Screening of Trichoderma isolates for their potential of biosorption of nickel and cadmium

Abstract Fourteen Trichoderma isolates were evaluated for their tolerance to two heavy metals, nickel and cadmium. Three isolates, MT-4, UBT-18, and IBT-I, showed high levels of nickel tolerance, whereas MT-4, UBT-18, and IBT-II showed better tolerance of cadmium than the other isolates. Under nickel stress, biomass production increased up to a Ni concentration of 60 ppm in all strains but then decreased as the concentrations of nickel were further increased. Among the nickel-tolerant isolates, UBT-18 produced significantly higher biomass upon exposure to nickel (up to 150 ppm); however, the minimum concentration of nickel required to inhibit 50% of growth (MIC50) was highest in IBT-I. Among the cadmium-tolerant isolates, IBT-II showed both maximum biomass production and a maximum MIC50 value in cadmium stress. As the biomass of the Trichoderma isolates increased, a higher percentage of nickel removal was observed up to a concentration of 40 ppm, followed by an increase in residual nickel and a decrease in biomass production at higher nickel concentrations in the medium. The increase in cadmium concentrations resulted in a decrease in biomass production and positively correlated with an increase in residual cadmium in the culture broth. Nickel and cadmium stress also influenced the sensitivity of the Trichoderma isolates to soil fungistasis. Isolates IBT-I and UBT-18 were most tolerant to fungistasis under nickel and cadmium stress, respectively.

Comparative in-vitro efficacy of fluoroquinolones against Streptococcus pneumoniae recovered from bacterial keratitis as determined by E-test.

Background and Objectives: The advent of new fluoroquinolones has drawn the attention for reliable methods on the in-vitro susceptibility testing of Streptococccus pneumoniae. This study attempts to determine the minimum inhibitory concentration (MIC) of second-generation (ciprofloxacin and ofloxacin), third-generation (levofloxacin) and the fourth-generation (moxifloxacin and gatifloxacin) fluoroquinolones against S. pneumoniae recovered from bacterial keratitis. Materials and Methods: In retrospect, the MICs of 50 strains of S. pneumoniae isolated from the corneal scrapes of patients with bacterial keratitis were determined against ciprofloxacin, ofloxacin, levofloxacin, gatifloxacin and moxifloxacin using E-tests. The National Committee of Clinical Laboratory Standards (NCCLS) susceptibility patterns and the potencies of the MICs were statistically compared. Results: The median MIC of ciprofloxacin (0.25μg/ml) was found to be lower than the median MICs of ofloxacin (0.5μg/ml) (P<0.449) and levofloxacin (1.0μg/ml) (P<0.001). The median MICs of gatifloxacin (0.1μg/ml) was lower than the median MICs of ciprofloxacin (0.25μg/ml) (P<0.001), ofloxacin (0.5μg/ml) (P<0.001) and levofloxacin (1.0μg/ml) (P<0.001). Moxifloxacin (0.06μg/ml) had showed lower median MICs than gatifloxacin (0.1μg/ml) (P<0.001) levofloxacin (1.0μg/ml) (P<0.001), ofloxacin (0.5μg/ml) (P<0.001) and ciprofloxacin (0.25μg/ml) (P<0.001). Moxifloxacin (0.06μg/ml) had a lower MIC50 (μg/ml) than gatifloxacin (0.1μg/ml), levofloxacin (1.0μg/ml), ciprofloxacin (0.25μg/ml) and ofloxacin (0.5μg/ml). MIC90 (μg/ml) of moxifloxacin (0.06μg/ml) was found to be lower than the MIC90 (μg/ml) of gatifloxacin (0.5μg/ml), levofloxacin (1.0μg/ml), ofloxacin (0.5μg/ml) and ciprofloxacin (0.5μg/ml). Conclusion: Based on in-vitro testing, the five portrayed fluoroquinolones 100% sensitivity to S. pneumoniae. However, the fourth-generation fluoroquinolone, moxifloxacin appeared to be more effective against S. pneumoniae than gatifloxacin, levofloxacin, ofloxacin and ciprofloxacin.