Multilocus sequence analysis and synergy tests of Burkholderia species isolated from cystic fibrosis and non-cystic fibrosis patients

Abstract

Background: Burkholderia spp. are problematic infectious agents for cystic fibrosis (CF) or chronic granulomatous disease patients. Due to the failure of identification with conventional techniques and high intrinsic resistance to most antibiotics, these infections very difficult to treat and can cause a marked reduction in life expectancy. The aim of this study was to identify Burkholderia spp. strains isolated from CF and non-CF patients with multilocus sequence analysis (MLSA). Also, the antibiotic resistance and synergies of antibiotics were evaluated. Methods & Materials: A total of 38 Burkholderia spp. (25 CF, 13 non-CF) isolates were analyzed. All the Burkholderia spp. were identified by MLSA. Antibiotic susceptibilities of ceftazidime, meropenem, trimethoprim/sulfamethoxazole (TMP-SXT) and levofloxacin were determined by broth microdilution method according to CLSI guidelines. Synergy tests are performed by checkerboard method. Results: Multilocus sequence analysis identified clinical isolates as B. cenocepacia (n = 16), B. contaminans (n = 11), B. gladioli (n = 4), B. dolosa (n = 4), B. multivorans (n = 2) and B. seminalis (n = 1). Among the 38 Burkholderia spp. isolates, overall rates of resistance to ceftazidime, meropenem, TMP-SXT, and levofloxacin was 34.2%, 65.8%, 50% and 39.5%, respectively. No significant difference in antibiotic resistance between cystic fibrosis and non-cystic fibrosis patients were detected. Synergy has shown between meropenem and TMP-SXT at two isolates. Antagonism has detected at 15 isolates (between meropenem and ceftazidime (n = 12); between ceftazidime and TMP-SXT (n = 3)) Conclusion: A variety of molecular approaches have been developed for the identification of closely related species and MLSA has successfully provided a reliable advanced discrimination method for Burkholderia isolates. Expression of several resistance mechanisms in species may lead to higher resistance, whereas antagonism between meropenem and ceftazidime might be attributed to the expression of the beta-lactamases.