The incidence of antibiotic resistance among coliform bacteria isolated from food.

Three-hundred-and-seventy-eight strains of coliform bacteria were isolated from specimens of commonly sold milk and food products. Klebsiella and Enterobacter spp. were predominating. Resistance to sulphonamides, streptomycin, and chloramphenicol occurred in only 5, 1, and 2 strains, respectively. No tetracycline-resistant strains were found. Two-hundred-and-two strains (54 %) were resistant to ampicillin. In genetic crosses with a sensitive strain of E. coli Κ 12 W 3132 transmissible R factors could not be demonstrated in any of the resistant coliform strains.It is concluded that food is not a significant source of antibiotic resistant enteric bacteria. It may, however, be suggested that food is a source of potentially pathogenic gram-negative bacteria which points out the importance of strict hygienic surveillance of food production.     

Antibiotic resistance in anaerobic and coliform bacteria from the intestinal tract of swine fed therapeutic and subtherapeutic concentrations of chlortetracycline

Chlortetracycline (CTC) resistance in anaerobic and coliform bacteria was examined in the large intestines of two groups of growing pigs that had received antibiotic-free diets since weaning. One group of pigs was from a low resistance herd (LR) that had not received antibiotics for 8 yr, while the other group of pigs was from a high resistance herd (HR) that routinely received antibiotics. After a 20-d adjustment period in a common production facility, LR pigs on an antibiotic-free diet had lower proportions of anaerobes (27%) and coliforms (22%) that were resistant to 25 micrograms CTC/ml than did similarly fed HR pigs (81 and 48%, respectively). Continued maintenance of LR and HR pigs on the antibiotic-free diet in a common production facility tended to increase resistance in anaerobes and coliforms from LR pigs to levels comparable with those in HR pigs at the end of an 85-d feeding trial, but not after 14 d. Administration of CTC in the feed at therapeutic (220 micrograms/g for 14 d) and growth-promoting (27.5 micrograms/g for 85 d) levels markedly increased percentages of resistant anaerobes and coliforms in LR pigs, but not in HR pigs after 14 d. Similar antibiotic effects were not seen at the end of the 85-d trial. These data demonstrate that, while exposure to antibiotics in feed may increase resistance in intestinal populations, other factors such as environment, cross-contamination and herd history can also influence the observed level of antibiotic resistance in swine.     

Reported antibiotic use in 90 swine farms in Alberta

Antibiotic use was described using a convenience sample of 90 Alberta swine farms representing approximately 25% of the Alberta market swine production. Data on the use of antibiotics were collected through an on-farm interview questionnaire. The vast majority of antibiotics were used in feed. The chlortetracycline/sulfamethazine/penicillin combination and tylosin were the most frequently used in-feed antibiotics in weaners and growers/finishers, respectively. The use of antibiotics through water was reported mostly occasionally in all categories. The use of injectable antibiotics was reported mostly in sick pigs. Penicillin was the most common in-water and injectable antibiotic in all categories. The apparent low frequency of critically important antimicrobials for use in humans (quinolones and 3rd generation cephalosporins) is an encouraging finding from a public health perspective. The widespread and frequently reported use of penicillin and tetracycline are of public health concern considering that both antimicrobials are also used for therapeutic purposes in human medicine.     

Differences in antibiotic resistance in Escherichia coli,isolated from East-European swine herds with or without prophylactic use of antibiotics

The aim of the study was to compare the resistance patterns of Escherichia coli isolates from pig herds with or without prophylactic use of anti-microbial substances. The presented pig units received either antibiotics or oregano as preventive feed additives. The trial was performed from April to October 2001, in the large 'country-corner', Hungary-Rumania-Serbia. Thirty of 39 evaluated herds suffered E. coli O139 K88 ac or ad LT STb caused losses, the remaining were negative for E. coli O139. Thirteen of the selected 30 herds produced with oregano feed supplementation (Oregpig Pecs, Hungary) antibiotic-free pigs. These units had no history of prophylactic antibiotic use since 1995. The remaining 17 herds routinely used prophylactic antibiotic feed supplementation. In each herd, pigs of four different age groups (suckling piglets, weaners. fattening swine and breeding sows), showing the clinical symptoms of wasting, were investigated. E. coli O139 K88 ac or ad LT STb were tested for their resistance to antibiotics, available in this region. Oregano-fed herds demonstrated high significantly (P < 0.001) lower MICs (microg/ml) for ampicillin, doxycyclin, enrofloxacin, gentamycin, oxytetracyclin and sulfamethacin compared to herds with prophylactic use of antibiotics. Resistance to ceftiofur revealed significant (P < 0.05) differences between the antibiotic- or oregano-treated units. The present results confirm literature data, that prophylactic use of antibiotics likely plays a role in inducing resistance of E. coli and other intestinal bacteria. Thus, imposing greater restrictions on antibiotic use in animal agriculture is likely to reduce but not eliminate the occurrence of resistant isolates.     

猪场环境中细菌分布情况及耐药性分析

从吉林省4家种猪场空气、粪便中分离到细菌296株,利用MALDI-TOF质谱对分离株进行鉴定,结果显示革兰氏阳性菌占细菌总数的76.7%,革兰氏阴性菌占23.3%。利用Vitek-32系统进行耐药性检测,结果显示凝固酶阴性葡萄球菌耐药情况严重,对青霉素类、四环素、红霉素等抗生素具有很高的耐药率。革兰氏阴性菌中94%的大肠埃希菌表现为多重耐药,其中29.4%为产ESBL菌株,仅有头霉素类、碳青霉烯类和部分复方制剂对其具有抑制作用。非发酵菌对氨苄西林、复方新诺明耐药率已达到35%以上。结果表明,吉林省某些猪场可能存在条件性病原菌及耐药菌株的污染和威胁,定期加强调查监测,对科学使用抗生素、防止耐药株的传播扩散具有重要的现实意义。     

猪源多重耐药大肠杆菌通过接合水平传播传递耐药性研究

为了检测多重耐药大肠埃希菌中可移动元件质粒在耐药性传播中的作用。采用质粒接合试验,筛选接合菌,并用K-B纸片测定接合前后细菌的耐药谱,并测定MIC值和MBC值,比较接合菌在接合前后耐药性变化。其结果70株供体菌中,一共接合成功31株,成功率达44.29%。通过药敏试验以及MIC值和MBC值的测定发现,接合后93.3%细菌的耐药谱型发生变化、76.7%接合菌最小抑菌浓度发生变化,56.7%接合菌的最小杀菌浓度发生变化。表明从菌株的耐药谱及对药物的抗性变化上可以初步判定,可移动元件质粒在传播细菌耐药性方面起到重要作用。     

细菌对抗生素耐药性的国内外研究现状

Fleming偶然的发现,20世纪最神奇的药物诞生于世,使细菌性疾病不再象往常那样殃及人类和畜禽的健康。然而,抗生素的产生与发展也符合自然界生物进化的规律,抗生素显威之时,耐药菌随之而生,呈迅猛增长,抗生素因之而逊色。抗生素的神圣使命不得不使人类、动物和植物的健康与生命安全带有严重的挑战。人类对它产生了怀疑,他们正在认真考虑自身安全,同时采取最有效地手段探索新物质,为自身服务,来解决细菌由于抗生素耐药性而对生物界造成的严重危害。     

抗生素的抗药性

饲用抗生素在饲料工业中得到了广泛的应用,但饲用抗生素的安全性一直存在争议。争议的焦点是抗药性的产生是否危及人类的健康。本文讨论了抗生素的定义、抗生素的应用、抗药性产生的理论、抗药性的危害性等问题。抗药性的产生虽然与饲用抗生素的使用有一定的关系,但归根到底是由于单细胞生物不断快速突变而产生的,人类自身对抗生素的使用也是一个不容忽视的问题。根据现有资料,仍不能对饲用抗生素是否危及人类健康作出明确回答。该文还对现在欧盟开始的禁止在饲料中添加抗生素以及“瑞典模式”作出了讨论。     

Effects of tylosin feeding on the antibiotic resistance of selected gram-positive bacteria in pigs

The effect of tylosin on macrolide resistance of gram-positive bacteria of pigs was determined. After an initial base-line period during which the pigs were given antibiotic-free feed, 1 group of 8 pigs was given tylosin feed (100 g/US ton of feed), and a 2nd group of 7 was given antibiotic-free feed. Samples were taken at 2- to 3-week intervals. For each pig, rectal, skin, and nasal swab samples were collected for enumeration of fecal streptococci and skin and nasal staphylococci. Percentages of macrolide resistant organisms of each group were tabulated on the basis of colony counts from antibiotic free and erythromycin-containing plates. After the introduction of tylosin into the feed of 1 group, a clear difference between the 2 groups with respect to the macrolide resistance of their gram-positive microflora was observed. The data indicate that tylosin feeding results in an increase in macrolide resistance of the bacterial flora of pigs.     

猪源大肠杆菌对20种抗生素的敏感试验

1935年第一个磺胺类药物-百浪多息的出现,开创了抗生素治疗的新纪元。抗生素的应用,对疾病的控制和预防发挥了巨大的作用,然而随着抗菌药物的广泛、持续和不当使用,细菌对抗菌药物的耐药性日趋普遍[1]。大肠杆菌是人和动物肠道的正常菌群成员之一,但某些血清型的大肠杆菌是病原菌,尤其对婴儿和幼畜(禽),常引起严重的腹泻和败血症。随着规模化养殖业的发展,病原性大肠杆菌对畜牧业所造成的损失已日益明显[2]。并且大肠杆菌血清型种类繁多,毒力因子组成各异,严重影响了临床大肠杆菌病的预防和控制。另一方面,随着细菌耐药性研究的不断深入,目…     

奶牛乳腺炎病原菌的分离鉴定及耐药性分析

2 0 0 2～ 2 0 0 3年采集上海地区 32个规模化奶牛场 433份奶样 ,共分离 2 54株细菌。其中包括金黄色葡萄球菌 48/2 54 (1 8 9% )、表皮葡萄球菌 34/2 54 (1 3 4% )、大肠杆菌 2 8/2 54 (1 1 0 % )、肺炎 /溶血巴氏杆菌 1 1 /2 54 (4 3 % )、无乳链球菌 2 5/2 54 (9 8% )、停乳链球菌 1 6/2 54(6 3 % )、乳房链球菌 1 5/2 54 (5 9% )及酵母菌 8/2 54 (5 9% )。表明葡萄球菌性乳腺炎仍占主导地位。药敏试验结果表明 ,分离菌株对临床常用的多种抗菌药物都产生了耐药性 ,耐药菌株的出现和抗生素的残留给乳腺炎的防治及食品安全带来了隐患     

猪附红细胞体病的研究进展

附红细胞体病是由附红细胞体感染机体引起的一种人畜共患的传染病，而附红细胞体则是寄生于红细胞表面、血浆及骨髓中的一类微生物。作者就猪附红细胞体的病原特点、流行病学、发病机理、临床症状、病理变化、诊断硬防治对策作一综述。     

The role of lysozyme in killing and lysis of coliform bacteria in the bovine animal 2. Effect of absorbing serum with bentonite or bacteria

Adding lysozyme in the presence of EDTA to bentonite-absorbed serum produced variable results in bacteriolytic tests either restoring lytic activity, potentiating existing activity or not affecting activity depending on the organism and serum used. Bactericidal activity, when removed by bentonite, was not restored by adding lysozyme. Absorbing sera with bacteria removed both bacteriolytic and bactericidal activity, the amount removed depending on the number of absorptions. Bacteriolytic, but not bactericidal, activity of sera absorbed with bacteria was restored by added lysozyme in the presence of EDTA. Serum absorbed with zymosar or antigen— antibody precipitates is inactive in bacterial killing.A requirement for added C′ in the bactericidal system can only be demonstrated in high dilutions of serum suggesting that C′ activity rather than antibody is the limiting factor.The experiments show that absorption techniques for removing lysozyme or antibody are non-specific and that lysozyme is involved in lysis but not in the killing of coliforms by bovine serum.