Endemic linezolid-resistant Staphylococcus epidermidis in a critical care unit.

The aim of this article was to report the emergence of patient infections with linezolid-resistant Staphylococcus epidermidis (LRSE) in a tertiary university hospital. Our objectives were to determine the molecular mechanism of the resistance, set up the genetic relationship among isolates, and analyze the relations between linezolid usage, period of treatment, and emergence of resistance in the hospital. The emergence of infection with linezolid-resistant S. epidermidis affecting 20 patients in a tertiary university hospital was investigated using repetitive sequence-based PCR (rep-PCR, DiversiLab System; BioMérieux, Inc., France). The presence of the G2576T mutation of 23S rRNA was screened by pyrosequencing. We determined the pattern of linezolid usage in the hospital as a whole and in the critical care unit that was most affected. G2576T mutation of 23S rRNA was detected in all linezolid-resistant S. epidermidis studied. Of these, 90% were genetically related and had been recovered from patients admitted to the same critical care unit. There had been an increase in linezolid usage in the hospital and in the critical care unit in the 2 years prior to the emergence of resistant strains. More strict control measures in hand washing and linezolid prescription were subsequently established, but no reduction in LRSE rates have yet been observed. Linezolid-resistant S. epidermidis emerged at our hospital, probably from a single strain originating in the critical care unit. The most likely explanation is that person-to-person spread of linezolid-resistant S. epidermidis led to skin colonization and, after linezolid treatment, this resistant staphylococci became the dominant cutaneous flora causing infection in some critical patients. In order to preserve the usefulness of this antibiotic as a therapeutic agent and to avoid a situation similar to methicillin-resistant Staphylococcus aureus, judicious use of antibiotics is essential.

[Comparison between Phoenix system and agar-based methods for antimicrobial susceptibility testing of Streptococcus spp]. / Comparación entre el sistema Phoenix y métodos basados en agar para el ensayo de sensibilidad a antibióticos en Streptococcus spp.

Introduction. Antibiotic resistance is an emerging problem among streptococcal species, especially for severe infections. Automated diagnostic systems for antimicrobial susceptibility testing, such as BD Phoenix, is a recently available instruments that makes it possible to obtain results within 12 h. Methods. Antimicrobial susceptibility testing results of the BD Phoenix system were compared to those obtained from Clinical Laboratory Standards Institute (CLSI) disk-diffusion method. Two-hundred different clinical isolates of streptococci were assayed: beta-hemolytic (n=65), viridans (n=87), S. penumoniae (n=48). Results. Overall, there was categorical agreement greater than 96.7% (94.8% for beta-hemolytic and 97.9% for viridans group) in relationship to the disk-diffusion method. The minor error rates were less than 10% for all the antibiotics. The greatest percentage of serious errors corresponded to erythromycin and clindamycin within the beta-hemolytic group (14.7%). Overall percentage of very serious errors was less 0.5%. The results for penicillin in viridans streptococci and S. pneumoniae results showed 89.7% and 91.7% of categorical agreement, respectively, using the Etest as reference. Conclusions. The automated BD Phoenix system is a very useful and effective diagnostic tool for quantitative testing of sensitivity to antibiotics in the streptococci group.

Comparación entre el sistema Phoenix y métodos basados en agar para el ensayo de sensibilidad a antibióticos en Streptococcus spp / Comparison between Phoenix system and agar-based methods for antimicrobial susceptibility testing of Streptococcus spp

Introducción. La resistencia a los antibióticos en el grupode los estreptococos es un problema emergente de especialimportancia en las infecciones graves. El sistema automatizadoBD Phoenix para identificación y antibiograma esun instrumento diagnóstico recientemente disponible quepermite obtener resultados en 12 h.Métodos. Se ha llevado a cabo un estudio comparativoentre el sistema BD Phoenix con paneles SMIC/ID-9 y el métododisco-difusión para la realización de estudios de sensibilidada antibióticos. Se utilizaron 200 aislamientos clínicosde estreptococos: betahemolíticos (n=65), viridans (n=87) yStreptococcus pneumoniae (n=48).Resultados. De forma global, en relación con el métododisco-difusión, hubo un acuerdo entre categorías superioral 96,7% (94,8% en betahemolíticos y 97,9% en viridans).Las tasas de errores menores fueron inferiores al 10% paratodos los antibióticos. El mayor porcentaje de errores gravescorrespondió a eritromicina y clindamicina dentro del grupode los betahemolíticos (14,7 %). El porcentaje global deerrores muy graves fue inferior al 0,5%. Los resultados parapenicilina en estreptococos viridans y S. pneumoniae presentaronun acuerdo entre categorías del 89,7 y 91,7% frentea Etest, respectivamente.Conclusiones. El sistema automatizado BD Phoenix esun instrumento diagnóstico de gran utilidad y efectividadpara el ensayo cuantitativo de la sensibilidad a los antibióticosen el grupo de los estreptococos (AU)

Introduction. Antibiotic resistance is an emergingproblem among streptococcal species, especially for severeinfections. Automated diagnostic systems for antimicrobialsusceptibility testing, such as BD Phoenix, is arecently available instruments that makes it possible toobtain results within 12 h.Methods. Antimicrobial susceptibility testing resultsof the BD Phoenix system were compared to those obtainedfrom Clinical Laboratory Standards Institute (CLSI)disk-diffusion method. Two-hundred different clinicalisolates of streptococci were assayed: beta-hemolytic(n=65), viridans (n=87), S. penumoniae (n=48).Results. Overall, there was categorical agreement greaterthan 96.7% (94.8% for beta-hemolytic and 97.9% for viridansgroup) in relationship to the disk-diffusion method.The minor error rates were less than 10% for all the antibiotics.The greatest percentage of serious errors correspondedto erythromycin and clindamycin within the beta-hemolyticgroup (14.7%). Overall percentage of very serious errors wasless 0.5%. The results for penicillin in viridans streptococciand S. pneumoniae results showed 89.7% and 91.7% of categoricalagreement, respectively, using the Etest as reference.Conclusions. The automated BD Phoenix system is avery useful and effective diagnostic tool for quantitativetesting of sensitivity to antibiotics in the streptococci group (AU)