Number Of Viable Organisms Research Articles

Relationships between PGL-1 antigen in serum, tissue and viability ofMycobacterium lepraeas determined by mouse footpad assay in multibacillary patients during short-term clinical trial

In connection with a 56-day controlled clinical trial for comparing the therapeutic effects between pefloxacin and ofloxacin in 21 lepromatous patients, we have studied the relationships between PGL-1 antigen level in serum and in skin and serum PGL-1 antibody titre on the one hand, and the viability of Mycobacterium leprae, as measured by serial mouse footpad inoculations, and other bactericidal parameters on the other. Before and during treatment, significant correlation was found between serum PGL-1 level and the morphological index (MI), and with the number of viable organisms per mg skin tissue. However, neither serum PGL-1 antibody titre nor skin PGL-1 antigen level showed significant change during the 56-day trial. Because the reduction of serum PGL-1 level was well correlated but less pronounced as compared with the evolution of viable organisms during treatment, the serum PGL-1 antigen assay may be useful as an early indicator of response to chemotherapy in short-term clinical trial, but it is unlikely to replace mouse footpad inoculation for the evaluation of viability of M. leprae.

The effect of pH and concentration on the rates of kill of benzoic acid solutions against E. coli.

Mathematical models were developed which related benzoic acid concentrations to their D-values at room temperature. Linear regression was used to determine D-values (i.e. the time required for a particular concentration of preservative at specified pH, temperature and medium to cause a 90% reduction in the number of viable organisms, e.g. Escherichia coli. A number of concentrations of benzoic acid at either pH 3 or pH 4 were used. Linear regression of the log D-values versus the log of the concentration was used to derive power curves (a minimum of four points per pH were examined). Concentration exponents, eta-values (the logarithmic values relating changes in rates of kill to specified changes in concentrations) and A-values (extrapolated D-values at 1% concentration), were determined. The effect of pH on the eta and A-values of benzoic acid on E. coli was investigated. Benzoic acid was found to be more sensitive to pH changes than was anticipated from the Henderson-Hasselbalch equation which relates dissociated and undissociated fractions at the two pH levels investigated. However, the sensitivity of preservative activity to dilution at both pH values (3 and 4), as given by the eta-value, remained similar.

Differential scanning calorimetry of bacteria.

Thermograms obtained by differential scanning calorimetry of a range of bacteria of different heat resistances were compared. Equations were derived to calculate the rate at which the numbers of viable organisms in a calorimeter decline as the temperature is raised at a constant rate. Vegetative bacteria scanned at 10 degrees C min-1 showed multi-peaked thermograms with four major peaks (denoted m, n, p and q) occurring in the regions 68-73, 77-84, 89-99 and 105-110 degrees C respectively. Exceptions were that peak m (the largest peak) occurred at 79-82 degrees C in Bacillus stearothermophilus and an additional peak, r, was detected in Escherichia coli at 119 degrees C. At temperatures below the main peak m there were major differences in thermograms between species. There was a direct relationship between the onset of thermal denaturation and the thermoresistance of different organisms. Heat-sensitive organisms displayed thermogram features which were absent in the more heat-resistant types. When samples were cooled to 5 degrees C and re-heated, a small endothermic peak, pr, was observed at the same temperature as p. Peaks p and pr were identified as the melting endotherms of DNA. In all vegetative organisms examined, maximum death rates, computed from published D and z values, occurred at temperatures above the onset of thermal denaturation, i.e. cell death and irreversible denaturation of cell components occurred within the same temperature range.

The Effect of Lysozyme and Ethylenediaminetetraacetic Acid on Salmonella on Broiler Parts

A dip system, consisting of lysozyme (1 mg/ml) and ethylenediaminetetraacetic acid (EDTA) (5 mg/ml), was studied to determine its effect on Salmonella-contaminated broiler parts. Enumeration of S. typhimurium from the broiler parts showed that both lysozyme and a lysozyme-EDTA mixture gave a significant reduction in the number of viable organisms. In a trypticase-soy broth solution, Salmonella growth was inhibited by EDTA while lysozyme showed little effect.

Effect of utilization of substrates on the composition of dental plaque

The microbiota in the mouth is subjected to substrate limitations. In this study we have evaluated the role of competition for carbon and energy substrates on the proportions of 2 microbial species in a simplified plaque ecosystem in gnotobiotic rats. Germ-free rats were inoculated with a combination of Streptococcus sanguis and Streptococcus mutans, or with a combination of Streptococcus milleri and S. mutans. The available carbon and energy sources were varied through the host's diet. 3 Experimental diets were tested: (i) a basal diet low in soluble carbohydrates; (ii) an arginine-supplemented diet; (iii) a sucrose-supplemented diet. Arginine is used for growth by S. sanguis and S. milleri, but not by S. mutans. Sucrose is rapidly fermented by all 3 species. The total number of viable organisms on the dentition increased when arginine or sucrose were supplied in the diet. With the arginine-supplemented diet, S. sanguis and S. milleri increased while S. mutans decreased. With the sucrose-supplemented diet, S. mutans increased while S. sanguis and S. milleri decreased. These results were explained by assuming that the organism with the highest growth rate on the supplementary substrate competes most favourably. Changes in the environmental pH, due to breakdown of sucrose and arginine, might also have affected the competition between the streptococci. In addition, production of extracellular glucans from sucrose could be a competitive advantage for S. mutans.

Illuminated Rose Bengal causes adenosine triphosphate (ATP) depletion and microbial death

Escherichia coli B/r exposed to visible light, oxygen and Rose Bengal was killed by singlet oxygen. There was no evidence of cytotoxicity when the organisms were suspended in non-illuminated dye (2 × 10-4 mol/1). Incubation in oxygenated dye before exposure to light induced a quicker onset of exponential death but the eventual rate was slower than that of organisms exposed continuously to light. The concentration of intracellular adenosine triphosphate (ATP) of illuminated E. coli B/r declined before there was a demonstrable reduction in the number of viable organisms. A carotenoid containing species of Rhodotorula was not killed by the irradiated dye even with a photoflux greater than that used for the coliform. There was no diminution in the ATP content of this yeast with illumination. Thus this study has shown that ATP photometry can be used to explore the kinetics of photoinactivation of sensitive micro-organisms.

Quantitation of Leishmania tropica major by Its Ability to Form Distinct Colonies on Agar-Based Media

The growth of the pathogen Leishmania tropica major on agar-based media was studied to further develop techniques that can be used to quantitate the number of viable organisms in infected tissues. Individual, intact amastigotes formed distinct, countable colonies on four different agar-based media. However, the largest colonies (0.35 mm) and highest plating efficiency (greater than 90%) were found on media formulated with a heart-infusion agar base. Use of this media in the quantitation of the organism should increase the sensitivity of the quantitation technique and allow one to collect more interpretable data on host-parasite interactions in experimental cutaneous leishmaniasis.

Freeze-Dried Mixed Cultures as Samples for Proficiency Tests and Collaborative Studies in Food Microbiology

A method is presented for preparing samples of freeze-dried mixtures of microorganisms for proficiency tests and collaborative studies. The samples may include most microorganisms that are found in routine analysis in food laboratories. Transport of samples during 48 h did not decrease the number of microorganisms, nor was the variability among samples significantly affected by transport. The standard deviation of counts after 5 weeks of storage varied from 0.04 (Staphylococcus aureus) to 0.17 (Clostridium perfringens) log unit. Storage of samples for 10 weeks decreased the number of viable organisms by 0.02-0.43 log unit. Variability among samples increased for Providencia alcalifaciens and Bacillus cereus after 10 weeks of storage. No significant increase was found for the other organisms.

Simulated surgical wound infection in mice: effect of stimulation on nonspecific host defense mechanisms.

Experiments were conducted to ascertain whether nonspecific host defenses could be enhanced in a reliable animal model simulating the local bacterial infection that frequently complicates surgical wounds. The test lesion was studied in detail and exemplifies the concept that the ultimate expression of the host-pathogen interaction is the capacity of that pathogen to persist or grow in a given host. Mice were challenged by intramuscular insertion of cotton suture impregnated with 10(7) to 10(8) Escherichia coli K-12. The mice were subsequently killed at intervals, and the suture and muscle mass were retrieved, homogenized, and quantitatively cultured. Numbers of viable organisms in tissue from control animals were compared with those from experimental animals that received BCG (Bacillus Calmette-Guérin) vaccine, a nonspecific immunostimulant, prior to bacterial challenge. Improved tissue antibacterial activity appeared in animals that had received BCG vaccine 13 days prior to bacterial challenge. Differing doses and intervals were not protective. Enhancement of nonspecific host defense mechanisms may be helpful in combination with current measures for improved control of surgical wound infection.

Basis and results of therapy with Beta-lactam antibiotics in experimental infections.

Experimental infections in animals and their chemotherapy are dependent on a variety of experimental conditions and parameters which may be themselves interrelated; the type and number of infecting organisms, the nature of the infection, the antibiotic chosen for therapy and its administration schedule can influence the results of animal studies. One additional factor which applies to dosage of penicillins is the phenomenon of the recovery period, i. e. the period of time which surviving bacteria need to resume growth after removal of the drug. The bactericidal effect probably strongly influences the period of time which is required before the number of viable organisms reach the level present at the time of infection. Thus one can assume that it is the extent of the bactericidal effect which influences the period of time between doses rather than the recovery period. Besides these parameters the physiological state of the infecting organism may also be important. The results of penicillin therapy vary considerably depending on the bacterial growth rate. Differences in the nature of infection in experimental animals and man and the physiology of animals and man do not allow close simulation of clinical infections under experimental conditions. However the factors discussed may provide some guidelines for rational antibiotic treatment in man.

Experimental Infection with Mycobacterium Avium, Serotype 2, in Pigs

Twelve pigs were inoculated orally with Mycobacterium avium. The doses used were 0.5, 2 or 10 mg daily for 5 days, or 10, 50 or 180 mg once (1 mg = 37 × 106 viable units). Two pigs were used per dose, 1 of which was sacrificed 3 days, the other 28/31 days after the last inoculation (Table 1). Three days after inoculation, M. avium was found in the tonsils and in the intestinal mucosa of all 6 pigs, and in the mesenteric lymph nodes of 4. Viable unit counts for tonsils and intestinal mucosa were highest in pigs inoculated with 180 mg×1 and 10 mg×5. Histopathologically these pigs showed activation of the lymphoid tissue in the tonsils, Peyer patches and mesenteric lymph nodes. Twenty-eight/31 days after inoculation a spreading of the infection had taken place in all pigs, most often to the liver, less frequently to the spleen and the lungs. The kidneys and the musculature were not infected (Table 4). A correlation was apparent between the size of dose and the number of viable organisms in the tissues. Divided doses gave about 10 times higher viable counts than a single dose with the same total number of organisms (Table 5). No gross lesions were found 28/31 days after inoculation. Microscopic granulomatous lesions were found in the tonsils of 6 pigs, in the intestinal mucosa of 4 pigs, in the mandibular and mesenteric lymph nodes of 6 pigs, in the retropharyngeal lymph nodes of 3 pigs, and less frequently in the parotid and hepatic lymph nodes (Table 3). Five of 6 pigs were weakly sensitive to avian tuberculin PPD, 1000 t.u. per dose, when tested 22/25 days after inoculation; 1 of these pigs cross-reacted to human tuberculin (Table 2).

Experimental Infection with Mycobacterium Avium, Serotype 2, in Pigs

Twelve pigs were inoculated orally with Mycobacterium avium. The doses used were 0.5, 2 or 10 mg daily for 5 days, or 10, 50 or 180 mg once (1 mg = 37 × 106 viable units). Two pigs were used per dose, 1 of which was sacrificed 3 days, the other 28/31 days after the last inoculation (Table 1). Three days after inoculation, M. avium was found in the tonsils and in the intestinal mucosa of all 6 pigs, and in the mesenteric lymph nodes of 4. Viable unit counts for tonsils and intestinal mucosa were highest in pigs inoculated with 180 mg×1 and 10 mg×5. Histopathologically these pigs showed activation of the lymphoid tissue in the tonsils, Peyer patches and mesenteric lymph nodes. Twenty-eight/31 days after inoculation a spreading of the infection had taken place in all pigs, most often to the liver, less frequently to the spleen and the lungs. The kidneys and the musculature were not infected (Table 4). A correlation was apparent between the size of dose and the number of viable organisms in the tissues. Divided doses gave about 10 times higher viable counts than a single dose with the same total number of organisms (Table 5). No gross lesions were found 28/31 days after inoculation. Microscopic granulomatous lesions were found in the tonsils of 6 pigs, in the intestinal mucosa of 4 pigs, in the mandibular and mesenteric lymph nodes of 6 pigs, in the retropharyngeal lymph nodes of 3 pigs, and less frequently in the parotid and hepatic lymph nodes (Table 3). Five of 6 pigs were weakly sensitive to avian tuberculin PPD, 1000 t.u. per dose, when tested 22/25 days after inoculation; 1 of these pigs cross-reacted to human tuberculin (Table 2).

Infektionsforsøg på svin med Mycobacterium avium, Serotype 2. 2. Peroral infektion med store doser af M. avium

Twelve pigs were inoculated orally with Mycobacterium avium. The doses used were 0.5, 2 or 10 mg daily for 5 days, or 10, 50 or 180 mg once (1 mg = 37 × 106 viable units). Two pigs were used per dose, 1 of which was sacrificed 3 days, the other 28/31 days after the last inoculation (Table 1). Three days after inoculation, M. avium was found in the tonsils and in the intestinal mucosa of all 6 pigs, and in the mesenteric lymph nodes of 4. Viable unit counts for tonsils and intestinal mucosa were highest in pigs inoculated with 180 mg×1 and 10 mg×5. Histopathologically these pigs showed activation of the lymphoid tissue in the tonsils, Peyer patches and mesenteric lymph nodes. Twenty-eight/31 days after inoculation a spreading of the infection had taken place in all pigs, most often to the liver, less frequently to the spleen and the lungs. The kidneys and the musculature were not infected (Table 4). A correlation was apparent between the size of dose and the number of viable organisms in the tissues. Divided doses gave about 10 times higher viable counts than a single dose with the same total number of organisms (Table 5). No gross lesions were found 28/31 days after inoculation. Microscopic granulomatous lesions were found in the tonsils of 6 pigs, in the intestinal mucosa of 4 pigs, in the mandibular and mesenteric lymph nodes of 6 pigs, in the retropharyngeal lymph nodes of 3 pigs, and less frequently in the parotid and hepatic lymph nodes (Table 3). Five of 6 pigs were weakly sensitive to avian tuberculin PPD, 1000 t.u. per dose, when tested 22/25 days after inoculation; 1 of these pigs cross-reacted to human tuberculin (Table 2).

The influence of protein source and basal dietary component on survival in acute experimental fowl typhoid in the chick (Gallus domesticus).

1. The influence of diet on the survival of chicks inoculated orally at 15 d of age with Salmonella gallinarum was determined, and in the first experiment the numbers of salmonellae were counted in blood 5 or 7 d after inoculation to assess their value in predicting survival. 2. Significantly more chicks survived among those given beef powder as the protein supplement in a starch-based diet than among those where fish flour replaced beef powder. The number of salmonellae in blood was significantly higher in chicks given the fish-flour diet than in those given the beef-powder diet, but the relationship between the number of viable organisms in blood and the final survival rate was not close. 3. Whale meat and soya-bean protein gave high survival rates, similar to that given by beef powder, and casein plus gelatin was slightly poorer in this respect. 4. For each high-protein food the level of survival from the acute disease was significantly greater with wheat than with starch as the basal component of the diet. 5. The addition of either condensed beef extract or fish solubles to a standard diet did not influence survival.

Subcutaneous multiplication of exfoliatin-producing staphylococci.

After subcutaneous inoculation of approximately 10(6) cocci, changes in staphylococcal populations were followed by the enumeration of organisms in excised tissues. In contrast to conventionaal Staphylococcus aureus strains, exfoliatin-producing strains were able to multiply in the subcutaneous tissues of neonatal and adult mice. Although strains capable of producing large quantities of exfoliatin were better able to proliferate than strains producing lesser amounts of toxin, it was not determined whether exfoliatin was directly responsible for the observed multiplication. Two variants exhibiting a partial loss in exfoliatin production showed minor changes in proliferative capability. A third strain, after being cured of its exfoliatin plasmid, manifested a marked reduction in exfoliatin production and was unable to multiply subcutaneously. With some strains multiplication proceeded for several hours but was then followed by a decline in the number of viable organisms. Histological sections of subcutaneous lesions revealed a rapid influx of neutrophils, but leukocytes accumulated in the region regardless of whether the organisms multiplied or were eliminated.

Neonatal escherichia coli septicemia—bacterial counts in blood

Bacterial counts in blood of E. coli (number of viable organisms per milliliter) are reported for 30 neonates whowere cultured because of suspected septicemia. Fifteen of the infants died; 13 of the deaths occurred within 48 hours after cultures were obtained and appropriate antibiotic therapy had been initiated. Thirty-five positive cultures were obtained from the 30 neonates; in 11 (31%) of the cultures the colony counts were in excess of 1,000/ml; in 5 (14%), the counts ranged from 50 to 1,000/ml; in 11 (31%), from 5 to 49/ml; in 8 (23%), from 0 to 4/ml. Seventy-three per cent (8/11) of the neonates with colony counts greater than 1,000/ml died.

The Viability of Salmonella typhimurium in Ice-Cream

The survival of Salmonella typhimurium in ice-cream Avas studied. In the inoculated ice-cream mix, the counts of S. typhimurium markedly increased after aging for 24 h. at 10°C, but during freezing at —5°C and cold storage of ice-cream at —20 °C there was a continual decrease in the number of viable organisms. The decrease, rapid at first, gradually slowed down. A sharp sudden drop in counts occurred at the end of the eleventh month and continued up to the twelvth month. Living S. typhimurium were still present after one year of storage at —-20°C. Das Überleben von Salmonella typhimurium in Eiscreme wurde untersucht. Die Anzahl von S. typhimurium nalim in mit diesem Mikroorganismus beimpfter, gemischter Eiscreme nach 24stündiger Lagerung bei 10 °C zu, aber während des Gefrierens bei — 5°C und kühler Lagerung bei —20 °C nahm die Zahl der lebensfähigen Organismen ab. Diese Abnahme erfolgte am Anfang rasch, wurde allmählich langsamer und vom Ende des elften Monats bis zum Ende des zwölften Monats plötzlich wieder schneller. Lebende S. typhimurium konnten nach einjähriger Lagerung bei — 20 °C festgestellt werden.

Inactivation of Alpha-Amylase in Wheat Flour with Microwaves*

ABSTRACTHigh alpha-amylase flour was exposed to microwave energy in a 1.8 KW 2450 MHz oven for periods ranging from 30 to 100 sec. The effect of the exposure on the enzyme activity was studied. The influence of the different exposures on the moisture content of the flour, its bacterial counts as well as its dough-development and the gassing power of the dough was determined.The 60-sec exposure of the flour to microwave energy reduced the enzyme activity to an acceptable level without any deleterious effects on the principal characteristics of the flour related to dough formation. This exposure drastically reduced the number of viable organisms in the flour, but seemed to cause a somewhat high loss in moisture.

Human plasma and the antibacterial effect of peritoneal dialysis solutions.

The influence of human plasma on the antibacterial effect of solutions for peritoneal dialysis was studied. The solutions contained 43 mEq per litre of either acetate or lactate as the source of base. Enough pooled human plasma was added to half of each solution to give a total concentration of a gramme of protein per litre. The numbers of viable organisms from 15 clinical isolates each of Staphylococcus aureus, Escherichia coli, and Pseudomonas species were counted before and after incubation in the four solutions. Numbers of viable Staph. aureus and E. coli diminished consistently after incubation in all four solutions, but the greatest decreases occurred in the acetate solution which contained no plasma. Plasma abolished the greater antibacterial effect of acetate on these organisms. Differences between numbers of viable Pseudomonas sp. after incubation in the four solutions were not significant. The diffusion of substances from plasma into dialysis fluids during peritoneal dialysis, therefore, may abolish the greater antibacterial effect of solutions made with acetate rather than lactate.

Recovery of bacteria from damages induced by heat.

SUMMARY: When Escherichia coli B was heated at 52° and subsequently incubated at 20° or at 37° in phosphate buffer, there was an increase in the number of viable organisms. No such increase was observed when the treated suspension was incubated at 0°5°. Untreated organisms did not increase in number when incubated in phosphate buffer, suggesting that the increase in viable number of heat-treated organisms was not due to division. The observed increase in number of viable organisms was time-dependent and complete in about 60 min., but could be stopped by exposing the treated organisms to X-ray doses greater than 1°5 krad., before or after the heat treatment. Growing the organisms in the presence of chloramphenicol 100 μg./ml. before heat treatment also blocked the repair mechanism, but this could be reestablished by growth in the absence of chloramphenicol for 30 min. before heat treatment.