Schistosoma mansoni: long-term culture of in vitro derived schistosomula

In vitro derived schistosomula were cultured under various conditions. Variables tested included concentration of organisms, type of culture vessel, frequency of media change, time of erythrocyte addition, antibiotic levels, heated vs unheated serum in the media, and fresh vs stored serum or erythrocytes. No differences were observed between cultures changed every 3 or every 7 days, but worm growth and development were retarded when the culture medium was changed every 2 weeks. Organisms cultured without changing the medium for 3 weeks did not survive. High levels of antibiotics also inhibited growth and resulted in increased mortality. None of the other factors tested resulted in remarkable differences between groups. Some cultures lived for as long as 69 days, and pairing of adult worms was observed as early as 55 days. Most of the cultures, however, were lost before that time from the outgrowth of contaminants which were probably present in the cultures from the outset.     

Modified antibiotics-methylated ampicillin and ethylated ampicillin-inhibit growth of ampicillin-resistant strain of bacteria

Bacterial resistance to antibiotics is a significant problem in health facilities and results in higher costs for health care and increased fatalities due to infection. The work presented here suggests that antibiotic molecular structure can be altered in a selected manner, which will revive the bacterial growth inhibiting capability. A bacterial strain PKK3535(DH1), which is resistant to the antibiotic ampicillin, was found to be highly growth inhibited by these altered forms of ampicillin when tested in tissue culture. The level of growth inhibition of bacterial strain PKK3535(DHI) was greater than 50%, for both molecular variants of ampicillin that were investigated. The bacteria strain used for testing was a clinical isolate obtained from the University Hospital of the University of Nebraska, Omaha. These two antibiotic variants were methylated ampicillin and ethylated ampicillin. The synthetic procedure for generating these variants is presented as well as the molecular structure. The methylated and ethylated ampicillin were found to be stable at 0 degrees C for many weeks, were somewhat less soluble than normal ampicillin, but dissolved in LB plate media. The resistant bacteria strain was plated onto LB media with altered ampicillin and profound inhibition of bacteria growth was seen within the first 24 hours of incubation. These molecular variants of ampicillin provide evidence of a means to combat the proliferation of resistant bacterial strains. The molecular alteration of antibiotics may provide a suitable means to study and combat the appearance of antibiotic-resistant bacteria.     

Selection of antibiotic-resistant standard plate count bacteria during water treatment.

Standard plate count (SPC) bacteria were isolated from a drinking-water treatment facility and from the river supplying the facility. All isolates were identified and tested for their resistance to six antibiotics to determine if drug-resistant bacteria were selected for as a consequence of water treatment. Among the isolates surviving our test procedures, there was a significant selection (P less than 0.05) of gram-negative SPC organisms resistant to two or more of the test antibiotics. These bacteria were isolated from the flash mix tank, where chlorine, alum, and lime are added to the water. Streptomycin resistance in particular was more frequent in this population as compared with bacteria in the untreated river water (P less than 0.01). SPC bacteria from the clear well, which is a tank holding the finished drinking water at the treatment facility, were also more frequently antibiotic resistant than were the respective river water populations. When 15.8 and 18.2% of the river water bacteria were multiply antibiotic resistant, 57.1 and 43.5%, respectively, of the SPC bacteria in the clear well were multiply antibiotic resistant. Selection for bacteria exhibiting resistance to streptomycin was achieved by chlorinating river water in the laboratory. We concluded that the selective factors operating in the aquatic environment of a water treatment facility can act to increase the proportion of antibiotic-resistant members of the SPC bacterial population in treated drinking water.     

Experimental Microbial Populations Thirty-five Years Later: The Influence of Food on the Symbiosis of Paramecium aurelia Syngen 4, 51.7

Changes in the nutrition of Paramecium aurelia affect its ability to serve as host for the bacteroid parasite, kappa, and the presence or absence of kappa affects its ability to grow in axenic culture. Loss of kappa, tested by the presence or absence of killer reaction, occurred in cultures of P. aurelia growing at a reduced division rate on autoclaved Enterobacter aerogenes in suspensions of lettuce and yeast autolysate 14–17 days after they had been rendered bacteria-free by washing. Killer Paramecium sterilized of bacteria by treatment with an antibiotic mixture of penicillin-G and streptomycin in combination with a nonbacterial nonliving culture medium, lost the ability to kill after from 6 to 48 hours in the sterilizing medium. The ciliates from which kappa had been lost during exposure to antibiotics could be transferred immediately and maintained in axenic culture, but those washed free of bacteria could not be maintained axenically until kappa had been lost during cultivation in a medium containing killed bacteria. It is suggested that a knowledge of the nutritional requirements of symbiotic microorganisms is essential for understanding the ecological aspects of eutrophication of aquatic environments.     

Chloraminated drinking water does not generate bacterial resistance to antibiotics in Pseudomonas aeruginosa biofilms

Aim: To determine if exposure of Pseudomonas aeruginosa biofilms to chloraminated drinking water can lead to individual bacteria with resistance to antibiotics. Methods and Results: Biofilms of P. aeruginosa PA14 were grown in drinking water in a Kadouri drip‐fed reactor; the biofilms were treated with either 0·5 mg l^‐1 or 1·0 mg l^‐1 of chloramine for 15 or 21 days; control biofilms were grown in water without chloramine. Fewer isolates with antibiotic resistance were obtained from the chloramine‐treated biofilms as compared to the control. Minimum inhibitory concentrations (MIC) for selected antibiotic‐resistant isolates were determined using ciprofloxacin, tobramycin, gentamicin, rifampicin and chloramphenicol. All of the isolates tested had increased resistance over the wildtype to ciprofloxacin, rifampicin and chloramphenicol, but were not resistant to tobramycin or gentamicin. Conclusions: Under these test conditions, there was no detectable increase in antibiotic resistance in P. aeruginosa exposed as biofilms to disinfectant residues in chloraminated drinking water. Significance and Impact of the study: Chloramine in drinking water, while unable to kill biofilm bacteria, does not increase the potential of P. aeruginosa to become resistant to antibiotics.     

Participation of gram-negative anaerobes in infections in hospitalized patients

The aim of the study was to assess the prevalence and antibiotic susceptibility profiles of strictly anaerobic Gram-negative bacteria isolated from clinical samples taken from hospitalized patients from 01.01.2007 to 31.12.2008. The specimens were cultured using media, incubated at 37 degrees C under anaerobic conditions. Biochemical identification and antibiotic susceptibility were done in an automated system ATB Expression (bioMerieux S.A, France). For selected strains of Bacteroides sp. sensitivity was determined using E-test (AB BIODISK, Sweden). Overall 1274 strains of obligate anaerobes were isolated. Gram-negative bacteria were cultured in number of 333 strains. Most frequently isolated was Bacteroides sp. (46,9%) and Prevotella sp. (29,7%). Isolated bacteria are still susceptible to imipenem (100%), metronidazole (100%) and beta-lactam antibiotics with beta-lactamase inhibitors: amoxicillin/clavulanate (97,8%) piperacillin/tazobactam (99,1%), ticarcillin/clavulanate (99,1%).     

Antibiotic Production by Anaerobic Bacteria

Soils from aerobic and anaerobic sources were investigated for the possible presence of bacteria which produce antibiotics under anaerobic conditions of growth. The screening techniques devised for this study yielded 157 soil bacteria which, during anaerobic growth, produced antibiotic activity against aerobic test bacteria.

Studies on choice of media, presence of oxygen, and changes in antibiotic activity during growth indicated that representative strains of these bacteria produced mixtures of antibiotics. The activity was heat labile.

     

老年患者血培养病原菌分布及耐药性调查

目的了解老年患者血液感染的病原菌种类以及对抗菌药物的耐药状况。方法对2290份老年住院患者血培养标本中186例培养阳性检出菌及药敏结果进行统计学分析。结果在分离的172株细菌中,革兰阴性菌、革兰阳性菌及真菌分别占54.7%、34.9%和10.5%;革兰阴性菌中以大肠埃希菌占绝对优势(20.9%),假单胞菌其次(10.5%),革兰阳性菌中以凝固酶阴性葡萄球菌(CNS)占绝对优势(20.9%),金黄色葡萄球菌仅为2.9%。药敏试验表明老年菌血症的病原菌对常用抗菌药物的耐药严重,尤其是CNS及假单胞菌属细菌表现为较高的耐药率及多重耐药性。结论老年菌血症病原菌以机会致病菌感染比例较高,致病菌耐药问题严重,及时监测老年致病菌的变迁和耐药发展趋势以指导临床用药至关重要。     

Induction of trap formation in nematode-trapping fungi by a bacterium

Three soil bacterial strains were identified as Chryseobacterium sp. TFB on the basis of their 16S rRNA gene sequences. Conidia of Arthrobotrys oligospora produced a few mycelial traps (MT) and conidial traps (CT) when cultured with bacterial cells that they did not produce when cultured with a bacterial cell-free culture filtrate. However, co-culture of A. oligospora with bacterial cells and bacteria-free filtrate simultaneously induced MT and CT in large amounts. With the increased concentration of bacteria-free filtrate, the number of typical CT increased, but conidial germination was progressively inhibited. Scanning electron microscopy of A. oligospora co-cultured with bacteria revealed that bacterial attachment to hyphae was a prerequisite to trap formation and that bacteria-free filtrate facilitated bacterial attachments to hyphae. The results that the addition of nutrients in co-culture medium decreased the number of traps suggest that this type of trap formation may be favoured at a low nutrient status. Eight fungi tested were able to form MT and CT when co-cultured with bacterial cells and bacteria-free culture filtrate, but the abilities varied among species. This study provides novel evidence that under laboratory conditions, soil bacteria attaching to hyphae could induce traps in nematode-trapping fungi.     

Kinetics of interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and beta-lactam antibiotics. A choice of models.

The simplest model for the interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and beta-lactam antibiotics involves the three following steps: (a) the formation of a reversible equimolar enzyme - antibiotic complex; (b) the irreversible transformation of this complex into a modified enzyme - antibiotic complex; and (c) the breakdown of this latter complex and the concomitant release of a regenerated enzyme and a modified antibiotic molecule. The dissociation constant for step 1 and the rate constants for steps 2 and 3 were measured with various beta-lactam antibiotics. With antibiotic such as benzylpenicillin, which behaves as a good 'substrate', steps 1 and 2 occur at enzymic velocities, whereas step 3 occurs at a very low velocity and hence is responsible for the low efficiency of the overall process.     

Axenic culture of Gyrodinium impudicum strain KG03, a marine red-tide microalga that produces exopolysaccharide

An exopolysaccharide-producing microalgal dinoflagellate was isolated from a red-tide bloom and designated strain KG03. A bacteria-free culture of strain KG03 was achieved using a modified wash with phototaxis and antibiotic treatment. Combined treatment with neomycin and cephalosporin was the most effective for eliminating the bacteria associated with the microalgae. Strain KG03 was identified as Gyrodinium impudicum by analyzing the ITS regions of the 5.8S rDNA, 18S rDNA, morphological phenotype and fatty acid composition. The exopolysaccharide production and cell growth in a 300-ml photobioreactor were increased 2.7- and 2.4-fold, respectively, compared with that in a flask culture at the first isolation step.     

呼吸道感染常见致病菌耐药趋势分析

目的：调查我院临床常见的G-致病菌在院内呼吸道感染病人的分布,并检测常用抗生素的种类对致病菌的效价情况,为呼吸道感染病人合理选用抗生素提供依据。方法：对来源于院内呼吸道感染病人的样本300个进行分离培养,用microscan au-toscan4（美国德灵半自动细菌分析仪）菌种鉴定及抗生素的药敏实验,回顾性分析肺部感染患者的痰细菌培养及药物敏感性测定结果。结果：从样本中分离获得825株主要致病菌,其中G＋致病菌389株,占47.2%,G-致病菌380株,占46.1%,真菌46株,占6.7%。G＋致病菌对检测10种抗生素的药敏性主要表现为传统的抗生素的疗效普遍偏低;而G-致病菌对检测的抗生素10种的药敏性情况表现出多元化态势。结论：院内呼吸道感染常见致病菌以革兰阴性菌为主,耐药性高,临床实践应重视病原学的监测,了解细菌的种类分布和耐药趋势,合理使用抗生素。     

Antibiotic Susceptibility Testing of Anaerobes: Comparison of Three Methods, Including an Automated Micro-method, and Evaluation of the Effect of Different Media

Disc-diffusion, agar-dilution and microdilution methods were compared for testing the antibiotic sensitivity of anaerobic bacteria. Eight antibiotics and 31 test organisms were used. There was a poor correlation between MIC values obtained by the agar-dilution and microdilution procedures. The test organisms showed an apparently increased sensitivity to the antibiotics when tested by the agar-dilution, as compared with the microdilution, procedures. Columbia Blood Agar and Thioglycollate Haemin agar, were evaluated for the disc-diffusion and agardilution procedures. There was a poor correlation between the MIC values and inhibition zone diameters for the two media, with lower MIC values and larger zones on Thioglycollate Haemin agar.     

复方避孕药物(EP-1) 对雄性大仓鼠繁殖器官的影响

鉴于传统化学灭杀方法存在的不足和缺陷,各国都在致力于研究无公害、可持续的鼠害防治技术与策略,其中不育控制是当前研究的一个热点：近年来我国在鼠类不育控制方面也开展了一些研究（张知彬等,1997a,1997b,2001;Shi et a1．．2002;Li et a1．,2006）。     

Residual Antibiotics in Decontaminated Human Cardiovascular Tissues Intended for Transplantation and Risk of Falsely Negative Microbiological Analyses

We investigated the presence of antibiotics in cryopreserved cardiovascular tissues and cryopreservation media, after tissue decontamination with antibiotic cocktails, and the impact of antibiotic residues on standard tissue bank microbiological analyses. Sixteen cardiovascular tissues were decontaminated with bank-prepared cocktails and cryopreserved by two different tissue banks according to their standard operating procedures. Before and after decontamination, samples underwent microbiological analysis by standard tissue bank methods. Cryopreserved samples were tested again with and without the removal of antibiotic residues using a RESEP tube, after thawing. Presence of antibiotics in tissue homogenates and processing liquids was determined by a modified agar diffusion test. All cryopreserved tissue homogenates and cryopreservation media induced important inhibition zones on both Staphylococcus aureus- and Pseudomonas aeruginosa-seeded plates, immediately after thawing and at the end of the sterility test. The RESEP tube treatment markedly reduced or totally eliminated the antimicrobial activity of tested tissues and media. Based on standard tissue bank analysis, 50% of tissues were found positive for bacteria and/or fungi, before decontamination and 2 out of 16 tested samples (13%) still contained microorganisms after decontamination. After thawing, none of the 16 cryopreserved samples resulted positive with direct inoculum method. When the same samples were tested after removal of antibiotic residues, 8 out of 16 (50%) were contaminated. Antibiotic residues present in tissue allografts and processing liquids after decontamination may mask microbial contamination during microbiological analysis performed with standard tissue bank methods, thus resulting in false negatives.     

AN IMPROVED METHOD FOR OBTAINING AXENIC CLONES OF PLANKTONIC BLUE-GREEN ALGAE1,2

Axenic clones from 5 isolates of Anabaena flosaquae, 1 isolate of Microcystis acruginosa, and 1 isolate of Aphanizomenon flos-aquae were obtained by a combination of steps that provided a 1000-fold reduction in the bacteria-algae ratio and permitted bacteria-free filaments or cells to be isolated and grown from agar pour plates. The first step consisted of the addition of phenol to a dark-treated culture to selectively reduce the numbers of actively growing bacteria while leaving the resting algal cells viable. The next steps involved washing the treated algal suspension on a Millipore filter pad or membrane followed by plating in washed agar containing buffered mineral medium plus vitamins and soil extract. The final steps consisted of incubating the agar pour plates, coring bacteria-free filaments or cells, culturing the agar cores in a buffered mineral medium, and rigorously testing the resulting cultures for bacteriological contamination. Between 50 and 90% of the cores grew, and of these about 50% were judged axenic. The method, with appropriate adaptations, should be suitable for obtaining axenic clones of other freshwater and marine algae.     

Development of a novel technique for axenic isolation and culture of thraustochytrids from New Zealand marine environments

Aims: To maintain axenic cultures of commercially important thraustochytrids, a novel procedure was developed for the isolation of zoospores and sporangium from heterotrophic seawater samples and axenic culture on solid media. Methods and Results: Thraustochytrid cultures were isolated from Whangapoua Harbour in North East New Zealand and subjected to two antibiotic and antifungal treatment regimes designed to eliminate bacteria and fungi. Antibiotic trial 1 was designed to determine the appropriate combination of antibiotics (including streptomycin/penicillin, ampicillin, rifampicin, nalidixic acid, tetracycline, gentamicin and the antifungal agent nystatin). Antibiotic trial 2 determined the optimal dosing frequency and concentration of the antibiotics, and antifungal found to be the most promising in trial 1. Axenic cultures were then spread plated onto nutrient agar containing the optimal antibiotic cocktail, and pure thraustochytrid colonies were purified on solid media using standard microbiological techniques. Conclusions: Removal of bacteria and fungi was best accomplished using a mixture of three antibiotics and one antifungal; rifampicin (300 mg l^?1), streptomycin/penicillin (25 mg l^?1) and nystatin (10 mg l^?1) were incorporated in seawater samples and incorporated into cultures every 24 h for a minimum of 2 days. Significance and Impact of the Study: The axenic isolation and culture of marine thraustochytrids from a marine habitat in New Zealand have significant implications for the biotechnological development of these potentially valuable protists. This method has global significance as it is reasonable to assume it could be used throughout the world to obtain axenic thraustochytrid cultures.     

Elimination of Pasteurella pneumotropica from a contaminated mouse colony by oral administration of Enrofloxacin.

Enrofloxacin, a fluoroquinolone bactericidal antibiotic, was administered in an attempt to eradicate Pasteurella pneumotropica (P. pneumotropica) from a contaminated mouse colony. Contaminated mice, maintained within 4 animal rooms, were administered Enrofloxacin in drinking water at a daily dosage of 25.5 mg/kg for 2 weeks. Following one week of Enrofloxacin treatment, mice were selected randomly from each room and examined for P. pneumotropica. This procedure was repeated two or three times until all mice examined tested negative for the Pasteurella strain. With the exception of one room, treated mice consistently tested negative for P. pneumotropica for up to 45 weeks following completion of Enrofloxacin treatment. Thus, oral administration of Enrofloxacin significantly eliminated P. pneumotropica from a contaminated mouse colony.     

Selective decontamination of the digestive tract of Syrian hamsters.

Conventional Syrian hamsters colonized with aerobic gram-negative bacteria such as Pasteurella pneumotropica and various Enterobacteriaceae species were successfully and permanently freed from these microorganisms by oral treatment for 4 weeks with dihydrostreptomycin and 'Orabase' premixed with appropriate antibiotics. Concomitant oral treatment with dimetridazol for the elimination of intestinal flagellates was unsuccessful. During treatment the animals were maintained under germ-free isolation conditions.