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.

Background: Multidrug-resistant bacteria represent a potential threat to patients in healthcare facilities, with higher abundance and more profound consequences in the developing world. Controlling the spread of these bacteria requires timely identification of clonally related isolates that are cross transmitted from one patient to another within healthcare facilities. The relatively high cost of sequencing-based typing methods hinders their routine use in low-income countries. This highlights the need for an alternative easily applicable molecular typing method that can be routinely used in laboratories with basic equipment and low financial resources, for epidemiologic investigation of outbreaks. Aim and methods: This study aimed to evaluate molecular typing of 30 multidrug-resistant (MDR) Klebsiella pneumoniae (K. pneumoniae) isolates, that were isolated in a previous hospital outbreak and were of previously identified clonal relatedness, by 2 non-sequencing-based typing methods: Plasmid Profile Analysis and Random Amplified Polymorphic DNA (RAPD). The obtained banding patterns were converted into binary data and phylogenetically analyzed by DARwin 6.0.21 software. Results: There was a statistically significant fair agreement between the 2 methods in grouping of the isolates into distinct clusters (Kappa=.23, p=.025). Both methods proved to be of high typeability of near 100% and discriminatory power of more than 0.9. Both methods fulfilled the performance and convenience criteria evaluated. Conclusion: Any of the two methods may be applicable for routine investigation of outbreaks by MDR bacteria in the developing world, when more precise molecular typing methods are not applicable for shortage of resources.