Biomedical subjects

Tasneem Fatma

Publications and source records attributed to Tasneem Fatma.

6 recordsLinked to original sources

PubMed2006

Effect of heavy metal stress on proline, malondialdehyde, and superoxide dismutase activity in the cyanobacterium Spirulina platensis-S5.

This study investigated toxic impacts of lead, copper, and zinc over a concentration gradient of 0.05-0.20 mg/L on proline, malondialdehyde (MDA), and superoxide dismutase (SOD) in the cyanobacterium Spirulina platensis-S5. Despite a reduction in growth of the test microorganism, its MDA, SOD, and proline contents increased under the heavy metal stress, corresponding to the concentration of the metal ion in the culture medium. Increased amount of MDA was indicative of formation of free radicals in the test microorganism under heavy metals stress(es), while increased levels of SOD and proline pointed to the occurrence of a scavenging mechanism.

Copper↗

PubMed2006

Characterisation of laboratory-generated vancomycin intermediate resistant Staphylococcus aureus strains.

Vancomycin has been the drug of choice for 30 years for the treatment of methicillin-resistant Staphylococcus aureus (MRSA). Emergence of decreased vancomycin susceptibility in MRSA strains presents a significant clinical problem with few therapeutic options. This study was performed to generate and characterise S. aureus strains with reduced susceptibility to vancomycin. Eighteen S. aureus strains were subjected to serial passaging on vancomycin to generate vancomycin intermediate resistant S. aureus (VISA) strains. Minimum inhibitory concentration (MIC) determination was performed for the parent and the passaged cultures with 13 different antibiotics. The strains were tested by the following five methods: simplified population analysis; CDC method; modified vancomycin agar screen; population analysis profile (PAP); and modified population analysis (PAP-area under the curve (AUC) ratio). Phenotypic changes such as doubling time, synergy with beta-lactam antibiotics and effect on norA efflux pumps were also studied for these strains. The result indicated that 8 VISA mutants (vancomycin MICs, 8-16 microg/mL) were generated in vitro from the 18 S. aureus strains. The CDC and modified agar methods proved to be the most sensitive and specific methods for detection of VISA strains. The PAP for all the VISA strains ranged from 12 microg/mL to > 16 microg/mL, with a PAP-AUC ratio of > 1.3. All mutants showed increased doubling time compared with their parent isolate. Synergism of the vancomycin and beta-lactam combinations was observed for all methicillin-resistant mutants. Upon acquisition of vancomycin resistance, a few mutants showed decreased oxacillin resistance. Two VISA strains were chosen for molecular characterisation of the mecA gene and one mutant showed genotypic changes with deletion of mecA. Loss of norA efflux pumps leading to fluoroquinolone sensitivity was also observed in four mutants.

Laboratories↗

PubMed2005

Adverse effect of staphylococci slime on in vitro activity of glycopeptides.

Adhesion to biomaterial is assumed to be a crucial step in the development of staphylococcal foreign body infections. Production of extracellular slime has major implications for the development and implementation of therapeutic strategies. The effect of extracted slime was investigated on the activity of vancomycin, teicoplanin, linezolid, quinupristin/dalfopristin, rifampicin and ranbezolid against 10 clinical and 4 ATCC staphylococcal isolates. The slime extract caused a 2- to 16-fold increase in the MICs of vancomycin and teicoplanin, with a shift in the MIC(90) from 2 to 32 (vancomycin) and 2 to 16 (teicoplanin), whereas the MICs of linezolid and quinupristin/dalfopristin were only moderately affected. In time-kill studies, a significant decrease in bacterial killing (>3 log(10) cfu/ml) was observed with vancomycin and teicoplanin (4 x MIC) after addition of slime (5 and 20 mg/ml), whereas the effect of killing by linezolid and quinupristin/dalfopristin was very modest. The rifampicin and ranbezolid MICs and kill curves were not influenced by the addition of slime. The present study thus indicated that slime interferes with the antimicrobial effect of glycopeptide drugs (vancomycin, teicoplanin), and that for effective prevention and treatment of prosthetic device-related infections, appropriate and newer antibiotics such as ranbezolid should be considered.

Anti-Bacterial Agents↗

PubMed2004

In vitro activity of RBx 7644 (ranbezolid) on biofilm producing bacteria.

Biofilm associated infections are becoming more common. Treatment outcome of device related infections cannot be predicted by the results of a standard susceptibility test such as the MIC. Microorganisms involved in device related infections have a slow growth rate and adhere to surfaces. Activity against glass adherent bacteria has been shown to be correlated with treatment outcome in animal models of catheter related infections. Drug efficacy can be predicted if glass adherent staphylococci are killed by low drug concentration. The eradication of bacteria adhering to glass beads and inhibition of biofilm formation by ranbezolid and three other antibiotics (quinupristin/dalfopristin, vancomycin and linezolid) was studied. The results indicated that ranbezolid required only (2-4 x MIC) for total clearance of glass-adherent MRSA 562 and MRSE 879, compared with vancomycin (8 x), quinupristin/dalfopristin (1-4 x) and linezolid (4-16 x MIC). In addition ranbezolid inhibited biofilm formation to a greater extent at sub MIC and MIC level. In conclusion, this study indicated that ranbezolid had potent activity against adherent staphylococci isolates and may prove useful in the prevention and treatment of device related infections caused by staphylococci.

Anti-Infective Agents↗

PubMed2004

Toxicological studies of pesticides on cytoplasmic streaming in Nitella.

In the present study, changes in velocity of cytoplasmic streaming in the giant internodal cells of Nitella for varying concentration of the pesticides, 2,4-D, dieldrin, malathion, methyl parathion and endosulfan, were measured. Marked decrease in the velocity of cytoplasmic streaming was found at the concentrations of 0.01, 0.1, 1, 10 and 100mM. Dieldrin was the most toxic to all the pesticides investigated, followed by methyl parathion, endosulfan, malathion and 2,4-D. Threshold values for dieldrin, methylparathion, endosulfan, malathion and 2,4-D as indicated by the onset of decrease in the normal cytoplasmic streaming velocity were less than 6.25 x 10(-6), 2.5 x 10(-5), 5 x 10(-5), 5 x 10(-5) and 1.25 x 10(-5)M respectively. Cessation of streaming was noticed above 1mM in dieldrin and above 10mM when exposed to methylparathion and endosulfan. Cessation of streaming was not seen up to 100mM concentration of 2,4-D and malathion.

Cytoplasm↗

PubMed2004

The impact of physical stresses on the growth of cyanobacterium Spirulina platensis-S5.

Cyanobacterium Spirulina is in ever increasing demand internationally due to its high value bio-chemical constituents which find application in areas like health foods and therapeutics, especially for its high protein content. The Spirulina protein is superior to practically all proteins including those from legumes, and is comparable to milk proteins for that matter. Moreover, interest in its phycocyanin, b-carotene, polyunsaturated acids (PUFA) and super oxide dismutase (SOD) contents has attracted the attention of researchers the world over towards protecting, promoting and preserving the production of this useful micro-organism. The present investigation deals with examining the impact of various physical stresses viz. intensity and photo-period of light, varying chromatic regimes, temperature, pH, etc., on the growth of Spirulina platensis-S5 to spell the appropriate conditions for raising the strain in laboratory. No earlier report of this kind is available, so far, to our knowledge. The experimental results suggested that 16 : 8 hours light : dark regime at light intensity of 2000 +/- 200 lux, temperature of 30 +/- 1 degrees C and pH of 9.1 are the optimal growth conditions for the test micro-organisim. The growth under different chromatic regimes observed the order yellow> red> green> blue.

Cells, Cultured↗