Photodynamic fungicidal efficacy of hypericin and dimethyl methylene blue against azole-resistant Candida albicans strains.

Antimicrobial photodynamic therapy (aPDT) is an emerging alternative to treat infections based on the use of photosensitisers (PSs) and visible light. To investigate the fungicidal effect of PDT against azole-resistant Candida albicans strains using two PSs with a different mechanism of action, hypericin (HYP) and 1,9-dimethyl methylene blue (DMMB), comparing their efficacy and the reactive oxygen species (ROS) species involved in their cytotoxicity. Azole-resistant and the azole-susceptible C. albicans strains were used. Solutions of 0.5 and 4 McFarland inoculum of each Candida strain were treated with different concentrations of each PS, and exposed to two light-emitting diode light fluences (18 and 37 J cm⁻²). Mechanistic insight was gained using several ROS quenchers. The minimal fungicidal concentration of HYP for ≥3 log10 CFU reduction (0.5 McFarland) was 0.62 µmol l⁻¹ for most strains, whereas for DMMB it ranged between 1.25 and 2.5 µmol l⁻¹. Increasing the fluence to 37 J cm⁻² allowed to reduce the DMMB concentration. Higher concentrations of both PSs were required to reach a 6 log10 reduction (4 McFarland). H2O2 was the main phototoxic species involved in the fungicidal effect of HYP-aPDT whereas ¹O2 was more important for DMMB-based treatments. aPDT with either HYP or DMMB is effective in killing of C. albicans strains independent of their azole resistance pattern. HYP was more efficient at low fungal concentration and DMMB at higher concentrations.

Comparative activity of ceftizoxime against aminoglycoside-resistant aerobic gram-negative bacilli.

The in vitro activity of ceftizoxime was compared with that of other beta-lactam antibiotics against 331 aminoglycoside (AG)-resistant clinical isolates. Two hundred and six AG-resistant, beta-lactamase producing, R-plasmid harbouring Enterobacteriaceae strains had MICs ranging from 0.0125 to 0.063 mg/l. AG-resistant Escherichia coli (36 strains) and Klebsiella pneumoniae (19) had MIC 90 values of 8 mg/l. Proteus rettgeri and P. vulgaris as well as Morganella morganii, resistant to several AGs, had MICs ranging from 0.5 to 4 mg/ml. Against all six isolates of AG-resistant Salmonella enteritidis the MIC90 was 0.5 mg/l. Twenty-seven strains of Serratia marcescens, most of which were resistant to beta-lactam and AG antibiotics, had MICs ranging from 0.5 to 8 mg/l. The AG-resistant strains of Enterobacteriaceae producing several AG-modifying enzymes (AAC(3); AAC(2'); AAC(6'); APH(3')) showed MICs ranging from 0.6 to 4 mg/l. Against 10 AG-resistant strains of Pseudomonas aeruginosa producing AAC(3), AAC(6') and APH(3') enzymes, the MICs ranged from 16 to 64 mg/l. In conclusion, ceftizoxime was equally or more active than cefotaxime, cefoperazone, ceftazidime and moxalactam against AG-resistant E. coli, Klebsiella, Morganella, Proteus, Serratia, Salmonella and R-plasmid harbouring Enterobacteriaceae. Ceftizoxime was less active than cefotaxime, moxalactam and ceftazidime against P. aeruginosa.

Differentiation between Trichophyton mentagrophytes and T. rubrum by sorbitol assimilation.

Trichophyton rubrum was easily differentiated from T. mentagrophytes by its ability to assimilate sorbitol with an API 20C AUX strip. One hundred percent of 36 T. rubrum strains and none of 147 T. mentagrophytes strains assimilated sorbitol.

[Phage count in the waters of the Canal Imperial de Aragón and the Ebro River in Saragossa]. / Recuento de fagos en aguas del Canal Imperial de Aragón y del río Ebro en Zaragoza.

Saragossa city supply channel and the river Ebro (up and downstream urban sewage) were studied for the presence of coliphages and B. fragilis phages and their relationship with the bacterian faecal indicators. In the supply channel the coliphages geometric mean was of 130 ufp/100 ml, and showed no correlation with faecal and total coliforms, but it showed indirect correlation with ambient temperature. In the river Ebro the coliphages geometric mean ranged from 290 to 8,000 ufp/100 ml; the relationship with total and faecal coliforms and faecal streptococci was high, but they were temperature independent. With the methodology utilized B. fragilis phages only were recovered in samples with faecal coliforms levels > 1 x 10(4) ufc/100 ml.