Pseudomonas aeruginosa may accumulate drug resistance mechanisms without losing its ability to cause bloodstream infections.
In this study, we systematically investigated the resistance mechanisms to beta-lactams, aminoglycosides, and fluoroquinolones of 120 bacteremic strains of Pseudomonas aeruginosa. Pulsed-field gel electrophoresis genotyping showed that 97 of these strains were represented by a single isolate, 10 by 2 and 1 by 3 clonally related isolates, respectively. Seventy-five percent (90 out of 120) of the bacteremic P. aeruginosa strains displayed a significant resistance to one or more of the tested antimicrobials (up to 11 for 1 strain). These strains were found to harbor a great diversity of resistance mechanisms (up to 7 in 1 strain), leading to various levels of drug resistance. Interestingly, 11 and 36% of the isolates appeared to overproduce the MexAB-OprM and MexXY-OprM efflux systems, respectively. Altogether, our results show that P. aeruginosa may accumulate intrinsic (overproduction of cephalosporinase AmpC, increased drug efflux, fluoroquinolone target mutations, and deficient production of porin OprD) and exogenous (production of secondary beta-lactamases and aminoglycoside-modifying enzymes) resistance mechanisms without losing its ability to generate severe bloodstream infections. Consequently, clinicians should be aware that multidrug-resistant P. aeruginosa may remain fully pathogenic.
Hocquet
Didier
D
Centre National de Référence Résistance aux antibiotiques: Pseudomonas aeruginosa, Hôpital Jean Minjoz, 25030 Besançon, Cedex, France. dhocquet@chu-besancon.fr
Berthelot
Philippe
P
Roussel-Delvallez
Micheline
M
Favre
Roger
R
Jeannot
Katy
K
Bajolet
Odile
O
Marty
Nicole
N
Grattard
Florence
F
Mariani-Kurkdjian
Patricia
P
Bingen
Edouard
E
Husson
Marie-Odile
MO
Couetdic
Gérard
G
Plésiat
Patrick
P
D000617:Aminoglycosides / Q000494:pharmacology / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000097:blood* / Q000453:epidemiology / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D024841:Fluoroquinolones / Q000494:pharmacology / Q000627:therapeutic use; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D011552:Pseudomonas Infections / Q000097:blood* / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D047090:beta-Lactams / Q000494:pharmacology / Q000627:therapeutic use
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D024841:Fluoroquinolones; D047090:beta-Lactams