ABSTRACT
INTRODUCTION: Pseudomonas aeruginosa (P. aeruginosa) modulates the expression of a myriad of virulence factors via two complicated hierarchical quorum-sensing (QS) cascade. This study shed light on the interrelation between P. aeruginosa QS systems and pyocyanin production. METHODOLOGY: Transcription analysis of lasR, rhlR, rhlI and phz genes using quantitative real time-reverse transcriptase PCR (qRT-PCR) assay, followed by sequencing of the autoinducer synthase (lasI gene) were applied for 15 P. aeruginosa strains recovered from diverse animal clinical sources. RESULTS: Expression studies revealed that most P. aeruginosa strains demonstrated statistically significant differences (p < 0.05) with a very wide range of transcript levels of QS and phz genes in comparison to P. aeruginosa ATCC 27853. We have identified significant positive correlations (r ≥ 0.3) between the expressions of QS and phz genes in eleven analyzed strains, whereas pyocyanin production positively correlated with the expression of lasR only in three strains (r ≥ 0.6). We further found that there was a negative correlation between the transcript levels of QS and phz genes in one bacterial strain. Analysis of lasI sequences showed point mutations explaining the alterations in pyocyanin expression. The deficiencies of lasI, lasR and rhlI with rhlR-dependent expression of phz in one strain were also recorded. CONCLUSIONS: These results provided new insights to the pivotal role of QS signal molecules on pyocyanin production presenting the las system as the dominant regulator.
ABSTRACT
INTRODUCTION: Salmonella serovars are one of the primary foodborne pathogens. Poultry consumption is responsible for the majority of disease cases worldwide. The prevalence of virulence determinants among Salmonella serovars appears to be lacking in Egypt. Therefore, this study investigated the occurrence, antibiotic resistance patterns, and virulence gene profiling of Salmonella serovars in broilers. METHODOLOGY: Three hundred samples from broiler chickens were examined for the presence of Salmonella by standard microbiological techniques. All Salmonella isolates were tested for their sensitivity against ten antibiotics and subjected to virulence genotyping by polymerase chain reaction (PCR). RESULTS: The overall isolation percentage of Salmonella was 17%. Seven different serovars were found, with the main one being Salmonella Typhimurium (52.94%). Salmonella isolates were sensitive to most of the tested antibiotics, but they exhibited absolute resistance against amoxicillin/clavulanic acid. Nine Salmonella strains (52.94%) were resistant to at least three antibiotics. Further PCR investigations into 17 Salmonella strains revealed different distribution patterns of eight virulence determinants among the isolates. The invA gene was the most prevalent one (100%), followed by hilA (88.24%), stn (58.82%), and fliC genes (52.94%), while each of sopB and pefA genes had a similar prevalence (41.18%), and sefC and spvC genes had the lowest prevalence (11.76 and 5.88%, respectively). PCR genotyping allowed grouping of Salmonella strains into ten genetic profiles. CONCLUSIONS: These results will help in understanding the spread of virulence genotypes and antibiotic resistance among Salmonella serovars in broilers.
