Bacteriophages as antimicrobial agents against major pathogens in swine: a review

In recent years, the development of antibiotic resistant bacteria has become a global concern which has prompted research into the development of alternative disease control strategies for the swine industry. Bacteriophages (viruses that infect bacteria) offer the prospect of a sustainable alternative approach against bacterial pathogens with the flexibility of being applied therapeutically or for biological control purposes. This paper reviews the use of phages as an antimicrobial strategy for controlling critical pathogens including Salmonella and Escherichia coli with an emphasis on the application of phages for improving performance and nutrient digestibility in swine operations as well as in controlling zoonotic human diseases by reducing the bacterial load spread from pork products to humans through the meat.     

猪尿液中抗菌药物快速筛选拭子法的建立

为防止抗菌药物在动物性食品中的残留,以枯草芽孢杆菌为受试菌,建立一种检测活体动物尿液中抗菌药物残留的快速筛选拭子法,进行宰前活体检疫.添加试验测定猪尿液中5类抗菌药物最低检测限分别为:β-内酰胺类青霉素和氨苄青霉素均为0.05mg/L;氨基糖苷类庆大霉素0.05mg/L、新霉素0.4mg/L;四环素类金霉素0.1mg/L;大环内酯类红霉素0.05mg/L和氟喹诺酮类恩诺沙星0.2mg/L.各抗菌药物添加回收率范围均在64.0%～107.7%,变异系数均小于15%.假阴性结果显示,除青霉素(5%)和氨苄青霉素(4%)出现假阴性外,红霉素、庆大霉素、新霉素、恩诺沙星和金霉素均未出现假阴性.与国外同类试剂盒比较,结果显示两者对10种抗菌药物的检测限一致.     

Beta-agonists as repartitioning agents: a review

Several beta-adrenergic agonist compounds are undergoing commercial development as carcase repartitioning agents. Significant increases in feed conversion efficiency, carcase lean content and decreases in carcase fatness have been reported consistently in all the major meat animal species. The use of these compounds is consistent with consumer demand for leaner meat but could prove controversial in the current political climate in the EC.     

5种植物提取物对猪致病菌的体外抗菌研究

本试验旨在采用气相色谱-质谱联机法对5种植物提取物进行成分分析,并采用试管倍比稀释法研究其对猪大肠杆菌、猪金黄色葡萄球菌的体外抑菌效果。结果表明,5种植物提取物的共有成分和主要成分为洋芹脑、吉马烯D、β-石竹烯、胡椒酮、α-蒎烯、4-萜烯醇、天然维生素E,且其对猪两种致病菌均有较好的抑制作用,其中广西华山蒟提取物杀菌效果最好。结论是5种植物提取物对猪两种致病菌呈现较好地体外抑杀效果,可能是因为其含有洋芹脑、吉马烯D、β-石竹烯、胡椒酮等活性抗菌成分所致。     

Trichinosis in a herd of swine: cannibalism as a major mode of transmission

In a herd of approximately 1,000 hogs, evaluation of muscle specimens collected at various intervals during a 12-year period (1973 to 1985) indicated continuous transmission of Trichinella spiralis. The farm's rat population and the incidence of trichinosis in the rats was high during 1974, but diminished markedly by 1978. In January 1984, a longitudinal investigation, using tracer pigs, was performed to determine whether rodents and/or other wild animals were involved in transmission of T spiralis on this farm. Tracer pigs exposed to rodents and wild animals did not become infected with T spiralis. The rodent population on the farm was small and none of the rodents trapped and examined were found to be infected. Hog cannibalism also was evaluated as a mode of T spiralis transmission. Results of the investigation indicated that hog cannibalism was the mode of transmission for trichinosis in the herd.     

Udder pathogens and their resistance to antimicrobial agents in dairy cows in Estonia

Background

The goal of this study was to estimate the distribution of udder pathogens and their antibiotic resistance in Estonia during the years 2007-2009.

Methods

The bacteriological findings reported in this study originate from quarter milk samples collected from cows on Estonian dairy farms that had clinical or subclinical mastitis. The samples were submitted by local veterinarians to the Estonian Veterinary and Food Laboratory during 2007-2009. Milk samples were examined by conventional bacteriology. In vitro antimicrobial susceptibility testing was performed with the disc diffusion test. Logistic regression with a random herd effect to control for clustering was used for statistical analysis.

Results

During the study period, 3058 clinical mastitis samples from 190 farms and 5146 subclinical mastitis samples from 274 farms were investigated. Positive results were found in 57% of the samples (4680 out of 8204), and the proportion did not differ according to year (p > 0.05). The proportion of bacteriologically negative samples was 22.3% and that of mixed growth was 20.6%. Streptococcus uberis (Str. uberis) was the bacterium isolated most frequently (18.4%) from cases of clinical mastitis, followed by Escherichia coli (E. coli) (15.9%) and Streptococcus agalactiae (Str. agalactiae) (11.9%). The bacteria that caused subclinical mastitis were mainly Staphylococcus aureus (S. aureus) (20%) and coagulase-negative staphylococci (CNS) (15.4%). The probability of isolating S. aureus from milk samples was significantly higher on farms that had fewer than 30 cows, when compared with farms that had more than 100 cows (p < 0.005). A significantly higher risk of Str. agalactiae infection was found on farms with more than 600 cows (p = 0.034) compared with smaller farms. The proportion of S. aureus and CNS isolates that were resistant to penicillin was 61.4% and 38.5%, respectively. Among the E. coli isolates, ampicillin, streptomycin and tetracycline resistance were observed in 24.3%, 15.6% and 13.5%, respectively.

Conclusions

This study showed that the main pathogens associated with clinical mastitis were Str. uberis and E. coli. Subclinical mastitis was caused mainly by S. aureus and CNS. The number of S. aureus and Str. agalactiae isolates depended on herd size. Antimicrobial resistance was highly prevalent, especially penicillin resistance in S. aureus and CNS.     

In vitro antimicrobial activity of sulfonamides against some porcine pathogens

The minimal inhibitory concentrations (MIC) of sulfonamides were determined against Bordetella bronchiseptica (n = 10), Pasteurella multocida (n = 10), Haemophilus pleuropneumoniae (n = 20), and Streptococcus suis (n = 10) strains isolated from pigs with atrophic rhinitis, pneumonia, or meningitis. Sulfonamides tested in an agar dilution method were sulfachloropyridazine, sulfadiazine, sulfadimethoxine, sulfamethazine, sulfadoxine, sulfisoxazole, sulfamerazine, sulfamethoxazole, sulfamethoxypyridazine, sulfanilamide, sulfatroxazole, and sulfisomidine. Results indicated that monotherapy of S suis infections with sulfonamides should not be encouraged because the MIC50 of all sulfonamides investigated was greater than 32 micrograms/ml. The MIC50 of the sulfonamides against B bronchiseptica ranged from 0.5 to 8 micrograms/ml, against P multocida from 2 to 32 micrograms/ml, and against H pleuropneumoniae from 8 to 64 micrograms/ml. The MIC50 of sulfachloropyridazine, sulfadiazine, sulfadimethoxine, sulfamerazine, and sulfamethoxazole for the gram-negative bacteria did not exceed 16 micrograms/ml. Among these compounds, sulfamethoxazole had the highest activity. The frequently prescribed sulfamethazine had an overall low antimicrobial activity.     

In vitro activity of flumequine in comparison with several other antimicrobial agents against five pathogens isolated in calves in The Netherlands

The in vitro activity of flumequine in comparison with several other drugs was tested against 17 P. multocida, 16 P. haemolytica, 21 S. dublin, 21 S. typhimurium and 21 E. coli strains, isolated in (veal) calves in the Netherlands. The MIC50 of flumequine for the respective pasteurellas was 0.25 and 1 microgram/ml, for the salmonellas and E. coli 0.5 micrograms/ml. In comparison with flumequine, enrofloxacin and ciprofloxacin showed higher in vitro activity, with MIC50 less than or equal to 0.008 micrograms/ml for ciprofloxacin. Decreased susceptibility of the pasteurellas was found for kanamycin, neomycin, streptomycin, gentamicin, oxytetracycline and doxycycline. The MIC50 of minocycline for P. multocida was 0.5 micrograms/ml and there was no cross resistance with the other tetracyclines. P. multocida was very susceptible to ampicillin (MIC50 less than or equal to 0.03 micrograms/ml), P. haemolytica, however, was 100% resistant to this drug. Both pasteurellas were susceptible to cephalothin and approximately 50% of the strains of both bacteria were resistant to chloramphenicol. The MIC50 of either spiramycin or tylosin was greater than or equal to their respective breakpoint-MIC values. Both pasteurellas were susceptible to the combination of trimethoprim and sulphamethoxazole. However, for P. multocida, the addition of sulphamethoxazole to trimethoprim had no synergistic effect on its MIC. In comparison with trimethorpim, aditoprim was less potent. Therefore only P. multocida was susceptible to aditoprim.     

赖氨酸在猪营养中的研究进展

猪的赖氨酸需要量一直是研究热点之一,主要原因是：赖氨酸是以谷实类及其加工副产品为基础日粮的第一限制性氨基酸,其需要量是建立猪理想蛋白模型的基础。并且,机体本身不能合成赖氨酸且脱氨基后赖氨酸不能更新复原,也不能被任何一种类似的氨基酸所代替,只能从饲料中摄人。在饲料中添加赖氨酸可以提高饲料中粗蛋白的利用率,而且赖氨酸几乎全部用于合成机体蛋白质,不会产生具有生物学意义的次级代谢物。     

Clays as dietary supplements for swine:A review

Clays are crystalline,hydrated aluminosilicate molecules composed of alkali and alkaline earth cations along with small amounts of various other elements.The best-known are montmorillonite,smectite,illite,kaolinite,biotite and clinoptilolite.The molecules in these clays are arranged in three-dimensional structures creating internal voids and channels capable of trapping a wide variety of molecules.As a result of this structure,clay minerals are regarded as a simple and effective tool for the prevention of the negative effects of many toxic compounds.Dietary supplementation with clays has been shown to improve weight gain and feed conversion in pigs.Where improvements in performance have been noted,one of the most likely explanations for the improvement is the fact clays increase nutrient digestibility.Clays reduce the speed of passage of feed along the digestive tract which allows more time for digestion.Feeding clays also causes morphological changes in the intestinal mucosa such as an increase in villus height and an increase in the villus height to crypt depth ratio.These changes increase the surface area of the gastrointestinal tract thus increasing nutrient digestibility.Several studies have indicated that feeding clay reduces the incidence,severity and duration of diarrhea in pigs.The mechanism for the reduction in diarrhea is likely due to increases in the numbers of Bifidobacteria and Lactobacillus and decreases in Clostridia and E.coli in the small intestine of pigs fed clays.In addition,the numbers of pigs born alive and weaned,birth weight and weaning weight have been shown to be higher for sows fed clays.Several studies have indicated that clays can help mitigate the effects of mycotoxins.The aim of the present review is to focus on the various clays which have been given attention in recent research and to discuss their potential to improve pig performance.     

Clays as dietary supplements for swine: A review

Clays are crystalline, hydrated aluminosilicate molecules composed of alkali and alkaline earth cations along with small amounts of various other elements. The best-known are montmorillonite, smectite, illite, kaolinite, biotite and clinoptilolite. The molecules in these clays are arranged in three-dimensional structures creating internal voids and channels capable of trapping a wide variety of molecules. As a result of this structure, clay minerals are regarded as a simple and effective tool for the prevention of the negative effects of many toxic compounds. Dietary supplementation with clays has been shown to improve weight gain and feed conversion in pigs. Where improvements in performance have been noted, one of the most likely explanations for the improvement is the fact clays increase nutrient digestibility. Clays reduce the speed of passage of feed along the digestive tract which allows more time for digestion. Feeding clays also causes morphological changes in the intestinal mucosa such as an increase in villus height and an increase in the villus height to crypt depth ratio. These changes increase the surface area of the gastrointestinal tract thus increasing nutrient digestibility. Several studies have indicated that feeding clay reduces the incidence, severity and duration of diarrhea in pigs. The mechanism for the reduction in diarrhea is likely due to increases in the numbers of Bifidobacteria and Lactobacillus and decreases in Clostridia and E. coli in the small intestine of pigs fed clays. In addition, the numbers of pigs born alive and weaned, birth weight and weaning weight have been shown to be higher for sows fed clays. Several studies have indicated that clays can help mitigate the effects of mycotoxins. The aim of the present review is to focus on the various clays which have been given attention in recent research and to discuss their potential to improve pig performance.     

Alternatives to antibiotics as growth promoters for use in swine production:a review

In the past two decades, an intensive amount of research has been focused on the development of alternatives to antibiotics to maintain swine health and performance. The most widely researched alternatives include probiotics, prebiotics, acidiflers, plant extracts and neutraceuticals such as copper and zinc. Since these additives have been more than adequately covered in previous reviews, the focus of this review will be on less traditional alternatives. The potential of antimicrobial peptides, clay minerals, egg yolk antibodies, essential oils, eucalyptus oil-medium chain fatty acids, rare earth elements and recombinant enzymes are discussed. Based on a thorough review of the literature, it is evident that a long and growing list of compounds exist which have been tested for their ability to replace antibiotics as feed additives in diets fed to swine. Unfortunately, the vast majority of these compounds produce inconsistent results and rarely equal antibiotics in their effectiveness. Therefore, it would appear that research is still needed in this area and that the perfect alternative to antibiotics does not yet exist.     

2008～2009年西南地区规模化猪场病原菌耐药性流行情况调查

本实验室对西南地区47个规模化猪场的364份病料进行细菌分离,并采用形态、显微观察结合16S rDNA PCR扩增测序鉴定菌株;共检出细菌509株,细菌分离率达84.3%,混合感染率为37.4%;主要病原为大肠杆菌(30.4%)、葡萄球菌(21.6%)、肺炎克雷伯菌(8.7%)、变形杆菌(8.5%)、链球菌(5.9%)、肠球菌(11.4%)。小鼠试验结果显示平均致死率高达37.3%。191株致病菌株的药敏试验显示,β-内酰胺酶抑制剂药物(AMC,SAM,TIM)和头孢噻呋(EFT)耐药率较低(≤18.8%),其他药物的耐药率高(≥34.1),多重耐药严重,以5重、6重耐药为主。     

African swine fever and classical swine fever: a review of the pathogenesis

This paper describes major pathogenetic mechanisms of African and Classical Swine Fever virus infections. The interactions between both viruses and the monocyte-macrophage-system result in the release of mediator molecules, which are important for the further progression of the diseases. The causes of the thrombocytopenia and the mechanisms of the haemorrhages, which are characteristic in both infections, are described. Apoptotic cell death is regarded as the predominant cause of lymphopenia in both virus infections.     

In vitro efficacy of a buffered chelating solution as an antimicrobial potentiator for antifungal drugs against fungal pathogens obtained from horses with mycotic keratitis

OBJECTIVE: To determine whether a novel third-generation chelating agent (8 mM disodium EDTA dehydrate and 20 mM 2-amino-2-hydroxymethyl-1, 3-propanediol) would act as an antimicrobial potentiator to enhance in vitro activity of antifungal medications against fungal isolates obtained from horses with mycotic keratitis. SAMPLE POPULATION: Fungal isolates (3 Aspergillus isolates, 5 Fusarium isolates, 1 Penicillium isolate, 1 Cladosporium isolate, and 1 Curvularia isolate) obtained from horses with mycotic keratitis and 2 quality-control strains obtained from the American Type Culture Collection (ATCC; Candida albicans ATCC 90028 and Paecilomyces variotii ATCC 36257). PROCEDURE: Minimum inhibitory concentrations (MICs) against fungal isolates for 4 antifungal drugs (miconazole, ketoconazole, itraconazole, and natamycin) were compared with MICs against fungal isolates for the combinations of each of the 4 antifungal drugs and the chelating agent. The Clinical and Laboratory Standards Institute microdilution assay method was performed by use of reference-grade antifungal powders against the fungal isolates and quality-control strains of fungi. RESULTS: Values for the MIC at which the antifungal drugs decreased the growth of an organism by 50% (MIC50) and 90% (MIC90) were decreased for the control strains and ophthalmic fungal isolates by 50% to 100% when the drugs were used in combination with the chelating agent at a concentration of up to 540 microg/mL. CONCLUSIONS AND CLINICAL RELEVANCE: The chelating agent increased in vitro activity of antifungal drugs against common fungal pathogens isolated from eyes of horses with mycotic keratitis.     

The application of antimicrobial peptides as growth and health promoters for swine

With the widespread ban on the use of antibiotics in swine feed,alternative measures need to be sought to maintain swine health and performance.Antimicrobial peptides(AMPs) are part of the nonspecific defense system and are natural antibiotics produced by plants,insects,mammalians,and micro-organisms as well as by chemical synthesis.Due to their broad microbicidal activity against various fungi,bacteria and enveloped viruses,AMPs are a potential alternative to conventional antibiotics for use in swine production.This review focuses on the structure and mechanism of action of AMPs,as well as their effects on performance,immune function and intestinal health in pigs.The aim is to provide support for the application of AMPs as feed additives replacing antibiotics in swine nutrition.     

Transmission of swine pathogens: different means, different needs

There seems to be two main types of pathogens that cause diseases in swine: those that are mainly introduced through direct pig contacts, and those that are often, and in some situations mainly introduced by indirect transmission means. In this review, the mange mite (Sarcoptes scabiei), toxigenic Pasteurella multocida and Brachyspira hyodysenteriae will be used as examples of the first type, and foot and mouth disease virus, Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome (PRRS) virus as examples of the second. It is now clear from various epidemiological studies as well as experimental and field data that aerosol transmission of some swine pathogens plays an important role in their epidemiology. As previous biosecurity programs did not take this factor into consideration, it can at least partially explain why many of these programs suffered frequent failures and why air filtration is now becoming increasingly popular in North America. Identifying and quantifying transmission means should be a priority for every important infectious disease for which it has not been done.     

Evaluation of activity of selected ophthalmic antimicrobial agents in combination against common ocular microorganisms

OBJECTIVE: To determine in vitro efficacy of gentamicin, tobramycin, and miconazole when used in combination, with or without atropine, against Pseudomonas or Aspergillus sp. PROCEDURE: Selected ophthalmic agents were combined for predetermined times. Sterile disks impregnated with the combined solutions were prepared and placed on Mueller-Hinton plates that were seeded with Pseudomonas or Aspergillus sp. Zones of growth inhibition were measured at postincubation hours 24 and 48. RESULTS: Tobramycin alone inhibited growth of Pseudomonas sp, whereas miconazole inhibited growth of Aspergillus sp. Significant differences in zones of growth inhibition when atropine was combined with tobramycin, when gentamicin was combined with miconazole, or when atropine was combined with miconazole and gentamicin, were not detected. CLINICAL RELEVANCE: Combining selected ophthalmic therapeutic agents for as long as 6 hours does not appear to alter the in vitro efficacy of the agents against microorganisms used in this study.     

Bioelectrophoresis: a rapid procedure for the identification of antimicrobial agents

Sensitivity discs were placed on 1% Noble agar for electrophoresis in a 20 mM phosphate-buffered, pH 8.5-8.8 system. The discs were removed after electrophoresis, and the agar was overlaid with Bacillus subtilis spores in Mueller-Hinton agar. After incubation at 37 C, each individual antimicrobial agent produced a distinctive identifying pattern of B. subtilis growth inhibition. The few antimicrobial agents with similar patterns could be easily differentiated by the use of a strain of Escherichia coli containing a multiple-resistance factor. Filter discs impregnated with commercial antibiotic preparations in buffer or serum yielded growth-inhibition patterns which usually resembled those obtained from corresponding sensitivity discs.