The Klebsiella species present a remarkable genetic and ecological diversity, being ubiquitous in nature. In particular, the Klebsiella pneumoniae species complex (KpSC) has emerged as a major public health threat in the world, being an interesting model to assess the risk posed by strains recovered from animals and the environment to humans. We therefore performed a genomic surveillance analysis of the KpSC using every public genome in Brazil, aiming to show their local and global relationships, and the connectivity of antibiotic resistance and virulence considering human, animal, and environmental sources. The 390 genomes from distinct sources encompassed the K. pneumoniae, Klebsiella quasipneumoniae subsp. quasipneumoniae, Klebsiella quasipneumoniae subsp. similipneumoniae, Klebsiella variicola subsp. variicola, Klebsiella variicola subsp. tropica, and Klebsiella grimontii species and subspecies. K. pneumoniae harbored dozens of antibiotic resistance genes, while most of the genomes belong to the high-risk pandemic CC258 occurring in humans, animals, and the environment. In K. pneumoniae ST11, a high prevalence of the virulence determinants yersiniabactin, colibactin, and T6SS was revealed in association with multi-drug resistance (MDR), including carbapenem resistance. A diversity of resistance genes is carried by plasmids, some shared between strains from different STs, regions, and sources. Therefore, here were revealed some factors driving the success of KpSC as a pathogen.

BACKGROUND Acinetobacter baumannii is a leading cause of nosocomial infections. This species is characterised by the presence of pandemic lineages (International Clones) that present a broad antimicrobial resistance profile.OBJECTIVE To perform the molecular epidemiology of carbapenem-resistant A. baumannii from a clinical setting in the Amazon Basin, and to characterise their antimicrobial resistance determinants.METHODS The genetic relationship of carbapenem-resistant A. baumannii were assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Class A, B and D β-lactamase genes were screened by polymerase chain reaction (PCR) and sequencing. The antimicrobial susceptibility profile was obtained by Disc-diffusion method and minimum inhibitory concentration (MIC) determination.FINDINGS All carbapenem-resistant A. baumannii strains belonged to three international clones, IC-1, IC-5 and IC-6, the latter recently reported by the first time in Brazil. The major determinant of carbapenem resistance in IC-1 and IC-5 strains was bla OXA-23, associated with ISAba1 and ISAba3, respectively, while IC-6 harboured the bla OXA-72.CONCLUSIONS The A. baumannii epidemiology in Brazilian Amazon Region was unknown. It was demonstrated that A. baumannii XDR international clones were responsible for nosocomial infections in Boa Vista during 2016-2018, revealing that the epidemiological scenario of A. baumannii infections in Amazon Region resembles those from the cosmopolitan regions worldwide.

Integrons are considered hot spots for bacterial evolution, since these platforms allow one-step genomic innovation by capturing and expressing genes that provide advantageous novelties, such as antibiotic resistance. The acquisition and shuffling of gene cassettes featured by integrons enable the population to rapidly respond to changing selective pressures. However, in order to avoid deleterious effects and fitness burden, the integron activity must be tightly controlled, which happens in an elegant and elaborate fashion, as discussed in detail in the present review. Here, we aimed to provide an up-to-date overview of the complex regulatory networks that permeate the expression and functionality of integrons at both transcriptional and translational levels. It was possible to compile strong shreds of evidence clearly proving that these versatile platforms include functions other than acquiring and expressing gene cassettes. The well-balanced mechanism of integron expression is intricately related with environmental signals, host cell physiology, fitness, and survival, ultimately leading to adaptation on the demand.

BACKGROUND Acinetobacter baumannii outbreaks have been associated with pandemic International Clones (ICs), but the virulence factors involved with their pathogenicity are sparsely understood. Pigment production has been linked with bacterial pathogenicity, however, this phenotype is rarely observed in A. baumannii. OBJECTIVES This study aimed to characterise the reddish-brown pigment produced by A. baumannii strains, and to determine its biosynthetic pathway by genomic approaches. METHODS Pigment characterisation and antimicrobial susceptibility were conducted by phenotypic tests. The clonal relationship was obtained by pulsed field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The genome of an A. baumannii was obtained for characterisation of genes involved with pigment production. FINDINGS The pyomelanin was the pigment produced by A. baumannii. Strains were extensively drug resistant and belonged to the IC-5/ST79. The pyomelanin biosynthetic pathway was determined and presented a particular architecture concerning the peripheral (tyrB, phhB and hpd) and central (hmgB, hmgC and hmgR) metabolic pathway genes. The identification of a distant HmgA homologue, probably without dioxygenase activity, could explain pyomelanin production. Virulence determinants involved with adherence (csuA/BABCDE and a T5bSS-carrying genomic island), and iron uptake (basABCDEFGHIJ, bauABCDEF and barAB) were characterised. MAIN CONCLUSION There is a biosynthetic pathway compatible with the pyomelanin production observed in persistent A. baumannii IC-5 strains.

Pseudomonas aeruginosa has been considered one of the major nosocomial pathogens associated with elevated morbidity and mortality worldwide. Outbreaks have been associated with few high-risk pandemic P. aeruginosa lineages, presenting a remarkable antimicrobial resistance. However, the biological features involved with the persistence and spread of such lineages among clinical settings remain to be unravel. This study reports the emergence of the ST309 P. aeruginosa lineage in South America/Brazil, more precisely, in the Amazon region. Global genomic analyses were performed with the Brazilian strain (PA834) and more 41 complete and draft ST309 genomes publicly available, giving insights about ST309 epidemiology and its resistome and mobilome. Antimicrobial susceptibility tests revealed that the Brazilian PA834 strain presented the XDR phenotype, which was mainly due to intrinsic resistance mechanisms. Genomic analyses revealed a heterogeneous distribution of acquired antimicrobial resistance genes among ST309 genomes, which included blaVIM-2, blaIMP-15 and qnrVC1, all of them associated with class 1 integrons. The mobilome mining showed the presence of Integrative and Conjugative Elements, transposons and genomic islands harbouring a huge arsenal of hevy metal resistance genes. Moreover, these elements also carried genes involved with virulence and adaptive traits. Therefore, the presence of such genes in ST309 lineage possibly accounted for the global spread and persistence of this emerging clone, and for its establishment as a pandemic lineage of clinical importance.