Antimicrobial in vitro activity of quinupristin/dalfopristin against gram-positive cocci isolated from 5 Brazilian centers: results from the local smart (L-SMART) surveillance study

Há alguns anos tem-se verificado um aumento progressivo da resistência de alguns cocos gram-positivos a determinados antimicrobianos. Este aumento da resistência tem sido observado principalmente no ambiente hospitalar, e as bactérias mais comumente envolvidas são os Staphylococcus spp. e os Enterococcus spp. Devido a este fato, novos antimicrobianos são avaliados para o tratamento de infecções causadas por estas cepas multirresistentes. A associação quinupristina/dalfopristina (Q/D), também conhecida como Synercid®, é um antibacteriano da classe das estreptograminas, de uso endovenoso, composto por dois derivados semi-sintéticos da pristinamicina. A combinação das estreptograminas B e A na razão de 30:70 tem atividade antimicrobiana voltada para cocos gram--positivos, como Staphylococcus spp., Streptococcus spp., incluindo S. pneumoniae e Enterococcus faecium, sendo o E. faecalis habitualmente resistente. Neste estudo foi avaliada a atividade in vitro de Q/D e outros oito antimicrobianos frente a 631 amostras de cocos gram-positivos isoladas de cinco centros brasileiros, complementadas com outras 20 cepas de E. faecium resistentes à vancomicina, provenientes dos Estados Unidos. Para a avaliação da sensibilidade aos antimicrobianos foi determinada a concentração inibitória mínima (MIC) pelo método do Etest (AB Biodisk, Solna, Suécia) e as cepas testadas foram: Staphylococcus aureus (n = 267), Staphylococcus coagulase negativo (n = 131), Streptococcus pneumoniae (n = 130), Streptococcus beta-hemolíticos (n = 28), Enterococcus faecalis (n = 44) e E. faecium (n = 51). A Q/D demonstrou excelente atividade contra Staphylococcus spp., independente de serem sensíveis ou resistentes à oxacilina. Para S. pneumoniae, a Q/D apresentou igualmente uma ótima atividade, inclusive para as cepas com resistência intermediária ou total para penicilina. Entre as cepas de E. faecium sensíveis à vancomicina, o MIC90 de Q/D obtido foi de 3µg/ml, sendo que 45% das cepas testadas foram sensíveis e 55% apresentaram sensibilidade intermediária à associação. Desta forma, pode-se afirmar que a associação Q/D representa uma nova opção para o tratamento endovenoso de infecções causadas por cocos gram-positivos, principalmente para as cepas multirresistentes, sendo também uma alternativa ao uso de glicopeptídeos.A progressive increase of resistance among Gram-positive cocci (GPC) towards some antimicrobial agents has been observed for the past few years. This rise of resistance, most often seen in Staphylococcus spp., and Enterococcus spp., has mainly been noticed in hospital environments. Due to these recent patterns of resistance, newly developed antimicrobial agents need to be evaluated for the treatment of infections caused by these multi-resistant microorganisms. Quinupristin/dalfopristin (Q/D), also known as Synercid®, is an antimicrobial agent of intravenous administration, composed of two semi-synthetic derivatives of pristinomycin belonging to the group of streptogramins. The combination of streptogramins B and A at 3:7 ratio has an antimicrobial activity against gram-positive cocci. This combination has potent activity against gram-positive cocci such as Staphylococcus spp., Streptococcus spp. including Streptococcus pneumoniae, and Enterococcus faecium. However, strains of E. faecalis are usually resistant to this compound. The aim of this study was to evaluate the in vitro activity of Q/D and other eight antibiotics against 631 strains of GPC isolated from five Brazilian centers. Additionally, 20 vancomycin-resistant strains of E. faecium provided by a reference center from the United States were also included in this study. Minimal Inhibitory Concentrations (MICs) were determined by E-test methodology (AB Biodisk, Solna, Sweden), using standardized and controlled procedures. The evaluated strains were as follows: Staphylococcus aureus (267), coagulase negative Staphylococcus (131), Streptococcus pneumoniae (130), b-hemolytic Streptococcus (28), Enterococcus faecalis (44), and E. faecium (51). Quinuprintin/dalfopristin presented an excellent activity against Staphylococcus spp., regardless if these were susceptible or not to oxacillin. Against S. pneumoniae, Q/D also presented excellent activitiy regardless of their susceptibility to penicillin. Among vancomycin susceptible E. faecium studied, the MIC90 was 3mg/ml where 45% of the strains were susceptible, and 55% revealed intermediate resistance to quinupristin/dalfopristin. Overall, Q/D showed good activity against Staphylococcus spp., Streptococcus spp. including S. pneumoniae, and Enterococcus faecium representing a new option for the treatment of infections caused by multi-resistant gram-positive cocci, as well as an alternative for the use of glycopeptides