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PubMed1987

Effect of inoculum size on in vitro activity of norfloxacin against fecal anaerobic bacteria. Rationale for selective decontamination of the digestive tract.

Previous studies have shown that anaerobic bacteria are susceptible to norfloxacin at the levels attained in the feces. Conversely, studies in laboratory animals and neutropenic humans using norfloxacin for selective decontamination of the digestive tract have shown that norfloxacin markedly reduces the aerobic enteric flora without reducing fecal anaerobic flora. In an effort to resolve this paradox, the effect of a 10(9) colony-forming units (cfu)/ml inoculum, which is more reflective of actual fecal counts than the standard 10(5) cfu/ml inoculum, on the activity of norfloxacin against two fecal Escherichia coli isolates and 16 fecal anaerobic isolates was studied. The results showed a marked inoculum effect at 10(9) cfu/ml for most anaerobic isolates but not for the E. coli strains tested. At 256 micrograms/ml, all E. coli were killed while the anaerobic bacteria maintained colony counts greater than or equal to 10(9) cfu/ml. Hence, the lack of anaerobic activity (minimal inhibitory concentration greater than or equal to 512 micrograms/ml) at higher fecal inocula might explain the utility of norfloxacin in selective decontamination of the bowel.

Adult↗

PubMedDate not supplied

Testing multiple variables on the growth of a mixed inoculum of Salmonella strains using gradient plates.

Six Salmonella strains were grown on two-dimensional sodium chloride-pH and temperature-pH gradient plates. Using image analysis the results were expressed in the form of three-dimensional wire frame graphs. On the temperature-pH gradient plates the optimum growth range was 20-30 degrees C and the minimum pH for visible growth was ca. pH 4, except for strain S. typhimurium CRA63 which grew over a narrower temperature and pH range. On the NaCl-pH gradient plates (whose NaCl gradient began at 2.75% (w/v) NaCl) the maximum concentration of salt at which growth was visible varied from 3.9% to 6.0%, and the minimum pH at which growth was observed varied from pH 4.7 to 5.4 according to the strain used. The incorporation of 0.02% (w/v) sodium nitrite reduced the maximum salt concentration and increased the minimum pH at which the strains could grow. The strains were combined and used in a mixed inoculum on NaCl-pH gradient plates containing 6 different concentrations of NaNO2 incubated at 6 different temperatures. Comparison of the data from the mixed inoculum with data from individual strains showed that, apart from one case, the mixed inoculum represented the extremes of the growth domains of the individual strains. The effect of NaNO2 on the ability of the strains to grow at different pH, NaCl concentrations and temperatures, was more clearly shown by subtracting the data of plates containing NaNO2 from the data of plates without NaNO2.

Hydrogen-Ion Concentration↗

PubMed1986

Evaluation of a rapid inoculum standardization system for antimicrobial susceptibility testing of bacterial isolates from the bovine mammary gland.

A commercially available rapid inoculum standardization system (RISS) was compared to the broth inoculum standardization method (BIS) for antimicrobial susceptibility testing of bacterial isolates from the bovine mammary gland. Overall agreement between RISS and the BIS method was 95.9%. RISS bypasses the 2-8 h incubation period required by BIS, thus providing antimicrobial susceptibility test data in a more timely manner. RISS was determined to be an acceptable alternative method to the BIS method for preparation of standardized inoculum for antimicrobial susceptibility testing of bovine mammary gland isolates.

Animals↗

PubMed1994

Inoculum effects on Etests and agar dilution minimum inhibitory concentrations. Piperacillin and piperacillin-tazobactam against Staphylococcus aureus.

Inoculum effects notoriously occur with beta-lactamase-positive staphylococci in dilution susceptibility tests with substrate beta-lactams. Etests, like dilution experiments, demonstrated such effects with piperacillin and, to a lesser extent, with its tazobactam combinations. When Etests were used with the recommended inoculum of approximately 10(6) colony-forming units (CFU/plate, the minimum inhibitory concentrations (MICs) of piperacillin-tazobactam found for beta-lactamase-positive Staphylococcus aureus isolates resembled those found by agar dilution for inocula of 10(4) CFU/spot but were two- to eightfold below those found by agar dilution for inocula of 10(6) CFU/spot; MICs of piperacillin itself by Etest were about fourfold below even those found by agar dilution with inocula of 10(4) CFU/spot. Inoculum effects for beta-lactamase-negative S. aureus were minimal by both methods.

Bacteriological Techniques↗

PubMed2004

Influence of the origin of the inoculum and the acclimation strategy on the degradation of 4-chlorophenol.

The influence of the inoculum source and the acclimation strategy on the 4-chlorophenol (4CP) degradation in a sequencing batch reactor (SBR) was studied. Three different sources of inocula were obtained from the aeration tank of domestic, municipal and industrial wastewater treatment plants. The acclimation was performed using two strategies, the first one fixing the reaction time, independent of the removal efficiency (fixed time) and the second one fixing a removal efficiency of 90% as 4CP (variable time). The degradative activity was followed for each condition. Bacterial identification was carried out at the beginning and at the end of the experiments. Variable time strategy produced a microbial community with higher specific activity compared with those obtained for the fixed time strategy. The microbial activity was dependent of the origin of the inoculum. Each inoculum presented different specific activity to 4CP degradation. It was observed that the use of the fixed time strategy for the acclimation reduced the bacterial community diversity.

Acclimatization↗

PubMed2005

Kinetic properties of a commercial and a native inoculum for aerobic milk fat degradation.

The aerobic fat biodegradation potential and growth characteristics of a commercial and a native inoculum (activated sludge from a dairy wastewater treatment pond), were evaluated. Batch tests were conducted with a medium based on butter oil, as the sole source of carbon, and mineral salts. Residual fat, biomass and CO(2) production were measured. Overall fat removal values were above 78% for both inocula. The growth kinetics of the commercial and native inocula followed Haldane and Monod models respectively. Both inocula showed a similar behaviour when butter oil concentration was under 360 mg/l; at higher values, the difference between the growth rates increased as a consequence of the inhibition exhibited by the commercial inoculum. The selection of an inoculum for bioaugmentation of bioreactors in the wastewater treatment requires a comprehensive knowledge of their degradation ability and tolerance to fluctuating compounds and of the operational conditions that will be utilized.

Animals↗

PubMed2006

Toxocara canis: effect of inoculum size on pulmonary pathology and cytokine expression in BALB/c mice.

Infection of mice with Toxocara canis results in pulmonary inflammation and the induction of a Th2 type of immune response. The aim of this study was to determine whether the effect of infection with this nematode depends on the inoculum size. Results indicate that mice infected with either a high or a low inoculum size showed, in a dose-dependent manner, pulmonary inflammation with eosinophil infiltration, increased levels of total IgE, and Toxocara-specific IgG1 that persisted up to 60 days p.i. Relative quantification of cytokine expression in lungs of mice infected with different doses showed proportional increased expression of the IL-4, IL-5, and IL-10 transcripts, whereas the expression of the IFN-gamma transcript was not different from that of uninfected controls. These results indicate that infection of BALB/c mice with T. canis results in chronic pulmonary inflammation and a dominant Th2 type of immune response, independent of the inoculum size.

Animals↗

PubMed2006

The role of initial inoculum on epidemic dynamics.

Transient dynamics are important in many epidemics in agricultural and ecological systems that are prone to regular disturbance, cyclical and random perturbations. Here, using a simple host-pathogen model for a sessile host and a pathogen that can move by diffusion and advection, we use a range of mathematical techniques to examine the effect of initial spatial distribution of inoculum of the pathogen on the transient dynamics of the epidemic. We consider an isolated patch and a group of patches with different boundary conditions. We first determine bounds on the host population for the full model, then non-dimensionalizing the model allows us to obtain approximate solutions for the system. We identify two biologically intuitive groups of parameters to analyse transient behaviour using perturbation techniques. The first parameter group is a measure of the relative strength of initial primary to secondary infection. The second group is derived from the ratio of host removal rate (via infection) to pathogen removal rate (by decay and natural mortality) and measures the infectivity of initial inoculum on the system. By restricting the model to mimic primary infection only (in which all infections arise from initial inoculum), we obtain exact solutions and demonstrate how these depend on initial conditions, boundary conditions and model parameters. Finally, we suggest that the analyses on the balance of primary and secondary infection provide the epidemiologist with some simple rules to predict the transient behaviours.

Animals↗

PubMed2001

The effect of inoculum size on the lag phase of Listeria monocytogenes.

The effect of inoculum size on population lag times of Listeria monocytogenes was investigated using the Bioscreen automated microtitre plate incubator and reader. Under optimum conditions, lag times were little affected by inoculum size and there was little variation between replicate inocula even at very low cell numbers. However, in media containing inhibitory concentrations of NaCl, both the mean lag time and variation between replicate inocula increased as the inoculum size became smaller. The variation in lag time of cells within a population was investigated in more detail by measuring the distribution of detection times from 64 replicate inocula containing only one or two cells capable of initiating growth. The variance of the lag time distribution increased with increasing salt concentration and was greater in exponential than in stationary phase inocula. The number of cells required to initiate growth increased from one cell under optimum conditions to 10(5) cells in medium with 1.8 M NaCl. The addition of spent medium from a stationary phase culture reduced the variance and decreased lag times. The ability to initiate growth under severe salt stress appears to depend on the presence of a resistant sub-fraction of the population, although high cell densities assist adaptation of those resistant cells to the unfavourable growth conditions by some unspecified medium conditioning effect. These results are relevant to the prediction of lag times and probability of growth from low numbers of stressed cells in food.

Adaptation, Physiological↗

PubMed1996

Nontypeable Haemophilus influenzae susceptibility: effect of inoculum size and beta-lactamase production.

The activities of cefixime, cefpodoxime, cefprozil, cefuroxime, loracarbef, and amoxicillin/clavulanate against 72 clinical isolates of nontypeable Haemophilus influenzae were determined by using an agar dilution method. The effects of beta-lactamase production and bacterial inoculum size were investigated. All antimicrobials exhibited a significant inoculum effect, demonstrating the importance of accurately determining inoculum size in the performance of antimicrobial susceptibility testing of H. influenzae.

Anti-Bacterial Agents↗

PubMed1995

Relationship between parasitical inoculum and immunological parameters in experimental toxocariasis.

Swiss female mice were inoculated with different infective doses of Toxocara canis eggs to evaluate the percentage of recuperated larvae in different organs and immunological parameters such as spleen index (SI), liver index (LI) and lung index (LuI) and blood eosinophilia during 3 weeks post infectionem (p.i.) with only one challenge. It was found that T. canis larvae arrived at the liver between 10 and 15 hours p.i. by the food-fishhook technique. When the inoculum was more than 200 eggs, there was a reinvasion of liver and lungs at 504 hours p.i. The larval arrival at the brain was delayed in an inverse relationship to the inoculum but the percentage of recovery was about 7 and 8%. The organic indexes were in a direct relationship with the inoculum size and the increase in eosinophilic levels in massive infections (2000 eggs) was in agreement with a strong immune response.

Animals↗

PubMedDate not supplied

Effect of inoculum composition and low KCl supplementation on the biological and rheological stability of an immobilized-cell system for mixed mesophilic lactic starter production.

Two strains of Lactococcus lactis subsp. lactis (L. lactis KB and KBP) and one of L. lactis subsp. lactis biovar. diacetylactis (L. diacetylactis MD) were immobilized separately in kappa-carrageenan-locust bean gum gel beads. Continuous fermentations were carried out in supplemented whey permeate in a 1-L pH-controlled stirred tank reactor inoculated with a 30% (v/v) bead inoculum and a bead ratio of 55:30:15 for KB, KBP, and MD, respectively. The process demonstrated a high productivity and microbial stability during the 7-week continuous culture. Compared with previous experiments carried out with an inoculum bead ratio of 33:33:33 for KB, KBP, and MD beads, respectively, the modification of the inoculum bead ratio had apparently little effect on free and immobilized, total and specific populations. A dominant behavior of L. diacetylactis MD over the other strains of the mixed culture was observed both with free-cell populations in the effluent and with immobilized-cell populations. Additional experiments were carried out with other strain combinations for continuous inoculation-prefermentation of milk. The data also confirmed the dominance of L. diacetylactis during long-term continuous immobilized-cell fermentations. This dominance may be tentatively explained by the local competition involved in the development of the bead cross-contamination and in citrate utilization by L. diacetylactis strains. The gel beads demonstrated a high rheological stability during the 7-week continuous fermentation even at low KCl supplementation of the broth medium (25 mM KCl).

Animals↗

PubMed2003

Influence of inoculum preparation on the growth of Penicillium chrysogenum.

AIMS: The influence of the spore preparation on subsequent fungal growth of Penicillium chrysogenum was assessed. METHODS AND RESULTS: The influence of four factors [the nature of the diluting solution (physiological water and physiological water added with Tween-80), the age of the sporulating culture (4, 8 and 12 days), the strain (737, 738 and 740) and the inoculum size (102, 103, 104 and 105 spores ml(-1)] on two responses (i.e. the radial growth rate, mu, and the lag time, lambda) was studied using an experimental screening methodology. CONCLUSIONS: The main conclusion was the strong effect of the inoculum size on lambda. In contrast, the diluting solution had no effect on both the experimental responses. In order to obtain the highest growth rates, it is recommended to use 4-day-old sporulating cultures with an inoculum size of 102 spores ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: There is a need for standardizing spore preparation in predictive mycology. The screening methodology is a powerful tool to determine the influence of qualitative and quantitative factors on various biological responses and can be applied widely in microbiology.

Culture Media↗

PubMed2002

Community shifts in a seeded 3-chlorobenzoate degrading membrane biofilm reactor: indications for involvement of in situ horizontal transfer of the clc-element from inoculum to contaminant bacteria.

Pseudomonas putida BN210, carrying the self- transferable clc-element encoding degradation of 3-chlorobenzoate on the chromosome, was used as inoculum in different membrane biofilm reactors treating 3-chlorobenzoate-contaminated model wastewater. Analysis of the bacterial population in the effluent and in the biofilm showed the loss of BN210 beyond detection from the reactors and the appearance of several novel 3-chlorobenzoate mineralizing bacteria mainly belonging to the beta-proteobacteria. In contrast, in non-inoculated reactors, no 3-chlorobenzoate degradation was observed and no 3-chlorobenzoate degraders could be recovered. Southern blots hybridization of genomic DNA using clc-element-specific probes and FIGE analysis indicated the presence of the complete clc-element in one or more copies in the isolates. Moreover, the isolates could transfer the clc genes to Ralstonia metallidurans recipients. Two representative reactor isolates, Ralstonia sp. strains KP3 and KP9 demonstrated a higher growth rate on 3-chlorobenzoate than strain BN210 in batch cultures. When BN210, KP3 and KP9 were simultaneously inoculated in a membrane reactor supplied with 3-chlorobenzoate, strain KP3 outcompeted the two other strains and remained the major 3-chlorobenzoate degrading population in the reactor. Our data suggest that in situ horizontal transfer of the clc-element from the inoculum to contaminant bacteria in the reactors was involved in the establishment of novel 3-chlorobenzoate degrading populations that were more competitive under the defined reactor conditions than the inoculum strain.

Biodegradation, Environmental↗

PubMed2000

Serum supplement, inoculum cell density, and accessory cell effects are dependent on the cytokine combination selected to expand human HPCs ex vivo.

BACKGROUND: The prolonged periods of pancytopenia associated with cord blood transplants suggest that in some cases cell numbers may be limiting. The possibility that limiting cell numbers may be overcome and prolonged periods of pancytopenia abrogated by the transplantation of human umbilical cord blood cells expanded ex vivo has led to efforts to define optimal culture conditions for these cells. STUDY DESIGN AND METHODS: Cord blood CD34+ cells were cultured with three cytokine combinations: SCF+G-CSF+GM-CSF+MGDF (SGGM); IL-6+ SCF+MGDF+Flt3-ligand (6SMF); and IL-1+IL-3+IL-6+G-CSF+GM-CSF+SCF+Epo (GFmix). Serum effects, inoculum concentration (cells/mL) seeding density (cell/cm(2)) and accessory cell effects on the expansion of CD34+ cells were determined. RESULTS: Cellular outputs were significantly higher with fetal calf serum (FCS) than with cord blood serum (CBS) or adult group AB serum (ABS) in the presence of 6SMF, however, CBS was as effective as FCS. The best seeding concentrations varied for each of the cytokine combinations, and inoculum densities exceeding 1000 cells per cm(2) proved detrimental for cultures containing GFmix and SGGM. Accessory cell studies indicated that populations expressing the CD33 antigen inhibited the expansion of purified CD34+ cells in the presence of GFmix or SGGM, but not in the presence of 6SMF. CONCLUSION: Serum supplement, inoculum cell concentration, seeding densities, and accessory cell effects are dependent upon the cytokine combination selected to expand cord blood HPCs ex vivo. Thus, each of these measures should be assessed to establish reproducible and reliable conditions for the selection of different cytokine combinations to culture cord blood HPCs.

Adult↗

PubMed1994

Effect of the inoculum size on susceptibility tests performed on sessily growing bacteria.

It has been clearly established that the inoculum size greatly affects the results of antibiotic susceptibility tests performed in both liquid and solid media in standard laboratory growth conditions (i.e. planktonic). Recently methods were developed to perform antibiotic susceptibility tests on bacteria growing in sessile conditions. The present study investigates the effect of the inoculum size on results obtained by these methods. Results show that the inoculum size does not affect tests performed in sessile conditions. A simple and reliable method is proposed to be applied to routine microbiological laboratory procedures.

Anti-Bacterial Agents↗

PubMed1993

Effect of pH, inoculum size, and incubation time on the susceptibility of Ureaplasma urealyticum to erythromycin in vitro.

Determinations of the susceptibility of Ureaplasma urealyticum to erythromycin in vitro as measured by the broth dilution method have shown wide variations with minimal inhibitory concentrations (MICs) from 0.04 to > or = 8 micrograms/mL, indicating a need for standardization. The effects of pH, inoculum size, and incubation were studied. In the broth dilution test, pH had an important effect. The apparent MIC was 4- to 16-fold higher at pH 6.0 than at pH 7.0, with the MIC falling progressively from values of 8 to > or = 8 micrograms/mL to values of 0.25 to 1 microgram/mL as the pH of the medium was increased in steps to pH 7.0. Large inocula also inflated the MICs 2- to 4-fold. In addition, the time of incubation influenced the apparent MIC, with increases of 4- to 16-fold between days 1 and 5. In agar dilution assays, MICs decreased from 2 micrograms/mL at pH 6.2 to 0.5 microgram/mL at pH 6.6. Since pH, inoculum level, and incubation time appear to be responsible for most of the variation in results, we propose that susceptibility testing for ureaplasmas can be improved by using medium with a more neutral pH than that usually used (pH 6) and by standardizing the inoculum size and incubation period.

Colony Count, Microbial↗

PubMed1986

Effects of inoculum size on the activity of carboxy- and ureido-penicillins and effects of combinations of ureido-penicillins with aminoglycosides against resistant Pseudomonas aeruginosa.

Effects of inoculum size on the comparative activity of carbenicillin, ticarcillin, mezlocillin, piperacillin and azlocillin against 20 strains of Pseudomonas aeruginosa known to be relatively resistant to carbenicillin were studied by using 10(4), 10(5) and 10(6) cfu/ml. Inoculum size markedly affected the susceptibility of Ps. aeruginosa to these antibiotics. An increase in the inoculum size from 10(4) to 10(5) cfu/ml had more effects on the MIC of the ureido-penicillins than the carboxy-penicillins. Mezlocillin, piperacillin and azlocillin with gentamicin or tobramycin showed mainly indifference. Synergism or antagonism were demonstrated against a few strains.

Azlocillin↗