Antibiofilm Effect of Biogenic Silver Nanoparticles Combined with Oregano Derivatives against Carbapenem-Resistant Klebsiella pneumoniae.

Resistant bacteria may kill more people than COVID-19, so the development of new antibacterials is essential, especially against microbial biofilms that are reservoirs of resistant cells. Silver nanoparticles (bioAgNP), biogenically synthesized using Fusarium oxysporum, combined with oregano derivatives, present a strategic antibacterial mechanism and prevent the emergence of resistance against planktonic microorganisms. Antibiofilm activity of four binary combinations was tested against enteroaggregative Escherichia coli (EAEC) and Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC): oregano essential oil (OEO) plus bioAgNP, carvacrol (Car) plus bioAgNP, thymol (Thy) plus bioAgNP, and Car plus Thy. The antibiofilm effect was accessed using crystal violet, MTT, scanning electron microscopy, and Chromobacterium violaceum anti-quorum-sensing assays. All binary combinations acted against preformed biofilm and prevented its formation; they showed improved antibiofilm activity compared to antimicrobials individually by reducing sessile minimal inhibitory concentration up to 87.5% or further decreasing biofilm metabolic activity and total biomass. Thy plus bioAgNP extensively inhibited the growth of biofilm in polystyrene and glass surfaces, disrupted three-dimensional biofilm structure, and quorum-sensing inhibition may be involved in its antibiofilm activity. For the first time, it is shown that bioAgNP combined with oregano has antibiofilm effect against bacteria for which antimicrobials are urgently needed, such as KPC.

Characterization of KPC-2-producing Klebsiella pneumoniae and affected patients of a pediatric hospital in Brazil.

Carbapenemase-producing Klebsiella pneumoniae (CPKp) infections are important threats to pediatric populations. Thus, a retrospective study was conducted in a Brazilian reference pediatric hospital, and 26 CPKp isolates obtained from 23 patients were characterized. The affected population had important underlying diseases, reflecting previous hospitalization and antibiotic use. Most CPKp isolates were resistant to all antibiotic classes, and blaKPC-2 was the only carbapenemase-encoding gene. blaCTX-M-15 was common among the isolates, and modification or absence of the mgrB gene was the cause of polymyxin B resistance. Ten different sequence types were identified, and clonal complex 258 was prevalent. Alleles wzi50 and wzi64 were the most recurrent ones regarding K-locus type, with a remarkable contribution of the epidemic ST11/KL64 lineage as a colonizer. Our findings show that lineages associated with the pediatric population are similar to those found in adults, reinforcing the need for epidemiological surveillance to effectively implement prevention and control measures.

BKC-2, a New BKC Variant Detected in MCR-9.1-Producing Enterobacter hormaechei subsp. xiangfangensis.

We characterized a multidrug-resistant (MDR) Enterobacter spp. isolate highlighting the genetic aspects of the antimicrobial resistance genes. An Enterobacter spp. isolate (Ec61) was recovered in 2014 from a transtracheal aspirate sample from a patient admitted to a Brazilian tertiary hospital and submitted to further microbiological and genomic characterization. Ec61 was identified as Enterobacter hormaechei subsp. xiangfangensis strain ST451, showing an MDR profile and the presence of genes codifying the new ß-lactamase variants BKC-2 and ACT-84 and the mobile colistin resistance gene mcr-9.1.

A mutation in the glycosyltransferase gene lafB causes daptomycin hypersusceptibility in Enterococcus faecium.

OBJECTIVES: To verify dissemination of daptomycin-non-susceptible Enterococcus faecium in a hospital where daptomycin was not in use and to understand the evolutionary pathways connecting daptomycin hypersusceptibility to non-susceptibility. METHODS: Clonality of 26 E. faecium was assessed by PFGE and the STs of these isolates were determined. The most daptomycin-susceptible isolate was evolved in vitro by stepwise daptomycin selection, generating isolates for genome comparisons. RESULTS: The spread of a high-risk daptomycin-non-susceptible VRE clone was detected, as was the occurrence of an unusual daptomycin-hypersusceptible strain (HBSJRP18). To determine the basis for daptomycin hypersusceptibility, we evolved HBSJRP18 in vitro and identified candidate genetic alterations potentially related to daptomycin susceptibility. Both lafB, encoding glycosyltransferase, which is putatively involved in lipoteichoic acid (LTA) biosynthesis, and dak, encoding a dihydroxyacetone kinase likely involved in fatty acid metabolism, were mutated in multiple independent experiments. Trans-complementation showed that the lafB polymorphism naturally occurring in HBSJRP18 caused its daptomycin hypersusceptibility. Fourier-transform infrared spectroscopy identified differences between the extracted LTA spectra from the hypersusceptible isolate and its revertant, as well as other non-susceptible variants, supporting a role for LafB in E. faecium LTA biosynthesis. Zeta potential difference was detected in one evolved dak mutant derivative. While much more susceptible to daptomycin, HBSJRP18 showed enhanced growth in the presence of piperacillin, suggesting that this, or another cell wall-targeting antibiotic, may have selected for the daptomycin-hypersusceptible phenotype. CONCLUSIONS: Our findings provide new information on the basis for daptomycin susceptibility in E. faecium, with implications for limiting the development and spread of daptomycin resistance.

Draft genome sequence of a CTX-M-15-producing Escherichia coli ST345 from commercial chicken meat in Brazil.

Escherichia coli, the main host of the CTX-M-15 extended-spectrum ß-lactamase (ESBL) enzyme, is widely distributed and exchanged between the environment, animals and humans. Therefore, identification of blaCTX-M-15-positive lineages in food has a significant impact on public health. In this regard, until the end of 1990s, ESBL-producing isolates were mainly associated with hospital-acquired infections, with a predominance of SHV- and TEM-type enzymes. In recent years, a new trend has been observed among ESBL-producers, where most isolates now harbour CTX-M-type, being further isolated from community-acquired infections. Nowadays, CTX-M-15 has been recognised as the most important ESBL variant, invading virtually all human and animal compartments, leading to a global pandemic. Thus, whilst the rapid emergence and dissemination of CTX-M-15 among E. coli isolates has generated a large genetic reservoir from which other members of the Enterobacteriaceae family can easily acquire this resistance gene, there are an increasing number of new reservoirs and transmission mechanisms that must be investigated. In this study, we present the draft genome sequence of a CTX-M-15-producing E. coli ST345 isolated from commercial chicken meat in Brazil. This draft genome can be used as a reference sequence for comparative analysis among CTX-M-15-producers.

High prevalence of bla(CTX-M) extended spectrum beta-lactamase genes in Klebsiella pneumoniae isolates from a tertiary care hospital: first report of bla(SHV-12), bla(SHV-31), bla(SHV-38), and bla(CTX-M-15) in Brazil.

The aim of this study was to investigate the presence and prevalence of bla(TEM), bla(SHV), and bla(CTX-M) and bla(GES)-like genes, responsible for extended spectrum beta-lactamases (ESBLs) production in clinical isolates of Klebsiella pneumoniae collected from a Brazilian tertiary care hospital. Sixty-five ESBL producing K. pneumoniae isolates, collected between 2005 and 2007, were screened by polymerase chain reaction (PCR). Identification of bla genes was achieved by sequencing. Genotyping of ESBL producing K. pneumoniae was performed by the enterobacterial repetitive intergenic consensus-PCR with cluster analysis by the Dice coefficient. The presence of genes encoding ESBLs was confirmed in 59/65 (90.8%) isolates, comprising 20 bla(CTX-M-2), 14 bla(CTX-M-59), 12 bla(CTX-M-15), 9 bla(SHV-12), 1 bla(SHV-2), 1 bla(SHV-2a), 1 bla(SHV-5), and 1 bla(SHV-31) genes. The ESBL genes bla(SHV-12), bla(SHV-31), and bla(CTX-M-15), and the chromosome-encoded SHV-type beta-lactamase capable of hydrolyzing imipenem were detected in Brazil for the first time. The analysis of the enterobacterial repetitive intergenic consensus-PCR band patterns revealed a high rate of multiclonal bla(CTX-M) carrying K. pneumoniae isolates (70.8%), suggesting that dissemination of encoding plasmids is likely to be the major cause of the high prevalence of these genes among the K. pneumoniae isolates considered in this study.