Identification and diversity of multiresistant Corynebacterium striatum clinical isolates by MALDI-TOF mass spectrometry and by a multigene sequencing approach

<p>Abstract</p> <p>Background</p> <p>The genus <it>Corynebacterium </it>is composed of Gram-positive bacteria that are widely distributed throughout the environment; these bacteria are also part of the normal microbiota of human skin and mucous membranes. Multiple studies have shown that species of this genus, including <it>C. striatum</it>, become pathogenic to humans under special conditions. Our aim was to determine the characteristics of clinical multiresistant strains of <it>C. striatum </it>that were isolated in our geographical region, to determine their diversity, and to compare them with the type strain and with related species. We studied fifty-two strains of <it>C. striatum </it>isolated from different hospitals from Mallorca, Spain, mainly from the Hospital Joan March in Bunyola, Mallorca. Most of the strains were isolated from sputum cultures of respiratory samples from patients with chronic obstructive pulmonary disease. To gain further insight into the genetic diversity of the strains, we analysed several housekeeping genes and other genes associated with antibiotic resistance. Strains were also characterised phenotypically by their antibiotic resistance profiles and by MALDI-TOF mass spectrometry analysis.</p> <p>Results</p> <p>The ITS1 region, <it>gyrA </it>and <it>rpoB </it>were chosen as the appropriate genes in the <it>C. striatum </it>genome to study the genetic diversity of <it>C. striatum </it>species and to discriminate between strains. After analysing these three genes, four sequence types (ST2, ST4, ST1 and ST11) were found to be the most abundant. Splits tree analysis of the strains demonstrated that these clinical isolates did not share any alleles with the type strain of the species. Recombination was detected within all of the <it>C. striatum </it>isolates, and different clonal populations were detected within the samples.</p> <p>Conclusions</p> <p>Our results demonstrate that the isolates were best identified using gene-based molecular methods; using these methods, the isolated strains were determined to be different from the type strain of <it>C. striatum</it>. The ITS1 region and the <it>gyrA </it>and <it>rpoB </it>genes were selected because of their variability and were the most useful tools for discriminating between strains. The phenotype and antibiotype characteristics of the strains did not seem suitable for typing purposes. MALDI-TOF mass spectrometry can be a useful method for identifying and discriminating between <it>C. striatum </it>strains.</p