Introduction: Pseudomonas aeruginosa is one of the most virulent nosocomial pathogens worldwide. Quorum sensing (QS) regulates the production of pathogenic virulence factors and biofilm formation in P. aeruginosa. The four genes lasR, lasI, rhlR,and rhlI were found to regulate this QS system. In this study, we aimed to assess the correlation between these four genes and QS-dependent virulence factors and to detect the inhibitory effect of clove oil on QS. Methodology: Fifty P. aeruginosa clinical isolates were collected. Susceptibility to different antibiotics was tested. Virulence factors including biofilm formation, pyocyanin production, and twitching motility were phenotypically detected. QS genes were amplified by polymerase chain reaction (PCR), and one strain subsequently underwent sequencing. The inhibitory effect of clove oil on virulence factors was also tested. Results: A positive correlation was found between biofilm formation and the presence of lasR and rhlI genes. Twitching motility was positively correlated with the presence of lasR, lasI, and rhlI genes. On the other hand, no correlation was found between pyocyanin production and any of the studied genes. Only one isolate amplified all the tested QS gene primers, but it did not express any of the tested virulence factors phenotypically. Sequence analyses of this isolate showed that the four genes had point mutations. Conclusions: Results emphasize the importance of QS in P. aeruginosa virulence; however, QS-deficient clinical isolates occur and are still capable of causing clinical infections in humans. Also, clove oil has an obvious inhibitory effect on QS, which should be clinically exploited.

Studies of the association between seronegative or occult (OCI) hepatitis C virus (HCV) infection, and hematological disorders have yielded controversial results. The aim of this study was to investigate seronegative and OCI HCV infections in among patients with different hematological disorders. This study included 90 anti-HCV-negative patients with either benign or malignant hematological disorders (group I), along with 20 age- and sex-matched apparently healthy subjects, who served as controls (group II). We tested for HCV RNA in sera and PBMCs by RT-nested PCR and for liver enzyme activity. Seronegativity and OCI were detected in 66.7 % and 20 % respectively, of the studied cases (group I). OCI was more evident in Hodgkin lymphoma and thalassemia. A significant increase in AST activity was observed in the seronegative and OCI groups and in ALT and AST in HCV-seronegative or OCI and negative HCV patients (p ≤ 0.05). Seronegativity and OCI are a significant clinical problem in patients with hematological disorders, warranting wider use of molecular tests combined with periodic evaluations of liver functions for diagnostic purposes.

Thirty-three Pseudomonas aeruginosa isolates, resistant to one or more β-lactams, were included in this study. Identification of tested strains was confirmed using MALDI-TOF/MS. Phenotypic and genotypic β-lactamase patterns were investigated. Most of the isolates were resistant to carbapenems (32 out of 33) and to the extended-spectrum cephalosporins (ESC) (30 out of 33). Phenotypically, the production of extended-spectrum beta-lactamase (ESBL), metallo-β-lactamases (MBL), and carbapenemases was detected in 10, 23, and 9 isolates, respectively. However, AmpC hyperproduction was not phenotypically detected among all isolates. Genotypically, ESBL and MBL encoding genes were detected in 23 and 27 isolates, respectively. Altogether 27 strains were detected as bla VIM positive and 16 strains carried bla OXA-10 gene. To the best of our knowledge, this is the first report of P. aeruginosa clinical isolates harboring bla VEB together with bla GES in Egypt, where 5 of our 30 ESCresistant isolates showed this genotype. Our results confirmed that resistance of P. aeruginosa isolates to β-lactam antibiotics is mediated via multiple β-lactamases belonging to different molecular classes. To the best of our knowledge, this is the first report of bla VEB among P. aeruginosa clinical isolates from Egypt. Ten isolates harbored bla VEB and five of them co-harbored bla VEB together with bla GES , bla VIM , and bla OXA-10.

No abstract

Background and Objectives: Pseudomonas aeruginosa is a problematic opportunistic pathogen causing several types of nosocomial infections with a high resistance rate to antibiotics. Production of many virulence factors in P. aeruginosa is regulated by quorum sensing (QS), a cell-to-cell communication mechanism. In this study, we aimed to assess and compare the inhibitory effect of azithromycin (AZM) and EPI- PAβN (efflux pump inhibitor- Phenylalanine-Arginine Beta-Naphthylamide) on QS system and QS-dependent virulence factors in P. aeruginosa clinical isolates. Materials and Methods: A total of 50 P. aeruginosa isolates were obtained from different types of clinical specimens. Isolates were investigated for detection of QS system molecules by AHL cross-feeding bioassay and QS-dependent virulence factors; this was also confirmed by detection of QS genes (lasR, lasI, rhlR, and rhlI) using PCR assay. The inhibitory effect of sub-MIC AZM and EPI PAβN on these virulence factors was assessed. Results: All the P. aeruginosa, producing QS signals C4 HSL, failed to produce C4 HSL in the presence of sub-MIC AZM, In the presence of EPI PAβN (20 µg/ml) only 14 isolates were affected, there was a significant reduction in QS-dependent virulence factors production (protease, biofilm, rhamnolipid and pyocyanin) in the presence of either 20 µg/ml EPI or subMIC of AZM with the inhibitory effect of AZM was more observed than PAβN. Conclusion: Anti-QS agents like AZM and EPI (PAβN) are useful therapeutic options for P. aeruginosa due to its inhibitory effect on QS-dependent virulence factors production without selective pressure on bacteria growth, so resistance to these agents is less likely to develop.