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Microb Drug Resist. 2017 Apr;23(3):267-271. doi: 10.1089/mdr.2016.0091. Epub 2016 Jul 6.

Rapid Assessment of Resistance to Antibiotic Inhibitors of Protein Synthesis in the Gram-Positive Pathogens, Enterococcus faecalis and Streptococcus pneumoniae, Based on Evaluation of the Lytic Response.

Author information

1
1 Unidad de Genética, Instituto de Investigación Biomédica de A Coruña (INIBIC), Complexo Hospitalario Universitario de A Coruña (CHUAC) , Sergas, Universidade da Coruña (UDC), A Coruña, Spain .
2
2 Laboratorio de Genética, Centro Oncológico de Galicia , A Coruña, Spain .
3
3 Unidad de Genética, Facultad de Biología, Universidad Autónoma de Madrid , Madrid, Spain .
4
4 Servicio de Microbiología, Complexo Hospitalario Universitario de A Coruña (CHUAC) , Sergas, Universidade da Coruña (UDC), A Coruña, Spain .

Abstract

A novel assay for rapid determination of resistance to antibiotic inhibitors of protein synthesis was developed for the gram-positive pathogens, Enterococcus faecalis and Streptococcus pneumoniae. To this purpose, a lytic response was obtained by a brief incubation with lysozyme or a mixture of lysozyme, Triton X-100, and EDTA for E. faecalis (n = 82) and S. pneumoniae (n = 51), respectively. Lysis was quantified by visualizing the released nucleoids. Antibiotic-susceptible bacteria treated with Clinical and Laboratory Standards Institute (CLSI) breakpoint doses of erythromycin, azithromycin, or doxycycline that inhibited protein synthesis demonstrated a large reduction of lysed cells with respect to the control, that is, without antibiotics. However, cell lysis prevention was much lower in nonsusceptible strains, with unsuccessful inhibition of protein synthesis. ROC analysis showed that a reduction value of ≥35.6% and ≥40.4% discriminates susceptible and nonsusceptible strains for erythromycin and for doxycycline, respectively, in E. faecalis, whereas ≥20.0% is adequate for both macrolides and doxycycline in S. pneumoniae. Resistant stains were identified in 90-120 min with sensitivity and specificity between 91.7% and 100%. This is a proof of concept that evaluation of the lytic response may be a rapid and efficient test for determination of resistance to antibiotic inhibitors of protein synthesis.

KEYWORDS:

Enterococcus faecalis; Streptococcus pneumoniae; antibiotic resistance; lytic response; protein synthesis inhibitors; rapid assay

PMID:
27383851
DOI:
10.1089/mdr.2016.0091
[Indexed for MEDLINE]

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