Resistance Mechanisms of Multiresistant Pseudomonas aeruginosa Strains from Germany and Correlation with Hypermutation

Abstract

In this study, we analyzed the mechanisms of multiresistance for 22 clinical multiresistant and clonally different Pseudomonas aeruginosa strains from Germany. Twelve and 10 strains originated from cystic fibrosis (CF) and non-CF patients, respectively. Overproduction of the efflux systems MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY-OprM was studied. Furthermore, loss of OprD, alterations in type II topoisomerases, AmpC overproduction, and the presence of 25 acquired resistance determinants were investigated. The presence of a hypermutation phenotype was also taken into account. Besides modifications in GyrA (91%), the most frequent mechanisms of resistance were MexXY-OprM overproduction (82%), OprD loss (82%), and AmpC overproduction (73%). Clear differences between strains from CF and non-CF patients were found: numerous genes coding for aminoglycoside-modifying enzymes and located, partially in combination with ␤-lactamase genes, in class 1 integrons were found only in strains from non-CF patients. Furthermore, multiple modifications in type II topoisomerases conferring high quinolone resistance levels and overexpression of MexAB-OprM were exclusively detected in multiresistant strains from non-CF patients. Correlations of the detected phenotypes and resistance mechanisms revealed a great impact of efflux pump overproduction on multiresistance in P. aeruginosa. Confirming previous studies, we found that additional, unknown chromosomally mediated resistance mechanisms remain to be determined. In our study, 11 out of 12 strains and 3 out of 10 strains from CF patients and non-CF patients, respectively, were hypermutable. This extremely high proportion of mutator strains should be taken into consideration for the treatment of multiresistant P. aeruginosa.

Parallel evolution and local differentiation in quinolone resistance in Pseudomonas aeruginosa

“…We find that mutations in gyrA are very common amongst resistant strains, regardless of the type of infection (CF vs non-CF) (Fig. 2), in accordance with previous suggestions (Henrichfreise et al, 2007). Similar patterns have been observed in numerous other species, with gyrA mutations common in Gram-negative bacteria (Piddock, 1999).…”

“…Thus, these data suggest an important role for nfxB-mediated resistance in samples from CF patients, with a major role for parC mutations, and for different efflux mechanisms in non-CF samples. These patterns have been hinted at in earlier studies (Henrichfreise et al, 2007;Jakics et al, 1992), but this is the first systematic analysis, to our knowledge, of quinolone resistance mutations between CF and non-CF isolates.…”

Characterization of Bacterial Infections in Allogeneic Hematopoietic Stem Cell Transplant Recipients Who Received Prophylactic Levofloxacin With Either Penicillin or Doxycycline

“…We hypothesize that a possible cross-resistance exists between fluoroquinolones and aminoglycosides, as has been described in vitro with P aeruginosa. 22,23 Rates of VRE colonization are increasingly reported in those who undergo HSCT, ranging from 10% to as high as 40% at some centers 24,25 ; however, numerous epidemiologic studies have noted a marginal (<5%) incidence of VRE infection in the HSCT patient population. 12,15,19 Although the earlier time period of our study is consistent with these trends, a few concerning features were identified.…”

Primary mechanisms mediating aminoglycoside resistance in the multidrug-resistant Pseudomonas aeruginosa clinical isolate PA7

“…A significant relationship between antibiotic use, for example, aminoglycoside, fluoroquinolone and cefepime, and the incidence of MexXY-overproducing P. aeruginosa has been reported (Hocquet et al, 2008). AMEs are also common determinants of aminoglycoside resistance in P. aeruginosa, except for CF isolates (Vogne et Henrichfreise et al, 2007;Sekiguchi et al, 2007;Samuelsen et al, 2010;Poole, 2011). Each AME has limited substrate specificity, but individual aminoglycoside-resistant P. aeruginosa isolates can carry multiple (2-5) AMEs and thus exhibit broad-spectrum aminoglycoside resistance (Poole, 2005).…”

“…Aminoglycoside resistance in P. aeruginosa has often arisen via acquired aminoglycoside-modifying enzymes (AMEs) and 16S rRNA methylases (RMTs), typically involving the MexXY endogenous efflux system (Poole, 2011). In particular, upregulation of the MexXY efflux pump is common, and MexXY has been implicated in aminoglycoside resistance in clinical isolates, particularly CF isolates (Sobel et al, 2003;Vogne et al, 2004;Henrichfreise et al, 2007;Islam et al, 2004;Hocquet et al, 2007;Vettoretti et al, 2009). A significant relationship between antibiotic use, for example, aminoglycoside, fluoroquinolone and cefepime, and the incidence of MexXY-overproducing P. aeruginosa has been reported (Hocquet et al, 2008).…”