Commensal Staphylococcus spp., Acinetobacter spp. and Stenotrophomonas maltophilia as reservoirs of antibiotic resistance genes

Staphylococcus species, Acinetobacter species and Stenotrophomonas maltophilia are of particular importance as they sometimes reside as flora on the intact skin and nasal passages of man and farm animals. Studies around the globe have shown them as “friends and foes” especially in immunocompromised individuals as they occur as commensals but sometimes as pathogens that infect, causing morbidity and consequently higher therapeutic cost. The occurrence of antibiotic resistance gene(s) in their genomes and their phenotypic display of resistance make them difficult to control and places a high demand on the assessment of such genes in the bacteria. In doing this, the less considered (commensals) have been described more recently as a reservoir for antibiotic resistance genes. The transfer of heavy metal and antibiotic resistance genes from Staphylococcus spp., a Gram positive bacterium to S. maltophilia and Acinetobacter species, Gram negative bacteria confer the resilience to control measures that is peculiar with the former on the latter. This attribute in Acinetobacter spp. and S. maltophilia have encouraged their inclusion in drug screening research. Intermittent assessment of resistance genes in the ecosystem should be embraced to foster appropriate measures against their spread.Keyword: Commensal, resistance genes, Staphylococcus, Acinetobacter, Stenotrophomonas maltophili

Vibrio Fluvialis: An Unusual Enteric Pathogen of Increasing Public Health Concern

In developing countries, the fraction of treated wastewater effluents being discharged into watersheds have increased over the period of time, which have led to the deteriorations of the qualities of major rivers in developing nations. Consequently, high densities of disease causing bacteria in the watersheds are regularly reported including incidences of emerging Vibrio fluvialis. Vibrio fluvialis infection remains among those infectious diseases posing a potentially serious threat to public health. This paper addresses the epidemiology of this pathogen; pathogenesis of its disease; and its clinical manifestations in humans

Performance of NiFe 2

Investigation into the reduction of Cr(VI) in aqueous solution was carried out through some batch photocatalytic studies. The photocatalysts used were silica coated nickel ferrite nanoparticles (NiFe2O4-SiO2), nickel ferrite titanium dioxide (NiFe2O4-TiO2), nickel ferrite silica titanium dioxide (NiFe2O4-SiO2-TiO2), and titanium dioxide (TiO2). The characterization of the materials prepared via stepwise synthesis using coprecipitation and sol-gel methods were carried out with the aid of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The reduction efficiency was studied as a function of pH, photocatalyst dose, and contact time. The effects of silica interlayer between the magnetic photocatalyst materials reveal that reduction efficiency of NiFe2O4-SiO2-TiO2 towards Cr(VI) was higher than that of NiFe2O4-TiO2. However, TiO2 was observed to have the highest reduction efficiency at all batch photocatalytic experiments. Kinetics study shows that photocatalytic reduction of Cr(VI) obeyed Langmuir-Hinshelwood model and first-order rate kinetics. Regenerability study also suggested that the photocatalyst materials can be reused

Synthesis, characterization and antibacterial screening of 2,4-diaminopyrimidine pyrimethamine and trimethoprim silver complexes

Air stable silver Ag(I) complexes of pyrimethamine and trimethoprim drugs have been synthesized and characterized by elemental analysis, Fourier transform infrared (FTIR) and ultraviolet visible (UV-Vis) spectroscopy, and conductivity measurement. The metal complexes formed a three and four coordinate geometry with the ligands acting as a monodentate molecule bonding to the silver ion in each case through the pyrimidine N (1) nitrogen. The complexes have non-electrolyte behaviour in dimethylformamide (DMF) solution with its low conductivity values. Silver complexes, their free ligands alongside the corresponding silver salts were screened against selected bacterial isolates. All the silver complexes showed enhanced antibacterial activities compared to their free ligands and potential antibacterial agents have been identified.Key words: Pyrimethamine, trimethoprim, silver complexes, antibacterial screening, minimum inhibitory concentration

Pathogenomics of Virulence Traits of Plesiomonas shigelloides That Were Deemed Inconclusive by Traditional Experimental Approaches

One of the major challenges of modern medicine includes the failure of conventional protocols to characterize the pathogenicity of emerging pathogens. This is particularly apparent in the case of Plesiomonas shigelloides. Although a number of infections have been linked to this microorganism, experimental evidence of its virulence factors (VFs), obtained by traditional approaches, is somewhat inconclusive. Hence, it remains unclear whether P. shigelloides is a true or opportunistic one. In the current study, four publicly available whole-genome sequences of P. shigelloides (GN7, NCTC10360, 302-73, and LS1) were profiled using bioinformatics platforms to determine the putative candidate VFs to characterize the bacterial pathogenicity. Overall, 134 unique open reading frames (ORFs) were identified that were homologous or orthologous to virulence genes identified in other pathogens. Of these, 52.24% (70/134) were jointly shared by the strains. The numbers of strain-specific virulence traits were 4 in LS1; 7 in NCTC10360; 10 in 302-73; and 15 in GN7. The pathogenicity islands (PAIs) common to all the strains accounted for 24.07% ORFs. The numbers of PAIs exclusive to each strain were 8 in 302-73; 11 in NCTC10360; 14 in GN7; and 18 in LS1. A PAI encoding Vibrio cholerae ToxR-activated gene d protein was specific to 302-73, GN7, and NCTC10360 strains. Out of 33 antibiotic multi-resistance genes identified, 16 (48.48%) genes were intrinsic to all strains. Further, 17 (22.08%) of 77 antibiotic resistance islands were found in all the strains. Out of 23 identified distinct insertion sequences, 13 were only harbored by strain LS1. The number of intact prophages identified in the strains was 1 in GN7; 2 in 302-73; and 2 in NCTC10360. Further, 1 CRISPR element was identified in LS1; 2 in NCTC10360; and 8 in 302-73. Fifteen (78.95%) of 19 secretion systems and secretion effector variants were identified in all the strains. In conclusion, certain P. shigelloides strains might possess VFs associated with gastroenteritis and extraintestinal infections. However, the role of host factors in the onset of infections should not be undermined

The aerobic dechlorination activities of two bacterial species isolated from a refuse dumpsite in Nigeria

Two bacterial species isolated using enrichment culture techniquesfrom the topsoil of a main refuse dumpsite in Nigeria were assessed for their dehalogenation potentials. The bacterial isolates were identified asbelo nging to the Bacillus and Pseudomonas genera. Axenic culturesof the isolates utilized monochloroacetic acid (MCA), trichloroacetic acid (TCA), trichloromethane (CHCl3) and tetrachloromethane (CCl4) as the sole source of carbon for growth up to a final substrate concentration of 0.1% (w/v). The mean generation timesof the isolatesin all the growth media ranged significantly (P < 0.05) from 2.41 to 10.04 h and were generally higher than that observed in glucose medium (1.46—1.51 h). The numbers of the chloride atoms in the different organochlorides were negatively correlated with the ability of the organisms to degrade the compounds. Dehalogenase specific activities of the cell-mediated culturesranged from 0.1 to 0.96 μg ml-1 chloride release (mg protein)-1 h-1 and were significantly (P < 0.05) higher than that of the cell-free extract [0.09—0.8 μg ml-1 chloride release (mg protein)-1 h-1]. The optimal pH of the dehalogenase activity was found to be 8.0, and the optimal temperature was between 30 and 35°C

The incidence of antibiotic resistance within and beyond the agricultural ecosystem : a concern for public health

The agricultural ecosystem creates a platform for the development and dissemination of antimicrobial resistance, which is promoted by the indiscriminate use of antibiotics in the veterinary, agricultural, and medical sectors. This results in the selective pressure for the intrinsic and extrinsic development of the antimicrobial resistance phenomenon, especially within the aquaculture-animal-manure-soil-water-plant nexus. The existence of antimicrobial resistance in the environment has been well documented in the literature. However, the possible transmission routes of antimicrobial agents, their resistance genes, and naturally selected antibiotic-resistant bacteria within and between the various niches of the agricultural environment and humans remain poorly understood. This study, therefore, outlines an overview of the discovery and development of commonly used antibiotics; the timeline of resistance development; transmission routes of antimicrobial resistance in the agro-ecosystem; detection methods of environmental antimicrobial resistance determinants; factors involved in the evolution and transmission of antibiotic resistance in the environment and the agro-ecosystem; and possible ways to curtail the menace of antimicrobial resistance.The South African Medical Research Council (SAMRC), National Research Foundation (NRF), and the United States Agency for International Development (USAID).www.MicrobiologyOpen.comam2021Plant Production and Soil Scienc

Emerging Aeromonas Species Infections and Their Significance in Public Health

Aeromonas species are ubiquitous bacteria in terrestrial and aquatic milieus. They are becoming renowned as enteric pathogens of serious public health concern as they acquire a number of virulence determinants that are linked with human diseases, such as gastroenteritis, soft-tissue, muscle infections, septicemia, and skin diseases. Proper sanitary procedures are essential in the prevention of the spread of Aeromonas infections. Oral fluid electrolyte substitution is employed in the prevention of dehydration, and broad-spectrum antibiotics are used in severe Aeromonas outbreaks. This review presents an overview of emerging Aeromonas infections and proposes the need for actions necessary for establishing adequate prevention measures against the infections

Bioflocculant production by a consortium of Streptomyces and Cellulomonas species and media optimization via surface response model

AbstractSpecies of actinobacteria previously isolated from Tyume River in the Eastern Cape Province of South Africa and identified by 16S rDNA sequence as Cellulomonas and Streptomyces species were evaluated as a consortium for the production of bioflocculant. Sucrose, peptone and magnesium chloride were the nutritional sources which supported optimal production of bioflocculant resulting in flocculation activities of 91%, 82% and 78% respectively. Response surface design revealed sucrose, peptone and magnesium chloride as critical media components following Plackett–Burman design, while the central composite design showed optimum concentration of the critical nutritional source as 16.0g/L (sucrose), 1.5g/L (peptone) and 1.6g/L (magnesium chloride) yielding optimal flocculation activity of 98.9% and bioflocculant yield of 4.45g/L. FTIR spectrometry of the bioflocculant indicated the presence of carboxyl, hydroxyl and amino groups, typical for heteropolysaccharide, while SEM imaging revealed an interwoven clump-like structure. The molecular weight distribution of the constituents of the bioflocculants ranged 494.81–18,300.26Da thus, an indication of heterogeneity in composition. Additionally, the chemical analyses of the purified bioflocculant revealed the presence of polysaccharides and proteins with neutral sugar, amino sugar and uronic acids in the following concentration: 5.7mg, 9.3mg and 17.8mg per 100mg. The high flocculation activity of the bioflocculant suggests commercial potential