Antibiotic resistance patterns of Acinetobacter calcoaceticus–A. baumannii complex species from Colombian hospitals

Introduction Only automated phenotypic methods are currently used in Colombian hospitals for identifying isolates of the Acinetobacter calcoaceticus-A. baumannii complex (ACB). The phenotypical similarities in these species mean that they cannot be differentiated by manual or automated methods, thereby leading to their identification as A. baumannii, or ACB complex in clinical settings. Our objective was to identify to the species level 60 isolates, from four hospitals, evaluate their antibiotic susceptibility, and detect resistance-related genes.Methods16S–23S rRNA internal transcribed spacer (ITS) region and rpoB gene partial sequences were amplified. Resistance genes for cephalosporin, carbapenem and aminoglycoside were detected by PCR. Possible mutations in the quinolone resistance-determining region (QRDR) were evaluated. The association of ISAba-1 with blaOXA and blaADC genes was determined by PCR. Amplification products of ITS region, rpoB gene and some resistance genes were sequenced and compared using the BLAST tool. Results: 16S-23S rRNA ITS region and partial rpoB gene sequence analysis allowed 51isolates to be identified as A. baumannii, 8 as A. nosocomialis, and 1 isolate as A. pitti. A. baumannii isolates were highly resistant to all antibiotics tested, while the others were susceptible to ciprofloxacin and ampicillin/sulbactam. Quinolone resistance, found only in A. baumannii, was associated with mutations in the QRDR region of gyrA and parC genes. Conclusion This is the first investigation in Colombia that has identified ACB complex species using molecular methods, and determined differences in antibiotic resistance and resistance genes among the species. It is of the highest importance to identify isolates to the species level for future resistance and epidemiology studies in our region (AU)

Introducción Actualmente, los hospitales en Colombia utilizan únicamente métodos fenotípicos automatizados para la identificación de aislamientos del complejo Acinetobacter calcoaceticus - baumannii (ACB). La similitud entre estas especies no permite que se diferencien por métodos fenotípicos ya sean estos manuales o automatizados, llevando a que los aislamientos se identifiquen como A. baumannii o como pertenecientes al complejo ACB en las instituciones hospitalarias. Nuestro objetivo fue identificar a nivel de especie, 60 aislamientos de cuatro hospitales, identificados como del complejo ACB, evaluar su resistencia a antibióticos y detectar genes de resistencia. Métodos Para la identificación de especies se amplificaron la región intergénica espaciadora de los genes 16S y 23S rRNA y la secuencia parcial del gen rpoB. Estos amplificados y algunos genes de resistencia se secuenciaron y se compararon utilizando la herramienta BLAST. Se detectaron por PCR genes de resistencia a cefalosporinas, carbapenemes y aminoglicósidos. Se evaluaron posibles mutaciones en la región determinante de resistencia a quinolonas (QRDR). Se determinó por PCR la asociación de ISAba-1con los genes blaOXA y blaADC. Resultados Con las secuencias de la región ITS 16S-23S rRNA y el gen rpoB, se identificaron 51 aislamientos (..) (AU)

Antibiotic resistance patterns of Acinetobacter calcoaceticus-A. baumannii complex species from Colombian hospitals.

INTRODUCTION: Only automated phenotypic methods are currently used in Colombian hospitals for identifying isolates of the Acinetobacter calcoaceticus-A. baumannii complex (ACB). The phenotypical similarities in these species mean that they cannot be differentiated by manual or automated methods, thereby leading to their identification as A. baumannii, or ACB complex in clinical settings. Our objective was to identify to the species level 60 isolates, from four hospitals, evaluate their antibiotic susceptibility, and detect resistance-related genes. METHODS: 16S-23S rRNA internal transcribed spacer (ITS) region and rpoB gene partial sequences were amplified. Resistance genes for cephalosporin, carbapenem and aminoglycoside were detected by PCR. Possible mutations in the quinolone resistance-determining region (QRDR) were evaluated. The association of ISAba-1 with blaOXA and blaADC genes was determined by PCR. Amplification products of ITS region, rpoB gene and some resistance genes were sequenced and compared using the BLAST tool. RESULTS: 16S-23S rRNA ITS region and partial rpoB gene sequence analysis allowed 51isolates to be identified as A. baumannii, 8 as A. nosocomialis, and 1 isolate as A. pitti. A. baumannii isolates were highly resistant to all antibiotics tested, while the others were susceptible to ciprofloxacin and ampicillin/sulbactam. Quinolone resistance, found only in A. baumannii, was associated with mutations in the QRDR region of gyrA and parC genes. CONCLUSION: This is the first investigation in Colombia that has identified ACB complex species using molecular methods, and determined differences in antibiotic resistance and resistance genes among the species. It is of the highest importance to identify isolates to the species level for future resistance and epidemiology studies in our region.