Multidrug-resistant microorganisms are a well-known global problem, and gram-negative bacilli are top-ranking. When these pathogens are associated with bloodstream infections (BSI), outcomes become even worse. Here we applied whole-genome sequencing to access information about clonal distribution, resistance mechanism diversity and other molecular aspects of gram-negative bacilli (GNB) isolated from bloodstream infections in Brazil. It was possible to highlight international high-risk clones circulating in the Brazilian territory, such as CC258 for Klebsiella pneumoniae, ST79 for Acinetobacter baumannii and ST233 for Pseudomonas aeruginosa. Important associations can be made such as a negative correlation between CRISPR-Cas and K. pneumoniae CC258, while the genes blaTEM, blaKPC and blaCTX−M are highly associated with this clone. Specific relationships between A. baumannii clones and blaOXA−51 variants were also observed. All P. aeruginosa ST233 isolates showed the genes blaVIM and blaOXA486. In addition, some trends could be identified, where a new P. aeruginosa MDR clone (ST3079), a novel A. baumannii clonal profile circulating in Brazil (ST848), and important resistance associations in the form of blaVIM−2 and blaIMP−56 being found together in one ST233 strain, stand out. Such findings may help to develop approaches to deal with BSI and even other nosocomial infections caused by these important GNB.

Introduction: Staphylococcus aureus bacteremia causes significant morbidity and mortality, mainly by methicillin-resistant S. aureus (MRSA). Currently, vancomycin is the main choice for the treatment of infections by MRSA. Broth microdilution (BMD) remains the gold standard for measuring vancomycin MIC. However, most clinical laboratories employ practical methods in the routines, but these methods may not determine accurate vancomycin MIC values. Objectives: This study aimed to evaluate the accuracy of VITEK®2, Phoenix® and Etest® methods against BMD. Materials and Methods: A total of 78 strains (27 methicillin-sensitive S. aureus and 51 MRSA) were isolated from bloodstream infections. The vancomycin MIC was determined following CLSI and the manufacturers' recommendations. We also performed SCCmec typing, in order to identify their vancomycin MIC ratio values. Results: Most of all isolates showed values of MIC = 1 μg/mL by BMD and Phoenix®, while Etest® and VITEK® 2 determined the majority with MIC = 1.5 and 0.5 μg/mL, respectively. Thus, Etest® and VITEK® 2 tended to overestimate and underestimate, respectively, the MIC values. Three MRSA isolates that were vancomycin susceptible by the BMD were vancomycin-intermediate by Etest®. The SCCmec II (39%) and IV (51%) were the most frequent, and there was no relationship between the type of SCCmec and the MIC values. Conclusions: The results showed that vancomycin MICs vary according to the test method. It is essential that clinicians consider the differences in MIC results determined by different methods, since the MIC value is generally the parameter used by clinicians to select the appropriate therapy.