bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Ecology of Chloramphenicol‐Resistance in Salmonella typhimurium and Escherichia coli in Calves with Endemic Salmonella Infection
Authors: LINTON A. H. , TIMONEY J. F. , HINTON M. 
Published: March 2008

A batch of 40 calves intensively reared on a milk replacer diet was monitored over 34 d for salmonella and Escherichia coli excretion patterns. A total of 1055 Esch. coli was isolated on unsupplemented bile lactose agar (BLA), and 537 on BLA supplemented with chloramphenicol, from 10 selected calves. The antibiotic resistance pattern and O‐serogroup were determined for each isolate.Salmonella typhimurium phage type DT 193 carrying six R determinants was detected in five calves on intake; after 14 d 28 were excreting the organism but by the time the calves left the farm (34 d) only a small number were found to be excreting the organism indicating that the infection was self limiting by about six weeks of age. In contrast, multiply resistant Esch. coli were being excreted in increasing numbers with time. Of the isolates on BLA 95.5% were resistant to at least one antibacterial agent and many were resistant to up to six agents. An unusually high proportion (49%) was resistant to chloramphenicol and this R determinant was frequently associated with R determinants for at least streptomycin, sulphonamide and tetracycline, a combination regularly present in the salmonellas. Chloramphenicol resistance is carried on an H2 plasmid in Salmonella typhimurium phage type 193 and it was found that 11% of 146 randomly selected isolates of Esch. coli, carrying the same range of R determinants, were infected with an H2 plasmid. H2 plasmids were found in a number of O‐sero‐groups of Esch. coli and chloramphenicol resistance was present in 37 O‐serogroups. It is suggested that transfer from the salmonellas to Esch. coli possibly took place before the calves entered the farm and the transconjugants were selected by the antibiotics used on the farm. Subsequent transfer between Esch. coli could explain the wide distribution of chloramphenicol‐resistance in many serogroups. The transfer of H2 plasmids is thermosensitive and no transfer could be demonstrated in vivo but occurred readily in voided faeces held at 28°C. The importance of Esch. coli as a reservoir of chloramphenicol resistance and the public health implications are discussed.
Separation of Non‐filamentous Micro‐organisms from Soil by Density Gradient Centrifugation in Percoll
Authors: MARTIN N. J. , MACDONALD R. M. 
Published: March 2008

Soil suspensions were homogenized, and desorbed non‐filamentous micro‐organisms were concentrated in a minimum volume of buffer by low speed centrifugation. The cells were separated from inanimate material by flotation at the interface between the buffer and a silica sol/polyvinyl pyrrolidone density gradient medium (Percoll). Cell suspensions were removed from the interface and fractionated according to density by high speed centrifugation on discriminating density gradients in Percoll.Preliminary experiments indicated that most non‐filamentous soil micro‐organisms had densities in the range 1.081–1.123 g%sol;ml while Rhizobium isolated from crushed root nodules on Percoll was split into two bands of densities 1.081–1.110 and 1.041–1.073 g/ml. The lighter cells were the more pleomorphic.The efficiency of extraction of cells from soil was governed by the extent of their desorption from inanimate particles. As rigorous desorption procedures damage cells, extraction efficiencies were low; 10–20% of cells counted microscopically in soil were recovered from density gradients. Electron microscopy of soil micro‐organisms isolated by this method showed an unusual range of surface ornamentations on cell‐like structures of bacterial dimensions.
Potassium Fluxes on Hyperosmotic Shock and the Effect of Phenol and Bronopol (2‐bromo‐2‐nitropropan‐1,3‐diol) on Deplasmolysis of Pseudomonas aeruginosa
Authors: KROLL R. G. , ANAGNOSTOPOULOS G. D. 
Published: March 2008

Potassium fluxes and the effect of phenol and bronopol on deplasmolysis of Pseudomonas aeruginosa were followed in sucrose and glycerol plasmolysing systems.In sucrose, K+ uptake related to the solute concentration. Proline increased the rate and overall K+ uptake, the latter by a factor of three. It was concluded that there was no rigid maximum in the accumulation of intracellular K+ as long as intracellular neutrality in electrical charges was maintained.In glycerol, K+ uptake was parallel with glycerol penetration. The process was reversed, however, on equilibration of glycerol. This suggested that glycerol inhibited K+ retention against a concentration gradient rather than that K+ was excluded as a consequence of the osmotic established steady state. This view was enforced by the fact that the reversal of K+ uptake occurred in 20 and 30% glycerol but not in 10%.Phenol and bronopol did not affect deplasmolysis in glycerol significantly, although some effect on K+ uptake and glycerol permeability could be seen. In the sucrose system, phenol acted according to its mode of action generally accepted, i.e. inhibiting deplasmolysis at low and allowing solute penetration at higher concentrations, whereas very high concentrations caused coagulation of the cytoplasm. Bronopol inhibited deplasmolysis, except at very low concentrations. Proline did not prevent the inhibition of deplasmolysis in either of the solute systems, except at the very low bronopol concentrations where the deplasmolysis rate only was affected.
Serological Activity of ‘Bacteroides fragilis’ Endotoxins—Strains Isolated in Poland
Authors: MEISEL‐MIKOŁAJCZYK FEUCJA , ROKOSZ ALICJA , GRZELAK‐PUCZYŃSKA IRENA 
Published: March 2008

Antigens were extracted by the phenol‐water method from each of the 11 strains of ‘Bacteroides fragilis’ species, isolated from clinical material. Nine of these strains had been identified by the direct immunofluorescence test (IFT) as ‘B. fragilis spp. fragilis’, and two as ‘B. fragilis ssp. thetaiotaomicrori’.These antigens were then used in the immunodiffusion test (ID), performed with antisera of six serotypes. Results of the ID test agreed in nine cases with those of IFT. An antigenic heterogeneity among strains of ‘B. fragilis ssp. fragilis’ strains was noted. Antigens prepared in the same way from two strains did not react in the ID test with any of the antisera used although cells were positively stained in the IFT by specific anti‐‘B. fragilis’ serotype conjugates.
Effect of Hyperbaric Carbon Dioxide Pressure on the Microbial Flora of Pork Stored at 4 or 14°C
Authors: BLICKSTAD E. , ENFORS S.‐O. , MOLIN G. 
Published: March 2008

Changes in the microbial flora of pork stored at 4 or 14°C were studied in 5 atm CO2, 1 atm CO2 or 1 atm air. The time needed for the total aerobic count at 4°C to reach 5 × 106 organisms/cm2 was about three times longer in 5 atm CO2 than in 1 atm CO2, and about 15 times longer in 5 atm CO2 than in air. At 14°C there was no difference in growth rate between 5 atm CO2 and 1 atm CO2. No off‐odour was detected after storage in 5 atm CO2 for 14 d, but the pork in 1 atm CO2 (6 d) was organoleptically unacceptable.The predominant organisms on the pork from the processing line were: Flavobacterium spp., Acinetobacter calcoaceticus, Pseudomonas spp., Micrococcus spp. and Moraxella spp. After aerobic storage at 4°C (8 d) or 14°C (3 d) more than 90% of the flora consisted of Pseudomonas spp. At 4°C all Pseudomonas spp. were of the non‐fluorescent type, whilst at 14°C 32% were Ps. putida and Ps. fluorescens. After storage in 1 atm CO2Lactobacillus spp. represented 66% of the flora at 14°C (6 d) and 100% at 4°C (40 d), with L. xylosus dominating. After storage in 5 atm CO2Lactobacillus spp. constituted the total flora at both temperatures with L. lactis (14°C) and L. xylosus (4°C) dominating.It was concluded that high partial pressures of CO2 have a considerable shelf‐life prolonging effect by (i) selecting the microflora towards Lactobacillus spp. and (ii) reducing the growth rate of these Lactobacillus spp. The controlling and growth inhibitory effect of CO2 was promoted by reduced temperatures.
Semi‐automated counting of bacteria and somatic cells in milk using epifluorescence microscopy and television image analysis
Authors: Pettipher G.L. , Rodrigues Ubaldina M. 
Published: March 2008

AbstractAn epifluorescent microscope fitted with a ‘Chalnicon’ closed circuit television camera linked to an Optomax System III image analyser was used to count bacteria and somatic cells on membrane filters prepared from milk by the direct epifluorescent filter technique (DEFT). For both bacteria and somatic cells, the semi‐automated DEFT count of low count milk exceeded the visual DEFT count but this difference became proportionately less as the count increased. There was close agreement between the semi‐automated and visual DEFT counts over the range 105‐5 times 106/ml for bacteria and 3 times 105‐5 times 106/ml for somatic cells. The semi‐automated DEFT count of bacteria and somatic cells correlated well with the plate count and Coulter count respectively, with correlation coefficients of 0.83 and 0.81.
The effect of spray washing on the development of bacterial numbers and storage life of lamb carcases
Authors: Kelly C.A. , Lynch B. , McLoughlin A.J. 
Published: March 2008

AbstractTotal bacterial numbers at the most highly contaminated sites on lamb carcases (in the crutch region and adjacent to the abdominal incision) were significantly reduced to log10 3.3/cm2 when spray washed with unchlorinated water at 80°C and to log10 2.8 when water at 80°C containing 450 μg/ml chlorine was used, whereas numbers on carcases which were cloth cleaned or spray washed with water at 10°C remained at approximately log10 4.0. During refrigerated storage, however, carcases treated by all methods developed similar numbers of bacteria and had the same storage life, evidently because spray washing did not affect numbers of bacteria on the diaphragm. Although initial numbers of bacteria at this site were low (log10 2.9), their numbers, and also the amount of slime, increased more rapidly there than at other sites. In addition, spray washing did not significantly affect numbers of Pseudomonas spp or Brochothrix thermosphacta, which accounted for <1% of the microflora after slaughter at each site but whose numbers were between log10 6.1 and 7.5/cm2 when carcases were rejected as spoiled.
Identification of bacteria of dairy origin using miniaturized test‐systems
Authors: Griffiths M.W. , Phillips J.D. 
Published: March 2008

AbstractOne hundred and forty‐four isolates of dairy origin were identified using a number of commercially available test kits. Agreement between these kits was acceptable for assignment of isolates to genera, but there was some variation between the kits for the identification of the isolates at specific level. The reasons for these variations are discussed. In terms of cost, ease of performance and accuracy, the identification systems manufactured by Roche Products Ltd (viz. the Oxi/Ferm tube and the Enterotube) are considered to be the best suited to the routine identification of dairy micro‐organisms.
Further development of a bacteriocin typing system for Clostridium perfringens
Authors: Scott H.G. , Mahony D.E. 
Published: March 2008

AbstractThe specificity of typing Clostridium perfringens with bacteriocins was improved by adding new bacteriocins and deleting others from the original typing set of ten. A total of 516 new isolates of Cl. perfringens were screened for bacteriocin production and, of these, 162 strains (31%) were found to be producers. The sensitivity patterns obtained by testing 40 bacteriocins against 200 isolates of Cl. perfringens were recorded and the data subjected to a computer analysis. A total of 18 bacteriocins capable of dividing the 200 isolates into 98 typing patterns was selected. The repro‐ducibility of the new system was tested by performing three sequential typings of 60 strains of Cl. perfringens. No variation was found in 73% of the strains, while a further 16% of the strains demonstrated a change in sensitivity to only one bacteriocin. Common serological types of Cl. perfringens were divisible into subtypes based upon both their ability to produce bacteriocins and their sensitivity to bacteriocins, suggesting a useful role for bacteriocin typing in conjunction with an already well‐established tool for typing Cl. perfringens.
A new direct plate method for the enumeration of Escherichia coli in frozen foods
Authors: Hall L.P. 
Published: March 2008

Hall, L.P. 1984. A new direct plate method for the enumeration of Escherichia coli in frozen foods. Journal of Applied Bacteriology56, 227–235.A new method has been devised, incorporating a resuscitant stage, which allows direct isolation of Escherichia coli biotype I, Irregular type II and Irregular type VI. Rapid indole tests on the distinctive colonies produced enable determinations of E. coli biotype I to be made within 24 h. This method employs materials of low cost and achieves complete recovery of injured cells. It also detects not only anaerogenic strains but those which are slow in producing acid from lactose or give negative results by other methods. If required, further study of isolates can be made after the indole test. Comparisons were made between conventional methods, the new method and a similar direct plate method. The implications of the higher counts obtained by the two latter methods are discussed in relation to microbiological specifications and standards for frozen foods.
Hypochlorite effects on spores and spore forms of Bacillus subtilis and on a spore lytic enzyme
Authors: Gorman S.P. , Scott E.M. , Hutchinson E.P. 
Published: March 2008

Gorman, S.P., Scott, E.M. & Hutchinson, E.P. 1984. Hypochlorite effects on spores and spore forms of‐Bacillus subtilis and on a spore lytic enzyme. Journal of Applied Bacteriology56, 295–303.Spores of Bacillus subtilis NCTC 10073 were converted to ion‐exchange (Ca, H) forms and coat‐defective (urea‐mercaptoethanol, urea‐dithiothreitol‐sodium lauryl sulphate) forms. The resistance of these to sodium hypochlorite (1000 parts/106 free chlorine) was compared and related to uptake from which the assumed monolayer capacities were calculated. Hypochlorite effects on spore protoplasts and cortical fragments were also examined in relation to DPA and hexosamine release. A spore lytic enzyme was extracted and examined in respect of hypochlorite activity. The results are discussed in terms of the mechanism and site of action of hypochlorite on the bacterial spore.
A comparison of isolation procedures for salmonellas from polluted water using two forms of Rappaport's medium
Authors: Fricker C.R. 
Published: March 2008

Fricker, C.R. 1984. A comparison of isolation procedures for salmonellas from polluted water using two forms of Rappaport's medium. Journal of Applied Bacteriology56, 305–309.The efficiency of Rappaport's broth (RB10) and Rappaport's broth containing novobiocin (NRB10) were compared for the isolation of salmonellas from polluted water, both as direct enrichment media and after pre‐enrichment in buffered peptone water. Ninety samples were examined and 41 were found to contain salmonellas by at least one of the procedures used. Direct inoculation of the sample into RB10 resulted in the recovery of salmonellas from only 29.3% of the samples found to be positive. The use of NRB10 as a direct enrichment medium increased the percentage recovery to 78.0% of the total positive samples. Pre‐enrichment in buffered peptone water allowed the recovery of salmonellas from a total of 41 samples whereas direct enrichment recovered them from only 32. No significant difference was demonstrated in the efficiencies of RB10 and NRB10 in recovering salmonellas after pre‐enrichment in buffered peptone water. Three selective agars were used; no significant difference in their ability to recover salmonellae was demonstrated.
A note on ‘plotless’ methods for estimating bacterial cell densities
Authors: Roser D. , Nedwell D.B. , Gordon A. 
Published: March 2008

Roser, D., Nedwell, D.B. & Gordon, A. 1984. A note on “plotless” methods for estimating bacterial cell densities. Journal of Applied Bacteriology56, 343–347.‘Plotless’ techniques for determining population densities have been developed for, and applied to, higher plant populations. They can often be carried out more rapidly than techniques involving total counts of individuals in plots, or quadrants, but such plotless techniques have not been generally applied to the estimation of densities of bacterial cells. Direct microscopical counting of cell numbers in a field of view, an example of a plot‐related method, has been traditionally used for micro‐bial cell counts. In this study ‘plot’ and ‘plotless’ methods on a variety of bacterial samples are compared. Estimates of bacterial cell density were obtained by measuring the distance of cells from a fixed point in a field of view. The values, which were more rapidly obtained, were directly correlated with total cell counts. Although there was some apparent deviation from a perfect 1:1 relationship with total counts, as indicated by a correlation coefficient less than 1.0, there were no significant differences between the replicated counts of bacteria on samples of tissue from the surface of Hypholoma basidiocarps (P < 0.05). This indicated that the methods of enumeration were comparable. The distance‐related estimates could readily be obtained from fields of view with cell densities varying over several orders of magnitude. It was more rapidly applied, particularly at high density, and the method was applicable not only to random cell distributions but also to the non‐random distributions encountered when microbial cells aggregated into micro‐colonies. The method appears to be particularly well‐suited for automated, digitized, direct counting procedures, as well as to estimating bacterial numbers on membrane filters and natural substrates.
A note on the temperature tolerance of Legionella
Authors: Dennis P.J. , Green D. , Jones B.P.C. 
Published: March 2008

Dennis, P.J., Green, D. & Jones, B.P.C. 1984. A note on the temperature tolerance of Legionella. Journal of Applied Bacteriology56, 349–350.A strain of Legionella pneumophila serogroup 1 isolated from the environment had a decimal reduction time in water at 50d̀C (D50) of 111 min, a D54 of 27 min and a D58 of 6 min. There was little loss of viability at 46d̀C. Other environmental organisms, a Pseudomonas sp., a Micrococcus sp. and a coliform survived less well at these temperatures. A species of Sarcina had a survival time greater than the L. pneumophila at all the temperatures tested. Other strains of legionellas were tested at 50d̀C and decimal reduction times calculated. These ranged from 80 min for another strain of L. pneumophia serogroup 1 to 216 min for L. bozemannii. Legionella micdadei did not survive well at 50d̀C.
Comparative study on Salmonella isolation from sewage—contaminated natural waters
Authors: Alcaide Elena , Martinez J.P. , Garay Esperanza 
Published: March 2008

Alcaide, E., Martinez, J.P. & Garay, E. 1984. Comparative study on Salmonella isolation from sewage contaminated natural waters. Journal of Applied Bacteriology56, 365–371.A comparative study of five factors influencing the isolation of salmonellas from sewage‐contaminated natural waters was carried out. The effect of pre‐enrichment in buffered peptone water was compared with single‐step enrichment in NR10 broth incubated at 43d̀C. A modification of NR10 has been compared with the original composition. Bismuth sulphite agar (BSA), Hektoen enteric agar (HE) and brilliant green agar (BGA) have been used as plating media. Other factors considered have been temperature of the water and sampling site. A total of 759 salmonella strains belonging to 36 different serotypes has been recovered in a two‐year study. All five factors considered in the study have shown a significant effect on the recovery of salmonellas. The combination of direct enrichment in NR10, followed by BSA or HE as plating media was most effective for the isolation of Salmonella. The influence of water temperature and characteristics of the sampling sites have also been discussed.
A survey of lactic acid bacteria in Italian silage
Authors: Grazia L. , Suzzi Giovanna 
Published: March 2008

Grazia, L. & Suzzi, G. 1984. A survey of lactic acid bacteria in Italian silage. Journal of Applied Bacteriology56, 373–379.Lactic acid bacteria, isolated from Italian ensiled products, were represented by strains of the genera Lactobacillus and Leuconostoc. The predominant strains were heterofermentative lactobacilli, with Lactobacillus buchneri being the most frequent. Among homofermentative lactic acid bacteria, strains of Lact. plantarum and Lact. casei were recovered. Almost all strains utilized malic acid and showed good acid‐tolerance, but only some of them were able to metabolize malic acid at extremely low pH; these were five homofermentative lactobacilli (4 Lact. plantarum and 1 Lacr. casei var. casei) and two heterofermentative lactobacilli (Lact. cellobiosus and Lactobacillus sp.).
A method for the enumeration of male‐specific bacteriophages in sewage
Authors: Havelaar A. H. , Hogeboom W. M. 
Published: March 2008

Havelaar, A.H. & Hogeboom, W.M. 1984. A method for the enumeration of male‐specific bacteriophages in sewage. Journal of Applied Bacteriology56, 439–447.Male‐specific bacteriophages adsorb to F‐pili and thus can only infect male host strains. A method was developed for the selective enumeration of these phages, based on the observation that in sewage there are few phages capable of infecting F‐‐salmonellas—usually less than 10 pfu/ml. Using a male Salmonella strain, constructed by the introduction of the plasmid F'42 lac::Tn5 into Salmonella typhimu‐riumphage type 3, plaque counts in secondary effluent were found to be in the range of 60–8200 pfu/ml. Practically all the phages detected had a host range restricted to male Salmonella or Escherichia coli strains, were resistant to chloroform and their infectivity was inhibited by RNase. Electron microscopy of lysates revealed phage particles that were morphologically identical to the male‐specific single‐strand RNA phages. Similar results were obtained with a strain of Salm. indiona carrying F'42 lac. A derivative of the Salm. typhimurium LT2 strain carrying an F‐plasmid (F'42 lac fin P301) derepressed for fertility inhibition by the resident plasmid pSLT was equally sensitive to male‐specific phages, but from sewage samples many other phages infecting F‐E. coli but not F‐Salmonella were isolated using this host strain.
Artificially induced symbiotic associations of L‐form bacteria and plants
Authors: Aloysius Sriyani K. D. , Paton A.M. 
Published: March 2008

Aloysius, S. K. D. & Paton, A.M. 1984. Artificially induced symbiotic associations of L‐form bacteria and plants. Journal of Applied Bacteriology56, 465–477.L‐forms of a small but varied selection of bacteria were found to enter viable plant cells and establish novel symbiotic relationships. Evidence is presented for the ability of the L‐forms to spread and to express at least some of their metabolic functions within plant tissue.
A note on isolation of spontaneous glucose‐resistant mutants of Bacillus subtilis
Authors: Majumdar S. , Das S.K. , Basu S. , Bose S.K. 
Published: March 2008

Majumdar, S., Das, S.K., Basu, S. & Bose, S.K. 1984. A note on isolation of spontaneous glucose‐resistant mutants of Bacillus subtilis. Journal of Applied Bacteriology56, 493–494.The addition of double doses of glucose delayed the initiation of sporulation in Bacillus subtilis B34 by 42 h. Heat‐treatment of the culture within the delay period, (selectively killing the vegetative cells and leaving the spores unaffected) followed by immediate plating, afforded a good method for isolating spontaneous glucose‐resistant sporulation mutants.