Staphylococcus coagulase negativos isolados de hemoculturas de recém-nascidos e efeito antibacteriano sinérgico in vitro de estatinas com um composto triazeno

Abstract

Bloodstream infections (BSI) are among the most frequent and serious infectious complications related to neonatal infections, responsible for high morbidity and mortality rates. Coagulase-negative staphylococci (CoNS) are the most isolated microorganisms, being Staphylococcus epidermidis the prevalent. CoNS have important virulence factors, such as biofilm formation and bacterial resistance, demonstrating the need for research on new drugs with antibacterial activity, or even drug repositioning. Triazenes (TZC) and statins are a promising alternative, due to significant biological activity. The objective of this study was to evaluate CoNS isolated from blood cultures of newborns (NB) admitted in the Hospital Universitário de Santa Maria (HUSM) in two years (2014, 2016/2017), and also the investigation of the in vitro synergistic antibacterial effect of statins and an inedited TZC compound {[1-(4-bromophenyl)-3-phenyltriazene N3-oxide-2 N1, O4](dimethylbenzylamine-2 C1, N4)palladium(II)} against standard American Type Culture Collection (ATCC) and ten CoNS (2014). CoNS were identified and had the susceptibility profile done through Vitek®2, and the minimum inhibitory concentration (MIC) of linezolid, tigecycline and vancomycin were determined by the broth microdilution method as well as the antibacterial activity of TZC and statins. Some clinical parameters of the newborns and the mortality rates were also evaluated. The biofilm production (2014) was verified through three phenotypic methodologies, in addition to the presence of icaACD genes. Isolates of S. epidermidis (2016/2017) were characterized in molecular epidemiology by whole genome sequencing (WGS). In 2014, of 131 NB, 176 CoNS were isolated; and in 2016/2017, 79 and 120, respectively, being S. epidermidis the prevalent in the Neonatal Intensive Care Unit (NICU). An increase in resistance indices was observed when compared the years 2014 and 2016/2017, especially to penicillin (71.26%, 99.17%) and oxacillin (76%, 84.17%). There was 100% susceptibility to linezolid, tigecycline and vancomycin. Regarding clinical significance, in 2014, 53.44% of the newborns were treated, and in 2016/2017, 78.48%, and the majority of cases were related to the use of a catheter. Regarding mortality rates, 15.71% of NB died in 2014 and 17.74% in 2016/2017. Regarding biofilm formation, 30.11% showed the icaACD genes concomitantly and 11.36% icaAC. Through congo red agar (CRA), adherence to the borosilicate tube (TM) and quantitative microplate technique (TCP), 42.04%, 38.64% and 40.91% of the isolates produced biofilm, respectively. When compared to the gold standard (presence of genes), CRA and TM presented low sensitivity and specificity. TCP had 99% sensitivity and 100% specificity; and it can be inferred that biofilm production is related to antimicrobial resistance. Of the isolates confirmed as S. epidermidis (2016/2017), 83.64% were resistant to methicillin (MRSE), most of them related to sequence type (ST) 2, associated with the staphylococcal chromosomal cassette mec (SCCmec) III and IVa. Regarding antibacterial activity, both ATCC strains and clinical isolates had MIC ≤ 528 μg/mL against TZC and statins, and the activity increased when TZC was associated with simvastatin, showing synergism (FICI ≤0.5). In this study, S. epidermidis was the prevalent, being associated with the use of catheter, and resistance rates increased over the years, evidencing the importance of intensifying control and prevention measures in this hospital. Still, CoNS were important pathogens in neonatal sepsis, responsible for significant mortality rates. In relation to biofilm production, CRA and TM showed low sensitivity and specificity when compared to the presence of the genes, whereas TCP, although a time-consuming technique, is a quantitative method that could be used to verify biofilm production in clinical isolates. In relation to antibacterial activity, TZC when associated with simvastatin demonstrated synergism.