Comparison of media for recovery of total coliform bacteria from chemically treated water

Five broth media and two solid media were compared for their ability to quantitatively recover total coliform bacteria from chemically treated water. M-Endo LES and mT7 media were used in the membrane filter technique. Lauryl tryptose broth, lactose broth, presence-absence broth, lactose broth with twice the amount of lactose, and lauryl tryptose broth with twice the amount of sodium lauryl sulfate were used in the fermentation tube procedure. The differences in recovery were not significant for the five broth media and M-Endo LES agar. The M-Endo LES and mT7 media were not significantly different; however, the five broth media did yield significantly higher counts than mT7.     

Comparison of media for recovery of total coliform bacteria from chemically treated water.

Five broth media and two solid media were compared for their ability to quantitatively recover total coliform bacteria from chemically treated water. M-Endo LES and mT7 media were used in the membrane filter technique. Lauryl tryptose broth, lactose broth, presence-absence broth, lactose broth with twice the amount of lactose, and lauryl tryptose broth with twice the amount of sodium lauryl sulfate were used in the fermentation tube procedure. The differences in recovery were not significant for the five broth media and M-Endo LES agar. The M-Endo LES and mT7 media were not significantly different; however, the five broth media did yield significantly higher counts than mT7.     

Impact of verification media and resuscitation on accuracy of the membrane filter total coliform enumeration technique.

Verification of membrane filter total coliform colonies was compared in lauryl tryptose broth, and m-LAC broth primary media and brilliant green-lactose-bile broth and EC broth secondary media. Verification in m-LAC broth yielded the greatest number of aerogenic isolates for both untreated surface water and drinking water samples. Verification in brilliant green-lactose-bile broth increased the number of false-negative reactions. At least 90% of the isolates aerogenic in primary verification media and anaerogenic in brilliant green-lactose-bile broth were representative of the coliform genera. The addition of a resuscitation step in the membrane filter technique did not yield greater numbers of verified coliforms per sample. Verification of both typical and atypical colonies in m-LAC broth resulted in a 10-fold increase in coliform numbers from untreated surface water. With drinking water, verification of both colony types resulted in an increase from less than 1 coliform per 100 ml to greater than 1/100 ml. A single-step verification in m-LAC broth is proposed as a more rapid and sensitive coliform verification procedure than the standard technique.     

Production of Shiga toxin by Shiga toxin-expressing Escherichia coli (STEC) in broth media: from divergence to definition

AIMS: To determine the suitability of eight different commercial broth media for Shiga toxin (Stx) production. METHODS AND RESULTS: Shiga toxin-producing Escherichia coli (STEC) strains producing Stx1 or Stx2 were grown at 37 degrees C (250 rev min(-1)) for 24 h in brain heart infusion broth, E. coli broth, Evans medium, Luria-Bertani broth, Penassay broth, buffered-peptone water, syncase broth and trypticase soy broth. Toxin production was measured by enzyme-linked immunosorbent assay (ELISA) in polymyxin-treated cell pellets and/or supernatants of cultures, ELISA optical densities reached 1 when isolates were grown for 2-4 h in E. coli broth in the presence of antibiotic. Besides, a collection of STEC-expressing Stx strains was evaluated and the Stx production was assayed in the supernatants and in polymyxin-treated pellets of bacterial growth after 4 h of cultivation in E. coli broth in the presence of antibiotic. CONCLUSIONS: The most suitable medium for Stx production was E. coli broth when the bacterial isolates were grown for 4 h in the presence of ciprofloxacin and the Stx production is detected in the supernatant. SIGNIFICANCE AND IMPACT OF THE STUDY: This study presents the first comprehensive comparison of different broth media with regard to Stx production to establish optimal culture conditions for STEC detection in routine diagnostic laboratories.     

The urea requirement and urease production of some human species of T-mycoplasmas.

Seven species of human T-mycoplasmas that grow in Fraction A and 20 mug urea/ml died when the urea was omitted. Two species would not grow in Fraction A broth containing 10 mug/urea/ml. The other five strains grew in broth containing 10 mug urea/ml and were adapted by serial passage in broth containing decreasing concentrations of urea to grow in broth containing 2.5 mug/ml urea, but not in broth containing 1.25 mug/ml. Therefore the minimal urea requirement is not the same for the growth of all strains of T-mycoplasmas. In exponential phase broth cultures, urease was detected only intracellularly, none being found in the medium.     

A NOTE ON THE USE OF ROGOSA AND MODIFIED ROGOSA MEDIA FOR THE ENUMERATION AND CULTURE OF LACTOBACILLI

SUMMARY: The modified Rogosa media (acetate broth and acetate agar) developed by Mabbitt & Zielinska (1956) have been compared with tomato juice media for the growth of representative Lactobacillus species.
Most of the species tested grew markedly better in acetate broth than in tomato dextrose broth, but some cultures did not grow well in the acetate broth although they grew normally in tomato dextrose broth. The acetate agar was satisfactory for counting those lactobacilli cultured at 30° but was inferior to tomato dextrose agar for counting those grown at 37°.     

蒺藜内生真菌发酵液抗菌及抗肿瘤活性初步研究

【目的】筛选出具有抗菌和抗肿瘤活性的蒺藜内生真菌。【方法】采用牛津杯法、稻瘟菌模型及肿瘤细胞模型评价蒺藜内生真菌PDB和察氏培养基发酵产物的抗菌活性和肿瘤细胞毒性。【结果】PDB培养基发酵液和察氏培养基发酵液抑菌圈直径大于10 mm的菌株分别占总菌株数的19.05%和23.81%。PDB培养基发酵液和察氏培养基发酵液对稻瘟菌的最小抑制浓度(MIC)低于10%的菌株分别占总菌株数的19.05%和47.61%。对肿瘤细胞抑制率高于50%的PDB发酵产物占PDB发酵产物总数的52.38%, 而对肿瘤细胞抑制率高于50%的察氏发酵产物占察氏发酵产物总数的28.57%。【结论】部分蒺藜内生真菌的发酵产物具有抗菌和抗肿瘤活性。     

Neutralization of the Bactericidal Effect of Cocoa Powder on Salmonellae by Casein

Four pre-enrichment media (nutrient broth, lactose broth, reconstituted non-fat dry milk and nutrient broth containing 5% (w/v) casein) were evaluated for the recovery of salmonellae from cocoa powder. Addition of 5% cocoa powder to nutrient broth and to lactose broth proved to be bactericidal to salmonellae. Heat-damaged Salmonella typhimurium were more sensitive than undamaged cells to cocoa powder and agitation increased the bactericidal effect. The bactericidal effects were minimized in pre-enrichment media that contained either 5% casein or nonfat dry milk.     

An evaluation of selective broths based on the bi-selenite ion and on hypertonic strontium chloride in Salmonellae detection in egg products.

Of the 104 isolations of Salmonella sp. from egg pulp, 97 were obtained from strontium chloride M broth, 42 from strontium selenite broth and 57 from strontium selenite A broth. The results suggest that the first medium may be used more successfully than bi-selenite based media for enrichment and subsequent detection of salmonellae in egg products; however, the growth of S. pullorum was not satisfactory in strontium chloride M broth.     

Assessment of the Accuprobe Listeria monocytogenes culture identification reagent kit for rapid colony confirmation and its application in various enrichment broths.

The Accuprobe Listeria monocytogenes Culture Identification Reagent Kit, a nonradioactive probe, was evaluated as a colony confirmation test and in different selective or nonselective enrichment broths. The probe was 100% sensitive and 100% specific when applied to isolated colonies. The minimal detection limit in physiological saline was established to be about 10(5) CFU of L. monocytogenes. Hybridization done directly in broths seeded with L. monocytogenes showed variable results. Three nonselective broths (Todd-Hewitt broth, brain heart infusion broth, and tryptic soy broth) and one selective broth (FDA) gave positive reactions at an inoculum of 5 x 10(6) CFU, whereas two other selective broths (UVM, and PALCAMY) gave negative reactions with up to 10(8) and 10(9) CFU. In FDA broth, the level of detection of L. monocytogenes was not modified by the presence of other organisms in mixed cultures.     

Assessment of the Accuprobe Listeria monocytogenes culture identification reagent kit for rapid colony confirmation and its application in various enrichment broths.

The Accuprobe Listeria monocytogenes Culture Identification Reagent Kit, a nonradioactive probe, was evaluated as a colony confirmation test and in different selective or nonselective enrichment broths. The probe was 100% sensitive and 100% specific when applied to isolated colonies. The minimal detection limit in physiological saline was established to be about 10(5) CFU of L. monocytogenes. Hybridization done directly in broths seeded with L. monocytogenes showed variable results. Three nonselective broths (Todd-Hewitt broth, brain heart infusion broth, and tryptic soy broth) and one selective broth (FDA) gave positive reactions at an inoculum of 5 x 10(6) CFU, whereas two other selective broths (UVM, and PALCAMY) gave negative reactions with up to 10(8) and 10(9) CFU. In FDA broth, the level of detection of L. monocytogenes was not modified by the presence of other organisms in mixed cultures.     

A novel strictly anaerobic recovery and enrichment system incorporating lithium for detection of heat-injured Listeria monocytogenes in pasteurized milk containing background microflora.

Heat-injured cells of Listeria monocytogenes were recovered from heated raw milk containing noninjured Enterococcus faecium by combining a simple method for obtaining strict anaerobiosis with a novel enrichment broth, Penn State University broth (PSU broth). Strictly anaerobic conditions were rapidly achieved by adding 0.5 g of filter-sterilized cysteine per liter to PSU broth and then purging the preparation with N2 gas. Little resuscitation or growth occurred in strictly anaerobic PSU broth without lithium chloride because of overgrowth by E. faecium. The growth of E. faecium decreased dramatically with increasing LiCl concentration; LiCl concentrations of 8 and 10 g/liter were completely bacteriostatic. The mechanism of inhibition by LiCl appeared to involve competition with the divalent cations Ca2+ and Mg2+. Heat-injured L. monocytogenes consistently recovered and grew rapidly in strictly anaerobic PSU broth containing 4, 6, or 7 g of LiCl per liter. The use of strictly anaerobic PSU broth containing 7 g of LiCl per liter permitted detection of severely heat-injured L. monocytogenes in one simple recovery-enrichment step by eliminating oxygen toxicity and inhibiting the growth of background microflora, without preventing the resuscitation and subsequent growth of heat-injured L. monocytogenes. L. monocytogenes heated in raw milk at 62.8 degrees C for 10, 15, and 20 min could be consistently recovered from strictly anaerobic PSU broth enrichment cultures at 30 degrees C after 48, 96, and 144 h, respectively, and hence, use of PSU broth may result in better recovery of both injured and noninjured cells from foods than currently used U.S. Department of Agriculture and Food and Drug Administration preenrichment procedures.     

THE DETERMINATION OF ESCHERICHIA COLI I IN SEA WATER

SUMMARY: For the determination of Escherichia coli I in sea water lactose broth frequently gave higher presumptive and confirmed counts than MacConkey's broth. In the presumptive count there were 53 cases where lactose broth gave larger numbers than MacConkey's broth, with 11 equal counts, and only 25 cases with smaller counts ( P =0·00137). After confirmation the corresponding numbers of cases were 39, 10 and 27 ( P =0·134).
In the samples giving most probable numbers (MPN) of less than 100 E. coli /100 ml lactose broth was superior to MacConkey's broth ( P =0·021). At higher MPN values both media were satisfactory, but with highly polluted water MacConkey's broth might give better recoveries due to the suppression of high concentrations of non-coli-aerogenes bacteria.
Samples stored for 24 or 48 hr before testing gave higher presumptive recoveries when examined with lactose broth than with MacConkey's broth, the values for P being 0·028 and 0·0027 respectively.
It appears that lactose broth without inhibitory ingredients could be used with advantage in the examination of sea water.     

Rheology and Hydrodynamic Properties of Tolypocladium inflatum Fermentation Broth and Its Simulation

A physico-chemical, two phase simulated pseudoplastic fermentation (SPF) broth was investigated in which Solka Floc cellulose fibre was used to simulate the filamentous biomass, and a mixture of 0.1% (w/v) carboxymethyl cellulose (CMC) and 0.15 M aqueous sodium chloride was used to simulate the liquid fraction of the fermentation broth. An investigation of the rheological behaviour and hydrodynamic properties of the SPF broth was carried out, and compared to both a fungal Tolypocladium inflatum fermentation broth and a CMC solution in a 50 L stirred tank bioreactor equipped with conventional Rushton turbines. The experimental data confirmed the ability of the two phase SPF broth to mimic both the T. inflatum broth bulk rheology as well as the mixing and mass transfer behaviour. In contrast, using a homogeneous CMC solution with a similar bulk rheology to simulate the fermentation resulted in a significant underestimation of the mass transfer and mixing times. The presence of the solid phase and its microstructure in the SPF broth appear to play a significant role in gas holdup and bubble size, thus leading to the different behaviours. The SPF broth seems to be a more accurate simulation fluid that can be used to predict the bioreactor mixing and mass transfer performance in filamentous fermentations, in comparison with CMC solutions used in some previous studies.     

土壤拮抗放线菌的分离筛选及其抑菌物质特性的研究

目的从土壤中筛选拮抗能力强且抑菌特性稳定的放线菌菌株。方法采用双层琼脂法筛选出4株拮抗放线菌菌株,然后采用杯碟法测这4株菌株发酵液提取物的抗菌谱、最小抑菌浓度、热稳定性和酸碱稳定性。结果 4株菌株发酵液提取物都能抑制金黄色葡萄球菌、大肠埃希菌、铜绿假单胞菌和白色念珠菌的生长。以金黄色葡萄球菌为指示菌测发酵液提取物的最小抑制浓度,6#和9#拮抗作用较强,发酵液提取物稀释0.125mg/ml仍有抑菌作用。6#菌株在100℃处理30min后仍有40%的抑菌活性。6#菌株发酵液提取物在碱性环境条件下比在酸性环境条件下稳定。结论 4株菌株中6#菌株发酵液提取物具有拮抗能力强、最小抑菌浓度低和在碱性条件下活性较稳定的特点。     

一种肠道硫酸盐还原菌的增菌培养基

目的针对已经分离、纯化的肠道硫酸盐还原菌,建立一种能快速、高效地培养菌体的培养基。方法比较营养丰富的GAM肉汤与常用于培养硫酸盐还原菌的选择性培养基Postgate的培养效果,摸索在GAM肉汤中添加不同浓度的硫酸盐对两种肠道硫酸盐还原菌-Desulfovibrio desulfuricans和Desulfovibrio intestina—zis的培养效果。确定效果最佳的改良GAM培养基配方,并测定在该培养基中D．desulful＇icans的生长曲线。结果与Postgate培养基相比,GAM肉汤能在2d内快速培养D．desulfugicans,但培养至6d时细菌数量大幅降低。在GAM肉汤中添加Na2SO4与FeSO4,在实验浓度范围内,均显著地促进硫酸盐还原菌的生长。在此基础上改良GAM肉汤培养基,培养得到的细菌数量较GAM肉汤显著提高。D．desulfuricans的生长曲线显示,2d时细菌生长达到最高峰,数量可达3．5×10^7 CFU／mL;培养6d,细菌数量为7．3×10^6 CFU／mL。结论基于GAM肉汤改良而得到的增菌培养基,能快速、高效地培养肠道硫酸盐还原菌,为后续进一步研究肠道硫酸盐还原菌的生理功能提供了支持。     

超声波对发酵液中提取透明质酸的影响

目的：提高发酵液中透明质酸的提取率。方法：应用超声波预处理发酵液的方法对醇沉法提取透明质酸的影响进行研究。结果：在超声波功率100W、处理温度15℃、处理时间10min时,透明质酸提取率相对于未经超声波处理的发酵液提高了38.6%。因此,超声波预处理透明质酸发酵液可以达到提高透明质酸提取率的目的。     

Effect of medium composition, agitation and the presence of EDTA on the antimicrobial activity of cryptolepine

The antimicrobial activity of cryptolepine is influenced by the type of medium employed, agitation and the presence of non-inhibitory concentrations of EDTA. The use of Mueller–Hinton broth (MHB), iso-sensitest broth and tryptone soya broth (TSB) produced lower minimum inhibitory concentrations (MICs) for some of the test organisms compared with nutrient broth or yeast dextrose broth (YDB). For example, a fourfold drop in MIC was recorded for Saccharomyces cerevisiae in MHB compared with the same organism tested in YDB. Agitation of the broths during incubation nearly always produced lower MICs for the bacteria, an eightfold decrease in MIC being recorded for Escherichia coli cultured in nutrient broth with agitation compared with a statically maintained culture. A non-inhibitory concentration (10⁻³ mol l⁻¹) of disodium EDTA enhanced the antimicrobial activity of cryptolepine. Against E. coli NCTC 11560, an eightfold decrease in MIC and minimum bactericidal concentration (MBC) was recorded when tested in the presence of EDTA.     

Pre-Enrichment and Enrichment Methods for Isolating Small Number of Campylobacteria from Contaminating Flora

A method was developed to detect fewer than 100 CFU of campylobacteria from SIFF transport medium to which thawing drip from deep frozen broiler carcasses was added as a source of contamination and which was then stored at room temperature for 20 h. The method was made possible by using pre–enrichment in 1 % buffered peptone water under a microaerophilic atmosphere for 5 h at 43°C before selective enrichment either in brucella enrichment broth and on brucella blood selective agar supplemented with Skirrow antibiotics or in CCD enrichment broth and on blood free CCD selective agar. The other pre–enrichment broth studied was alkaline peptone water with reducing agents (RAPW) and the other enrichment broths and selective agars were Preston broth and agar, THAL broth and alkaline tryptose broth (ATB) and brucella agar with ATB antibiotics. Contaminating flora can be a problem when using enrichment broths and selective agars with limited antibiotic supplementation.     

Nitrogen fixation system of tungsten-resistant mutants of Azotobacter vinelandii.

Mutants of Azotobacter vinelandii ATCC 12837 were isolated which could fix N2 in the presence of high tungsten concentrations. The most studied of these mutants (WD2) grew well in N-free modified Burk broth containing 10 mM W, whereas the wild type would not grow in this medium. WD2 would also grow in Burk N-free broth at about the same rate as the wild type. WD2 in broth containing W exhibited 22% of the whole cell acetylene reduction activity of the wild type in broth containing Mo and showed a lowered affinity for acetylene. Two-dimensional gel electrophoresis experiments showed that N2-fixing cells of WD2 from broth containing W or Mo did not produce significant amounts of component I of native nitrogenase protein. Electron spin resonance spectra of whole cells and cell-free extracts of WD2 from broth containing W lacked any trace of the g = 3.6 resonance associated with FeMoCo.