Bacteria inocula, effects

In a number of cases, microbial resistance is mediated by the production of bacterial enzymes that attack the antibiotic molecule, changing its structure to an inactive form. This can lead to a so-called inoculum effect, in which a susceptible antibiotic is apparently less potent when larger numbers of bacteria are present in the medium than when fewer cells are employed. The more bacteria that are present, the more antibiotic-destroying enzyme that is present, and the more antibiotic that is required to overcome this to achieve the desired response. An antibiotic that is not enzyme modified is comparatively free of inoculum effects. 

Moxalactam is active against most commonly encountered anaerobic bacteria (6,10,14,23-25,29,30,35-37) and is more active against certain strains than cefotaxime, cefoperazone, and cefoxitin. For many isolates, the concentration of moxalactam required for bactericidal activity is the same as or twofold greater than the MIC (23,27,28). For most bacterial strains, increasing the inoculum size has little or no effect on the MIC of moxalactam (6,9,10,13,16,21). 

In our further study we investigated effects of various numbers of virulent (strain C) and avirulent (strain A) E. coli on serum microbiostasis. Bovine serum was distributed in 1-ml quantities into small screw-topped tubes and was infected with various numbers of strain A or strain C bacteria. After 12- and 24-hr incubation at 37 °C, samples of infected sera were plated on IPAM. Numbers of bacteria were determined by counting bacterial colonies on plates after 12-hr incubation. Results showed that bovine serum inhibited bacilli of avirulent strain A if the inoculated serum contained less than 12,000 bacilli per 1 ml of serum. Larger inocula of strain A multiplied in serum but at a slower rate than in broth medium (Table III). Bacteria of virulent strain C overcame the iron starvation in bovine serum even when serum was inoculated with as few as 100 cells/ml of serum. The results of this study showed that the rate of bacterial multiplication in bovine serum is determined partly by bacterial numbers in the inoculum. Small inocula of virulent and avirulent bacteria were more inhibited than large inocula. The growth of even minute inocula of virulent bacteria in bovine serum... 

Two methods are used to determine the expected effects of combination antibiotic therapy. For the most part, both methods are not used commonly in the clinical microbiology laboratory owing to the substantial labor involved with these tests and the lack of strong correlation with clinical outcome in the majority of infections. The first method is the microtiter fractional inhibitory concentration (FlC, or checkerboard method). The FlC is performed in a similar manner to the microtiter broth MIC except that two antibiotics are tested in the same microtiter plate. Twofold serial dilutions of one antibiotic are made in one direction on the plate (e.g., from right to left), whereas dilutions of the second antibiotic are made from the other direction on the same plate (e.g., from top to bottom). This method produces all possible combinations of twofold concentrations for the two drugs being tested. An inoculum of test bacteria is added to all wells, and the results are read in a similar manner as the MIC test. The FlC is expressed mathematically by calculation of the FlC index. The FlC index is calculated as... 

Evaluated the effect of environmental factors on hydrogen production using mixed culture. Successfully enriched naturally available mixed seed to culture hydrogen producing bacteria. Enhanced the hydrogen production through preheat treatment of seed inoculum at 70-90°C for 15 - 20 minutes followed by repeated heat treatment of settled returned sludge. 

The results of antimicrobial activities of polyester and polypropylene treated fabric with different bacteria are indicated in Tables 1-5. The inoculum was a nutrient broth culture containing 0.5x10, Ixio and 1.5 xlO /mL colony-forming units (CPU) of the bacterium. The results show that 1% and higher concentration of CTAB on both polyester and polypropylene fabrics reasonably inhibit the growth of E. coli at pH=7 and S. aureus and P. aeroginosa at pH=5.5 (pH=5.5 is the pH of body skin). This test can not be used for viscose nonwoven because of disturbing effect of adhesive used for fabric production. 

Some commercial silage additives now contain enzymes along with an inoculum of suitable strains of lactic acid bacteria. The enzymes are usually cellulases and hemicellulases, which degrade the cell walls of plants, thus releasing sugars, which are then available for fermentation by the lactic acid bacteria. The enzymes appear to be most effective when added to young herbage ensiled at low dry matter content. 

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