RESUMO
This study investigated within-host heterogeneity of 66 Pseudomonas aeruginosa populations from pneumonia in 51 critically ill ventilated patients by examining 30 colonies per bronchoalveolar lavage (BAL). Differences in antibiotic susceptibility and quorum-sensing (QS) phenotypes were observed between the members of 14 (21.2%) and 10 (15.2%) populations, respectively. A significant association was found between QS deficiency and ceftazidime resistance. QS deficiency was associated with various lasR modifications, and was observed in 25 of 51 (49.0%) patients, including seven patients who received ≤48 h of ventilation. This study confirms the need to examine diverse colonies when analysing BAL cultures, particularly in ß-lactam-exposed patients, to avoid missing ceftazidime- or imipenem-resistant isolates.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Farmacorresistência Bacteriana , Pneumonia/microbiologia , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/genética , Transativadores/genética , Proteínas de Bactérias/metabolismo , Lavagem Broncoalveolar , Ceftazidima/farmacologia , DNA Bacteriano , Variação Genética , Humanos , Imipenem/farmacologia , Unidades de Terapia Intensiva , Testes de Sensibilidade Microbiana , Mutação , Percepção de Quorum , Transativadores/metabolismo , beta-Lactamas/farmacologiaRESUMO
Treatment with antibiotics leads to the selection of isolates with increased resistance. We investigated if evolution towards resistance was associated with virulence changes, in the context of P. aeruginosa ventilator-associated pneumonia (VAP). Four patients were selected because they had multiple VAP episodes during short periods (12 days to 5 weeks), with emergence of resistance. We performed whole-genome sequencing of 12 P. aeruginosa from bronchoalveolar lavages or blood culture (3 isolates per patient). Production of quorum sensing-dependent virulence factors, serum resistance, cytotoxicity against A549 cells, biofilm production, and twitching motility were studied. Each patient was infected with a unique strain. For all patients, resistance development was explained by genetic events in ampD, mexR or oprD. Additional variations were detected in virulence- and/or fitness-associated genes (algB, gacA, groEL, lasR, mpl, pilE, pilM, rhlR) depending on the strain. We noticed a convergence towards quorum sensing deficiency, correlated with a decrease of pyocyanin and protease production, survival in serum, twitching motility and cytotoxicity. In one patient, changes in pilM and pilE were related to enhanced twitching. We show that the emergence of resistance in P. aeruginosa is associated with virulence modification, even in acute infections. The consequences of this short-term pathoadaptation need to be explored.