- Volume 66, Issue 10, 2017

Purpose. Pseudomonas aeruginosa is one of the agents that are commonly implicated in nosocomial infections. However, it is also present as a commensal in various body sites of healthy persons, making the diagnosis of infection by culture difficult. A number of virulence factors expressed by the organism have been implicated in its pathogenicity. We undertook this study to identify the host and organism factors associated with infection.

Methodology. Pathogenic, colonizing and environmental isolates were tested for apr, lasB, the T3SS effector exoenzymes (exoS, exoT, exoU and exoY) and toxA genes, biofilm production and antimicrobial susceptibility. The isolates were further typed by RAPD.

Results. Eighty-seven isolates from 61 patients, including 11 environmental isolates, were obtained. None of the virulence factors were found to be significantly associated with infection, and nor was the antimicrobial susceptibility. The presence of the exoU gene and infection by MDR strains correlated significantly with the duration of hospital stay. Positivity for exoS and exoU genes was found to be strongly correlated with multi-drug resistance. exoU positivity correlated strongly with fluoroquinolone resistance. Sinks in the ward and intensive care unit were found to be a niche for XDR P. aeruginosa. Eighty-five isolates were typeable using the ERIC2 primer, showing 71 distinct RAPD patterns with >15 % difference in UPGMA-generated dice coefficients.

Conclusions. exoU positivity is associated with severe disease, as evidenced by the longer duration of hospital stay of these patients. However, the presence of virulence factors or multi-drug resistance in the cultured strain should not prompt the administration of anti-pseudomonal chemotherapy.

Purpose. The current study has been designed to delineate the efficacy of geraniol (GE) on biofilm formation in Staphylococcus epidermidis as well as the effect of subinhibitory concentrations of GE on the development of adaptive resistance.

Methodology. Biofilm biomass quantification assay was performed to evaluate the antibiofilm activity of GE against S. epidermidis. Microscopic observation of biofilms and extracellular polymeric substance (EPS), slime and cell surface hydrophobicity (CSH) production were also studied to support the antibiofilm potential of GE. In addition, S. epidermidis was examined for its adaptive resistance development upon continuous exposure of GE at its subinhibitory concentrations.

Results/Key findings. The MIC of GE against S. epidermidis was 512 µg ml−1. Without hampering the growth of the pathogen, GE at its sub-MICs (50, 100, 150 and 200 µg ml−1) exhibited a dose-dependent increase in antibiofilm activity. The minimal biofilm inhibitory concentration (MBIC) of GE was found to be 200 µg ml−1 with a maximum biofilm inhibition of 85 %. Disintegrated biofilm architecture, reduced EPS, slime and CSH production validated the antibiofilm efficacy of GE. Although the action of GE on preformed biofilm is limited, a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay and live/dead cell staining method revealed reduction in the viability (47 %) of biofilm inhabitants at 2×MIC concentration. Sequential exposure of S. epidermidis to the sub-MICs of GE resulted in poor development of adaptive resistance with diminished biofilm formation.

Conclusion. The present study highlights the potential of GE as a suitable candidate for the control of biofilm-mediated S. epidermidis infections.