Reduced expression of virulence factors in multidrug-resistant Pseudomonas aeruginosa strains

Abstract

MDR Pseudomonas aeruginosa strains are isolated from clinical specimens with increasing frequency. It seems that acquiring genes which determine antibiotic resistance usually comes at a biological cost of impaired bacterial physiology. There is no information on investigations comparing phenotypic differences in MDR and MDS P. aeruginosa strains in literature. The study included 150 clinical P. aeruginosa isolates (75 classified as MDS and 75 as MDR). PFGE analysis revealed five pairs of identical isolates in the group of MDR strains and the results obtained for these strains were not included in the statistical analyses. MDR strains adhered to polystyrene to a lesser extent than MDS strains. The growth rate in the liquid medium was significantly lower for MDR strains. Detectable amounts of alginate were present in the culture supernatants of seven MDS and six MDR strains. The MDR P. aeruginosa strains which were investigated produced significantly lower amounts of extracellular material binding Congo Red, lower lipolytic, elastase, LasA protease, phospholipase C activity and pyocyanin quantity in culture supernatants when compared with MDS strains. No significant differences were observed between MDR and MDS strains in proteolytic activity. In conclusion, the MDR P. aeruginosa strains have impaired virulence when compared to MDS strains.

Characteristics and determinants of outcome of hospital-acquired bloodstream infections in intensive care units: the EUROBACT International Cohort Study

“…Interestingly, XDR infection did not have a greater influence on 28-day mortality than MDR infection, despite a further increase in time to adequate therapy. This finding is consistent with experimental studies suggesting that resistance to antimicrobial agents may be associated with decreases in bacterial fitness, metabolic activity [28] or virulence [29]. The strong relationship between absence of source control and mortality in our study further supports the widely recognised importance of source control in patients with infection or sepsis [22].…”

Association between infections caused by multidrug-resistant gram-negative bacteria and mortality in critically ill patients

“…Probably, this question cannot be answered by such type of clinical studies where different gram-negative bacteria of nonsimilar virulence are usually examined together [60] . For example, P. aeruginosa isolates are known to be extremely virulent; however, as it has been shown, MDR P. aeruginosa strains have impaired virulence when compared to susceptible ones [63] . Theoretically, an increased intrinsic virulence of resistant gram-negative strains could explain, at least in part, an adverse clinical outcome.…”

The Role of Substance P in Pulmonary Clearance of Bacteria in Comparative Injury Models

“…Our current pharmacologic arsenal may be ineffective against resistant pathogens, but prior evidence has shown the pathogens still may be susceptible to host innate immune defenses. 24,25 Pathogens themselves may alter innate immune responses as a result of modifications acquired alongside resistance. 26 Host defenses, especially neutrophils, play an important role as the frontline of containment and resolution of infections.…”