefficients of OTC as compared to SCP. Transmission electron micrographs showed changes in cell structures of S. decolorationis S12 grown in medium with OTC. Detached cell walls and large vacuoles in internal cell contents were found in OTC-treated cells. The results of the present study indicated that the inhibition of antibiotic on the reduction activity of S. decolorationis S12 may be due to a decrease in live S. decolorationis S12 population and/or damages of their cell structure in this reduction system.

A rapid assay for dihydropteroate synthase activity suitable for identification of inhibitors.

The enzymes 6-hydroxymethylpterin pyrophosphokinase (HPPK) and dihydropteroate synthase (DHPS) catalyze sequential steps in folate biosynthesis. They are present in microorganisms but absent in mammals and therefore are especially suitable targets for antimicrobials. Sulfa drugs (sulfonamides and sulfones) currently are used as antimicrobials targeting DHPS, although resistance to these drugs is increasing. The most widely used assay that measures activity of these enzymes, to assess new inhibitors in vitro, is not amenable to automation. This article describes a simple, coupled, enzymatic spectrophotometric assay where the product of the DHPS reaction, dihydropteroate, is reduced to tetrahydropteroate by excess dihydrofolate reductase (DHFR) using the cofactor NADPH. The oxidation of NADPH is monitored at 340 nm. The activity of both HPPK and DHPS can be measured in this assay, and it has been used to measure kinetic parameters of wild-type and sulfa drug-resistant DHPS enzymes to demonstrate the utility of the assay. It is a sensitive and reproducible assay that can be readily automated and used in multiwell plates. This NADPH-coupled microplate photometric assay could be used for rapid screening of chemical libraries for novel inhibitors of folate biosynthesis as the first step in developing new antimicrobial drugs targeting the folate biosynthetic pathway.

Changes in antibacterial activity of triclosan and sulfa drugs due to photochemical transformations.

Sulfa drugs and triclosan represent two classes of antibacterials that have been found in natural waters and for which photodegradation is anticipated to be a significant loss process. Parent antibacterial compounds and the products of photolysis reactions were compared for three sulfa drugs and triclosan to determine the extent to which photolysis affects their antibacterial potency on Escherichia coli DH5alpha. Sulfathiazole (median effective concentration [EC50] = 20.0 microM), sulfamethoxazole (EC50 = 12.3 microM), and sulfachloropyridazine (EC50 = 6.9 microM) inhibited bacterial growth but did not affect respiratory activity. Photolysis products of these sulfa drugs did not retain any measurable ability to inhibit growth. Triclosan inhibited both the growth (EC50 = 0.24 microM) and respiratory activity of E. coli DH5alpha. Triclosan photolysis products also exhibited no measurable effect on growth or respiratory activity. These experiments indicate that the products of triclosan and sulfa drug photolysis are unlikely to possess antibacterial activity in natural waters. The rapid screening method used for these two classes of compounds will be useful for helping to identify photolabile antibacterial compounds, for which photoproducts could require further investigation.

Pollution-induced community tolerance of soil microbial communities caused by the antibiotic sulfachloropyridazine.

Little is known about the environmental hazards linked to the treatment of farm animals with antibiotics and subsequent spreading of manure, especially regarding soil microbial communities. In this investigation, pollution-induced community tolerance (PICT) of bacteria from soils artificially spiked with the sulfonamide sulfachloropyridazine (SCP) was investigated. Tolerance of the bacterial communities after 3 weeks' exposure to SCP was determined by analyzing the sensitivity of 31 microbial metabolic processes in microtiter plates. Bacterial suspensions extracted from soils containing higher concentrations of SCP showed an increased tolerance of their metabolic activities to this antibiotic. An increase in tolerance by 10% was found at 7.3 mg/kg dw SCP. The PICT effect could be demonstrated by both a shift in the tolerance of the average of all metabolic activities and a shift of the physiological process sensitivity distributions made up from the single metabolic processes. The PICT effect was accompanied by smaller changes in the community-level physiological profile (CLPP). To conclude, PICT has been shown to be a versatile and illustrative method for the detection of the effects of antibacterial agents on soil microorganisms.

Pharmacokinetics and therapeutic potential for repeated oral doses of trimethoprim/sulphachlorpyridazine in horses.

The pharmacokinetic parameters of a powder formulation of trimethoprim/sulphachlorpyridazine were studied in eight healthy horses which received 5 mg/kg trimethoprim and 25 mg/kg sulphachlorpyridazine 12-hourly with concentrate for five days. The intake of the medicated concentrate by the horses was variable during the first two days, but after they became accustomed to the taste the intake by all the horses during the last three days was good. Faecal samples taken before and on the last day of the drug administrations were negative when cultured for salmonella. Compared with the results of a previous single-dose experiment, higher plasma concentrations and a higher area under the curve for both the drugs were observed. The repeated doses provided plasma concentrations above the minimal inhibitory concentration for Streptococcus zooepidemicus, S equi, Actinobacillus equuli and Rhodococcus equi isolated from the respiratory tract of horses. Synergism between the two drugs occurred at different drug concentration ratios with different bacterial species.

In vitro antimicrobial susceptibility of Pasteurella haemolytica and Pasteurella multocida recovered from cattle with bovine respiratory disease complex.

The antimicrobial susceptibilities of 421 Pasteurella haemolytica and 158 P. multocida isolates recovered from cattle with respiratory disease were determined with a microdilution minimal inhibitory concentration test system. Isolates were analyzed for patterns of resistance to ampicillin, ceftiofur, erythromycin, gentamicin, penicillin, spectinomycin, sulfachlorpyridazine, sulfadimethoxine, tetracycline, and tylosin. All isolates tested were found susceptible to ceftiofur and sulfachlorpyridazine. Pasteurella haemolytica isolates were resistant to ampicillin, penicillin, sulfadimethoxine, tetracycline, and tylosin. Pasteurella multocida isolates were resistant to sulfadimethoxine, tetracycline, and tylosin.

Development of sulphonamide-trimethoprim combinations for urinary tract infections. Part I: Comparison of the antibacterial effect of sulphonamides alone and in combination with trimethoprim.

Plasma half life and in vitro activity were major criteria for selection of sulphonamides which are likely to give a strong synergistic action with trimethoprim in vivo. On the basis of literature data six sulphonamides, sulphadiazine, sulphachloropyridazine, sulphamethoxazole, sulphaisodimidine, sulphamerazine and sulphamethomidine appeared particularly suitable for combination with trimethoprim. An investigation of the activity in vitro of these compounds and their combinations with the latter against clinically isolated, sulphonamide-sensitive Klebsiella-Enterobacter and Escherichia coli strains showed optimal synergy at trimethoprim-sulphonamide ratios between 1:10 and 1:40, but that appreciable mutual potentiation occurred within a rather broad range of concentration ratios. Limited experiments indicated that synergy occurs less frequently and is less pronounced against sulphonamide resistant bacteria. The different sulphonamides behaved rather similarly in their combinations with trimethoprim, and in order to find the best sulphonamide, detailed comparisons of the pharmacokinetic properties of the different combinations are necessary.

Development of sulphonamide-trimethoprim combinations for urinary tract infections. Part 2: Comparative pharmacokinetics of five sulphonamides.

The pharmacokinetics and renal excretion of the sulphonamides sulphachloropyridazine, sulphadiazine, sulphaisodimidine, sulphamerazine, and sulphamethoxazole were investigated in a cross-over study with doses of 800 mg each. The serum half-life, urine levels, distribution volume, protein binding and potential antibacterial activity in the urine renders sulphadiazine the preferred component in a combination tablet together with trimethoprim for the treatment of urinary tract infections.

Characterization of enterotoxigenic bovine Escherichia coli.

Among 300 isolates of bovine Escherichia coli, 56 which had been found enterotoxigenic in calf gut loops were characterized on the basis of O and K antigens, colonial morphology and resistance to seven antimicrobial drugs. The 56 isolates enterotoxigenic in the calf were compared with the nonenterotoxigenic ones. Of the 56 enterotoxigenic E. coli the majority possessed the A type of K antigen and had OK groups, O9:K(PS274) or O101:K(RVC118). Fourteen of these isolates had the K99 antigen. None of 27 isolates found enterotoxigenic in the piglet but not in the calf possessed the K99 antigen or belonged to OK groups O9:K(PS274) or O101:K(RVC118). Comparison of the patterns of resistance to seven antimicrobial drugs showed that all enterotoxigenic and nonenterotoxigenic isolates were susceptible to nitrofurantoin and sulphachlorphyridiazine and that there was no significant difference in the patterns between the two groups. The majority of enterotoxigenic isolates were mucoid, whereas most of the nonenterotoxigenic isolates were nonmucoid.