Multidrug-resistant Acinetobacter baumannii as an emerging concern in hospitals.

Acinetobacter baumannii has become a major concern for scientific attention due to extensive antimicrobial resistance. This resistance causes an increase in mortality rate because strains resistant to antimicrobial agents are a major challenge for physicians and healthcare workers regarding the eradication of either hospital or community-based infections. These strains with emerging resistance are a serious issue for patients in the intensive care unit (ICU). Antibiotic resistance has increased because of the acquirement of mobile genetic elements such as transposons, plasmids, and integrons and causes the prevalence of multidrug resistance strains (MDR). In addition, an increase in carbapenem resistance, which is used as last line antibiotic treatment to eliminate infections with multidrug-resistant Gram-negative bacteria, is a major concern. Carbapenems resistant A. baumannii (CR-Ab) is a worldwide problem. Because these strains are often resistant to all other commonly used antibiotics. Therefore, pathogenic multi-drug resistance A. baumannii (MDR-Ab) associated infections become hard to eradicate. Plasmid-mediated resistance causes outbreaks of extensive drug-resistant. A. baumannii (XDR-Ab). In addition, recent outbreaks relating to livestock and community settings illustrate the existence of large MDR-Ab strain reservoirs within and outside hospital settings. The purpose of this review, proper monitoring, prevention, and treatment are required to control (XDR-Ab) infections. Attachment, the formation of biofilms and the secretion of toxins, and low activation of inflammatory responses are mechanisms used by pathogenic A. baumannii strain. This review will discuss some aspects associated with antibiotics resistance in A. baumannii as well as cover briefly phage therapy as an alternative therapeutic treatment.

Prevalence of Genes Involved in Colistin Resistance in Acinetobacter baumannii: First Report from Iraq.

Background and Aim: Colistin is increasingly being used as a "last-line" therapy to treat infections caused by multidrug-resistant (MDR) Acinetobacter baumannii isolates, when essentially no other options are available in these days. The aim of this study was to detect genes associated with colistin resistance in A. baumannii. Methods: One hundred twenty-one isolates of A. baumannii were collected from clinical and environmental samples during 2016 to 2018 in Baghdad. Isolates were diagnosed as A. baumannii by using morphological tests, Vitek-2 system, 16SrRNA PCR amplification, and sequencing. Antibiotic susceptibility test was carried out using disk diffusion method. Phenotypic detection of colistin resistance was performed by CHROMagar™ COL-APSE medium and broth microdilution method for the determination of the minimal inhibitory concentration. Molecular detection of genes responsible for colistin resistance in A. baumannii was performed by PCR. Results: Ninety-two (76%) of the 121 A. baumannii isolates were colistin resistant. Twenty-six (21.5%) of the 121 isolates showed positive growth on CHROMagar Acinetobacter base for MDR. PCR detected mcr-1, mcr-2, and mcr-3 genes in 89 (73.5%), 78 (64.5%), and 82 (67.8%) A. baumannii isolates, respectively. Seventy-eight (64.5%) of the 121 isolates harbored the integron intI2 gene and 81 (66.9%) contained intI3 gene. Moreover, 60 (49.6%) of the 121 isolates were positive for the quorum sensing lasI gene. Conclusion: The presence of a large percentage of colistin-resistant A. baumannii strains in Baghdad may be due to the presence of mobile genetic elements, and it is urgent to avoid unnecessary clinical use of colistin.

Screening, nutritional optimization and purification for phytase produced by Enterobacter aerogenes and its role in enhancement of hydrocarbons degradation and biofilm inhibition.

In this study, a novel isolate of Enterobacter aerogenes isolated from contaminated soils with hydrocarbons had extracellular phytate-degrading activity. Enterobacter aerogenes isolates were identified by biochemical tests and confirmed by16S rRNA gene products (amplified size 211bp) for genotypic detection. The phytase activity was reached to maximum activity when this isolate was cultivated under the optimal conditions which consisted of using minimal salt medium containing 1%(w/v) rice bran as a sole source for carbon and 2% (w/v) yeast extract at pH 5.5 and temperature of 50°C for 48 h. The phytase had purified to homogeneity by 50% ammonium sulphate precipitation, ion exchange and gel filtration chromatography with 75.7 fold of purification and a yield of 30.35%. The purified phytase is a single peptide with approximate molecular mass of 42 kDa as assessed by SDS-PAGE. The highest degradative ability by Enterobacter aerogenes of black oil, white oil and used engine oil had observed after 72 h of incubation. Rapid degradation of black oil and used engine oil had also observed while slow degradation of white oilat all time of incubation. The purified phytase inhibited biofilm formation ability in a dose-dependent manner for all Gram-negative and Gram-positive biofilm-forming bacteria and a significant difference in cell surface hydrophobicity was observed after exposure of planktonic cells to phytase for hour. The hydrolyzing effect of phytase released by Enterobacter aerogenes for complex salts of phosphorus that are insoluble in the soil led to increase of phosphorus concentrations and enhanced the ability of Enterobacter aerogenes to degrade a specific hydrocarbon in contaminated soil so that the phytase has a promising application in bioremediation of contaminated soils with hydrocarbons.

Two NAD-linked redox shuttles maintain the peroxisomal redox balance in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, peroxisomes are the sole site of fatty acid ß-oxidation. During this process, NAD+ is reduced to NADH. When cells are grown on oleate medium, peroxisomal NADH is reoxidised to NAD+ by malate dehydrogenase (Mdh3p) and reduction equivalents are transferred to the cytosol by the malate/oxaloacetate shuttle. The ultimate step in lysine biosynthesis, the NAD+-dependent dehydrogenation of saccharopine to lysine, is another NAD+-dependent reaction performed inside peroxisomes. We have found that in glucose grown cells, both the malate/oxaloacetate shuttle and a glycerol-3-phosphate dehydrogenase 1(Gpd1p)-dependent shuttle are able to maintain the intraperoxisomal redox balance. Single mutants in MDH3 or GPD1 grow on lysine-deficient medium, but an mdh3/gpd1Δ double mutant accumulates saccharopine and displays lysine bradytrophy. Lysine biosynthesis is restored when saccharopine dehydrogenase is mislocalised to the cytosol in mdh3/gpd1Δ cells. We conclude that the availability of intraperoxisomal NAD+ required for saccharopine dehydrogenase activity can be sustained by both shuttles. The extent to which each of these shuttles contributes to the intraperoxisomal redox balance may depend on the growth medium. We propose that the presence of multiple peroxisomal redox shuttles allows eukaryotic cells to maintain the peroxisomal redox status under different metabolic conditions.