Antibiotic Susceptibility and Molecular Mechanisms of Macrolide Resistance in Streptococci Isolated from Adult Cystic Fibrosis Patients.

In this study, we assessed the antibiotic resistance in 413 streptococci isolates from adult CF patients against nine antibiotics relevant in CF treatment. We observed very low rates of cephalosporin resistance (cefepime and ceftriaxone, <2%) and higher rates of resistance to tetracycline (~34%) and trimethoprim/sulfamethoxazole (~45%). The highest rate of antibiotic resistance was to the macrolides (azithromycin (56.4%) and erythromycin (51.6%)). We also investigated the molecular mechanisms of macrolide resistance and found that only half of our macrolide resistant streptococci isolates contained the mef (efflux pump) or erm (methylation of 23S ribosomal target site) genes. The majority of isolates, however, were found to have point mutations at position 2058 or 2059 of the 23S ribosomal subunit, a molecular mechanism of resistance not commonly reported in the non-pyogenic and non-pneumococcal streptococci and unique in comparison to previous studies. The high rates of resistance observed here may result in poor outcomes where specific streptococci are contributing to CF airway disease and serve as a reservoir of resistance genes within the CF airway microbiome. PMID: 26408040 [PubMed - as supplied by publisher]
Source: Journal of Medical Microbiology - Category: Microbiology Authors: Tags: J Med Microbiol Source Type: research