Sodium Polyanethol Sulfonate Sensitivity of Anaerobic Cocci

Growth of Peptostreptococcus anaerobius was shown to be totally inhibited by sodium polyanethol sulfonate (SPS). Other anaerobic cocci grew in the presence of SPS although some strains of Peptococcus prevotii and Peptococcus magnus showed delayed growth. A SPS disk assay for the presumptive identification of P. anaerobius is described.     

Detection of Bacteremia in Children with Sodium Polyanethol Sulfonate: a Prospective Clinical Study

A prospective study was made of 1,000 consecutive duplicate blood cultures obtained from sick children to evaluate the usefulness of sodium polyanethol sulfonate (SPS). With the small volumes of blood (1 to 5 ml) usually obtained for blood cultures in children, SPS did not increase the frequency of recovery of organisms judged to be associated with clinical infections, with the possible exception of Diplococcus pneumoniae. However, the use of SPS was associated with an increased frequency of recovery of organisms judged to be contaminants, such as Staphylococcus epidermidis and propionibacteria, possibly because SPS enhanced the recovery of a very small inoculum of skin bacteria.     

New Method of Grouping Beta-Hemolytic Streptococci Directly on Sheep Blood Agar Plates by Coagglutination of Specifically Sensitized Protein A-Containing Staphylococci

A technique is described that allows the grouping of beta-hemolytic streptococci directly upon the primary colony. This was accomplished by applying a small drop of specifically sensitized protein A-containing Staphylococcus aureus over a colony of streptococci, rocking the plate to allow mixing of the particles with the soluble group-specific polysaccharide, which in the case of beta-hemolytic streptocicci was produced in abundance during colony formation, and observing for agglutination of the sensitized particles. Such a simple test for group A beta-hemolytic streptococci should allow accurate identification of group A streptococci in small laboratories, such as in clinics or physicians' offices, as well as in the larger public health and private laboratories.     

Use of Sealed Agar Plates for Bacterial Cultures Under Jungle Conditions

Commercially available sealed blood-agar plates have been demonstrated to retain their usefulness for as long as 3 months under jungle conditions without refrigeration.     

Stability of Antibiotics and Chemotherapeutics in Agar Plates

The stability of chemotherapeutic agents incorporated into agar plates was studied by comparison of minimum inhibitory concentrations on fresh and stored plates and by direct bioassay of the chemotherapeutic agar plates. Plates were stored in sealed bags at 4 C. No loss of bioactivity was demonstrated after 30 days of storage in plates containing methicillin, erythromycin, cephalothin, tetracycline, chloramphenicol, kanamycin, streptomycin, polymyxin B, or nalidixic acid. Penicillin G, ampicillin, and nitrofurantoin showed statistically significant losses of activity after 4 weeks. None of the chemotherapeutics tested showed significant loss in activity after 1 week.     

Hair Sheep Blood,Citrated or Defibrinated,Fulfills All Requirements of Blood Agar for Diagnostic Microbiology Laboratory Tests

Background

Blood agar is used for the identification and antibiotic susceptibility testing of many bacterial pathogens. In the developing world, microbiologists use human blood agar because of the high cost and inhospitable conditions for raising wool sheep or horses to supply blood. Many pathogens either fail to grow entirely or exhibit morphologies and hemolytic patterns on human blood agar that confound colony recognition. Furthermore, human blood can be hazardous to handle due to HIV and hepatitis [1], [2]. This study investigated whether blood from hair sheep, a hardy, low-maintenance variety of sheep adapted for hot climates, was suitable for routine clinical microbiology studies.

Methods and Findings

Hair sheep blood obtained by jugular venipuncture was anticoagulated by either manual defibrination or collection in human blood bank bags containing citrate-phosphate-dextrose. Trypticase soy 5% blood agar was made from both forms of hair sheep blood and commercial defibrinated wool sheep blood. Growth characteristics, colony morphologies, and hemolytic patterns of selected human pathogens, including several streptococcal species, were evaluated. Specialized identification tests, including CAMP test, reverse CAMP test, and satellite colony formation with Haemophilus influenzae and Abiotrophia defectiva were also performed. Mueller-Hinton blood agar plates prepared from the three blood types were compared in antibiotic susceptibility tests by disk diffusion and E-test.

Conclusions

The results of all studies showed that blood agar prepared from citrated hair sheep blood is suitable for microbiological tests used in routine identification and susceptibility profiling of human pathogens. The validation of citrated hair sheep blood eliminates the labor-intensive and equipment-requiring process of manual defibrination. Use of hair sheep blood, in lieu of human blood currently used by many developing world laboratories and as an alternative to cost-prohibitive commercial sheep blood, offers the opportunity to dramatically improve the safety and accuracy of laboratory diagnosis of pathogenic bacteria in resource-poor countries.     

Modeling Surface Growth of Escherichia coli on Agar Plates

Surface growth of Escherichia coli cells on a membrane filter placed on a nutrient agar plate under various conditions was studied with a mathematical model. The surface growth of bacterial cells showed a sigmoidal curve with time on a semilogarithmic plot. To describe it, a new logistic model that we presented earlier (H.Fujikawa et al., Food Microbiol. 21:501-509, 2004) was modified. Growth curves at various constant temperatures (10 to 34°C) were successfully described with the modified model (model III). Model III gave better predictions of the rate constant of growth and the lag period than a modified Gompertz model and the Baranyi model. Using the parameter values of model III at the constant temperatures, surface growth at various temperatures was successfully predicted. Surface growth curves at various initial cell numbers were also sigmoidal and converged to the same maximum cell numbers at the stationary phase. Surface growth curves at various nutrient levels were also sigmoidal. The maximum cell number and the rate of growth were lower as the nutrient level decreased. The surface growth curve was the same as that in a liquid, except for the large curvature at the deceleration period. These curves were also well described with model III. The pattern of increase in the ATP content of cells grown on a surface was sigmoidal, similar to that for cell growth. We discovered several characteristics of the surface growth of bacterial cells under various growth conditions and examined the applicability of our model to describe these growth curves.     

Use of Hydrogen Peroxide Treatment and Crystal Violet Agar Plates for Selective Recovery of Bacteriophages from Natural Environments

Hydrogen peroxide inactivated bacteriophages and bacteria at different rates. A concentration of 0.1% hydrogen peroxide reduced the numbers of several bacteria by an average of 94% but caused an average of 25% inactivation in the numbers of bacteriophages tested. Treating natural samples with hydrogen peroxide selectively reduced the indigenous bacterial flora and permitted better visualization of plaques of lawns of Escherichia coli C-3000. In some cases indigenous gram-positive bacteria were relatively resistant to hydrogen peroxide, but their growth could be limited by incorporation of crystal violet into the bottom agar used for plaque assays. The use of hydrogen peroxide treatment and crystal violet-containing plates permitted recovery of more phages from natural samples than did other procedures, such as chloroform pretreatment or the use of selective plating agar such as EC medium.     

3'-大豆苷元磺酸钠的体外抗氧化研究

为研究3'-大豆苷元磺酸钠(DSS)的体外抗氧化活性,测定了DSS对超氧自由基(O2·)、羟基自由基(·OH)和1,1-二苯基-2.苦苯肼自由基(DPPH·)的清除能力,及其对Fe2 诱导的脂质过氧化反应和β-胡萝卜素/亚油酸自氧化体系的抑制作用.结果表明,DSS对DPPH·有一定的清除能力,对超氧自由基的清除能力较强,能很好地清除·OH自由基,对脂质过氧化有一定的抑制作用,对β-胡萝卜素/亚油酸自氧化体系有明显的抑制作用.说明DSS的药理作用可能与其较强的抗氧化能力有关.