Concentration dependent exposure of vancomycin and teicoplanin induces vanG regulon in Staphylococcus aureus.

Therapeutic options for staphylococcus infections have been raised due to the emergence of VISA and VRSA. Six isolates of Staphylococcus aureus of clinical origin which were previously confirmed to carry vanG were selected for this study. Antimicrobial susceptibility was performed by disc diffusion method. Transcriptional expression of vanG and vanSG showed down regulation against vancomycin and teicoplanin but expression was increased with increasing concentration of antibiotics. vanUG, vanRG showed up regulation against glycopeptide exposure. The present study underscored that expression of vanG and its regulatory gene operons are dependent on concentration of vancomycin and teicoplanin exposure in S.aureus.

Transcriptional Response of vanB Operon in Staphylococcus aureus Against Vancomycin and Teicoplanin Stress.

Staphylococcus aureus is a global pathogen and is responsible for causing severe life-threatening infections. The current study was designed to investigate transcriptional expression of different core, regulatory, and accessory genes within vanB operon under differential exposure of vancomycin and teicoplanin. Four isolates selected for the study, were confirmed to harbour vanB gene in which three isolates showed MIC breakpoint above 16 µg/ml and one isolate above 8 µg/ml against vancomycin while teicoplanin showed higher MIC breakpoint as compared to vancomycin. Antibiotic susceptibility results showed that these isolates were susceptible towards imipenem and linezolid. Transcriptional expressional analysis of the core gene of vanB operon showed that expression of vanB is increased under vancomycin stress but is inversely proportional to increase in the concentration of the vancomycin while under teicoplanin stress the expression of vanB showed no significant pattern. Similar expressional pattern was found for vanH gene for both the glycopeptides. In case of vanX, expression was significantly increased at 1 µg/ml exposure of vancomycin, however, no pattern could be observed in case of teicoplanin stress. In case of regulatory gene, vanR, significant increase in expression was observed under vancomycin and teicoplanin stress of 1 µg/ml, however vanS, showed significant increase in the expression under 1 µg/ml of vancomycin. The accessory gene, vanY showed marginal increase in expression under both the antibiotic, while in case of vanW, the expressional pattern was found to be inversely proportional to the increasing antibiotic concentration.

Cyathea gigantea (Cyatheaceae) as an antimicrobial agent against multidrug resistant organisms.

BACKGROUND: Rapid emergence of multidrug resistant (MDR) organisms in hospital and community settings often result into treatment failure, thus leading the clinicians with fewer treatment options. Cyathea gigantea, an ethnomedicinally important fern used in cuts and wound infections. So, if this medicinal plant is used in treating the MDR infections then it might bring certain relief in future treatment options. METHODS: Antibacterial activity of C. gigantea against MDR bacteria was assed using well diffusion and broth microdilution methods to determine the diameters of growth inhibition zones, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Synergistic activity was also determined with the conventional antibiotics by disc diffusion method followed by FIC index of each of the tested antibiotic was calculated. The active extract was then subjected to fractionation by column chromatography and antibacterial activity was done with each of the collected fractions. RESULTS: Crude extract of C. gigantea was found to be active against all the tested organisms. The MIC was 200 µg/ml against Gram-positive i.e., Staphylococcus aureus ATCC 25923 and 400 µg/ml against Gram-negative i.e., Escherichia coli ATCC 25922 and Pseudomonas aeruginosa PAO1, while the MBC was 400 µg/ml in case of Gram-positive and 800 µg/ml for Gram-negative. The synergistic activity revealed that the plant extract increased the antibacterial property of the studied antibiotics and the FIC index showed that significant synergistic activity was shown by ciprofloxacin followed by tetracycline, ampicillin and oxacillin. Antibacterial activity with the fractionated extract showed that the FR II, FR III and FR IV were active against both Gram-positive and Gram-negative bacteria, whereas FR I, FR V and FR VI did not show antibacterial property against any of the tested bacteria. CONCLUSIONS: Extracts of C. gigantea was found active against both selected Gram-positive and Gram-negative organisms and thus offers the scientific basis for the traditional use of the fern. The present study also provides the basis for future study to validate the possible use against multidrug resistant organisms.

Transcriptional response of OmpC and OmpF in Escherichia coli against differential gradient of carbapenem stress.

OBJECTIVE: This study was designed to investigate the transcriptional response of OmpF and OmpC along with an antisense RNA, MicF under concentration gradient carbapenem exposure. RESULT: An elevation in the expression of OmpF gene under concentration gradient imipenem stress from a particular concentration was observed. For OmpC gene a significant decrease in the expression was noticed under concentration gradient imipenem and meropenem stress. The study showed reduction in the expression of OmpC gene against imipenem and meropenem possibly preventing the entry of carbapenem antibiotic inside the cell indicating a possible role in carbapenem resistance.