Genes and Proteins Involved in qnrS1 Induction

First report of coexistence of blaKPC-2 and blaNDM-1 in carbapenem-resistant clinical isolates of Klebsiella aerogenes in Brazil

Klebsiella aerogenes is an important opportunistic pathogen with the potential to develop resistance against last-line antibiotics, such as carbapenems, limiting the treatment options. Here, we investigated the antibiotic resistance profiles of 10 K. aerogenes strains isolated from patient samples in the intensive-care unit of a Brazilian tertiary hospital using conventional PCR and a comprehensive genomic characterization of a specific K. aerogenes strain (CRK317) carrying both the blaKPC-2 and blaNDM-1 genes simultaneously. All isolates were completely resistant to β-lactam antibiotics, including ertapenem, imipenem, and meropenem with differencing levels of resistance to aminoglycosides, quinolones, and tigecycline also observed. Half of the strains studied were classified as multidrug-resistant. The carbapenemase-producing isolates carried many genes of interest including: β-lactams (blaNDM-1, blaKPC-2, blaTEM-1, blaCTX-M-1 group, blaOXA-1 group and blaSHVvariants in 20-80% of the strains), aminoglycoside resistance genes [aac(6')-Ib and aph(3')-VI, 70 and 80%], a fluoroquinolone resistance gene (qnrS, 80%), a sulfonamide resistance gene (sul-2, 80%) and a multidrug efflux system transporter (mdtK, 70%) while all strains carried the efflux pumps Acr (subunit A) and tolC. Moreover, we performed a comprehensive genomic characterization of a specific K. aerogenes strain (CRK317) carrying both the blaKPC-2 and blaNDM-1 genes simultaneously. The draft genome assembly of the CRK317 had a total length of 5,462,831 bp and a GC content of 54.8%. The chromosome was found to contain many essential genes. In silico analysis identified many genes associated with resistance phenotypes, including β-lactamases (blaOXA-9, blaTEM-1, blaNDM-1, blaCTX-M-15, blaAmpC-1, blaAmpC-2), the bleomycin resistance gene (bleMBL), an erythromycin resistance methylase (ermC), aminoglycoside-modifying enzymes [aac(6')-Ib, aadA/ant(3")-Ia, aph(3')-VI], a sulfonamide resistance enzyme (sul-2), a chloramphenicol acetyltransferase (catA-like), a plasmid-mediated quinolone resistance protein (qnrS1), a glutathione transferase (fosA), PEtN transferases (eptA, eptB) and a glycosyltransferase (arnT). We also detected 22 genomic islands, eight families of insertion sequences, two putative integrative and conjugative elements with a type IV secretion system, and eight prophage regions. This suggests the significant involvement of these genetic structures in the dissemination of antibiotic resistance. The results of our study show that the emergence of carbapenemase-producing K. aerogenes, co-harboring blaKPC-2 and blaNDM-1, is a worrying phenomenon which highlights the importance of developing strategies to detect, prevent, and control the spread of these microorganisms.

Emergence of mcr-8.2-harboring hypervirulent ST412 Klebsiella pneumoniae strain from pediatric sepsis: A comparative genomic survey

Emerging mobile colistin resistance (mcr) genes pose a significant threat to public health for colistin was used as the last resort to treat multidrug-resistant (MDR) pathogenic bacterial infections. Hypervirulent Klebsiella pneumoniae (hvKP) is a clinically significant pathogen resulting in highly invasive infections, often complicated by devastating dissemination. Worryingly, the untreatable and severe infections caused by mcr-harbouring hvKP leave the selection of antibiotics for clinical anti-infective treatment in a dilemma. Herein, we screened 3,461 isolates from a tertiary teaching hospital from November 2018 to March 2021, and an mcr-8.2-harbouring hvKP FAHZZU2591 with a conjugative plasmid was identified from paediatric sepsis. This is the first report of MCR-8-producing hvKP from paediatric sepsis to our best knowledge. The susceptibility, genetic features, and plasmid profiles of the isolate were investigated. Further, we assessed the virulence potential of FAHZZU2591 and verified its pathogenicity and invasive capacity using a mouse model. The phylogenetic analysis of mcr-8-bearing K. pneumoniae revealed that China is the predominant reservoir of the mcr-8 gene, and the clinic is the primary source. Our work highlights the risk for the spread of mcr-positive hvKP in clinical, especially in paediatric sepsis, and the persistent surveillance of colistin-resistance hvKP is urgent.

Overexpression of mfpA Gene Increases Ciprofloxacin Resistance in Mycobacterium smegmatis

Fluoroquinolones (FQs) are antibiotics useful in the treatment of drug-resistant tuberculosis, but FQ-resistant mutants can be selected rapidly. Although mutations in the DNA gyrase are the principal cause of this resistance, pentapeptide proteins have been found to confer low-level FQ resistance in Gram-negative bacteria. MfpA is a pentapeptide repeat protein conserved in mycobacterial chromosomes, where it is adjacent to a group of four highly conserved genes termed a conservon. We wished to characterize the transcriptional regulation of the mfpA gene and relate its expression to ciprofloxacin resistance in M. smegmatis. Reverse transcription PCR showed that mfpA gene is part of an operon containing the conservon genes. Using a transcriptional fusion, we showed that a promoter was located 5' to the mfpEA operon. We determined the promoter activity under different growth conditions and found that the expression of the operon increases slightly in late growth phases in basic pH and in subinhibitory concentrations of ciprofloxacin. Finally, by cloning the mfpA gene in an inducible vector, we showed that induced expression of mfpA increases the ciprofloxacin Minimal Inhibitory Concentration. These results confirm that increased expression of the mfpA gene, which is part of the mfpEA operon, increases ciprofloxacin resistance in M. smegmatis.

Exposure to sub-inhibitory ciprofloxacin and nitrofurantoin concentrations increases recA gene expression in uropathogenic Escherichia coli: The role of RecA protein as a drug target

Sub-inhibitory concentrations (sub-MIC) of antimicrobial agents can lead to genetic changes in bacteria, modulating the expression of genes related to bacterial stress and leading to drug resistance. Herein we describe the impact of sub-MIC of ciprofloxacin and nitrofurantoin on three uropathogenic Escherichia coli strains. Disk-diffusion assays with different antimicrobial agents were tested to detect phenotype alterations, and quantitative real-time PCR (qRT-PCR) was performed to analyze the expression of ompF and recA genes. Significant reduction on the susceptibility to ciprofloxacin and nitrofurantoin was detected on disk diffusion test. The qRT-PCR results revealed a 1.2-4.7 increase in recA expression in all E. coli studied, while the ompF expression varied. Because RecA was pointed as an important component to the development of drug resistance, molecular docking studies were performed with three experimentally known inhibitors of this enzyme. These studies aimed to understand the inhibitory binding mode of such compounds. The results confirmed the ADP/ATP binding site as a potential site of inhibitor recognition and a binding mode based on π-stacking interactions with Tyr103 and hydrogen bonds with Tyr264. These findings can be useful for guiding the search and design of new antimicrobial agents, mainly concerning the treatment of infections with resistant bacterial strains.

Cold shock induces chromosomal qnr in Vibrio species and plasmid-mediated qnrS1 in Escherichia coli

qnr genes are found in aquatic bacteria and preceded the development of synthetic quinolones. Their natural functions are unknown. We evaluated the expression of chromosomal qnr in Vibrio species in response to environmental stresses and DNA damaging agents. Sub-inhibitory concentrations of quinolones, but not other DNA damaging agents, induced the expression of chromosomal qnr by more than five times in Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio mytili Cold shock also induced the expression of qnr in V. parahaemolyticus, V. vulnificus, and V. mytili, as well as qnrS1 in Escherichia coli qnrS1 induction by cold shock was not altered in ΔihfA or ΔihfB mutants or in a strain over-expressing dnaA, that otherwise directly modulate qnrS1 induction by ciprofloxacin. In contrast, qnrS1 induction by cold shock was reduced in a ΔcspA mutant in the cold shock regulon compared to the wild type. In conclusion, cold shock as well as quinolones induce chromosomal qnr in Vibrio species, and the related qnrS1 in E. coli.