Prevalence of Clinical Integrons and Potential, Integron-Encoded
Extanded Spectrum Beta-Lactamases Among Clinical Strains
of Klebsiella pneomoniae from Puerto Rico
Glendalis Vargas1, Carlos M. Rodríguez Minguela1, Joselyn M. Rodríguez Vega1,
Doris Vera2, Sonia Saavedra2,
1Department of Biology, University of Puerto Rico, Mayagüez, PR,
2Veteran Affairs Hospital, Río Piedras, PR
The integron platform is a gene capture module which is being increasingly documented as a key element that facilitates the dispersal of extended spectrum β-lactamases (ESBLs) a group of enzymes that catalyze the chemical inactivation of the most widely used antibiotics, the β-lactam drugs. In this project we applied PCR-based methods to evaluate if ESBL-mediated resistance in a collection of 15 clinical strains of Klebsiella pneumoniae was integron-encoded and to determine whether specific strain genotypes show any pattern in respect to the presence of a particular integron class or integron-encoded antibiotic resistance determinant. Based on BOX-PCR genomic fingerprinting we have identified six different genotypes among the tested strains. All strains were positive for the presence of class 1 integrons while class 2 and class 3 integrons were not detected. The detected class 1 integrons appeared to be diverse in terms of their gene cassette content as amplification products using a cassette-targeted PCR assay ranged from 1.2 to 2.5kb. Five of the isolates show the presence of gene cassettes ranging from 2.4-2.5Kb while three cultures presented cassettes ranging from 1.2-1.5Kb. A single culture show one cassette of 1.2kb whereas only one strain produced two gene cassettes of 1.8-2.5kb suggesting the presence of two class 1 integrons in the same strain. However 5 strains did not yield a PCR product after several attempts of gene cassette amplification were preformed, suggesting the presence of unloaded integrons or class 1 integrons variants lacking at least a conserved priming site. Moreover, integron gene cassette content appeared to be related to specific bacterial genotypes as amplified gene cassettes of a particular size were associated with certain clonal lineages. The sequencing analysis of gene cassettes is currently under progress to determine if ESBL resistance is conferred by integrons. So far we have identified partial sequences of a dehydrofolate reductase, aminoglycoside adenyltransferase and an efflux pump which are implicated in conferring resistance against trimethoprim and quaternary ammonium compounds respectively. We plan to extend this analysis to a larger set of strains to gain a comprehensive vision of dispersal trends of integron-encoded resistance determinants at the local clinical scenario.
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