BACKGROUND Healthcare-associated infections due to multidrug-resistant (MDR) bacteria such as Pseudomonas aeruginosa are significant public health issues worldwide. A system biology approach can help understand bacterial behaviour and provide novel ways to identify potential therapeutic targets and develop new drugs. Gene regulatory networks (GRN) are examples of in silico representation of interaction between regulatory genes and their targets. OBJECTIVES In this work, we update the MDR P. aeruginosa CCBH4851 GRN reconstruction and analyse and discuss its structural properties. METHODS We based this study on the gene orthology inference methodology using the reciprocal best hit method. The P. aeruginosa CCBH4851 genome and GRN, published in 2019, and the P. aeruginosa PAO1 GRN, published in 2020, were used for this update reconstruction process. FINDINGS Our result is a GRN with a greater number of regulatory genes, target genes, and interactions compared to the previous networks, and its structural properties are consistent with the complexity of biological networks and the biological features of P. aeruginosa. MAIN CONCLUSIONS Here, we present the largest and most complete version of P. aeruginosa GRN published to this date, to the best of our knowledge.

BACKGROUND Polymyxins are currently used as a “last-line” treatment for multidrug-resistant Gram-negative infections. OBJECTIVES To identify the major mechanisms of resistance to polymyxin and compare the genetic similarity between multi-drug resistant Klebsiella pneumoniae strains recovered from inpatients of public hospitals in the Mid-West of Brazil. METHODS 97 carbapenems non-susceptible K. pneumoniae were studied. β-lactamases (bla OXA-48, bla KPC, bla NDM, bla CTX-M, bla SHV, bla TEM, bla IMP, bla VIM) and mcr-1 to mcr-5 genes were investigated by polymerase chain reaction (PCR). Mutations in chromosomal genes (pmrA, pmrB, phoP, phoQ, and mgrB) were screened by PCR and DNA sequencing. Clonal relatedness was established by using pulsed-field gel electrophoresis and multilocus sequence typing. FINDINGS K. pneumoniae isolates harbored bla KPC (93.3%), bla SHV (86.6%), bla TEM (80.0%), bla CTX-M (60%) genes. Of 15 K. pneumoniae resistant to polymyxin B the authors identified deleterious mutations in pmrB gene, mainly in T157P. None K. pneumoniae presented mcr gene variants. Genetic polymorphism analyses revealed 12 different pulsotypes. MAIN CONCLUSIONS Deleterious mutations in pmrB gene is the main chromosomal target for induction of polymyxin resistance in carbapenem-resistant K. pneumoniae in public hospitals in the Mid-West of Brazil.

ABSTRACT Nosocomial bacterial infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) is associated with high mortality in neurosurgical patients. There are few reports in the literature on meningitis caused by CRKP. We report two cases of CRKP meningitis after neurosurgery. The K. pneumoniae identification and antimicrobial susceptibility testing were performed using the Vitek Compact System. Minimum inhibitory concentrations of polymyxin B were determined using the broth microdilution method. Molecular typing of K. pneumoniae isolates was investigated using multilocus sequence typing. Antimicrobial susceptibility testing showed that the K. pneumoniae isolates were multidrug resistant and co-produced extended-spectrum β-lactamases and KPC enzymes. The patients were treated with intrathecal polymyxin. Genetic polymorphism analyses revealed two different K. pneumoniae clones (ST1298 and ST2687), which were observed for the first time in CRKP infections. We recommend intravenous administration of intrathecal polymyxin for treating meningitis caused by multidrug-resistant K. pneumoniae .

BACKGROUND Healthcare-associated infections caused by bacteria such as Pseudomonas aeruginosa are a major public health problem worldwide. Gene regulatory networks (GRN) computationally represent interactions among regulatory genes and their targets. They are an important approach to help understand bacterial behaviour and to provide novel ways of overcoming scientific challenges, including the identification of potential therapeutic targets and the development of new drugs. OBJECTIVES The goal of this study was to reconstruct the multidrug-resistant (MDR) P. aeruginosa GRN and to analyse its topological properties. METHODS The methodology used in this study was based on gene orthology inference using the reciprocal best hit method. We used the genome of P. aeruginosa CCBH4851 as the basis of the reconstruction process. This MDR strain is representative of the sequence type 277, which was involved in an endemic outbreak in Brazil. FINDINGS We obtained a network with a larger number of regulatory genes, target genes and interactions as compared to the previously reported network. Topological analysis results are in accordance with the complex network representation of biological processes. MAIN CONCLUSIONS The properties of the network were consistent with the biological features of P. aeruginosa. To the best of our knowledge, the P. aeruginosa GRN presented here is the most complete version available to date.

Acinetobacter baumannii is an important pathogen frequently associated with nosocomial outbreaks around the world. In Brazil, A. baumannii has become particularly problematic because of its prevalence and the carbapenems resistance. Here, we report the draft genome sequence of a multidrug-resistant A. baumannii (ST15/CC15) isolated in 2009 from the state of Espírito Santo (Southeast Brazil). We observed important resistance determinant genes in an estimated genome size of 4,102,788 bp with 3,862 predicted coding regions. A detailed report of the genomic data analysis might help to understand the specific features of highly successful strains belonged to a relevant complex clonal in different Brazilian geographical regions.

The emergence of multidrug-resistant Enterobacteriaceae strains producing carbapenemases, such as NDM-1, has become a major public health issue due to a high dissemination capacity and limited treatment options. Here we describe the draft genome of three NDM-1-producing isolates: Providencia rettgeri(CCBH11880), Enterobacter hormaecheisubsp. oharae(CCBH10892) and Klebsiella pneumoniae(CCBH13327), isolated in Brazil. BesidesblaNDM-1, resistance genes to aminoglycosides [aadA1, aadA2,aac(6’)-Ib-cr] and quinolones (qnrA1,qnrB4) were observed which contributed to the multidrug resistance profile. The element ISAba125 was found associated to theblaNDM-1 gene in all strains.