Silver nanoparticles (AgNPs) of different shapes and sizes were prepared by solution-based chemical reduction routes. Silver nitrate was used as a precursor, tri-sodium citrate (TSC) and sodium borohydride as reducing agents, while polyvinylpyrrolidone (PVP) was used as a stabilizing agent. The morphology, size, and structural properties of obtained nanoparticles were characterized by scanning electron microscopy (SEM), UV-visible spectroscopy (UV-VIS), and X-ray diffraction (XRD) techniques. Spherical AgNPs, as depicted by SEM, were found to have diameters in the range of 15 to 90 nm while lengths of the edges of the triangular particles were about 150 nm. The characteristic surface plasmon resonance (SPR) peaks of different spherical silver colloids occurring in the wavelength range of 397 to 504 nm, whereas triangular particles showed two peaks, first at 392 nm and second at 789 nm as measured by UV-VIS. The XRD spectra of the prepared samples indicated the face-centered cubic crystalline structure of metallic AgNPs. The in vitro antibacterial properties of all synthesized AgNPs against two types of Gram-negative bacteria, Pseudomonas aeruginosa and Escherichia coli were examined by Kirby–Bauer disk diffusion susceptibility method. It was noticed that the smallest-sized spherical AgNPs demonstrated a better antibacterial activity against both bacterial strains as compared to the triangular and larger spherical shaped AgNPs.

Chlorhexidine (CHX) is used in oral care products to help control dental plaque. In this study dental plaque bacteria were grown on media containing 2 μg/ml chlorhexidine gluconate to screen for bacteria with reduced CHX susceptibility. The isolates were characterized by 16S rRNA gene sequencing and antibiotic resistance profiles were determined using the disc diffusion method. The isolates were variably resistant to multiple drugs including ampicillin, kanamycin, gentamicin and tetracycline. Two species, Chryseobacterium culicis and Chryseobacterium indologenes were able to grow planktonically and form biofilms in the presence of 32 μg/ml CHX. In the CHX and multidrug resistant C. indologenes we demonstrated a 19-fold up-regulation of expression of the HlyD-like periplasmic adaptor protein of a tripartite efflux pump upon exposure to 16 μg/ml CHX suggesting that multidrug resistance may be mediated by this system. Exposure of biofilms of these resistant species to undiluted commercial CHX mouthwash for intervals from 5 to 60 s indicated that the mouthwash was unlikely to eliminate them from dental plaque in vivo. The study highlights the requirement for increased vigilance of the presence of multidrug resistant bacteria in dental plaque and raises a potential risk of long-term use of oral care products containing antimicrobial agents for the control of dental plaque.

Carcinogenic effects of arsenic through consumption of contaminated water are an alarming threat and there is an emergent need to reduce extremely high levels of toxic arsenic from environment. Bacterial biofilms produce polyanionic extracellular polymeric substance (EPS) that is considered an excellent biosorbent material for the remediation of toxic metals and metalloids. This study was aimed to investigate the role of bacterial EPS in arsenic bioremediation. EPS was extracted from biofilm forming and arsenic reducer bacterial strains that were isolated from industrial waste water and characterized biochemically. Fourier transform infrared spectroscopy was also performed to study functional groups. Both Exiguobacterium profundum PT2 and Ochrobactrum ciceri SW1 exhibited enhanced EPS production in the presence of arsenic. Arsenic stress increased protein and carbohydrate contents in the EPS of both bacterial strains as indicated by the peaks of 1363 to 1613 and 1035 to 1218 cm⁻¹ wavenumbers, respectively to cope with arsenic present in the surroundings. Shifting of peaks in As⁵⁺ treated samples from 1363 to 1379, 847 to 800 and 1211 to 1134 cm⁻¹ demonstrated the involvement of proteins, carbohydrates and phosphates in the sequestration of arsenic. Scanning electron microscopic examination of EPS revealed structural alterations such as the presence of closely embedded large clumps with interstitial spaces between stacked layers of the EPS of E. profundum PT2 treated with As⁵⁺ displayed the enhanced polysaccharide content and arsenic sorption. Therefore, increased production of bacterial EPS with large number of polyanionic functional groups on its surface having tendency to sequester arsenic through electrostatic or covalent interactions presented EPS an excellent biosorbent material for arsenic bioremediation.

Aims The aim of this study was to analyse arsenic (As) transformation and biosorption by indigenous As-resistant bacteria both in planktonic and biofilm modes of growth. Methods and Results As-resistant bacteria were isolated from industrial waste water and strain PT2, and identified as Exiguobacterium profundum through 16S rRNA gene sequencing was selected for further study. As transformation and biosorption by E. profundumPT2 was determined by HPLC-ICP-MS analysis. Planktonic cultures reduced 3·73 mmol l⁻¹ As⁵⁺ into As³⁺ from artificial waste water effluent after 48-h incubation. In case of biosorption, planktonic cultures and biofilms exhibited 25·2 and 29·4 mg g⁻¹ biomass biosorption, respectively. As biosorption kinetics followed Freundlich isotherm and pseudo second-order model. Biofilm formation peaked after 3 days of incubation, and in the presence of As stress, biofilm formation was significantly affected in contrast to control (P < 0·05). Homogeneous nature of mature biofilms with an increased demand of nutrients was revealed by minimum roughness and maximum surface to biovolume ratio measured through CLSM analysis. Conclusion Indigenous As-resistant E. profundumPT2 was found capable of As transformation and biosorption both in the form of planktonic cultures and biofilms. Significance and Impact of the Study Indigenous biofilm forming E. profundum PT2 revealing As biosorption and biotransformation potential is presented an eco-friendly and cost-effective source for As remediation that can be implemented for waste water treatment.

The common prevalent diseases in the age of 0 to 6 are related to urinary tract infections. If not properly diagnosed, they will lead to urological and nephrological complications. Uropathogens are developing resistance against most drugs and are harder to treat. A study was done on the inpatients and outpatients of the two hospitals located in Lahore. A total of 39,750 samples that were both male and female were collected. Escherichia and Klebsiella were found in 234 samples based on biochemical characterization, growth on CLED agar, and white blood cell/pus cell (WBC) microscopy. In comparison to males, female samples had a higher number of uropathogens (1:1.29). From the samples of Shaikh Zayed Hospital (SZH), the ratio of Klebsiella to Escherichia (1:1.93) was reported, while this ratio was 1.84:1 from the Children Hospital (CH). The incidence of UTI was higher in the month of September. Randomly selected Escherichia and Klebsiella were verified via a 16S rRNA sequence. Antibiotic resistance profiling of isolated bacterial strains was done against 23 antibiotics. The most efficient antibiotics against Klebsiella and Escherichia were colistin sulphate (100% sensitivity against bacteria from CH; 99.3% against strains from SZH) and polymyxin B (100% sensitivity against strains from SZH; 98.8% against strains from CH). Sensitivity of the total tested strains against meropenem (74%, SZH; 70% CH), Fosfomycin (68%, SZH; 73% CH strains), amikacin (74% SZH; 55% CH), and nitrofurantoin (71% SZH;67% CH) was found, Amoxicillin, ampicillin, and cefuroxime showed 100 to ≥90% resistance and are the least effective.