Molecular epidemiology and adaptive genetic characteristics of Pseudomonas aeruginosa related to chronic infection in patients with Cystic Fibrosis and their correlation with clinical data

Author(s)

Natália Candido Caçador

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2016-08-29

Examining board members

Ana Lucia da Costa Darini; Afonso Luis Barth; Lucia Helena Faccioli; Carlos Emilio Levy

• Advisor: Ana Lucia da Costa Darini

Abstract

The chronic airway infection by P. aeruginosa (PA) is the leading cause of morbidity and mortality in cystic fibrosis (CF) patients, due to continuous degradation of the pulmonary tissue. This leads to decline in lung function, which is generated by the related infection and inflammation. The aim of this study was to analyze genetic characteristics associated with the adaptation of PA to the airways of patients with chronic pulmonary infection attended at the CF Reference Center from the Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto - USP; and to correlate these findings with the results of molecular typing, antibiotic resistance, chronicity and clinical data of patients in clinical follow-up from July/2011 to April/2014. The genetic characteristics of isolates investigated includes the research of 18 virulence genes and the quorum sensing system genes (lasR and rhlR genes), association between mutations and conversion to the mucoid phenotype (algTmucABD operon), and characterization of hypermutable strains (mutS and mutL genes). Identification of PA was performed by PCR and MALDI-TOF, which showed a high correlation. The patients\' clinical data considered were: body mass index, Shwachman score, forced vital capacity measures and forced expiratory volume in one second. The percentage of patients with chronic PA infection observed was similar to the data available in the literature; however, a worrying high incidence in young patients was noticed. The macrorestriction profile of genomic DNA by PFGE proved to be useful to define chronic/intermittent colonization in association with clinical criteria and it confirmed interpatient transmission, in combination with the detection of mutations in the mucA and mucD genes. High occurrence of virulence genes was detected for the vast majority of isolates from chronic CF patients. Antibiotic resistance for PA isolates was low and is in accordance with national and international literature and antibiotic therapy adopted in the hospital. There was no resistance to carbapenems and fluoroquinolones by the presence of plasmid mediated resistance genes. Mutations in the mucA gene were the main mechanism to conversion to mucoidy, and the non-mucoid revertants occurred mainly by mutations in the algT gene. New mutations in mutS and mutL genes were detected, which support the idea that hypermutation in PA is associated with mutations in the DNA mismatch repair system. The quorum sensing system of the isolates is partially damaged due to several mutations in the lasR gene, but all isolates maintain an intact rhlR gene, which holds some quorum sensing activity with production of important virulence factors. Patients with chronic PA infection with isolation of other non-fermenting gram-negative rods had greater change in lung function compared with patients with chronic PA infection with or without isolation of Staphylococcus aureus. The changes presented in the algTmucABD operon, quorum sensing and hypermutability contribute to the chronicity of CF patients in relation to infection by P. aeruginosa. (AU)

• FAPESP's process: 13/13358-0 - Classical and molecular epidemiology of Pseudomonas aeruginosa isolated from patients with Cystic Fibrosis
• Grantee: Natália Candido Caçador
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)