Efficient production of endotoxin depleted bioactive α-hemolysin of uropathogenicEscherichia coli

Antimicrobial resistance and genomic characterization of Escherichia coli from pigs and chickens in Zhejiang, China

Escherichia coli is considered an opportunistic pathogen and an indicator for antimicrobial resistance (AMR) monitoring. Despite many reports on its AMR monitoring, studies based on genome-based analysis of AMR genes are still insufficient. Here, 181 E. coli strains were isolated from anal swab samples collected from pigs and chickens of animal farms located in Eastern China and sequenced through the Illumina platform. The results showed that 87.85% (159/181) of the E. coli isolates were multidrug-resistant (MDR). Ampicillin (AMP)- spectinomycin (SPT)- tetracycline (TET)- florfenicol (FFC)- sulfisoxazole (SF)- trimethoprim/sulfamethoxazole (SXT) was the predominant AMR pattern. By whole-genome sequencing, we found that ST10 (10.49%, 19/181) and ST48 (7.18%, 13/181) were major sequence types. IncFIB and IncX1 were the most prevalent plasmid replicons. The AMR genes bla NDM-5 (1.10%, 2/181), mcr-1 (1.10%, 2/181), tet(X4) (1.10%, 2/181), and cfr (6.08%, 2/181) were also found in these isolates. In addition, among the 169 virulence genes detected, we identified astA (37.02%, 67/181), hlyA (1.66%, 3/181), hlyB (1.66%, 3/181) and hlyD (1.66%, 3/181), which were closely related to heat-stable enterotoxin 1 and α-hemolysin. In addition, there were 33 virulence genes associated with the iron uptake system, and 46 were adhesion-related genes. Our study highlighted the need for routine surveillance of AMR with advanced genomic approaches, providing up-to-date data on the prevalence of AMR for the development and execution of antimicrobial stewardship policy.

In Silico Prediction and Design of Uropathogenic Escherichia coli Alpha-Hemolysin Generate a Soluble and Hemolytic Recombinant Toxin

The secretion of α-hemolysin by uropathogenic Escherichia coli (UPEC) is commonly associated with the severity of urinary tract infections, which makes it a predictor of poor prognosis among patients. Accordingly, this toxin has become a target for diagnostic tests and therapeutic interventions. However, there are several obstacles associated with the process of α-hemolysin purification, therefore limiting its utilization in scientific investigations. In order to overcome the problems associated with α-hemolysin expression, after in silico prediction, a 20.48 kDa soluble α-hemolysin recombinant denoted rHlyA was constructed. This recombinant is composed by a 182 amino acid sequence localized in the aa542–723 region of the toxin molecule. The antigenic determinants of the rHlyA were estimated by bioinformatics analysis taking into consideration the tertiary form of the toxin, epitope analysis tools, and solubility inference. The results indicated that rHlyA has three antigenic domains localized in the aa555–565, aa600–610, and aa674–717 regions. Functional investigation of rHlyA demonstrated that it has hemolytic activity against sheep red cells, but no cytotoxic effect against epithelial bladder cells. In summary, the results obtained in this study indicate that rHlyA is a soluble recombinant protein that can be used as a tool in studies that aim to understand the mechanisms involved in the hemolytic and cytotoxic activities of α-hemolysin produced by UPEC. In addition, rHlyA can be applied to generate monoclonal and/or polyclonal antibodies that can be utilized in the development of diagnostic tests and therapeutic interventions.

Uropathogenic Escherichia coli in India-an Overview on Recent Research Advancements and Trends

Urinary tract infection (UTI), a prevalent disease in India, also ranks among the most common infections in developing countries. The rapid emergence of antibiotic-resistant uropathogenic Escherichia coli (UPECs), the leading etiologic agent of UTI, in the last few years, led to an upsurge in the health care cost. This caused a considerable economic burden, especially in low-middle income country, India. This review aimed to provide an explicit overview of the recent advancements in E. coli-mediated UTI in India by incorporation of valuable information from the works published in PubMed and Google Scholar in the last six years (2015 to August, 2020). The literature survey demonstrated UPECs as the most predominant uropathogen in India, especially among females, causing both asymptomatic bacteriuria (ABU) and symptomatic UTI. An overall increasing national trend in resistance to penicillins, cephalosporins, aminoglycosides, fluoroquinolones, and sulfonamides was perceived irrespective of ABU and symptomatic UPECs during the aforementioned study period. High incidences of multidrug resistance, extended-spectrum β-lactamases, metallo β-lactamases, and AmpCs in UPECs were reported. Notable information on the pathogenic profiles, phylogroups, pathogenicity islands, and evidence of pathoadaptive FimH mutations was described. Alternative therapeutics and potential drug targets against UPECs were also reconnoitered. Therefore, the nationwide widespread occurrences of highly virulent MDR UPEC together with the limited availability of therapeutics highlighted the urgent need for promotion and invention of alternative therapeutics, search for which had already been started. Moreover, investigation of several mechanisms of UPEC infection and the search for potential drug targets might help to design newer therapeutics.

α-Hemolysin of uropathogenic E. coli regulates NLRP3 inflammasome activation and mitochondrial dysfunction in THP-1 macrophages

Hemolysin expressing UPEC strains have been associated with severe advanced kidney pathologies, such as cystitis and pyelonephritis, which are associated with an inflammatory response. Macrophages play an important role in regulating an inflammatory response during a urinary tract infection. We have studied the role of purified recombinant α-hemolysin in inducing inflammatory responses and cell death in macrophages. Acylation at lysine residues through HlyC is known to activate proHlyA into a fully functional pore-forming toxin, HlyA. It was observed that active α-hemolysin (HlyA) induced cleavage of caspase-1 leading to the maturation of IL-1β, while inactive α-hemolysin (proHlyA) failed to do so in THP-1 derived macrophages. HlyA also promotes deubiquitination, oligomerization, and activation of the NLRP3 inflammasome, which was found to be dependent on potassium efflux. We have also observed the co-localization of NLRP3 within mitochondria during HlyA stimulations. Moreover, blocking of potassium efflux improved the mitochondrial health in addition to a decreased inflammatory response. Our study demonstrates that HlyA stimulation caused perturbance in potassium homeostasis, which led to the mitochondrial dysfunction followed by an acute inflammatory response, resulting in cell death. However, the repletion of intracellular potassium stores could avoid HlyA induced macrophage cell death. The findings of this study will help to understand the mechanism of α-hemolysin induced inflammatory response and cell death.