Analysis of class 2 integrons as a marker for multidrug resistance among Gram negative bacilli

Argentinian Integron Study Group ,Cecilia Rodríguez,D Centrón,Gabriela Del V Delgado,Marcelo H Cassini,María S Ramírez

doi:10.3934/genet.2016.4.196

Abstract

AbstractClass 1 and 2 integrons are considered the paradigm of multidrug resistant (MDR) integrons. Although class 1 integrons have been found statistically associated to Enterobacteriaceae MDR isolates, this type of study has not been conducted for class 2 integrons. Escherichia coli and 3 species that were found that harbored more than 20% of class 2 integrons in clinical isolates, were selected to determine the role of intI2 as MDR marker. A total of 234 MDR/191 susceptible non-epidemiologically related isolates were analyzed. Seventy-four intI2 genes were found by PCR and sequencing. An intI2 relationship with MDR phenotypes in Acinetobacter baumannii and Enterobacter cloacae was found. No statistical association was identified with MDR E. coli and Helicobacter pylori isolates. In other words, the likelihood of finding intI2 is the same in susceptible and in MDR E. coli and H. pylori strains, suggesting a particular affinity between the mobile element Tn7 and some species. The use of intI2 as MDR marker was species-dependent, with fluctuating epidemiology at geographical and temporal gradients. The use of intI2 as MDR marker is advisable in A. baumannii, a species that can reach high frequencies of this genetic element.

Highlights

The integron/cassettes system is a successful double component genetic mechanism associated to Lateral Genetic Transfer
The multidrug resistant (MDR) isolates of H. pylori, E. cloacae and A. baumannii showed a decrease in the frequency of intI2-positive isolates (37.5 vs 6.6%, 33.0 vs 12.0% and 50.0 vs 43.2%, respectively) [8,19]
We found that the use of intI2 as MDR marker is species dependent, a main difference with intI1 gene [3]

Summary

Introduction

The integron/cassettes system is a successful double component genetic mechanism associated to Lateral Genetic Transfer. Class 1 integrons are usually found in the 20% up to 80% of Enterobacteriaceae and Pseudomonas aeruginosa clinical isolates around the world [2,3,4,5,6,7]. They have been found with many arrays of ARGCs within the variable region [2,3,4]. Most intI2 have been found harboring the same allele with a stop codon at position 179 resulting in a nonfunctional IntI2 [8,10] This phenomenon could be an explanation for the few arrays of ARGC documented in the literature. Recent studies identified the emergence of class 2 integrons with novel ARGC arrays in Enterobacteriaceae and A. baumannii strains [5,8,12], suggesting that these species are active reservoirs

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Discussion

Conclusion