Distribution of resistance determinants and mobile elements involved in horizontal genetic transfer in clinical isolates of Achromobacter spp.

ADAMS C.; TRAGLIA G.; ALMUZARA M.N.; MERKIER A.K.; GALANTERNIK L.; VAY C.A; CENTRON D.; RAMIREZ M.S.

Santa Clara, California

Simposio; Twenty-Fourth Annual CSU Biotechnology Symposium; 2012

CSU California State University

Achromobacter spp. are gram-negative bacilli widely distributed in nature including the healthy human gastrointestinal tract. However, they are opportunistic nosocomial and community pathogens with A. xylosoxidans being the species most commonly associated with Achromobacter spp. infection. Numerous cases of A. xylosoxidans infections are documented in immunocompromised and cystic fibrosis (CF) patients. In Argentina, the relative frequency of A. xylosoxidans among the uncommon non-glucose-fermenting gram-negative bacilli infections has been increasing and now it accounts for 6.6 % of total non-glucose-fermenting gram-negative bacilli infection isolates. Although clinical Achromobacter spp. isolates usually show multiple drug resistance, the relative low attention paid to this pathogen resulted in poor understanding of their resistance mechanisms. To gain insights into the genetic characteristics of the resistance determinants, 30 non-epidemiological Achromobacter spp. clinical isolates from Argentina were studied to detect and characterize genetic elements associated to resistance determinants. All isolates were identified using standard biochemical tests and API 20NE (Biomeriux), and the species level was confirmed by sequencing the 16S rRNA gene, showing a high prevalence of A. xylosoxidans (27/30). The clonal relationships analysis using the macrorestriction technique exposed the presence of 15 different clones among the 27 A. xylosoxidans isolates included in the study. Total DNA was used to perform PCR amplifications reactions according to manufacturers instructions (Promega, Madison, WI). Specific primers of R plasmids (IncP, IncW, IncA/C, IncN, IncFII), and transposons or insertion sequences (IS) related to antimicrobial determinants (Tn1331, Tn3, Tn7, IS26, IS1999, IS440) circulating in our hospitals were used in PCR reactions in every isolate. The presence and characterization of class 1 and 2 integrons was also done. Class 1 and class 2 integrons were detected in 10 and 3 of the isolates, respectively. Their variable regions were characterized by polymerase chain reaction (PCR) cartography. IS26 and IS440 were found in 2 and 7 isolates, respectively. IncP plasmids, usually wide host range, were identified in 10 isolates. In total 18 of the 30 Achromobacter spp. isolates were positively identified as carriers of at least one of these genetic elements that are commonly associated to the presence and transfer of resistance genes. These results support supporting the hypothesis that Achromobacter spp. is becoming a reservoir of resistance determinants associated to horizontal gene transfer in gram-negative bacteria.