Enterococcus, a Gram-positive facultative anaerobic cocci belonging to the lactic acid bacteria of the phylum Firmicutes, is known to be able to resist a wide range of hostile conditions such as different pH levels, high concentration of NaCl (6.5%), and the extended temperatures between 5°C and 65°C. Despite being the third most common nosocomial pathogen, our understanding on its virulence factors is still poorly understood. The current study was aimed to determine the prevalence of different virulence genes in Enterococcus faecalis and Enterococcus faecium. For this purpose, 79 clinical isolates of Malaysian enterococci were evaluated for the presence of virulence genes. pilB, fms8, efaAfm, and sgrA genes are prevalent in all clinical isolates. In conclusion, the pathogenicity of E. faecalis and E. faecium could be associated with different virulence factors and these genes are widely distributed among the enterococcal species.
Although analysis of toxin-antitoxin (TA) systems can be instructive, to date, there
is no information on the prevalence and identity of TA systems based on a large panel
of Acinetobacter baumannii clinical isolates. The aim of the
current study was to screen for functional TA systems among clinical isolates of
A. baumannii and to identify the systems’ locations. For this
purpose, we screened 85 A. baumannii isolates collected from
different clinical sources for the presence of the mazEF, relBE
and higBA TA genes. The results revealed that the genes coding
for the mazEF TA system were commonly present in all clinical
isolates of A. baumannii. Reverse transcriptase-polymerase chain
reaction analysis showed that transcripts were produced in the clinical isolates. Our
findings showed that TA genes are prevalent, harboured by chromosomes and transcribed
within A. baumannii. Hence, activation of the toxin proteins in
the mazEF TA system should be investigated further as an
effective antibacterial strategy against this bacterium.
The toxin–antitoxin (TA) system is a regulatory system where two sets of genes encode the toxin and its corresponding antitoxin. In this study, the prevalence of TA systems in independently isolated clinical isolates of Enterococcus faecium and Enterococcus faecalis was determined, the dominant TA system was identified, different virulence genes in E. faecium and E. faecalis were surveyed, the level of expression of the virulence and TA genes in normal and stress conditions was determined, and finally their associations with the TA genes were defined. Remarkably, the analysis demonstrated higBA and mazEF in all clinical isolates, and their locations were on chromosomes and plasmids, respectively. On the other hand, a quantitative analysis of TA and virulence genes revealed that the expression level in both genes is different under normal and stress conditions. The results obtained by anti-mazF peptide nucleic acids demonstrated that the expression level of virulence genes had decreased. These findings demonstrate an association between TA systems and virulence factors. The mazEF on the plasmids and the higBA TA genes on the chromosomes of all E. faecium and E. faecalis strains were dominant. Additionally, there was a decrease in the expression of virulence genes in the presence of anti-mazF peptide nucleic acids. Therefore, it is suggested that mazEF TA systems are potent and sensitive targets in all E. faecium and E. faecalis strains.
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