Incidence and antimicrobial profile of extended-spectrum ß-lactamase producing gram-negative bacterial isolates: An in-vitro and statistical analysis.

OBJECTIVES: There is an extensive incidence of extended-spectrum beta-lactamases (ESBLs), principally in the hospital environment across the world. The present study was designed to discover the frequency of ESBL-production among the clinical isolates of Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa. The study also focused on determining their liability to the selected antimicrobials. METHODS: Two hundred ten (210) clinical specimens were tested for the occurrence of ESBL using the double-disc synergy test. The molecular, physicochemical, absorption, distribution, metabolism, excretion, and toxicity were checked through an online server. RESULTS: Among the screened clinical isolates, E. coli (n=44), K. pneumonia (n=34) and P. aeruginosa (n=14) were ESBL markers. The ESBL producing isolates exhibited co-resistance to diverse categories of antibiotics. It was observed that all the ESBL-producing isolates were sensitive towards imipenem and faropenem with minimal proportion of resistance. CONCLUSION: The imipenem and faropenem can be recommended as the drugs of selection due to a lesser amount of resistance as compared to other antibiotics in this study.

Antimicrobial photodynamic activity of toluidine blue encapsulated in mesoporous silica nanoparticles against Pseudomonas aeruginosa and Staphylococcus aureus.

In the present study, the antimicrobial and antibiofilm efficacy of toluidine blue (TB) encapsulated in mesoporous silica nanoparticles (MSN) was investigated against Pseudomonas aeruginosa and Staphylococcus aureus treated with antimicrobial photodynamic therapy (aPDT) using a red diode laser 670 nm wavelength, 97.65 J cm-2 radiant exposure, 5 min). Physico-chemical techniques (UV-visible (UV-vis) absorption, photoluminescence emission, excitation, and FTIR) and high-resolution transmission electron microscopy (HR-TEM) were employed to characterize the conjugate of TB encapsulated in MSN (TB MSN). TB MSN showed maximum antimicrobial activities corresponding to 5.03 and 5.56 log CFU ml-1 reductions against P. aeruginosa and S. aureus, respectively, whereas samples treated with TB alone showed 2.36 and 2.66 log CFU ml-1 reductions. Anti-biofilm studies confirmed that TB MSN effectively inhibits biofilm formation and production of extracellular polymeric substances by P. aeruginosa and S. aureus.

Correction: Synthesis and antimicrobial photodynamic effect of methylene blue conjugated carbon nanotubes on E. coli and S. aureus.

Correction for 'Synthesis and antimicrobial photodynamic effect of methylene blue conjugated carbon nanotubes on E. coli and S. aureus' by Paramanantham Parasuraman et al., Photochem. Photobiol. Sci., 2019, DOI: 10.1039/c8pp00369f.

Synthesis and antimicrobial photodynamic effect of methylene blue conjugated carbon nanotubes on E. coli and S. aureus.

Catheter-related bloodstream infections (CRBSIs) are one of the leading causes of high morbidity and mortality in hospitalized patients. The proper management, prevention and treatment of CRBSIs rely on the understanding of these highly resistant bacterial infections. The emergence of such a challenge to public health has resulted in the development of an alternative antimicrobial strategy called antimicrobial photodynamic therapy (aPDT). In the presence of a photosensitizer (PS), light of the appropriate wavelength, and molecular oxygen, aPDT generates reactive oxygen species (ROS) which lead to microbial cell death and cell damage. We investigated the enhanced antibacterial and antibiofilm activities of methylene blue conjugated carbon nanotubes (MBCNTs) on biofilms of E. coli and S. aureus using a laser light source at 670 nm with radiant exposure of 58.49 J cm-2. Photodynamic inactivation in test cultures showed 4.86 and 5.55 log10 reductions in E. coli and S. aureus, respectively. Biofilm inhibition assays, cell viability assays and EPS reduction assays showed higher inhibition in S. aureus than in E. coli, suggesting that pronounced ROS generation occurred due to photodynamic therapy in S. aureus. Results from a study into the mechanism of action proved that the cell membrane is the main target for photodynamic inactivation. Comparatively higher photodynamic inactivation was observed in Gram positive bacteria due to the increased production of free radicals inside these cells. From this study, we conclude that MBCNT can be used as a promising nanocomposite for the eradication of dangerous pathogens on medical devices.

Antimicrobial photodynamic activity of rose bengal conjugated multi walled carbon nanotubes against planktonic cells and biofilm of Escherichia coli.

BACKGROUND: The global threat of antimicrobial resistance especially due to the bacterial biofilms has engaged researchers in the search of new treatment modalities. Antimicrobial photodynamic inactivation (aPDI) is one of the alternative treatment modalities which kills bacteria by generating endogenous reactive oxygen species (ROS). In this work authors evaluated the antibacterial and antibiofilm efficacy of rose Bengal (RB) conjugated to CNT against E. coli. METHODS: The interaction of anionic dye to the CNT was studied using UV-vis spectroscopy, HRTEM, FTIR and spectrofluorometry. Phototoxicity of RBCNT conjugate against E. coli was studied using a green light of 50 mW and radiant exposure of 1674.7 J/ cm2 for 10 min. The antibiofilm activity and mechanism of action of RBCNT conjugate in presence of light was evaluated. RESULTS: The loading and encapsulation was found to be 15.46 ± 1.05 and 61.85 ± 4.23% respectively. The photodynamic inactivation of planktonic cells of E. coli was found to 5.46 and 3.56 log10 CFU/ml reduction on treatment with RBCNT and RB respectively. The conjugate also exhibited efficient and enhanced antibiofilm activity against E. coli. The study of mechanism of action has confirmed cell membrane and DNA damage were the two main targets of aPDI. CONCLUSION: This report has concluded the efficient photodynamic inactivation occurred in Gram negative bacteria E. coli due to the increased production of ROS inside the bacterial cells. Hence, the newly synthesized RBCNT conjugate can be efficiently utilized to control infections caused by E. coli.