Drug resistance of bacteria isolated from the intestine of yellowtail cultured with feeds containing various drugs

ABSTRACT: In order to ascertain whether the use of drugs as feed additive for fish may cause drug resistance of bacteria in the intestinal tract, viable counts and bacterial flora in the intestine of yellowtail cultivated with the feeds in the presence or absence of various drugs, drug resistance of the flora were determined. Viable counts in the intestine were lowered remarkably by the administration of each drug, suggesting that bacterial growth in the intestinal tract was inhibited by various drugs. Bacterial flora in the intestine consisted mainly of coryneform bacteria, Staphylococcus and Bacillus regardless of whether drugs were administered or not. In these floras, significant differences could not be observed for their resistance to respective drugs among the isolates from fish cultivated with feeds containing or not containing each drug. In addition, these floras mainly showed resistance to various combinations comprising from one to seven drugs; moreover, the majority of resistant strains were multidrug-resistant.     

The influence of anti-inflammatory therapy on bacterial clearance following intramammary Escherichia coli challenge in goats

Coliform mastitis in dairy cattle frequently results in systemic disease with occasional deaths in association with endotoxic shock. Systemic anti-inflammatory therapy has been used to alter the course of endotoxic shock in severe cases. Use of anti-inflammatory therapy has been questioned on the basis that such treatment may compromise immune function and decrease clearance of bacteria from infected mammary glands. The purpose of this investigation was to determine whether anti-inflammatory therapy influenced bacterial clearance following intramammary challenge of lactating goats with Escherichia coli.Standardized quantities of a pathogenic coliform culture were infused through the teat canal into one half of the mammary gland in 18 goat does. The does were then randomly assigned to receive one of three intravenous treatments: saline (controls), one dose of steroid (dexamethasone), or two doses of a non-steroidal anti-inflammatory agent (flunixin meglumine). The clinical signs, milk production, complete blood counts, serum clinical chemistry values, milk bacterial cultures and milk somatic cell concentrations were monitored sequentially.Goats treated with anti-inflammatory agents exhibited some improvement in clinical response to challenge with E. coli (e.g. rectal temperature, degree of appetite suppression) as compared to saline controls. There were no significant differences between treatments in the degree of inflammation present in the mammary glands or supramammary lymph nodes examined at necropsy. The most important finding was that anti-inflammatory therapy did not adversely influence the clearance of E. coli from challenged glands.     

Incidence of drug resistance and transmissible R factors in strains of E. coli isolated from faeces of healthy pigs

Two hundred and twenty-six strains of E. coli were isolated from faeces of 107 pigs at different ages and without clinical signs of infectious diseases. The resistance of the strains to sulphonamide, tetracycline, streptomycin, chloramphenicol, ampicillin, and nalidixic acid was determined. In 74 % of the animals the predominant E. coli flora was found to be resistant to one or more of the drugs mentioned. Fifty-three % of the strains were resistant. Multiple resistance was predominant among resistant strains (67 %). R factors transmissible to a sensitive strain of E. coli K12 W3132 were demonstrated in 28 %. The proportion of resistant strains was largest in young animals (0–14 weeks) accounting for 65 % of the strains isolated, as compared to 43 % of strains from pigs and sows (6 months or more). The incidence of resistance to sulphonamide, tetracycline, and streptomycin was high, whereas most of the strains were sensitive to ampicillin and chloramphenicol. All strains were sensitive to nalidixic acid.The incidence of resistance to antibiotics in a population of pigs to whom these drugs are not fed but applied as therapeutic agents solely seems rather high. When based on clinical findings only, the value is therefore questionable of sulphonamide, tetracycline and streptomycin treatment of infectious diseases caused by E. coli.     

Observations on production of hemolysin, heat-labile enterotoxin and antimicrobial drug resistance among enterotoxigenic Escherichia coli from pigs.

A total of 52 isolates of Escherichia coli belonging to enterotoxigenic serotypes from piglets with diarrhea were examined for hemolysis, production of cholera-like enterotoxin (LT) and susceptibility to 10 antimicrobial drugs. A strong association between production of LT and hemolysis was seen. Ninety percent of 29 hemolylic isolates were LT⁺ whereas 100% of 23 nonhemolytic isolates were LT⁻ in a commercial latex agglutination assay. Antimicrobial susceptibility tests employing disc diffusion showed that resistance to trimethoprim-sulfamethoxazole (TMS), neomycin and tetracycline was significantly less among LT⁺ isolates compared to LT⁻ ones. Enrofloxacin was the only antimicrobial drug to which all the 52 isolates were susceptible.     

蛤蚧口腔疾病病原研究(第二报)——预防及治疗试验

对蛤蚧口腔溃疡病主要病原——铜绿色假单孢菌进行药物预防及治疗对比试验。试验结果表明:15种药物敏感试验中,对磺胺、青霉素和卡那霉素等3种药物最为敏感,并将之配成软膏,作治疗对比试验。结果磺胺治愈率最为理想。重复治疗试验、田间扩大治疗试验,试验结果与实验室治疗试验结果差异不大。另外选用高锰酸钾溶液作为蛤蚧口腔、体表及房舍用具的消毒剂,对预防蛤蚧口腔溃疡病有较好效果。     

体外培养对布氏锥虫伊氏亚种药敏性的影响

用小鼠治疗试验和体外药敏试验观察了4个布氏锥虫伊氏亚种虫株在长期体外培养条件下药敏性的稳定性.各虫株的原始群体、连续培养30d和90d的群体对贝尼尔、苏拉灭、安锥赛和硫胂聚氰胺的敏感性基本相同,说明连续培养90d各虫株对上述4种抗锥虫药的敏感性无明显改变.     

沙拉沙星等几种抗菌药物的体外抗菌作用及诱导耐药性的对比试验

本文研究了沙拉沙星的体外抗菌作用及诱导耐药性。结果表明:沙拉沙星抗菌谱广,尤其是对革兰氏阴性菌抗菌活性强,其最小抑菌浓度(MIC)大都小于或等于1.25μg/ml,明显优于环丙沙星、头孢氨苄和新霉素,对猪链球菌的抗菌作用较弱,其MIC为1.6μg/ml;沙拉沙星对鸡大肠杆菌O78、猪大肠杆菌O138、鸡白痢沙门氏菌C79-13、禽多杀性巴氏杆菌C48-1均可产生明显的抗菌后效应。细菌对沙拉沙星单步自发耐药频率低,虽然通过诱导试验可培育出耐药菌株,但对革兰氏阴性菌的抗菌作用明显优于几种对照药物。     

Novobiocin Inhibits Both UDP-Glucuronosyltransferase and Cytochrome P450-Mediated Enzyme Activities in Pig Liver Microsomes

The effects of novobiocin (range 0.0125–2 mmol/L) on the hydroxylation of testosterone, the N-demethylation of erythromycin, and the glucuronidation of -naphthol and paracetamol were studied using pig hepatic microsomes, pooled from five animals. The final concentrations of these substrates in the incubation mixtures were selected to meet V_max conditions. Novobiocin caused a concentration-dependent inhibition of the glucuronidation of paracetamol; the formation of -naphthol-glucuronide was reduced to a lesser degree. These results confirm and extend earlier findings in laboratory animal species that novobiocin inhibits UDP-glucuronosyltransferases (UDPGTs). Moreover, novobiocin strongly inhibited 6-hydroxylation of testosterone. The microsomal N-demethylation of erythromycin and hydroxylation of testosterone at the 15 position were less affected by novobiocin. These results suggest that novobiocin inhibits not only UDPGTs, but also cytochrome P450 (CYP) enzyme activities, probably those belonging to the CYP3A subfamily. More research is needed to reveal which CYPs and UDPGTs are affected by novobiocin in vivo, in order to improve the understanding and probably the predictability of potential drug interactions with this antibiotic.     

Comparative effects of abamectin and two formulations of ivermectin on the survival of larvae of a dung-breeding fly

Objectives To compare the survival of larvae of a dung-breeding fly in the faeces of cattle treated either with an injectable formulation of abamectin, or with oral or injectable formulations of ivermectin.
Design Replicated bioassays were conducted on larvae of the bush fly, Musca vetustissima, using faeces collected before and at intervals after drug treatment.
Animals Two cows and their calves were allocated to each of three drug treatments and dosed according to individual weights.
Procedures Differences in the proportions of larvae pupariating were used as measures of the toxicity of drug residues.
Results Development of fly larvae was inhibited in all faeces collected 1 to 4 days after treatment. In cattle treated with oral ivermectin, there was reduced larval survival in faeces collected 8 and 16 days after treatment, but by day 32, survival was equivalent to that recorded in the faeces of untreated cattle. With injectable ivermectin, there was no survival at day 8, limited survival at day 16 and, at day 32, survival was not significantly affected. With injectable abamectin, survival was completely suppressed until day 32, at which time the number of pupariating larvae did not differ significantly from that recorded in faeces from untreated animals.
Conclusion The oral formulation of ivermectin is eliminated more rapidly than the injectable formulation and, as a consequence, is likely to be less harmful to dung-feeding insects. Abamectin and ivermectin appear to equally toxic larvae of M vetustissima.     

Ocular parameters related to drug delivery in the canine and equine eye: aqueous and vitreous humor volume and scleral surface area and thickness

OBJECTIVE: To measure the ocular surface area, scleral thickness, and the aqueous and vitreous humor volumes in the canine and equine eye. Animals studied Fourteen canine and 16 equine cadaver eyes. PROCEDURE: Eyes were measured either fresh or following fixation in formalin. Ocular surface area was calculated using the fluid displacement method. Globes were hemisected and aqueous and vitreous humor were collected and quantitated. Scleral thickness was measured by digital caliper, by image projection, and by ultrasonic biomicroscopy (UBM). RESULTS: Mean +/- standard deviation (SD) scleral surface areas in canine and equine eyes were 12.87 +/- 2.24 and 57.23 +/- 5.63 cm2, respectively. Mean +/- SD aqueous humor volume was 0.77 +/- 0.24 in the dog and 3.04 +/- 1.27 mL in the horse. Mean vitreous humor volume was 1.7 +/- 0.86 mL for the canine eye and 26.15 +/- 4.87 mL for the equine eye. In canine and equine eyes, the sclera was thinnest at the ocular equator: 0.34 +/- 0.13 mm (canine) and 0.53 +/- 0.1 (equine). There were no significant differences between the direct caliper and projected thickness measurements or differences between measurements in the superior, inferior, nasal, and temporal quadrants of the eye. Scleral thickness in fresh tissue was greater than in fixed tissue at most sites. CONCLUSIONS: The UBM measurement method appeared to be most consistent and reproducible when compared to direct measurement techniques. Formalin fixation of the eyes was associated with significantly thinner scleral tissue than with fresh ocular tissue.