Critical threat associated with carbapenem-resistant gram-negative bacteria: prioritizing water matrices in addressing total antibiotic resistance

Rational design of synthetic antimicrobial peptides based on the Escherichia coli ShoB toxin

Antibiotic resistance is an escalating global concern, necessitating the development of novel antibiotics with unique mechanisms of action, and preferably also with a lowered propensity for resistance development. Type-I Toxin-Antitoxin (TA) systems that are ubiquitous in bacterial genomes consist of a genetic toxin element encoding a hydrophobic peptide and an antitoxin element producing an sRNA that inhibits the toxin translation. Although the biological roles of these membrane-associated toxins remain incompletely understood, their inherent lethality upon overexpression suggests a potential as antimicrobial agents. In this study, we explore the ShoB toxin from the shoB-ohsC TA system in Escherichia coli (E. coli) as a basis for designing synthetic antimicrobial peptides for exogenous delivery. We demonstrate that ShoB-derived peptides can retain antimicrobial efficacy when modified into shorter, cationic analogs with enhanced solubility. Our most promising hits exhibit rapid bactericidal action and frequency of resistance within E. coli cultures indicate a limited tendency for resistance development. These findings highlight that type-I TA systems constitute a novel source of potential peptide-based antibiotics, thereby offering an alternative largely unexplored strategy to combat antibiotic-resistant bacterial infections.

Mechanisms, therapeutic strategies, and emerging therapeutic alternatives for carbapenem resistance in Gram-negative bacteria

Carbapenem-resistant Gram-negative bacteria (CR-GNB) have experienced an alarming surge in prevalence in recent years, escalating into a critical global healthcare crisis. As carbapenems represent the last line of defense against such pathogens, infections caused by CR-GNB have become increasingly challenging to treat, given the restricted therapeutic options and heightened mortality risks. The discovery and development of alternative therapeutic strategies that present novel avenues against multi-drug-resistant organisms are gaining increased attention, presenting a pressing need for innovative solutions. Our comprehensive review delves into the multifaceted landscape of carbapenem resistance in Gram-negative bacteria in response to this urgent challenge. The scope of this review aims to provide an up-to-date and in-depth exploration regarding the mode of action of carbapenem and the resisting mechanisms of carbapenem in GNB. Additionally, it discusses the state of the art of some clinical therapies for the treatment of infections caused by CR-GNB. Moreover, it describes several combinational and alternative therapies to combat CR-GNB, including the computational approach of "molecular docking". In light of the conclusions of this review, we call for the implementation of these strategies to develop comprehensive approaches to mitigate carbapenem resistance in Gram-negative bacteria.

Genome-centric metagenomes unveiling the hidden resistome in an anchialine cave

BACKGROUND

Antibiotic resistance is a critical global concern, posing significant challenges to human health and medical treatments. Studying antibiotic resistance genes (ARGs) is essential not only in clinical settings but also in diverse environmental contexts. However, ARGs in unique environments such as anchialine caves, which connect both fresh and marine water, remain largely unexplored despite their intriguing ecological characteristics.

RESULTS

We present the first study that comprehensively explores the occurrence and distribution of ARGs and mobile genetic elements (MGEs) within an anchialine cave. Utilizing metagenomic sequencing we uncovered a wide array of ARGs with the bacitracin resistance gene, bacA and multidrug resistance genes, being the most dominant. The cave's microbial community and associated resistome were significantly influenced by the salinity gradient. The discovery of novel β-lactamase variants revealed the cave's potential as a reservoir for previously undetected resistance genes. ARGs in the cave demonstrated horizontal transfer potential via plasmids, unveiling ecological implications.

CONCLUSIONS

These findings highlight the need for further exploration of the resistome in unique environments like anchialine caves. The interconnected dynamics of ARGs and MGEs within anchialine caves offer valuable insights into potential reservoirs and mechanisms of antibiotic resistance in natural ecosystems. This study not only advances our fundamental understanding but also highlights the need for a comprehensive approach to address antibiotic resistance in diverse ecological settings.

Hospital and municipal wastewater as a source of carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa in the environment: a review

The increase in the prevalence of carbapenem-resistant Gram-negative bacteria, in particular Acinetobacter baumannii (CRAB) and Pseudomonas aeruginosa (CRPA), poses a serious threat for public health worldwide. This article reviews the alarming data on the prevalence of infections caused by CRAB and CRPA pathogens and their presence in hospital and municipal wastewater, and it highlights the environmental impact of antibiotic resistance. The article describes the key role of antibiotic resistance genes (ARGs) in the acquisition of carbapenem resistance and sheds light on bacterial resistance mechanisms. The main emphasis was placed on the transfer of ARGs not only in the clinical setting, but also in the environment, including water, soil, and food. The aim of this review was to expand our understanding of the global health risks associated with CRAB and CRPA in hospital and municipal wastewater and to analyze the spread of these micropollutants in the environment. A review of the literature published in the last decade will direct research on carbapenem-resistant pathogens, support the implementation of effective preventive measures and interventions, and contribute to the development of improved strategies for managing this problem.

Virulence Signatures, Integrons, and Antibiotic Resistance Genes in Bacterial Strains Recovered from Selected Commercial Dairy Products and Fresh Raw Meat

Bacterial species responsible for food infections and intoxication are sometimes carried through the food production and processing. Very few published literatures exist on integrons among antibiotic-resistant staphylococcal strains from foods of animal origin in Gauteng Province, South Africa, hence this study. A total of 720 samples (360 meat and 360 dairies) from a community abattoir of a research farm in South Africa, using conventional bacteriological and molecular methods. Nine (9) bacterial strains, including Bacillus subtilis AYO-123, Acinetobacter baumannii AYO-241, Staphylococcus lentus AYO-352, among others were identified and submitted to GenBank. More bacterial strains were recovered from raw meat (90.5%) than dairy products (9.5%). Resistance was shown (0-100%) to Imipenem, Meropenem, Norfloxacin, Clindamycin, and 22 other antibiotics, without any carbapenem-resistant Acinetobacter baumannii and methicillin/vancomycin-resistant Staphylococcus species (MRSS/VRSS). Virulence genes for fibronectin-binding protein A (FnbA) were predominant (56.24%) followed by the circulating nucleic acids (cna) gene (43.75%). Others were staphylococcal enterotoxin A (sea, 41%), staphylococcal enterotoxin B (seb, 23.5%). Co-presence of sea and seb genes occurred in 11.76% of the isolates, but no coa genes was amplified. Antibiotic resistance genes (ARGs), tetK (70.58%), linA (29.4%), and ermA (11.76%) were detected, but none of the mecA and vat genes was amplified. Class 2 integron (50%) was more predominantly detected than integron 1 (25%), but no Class 3 integron was detected. Bacteria with both the detected virulence and antibiotic resistance genes are of potential risks to human health.

Effects of sewer biofilms on the degradability of carbapenems in wastewater using laboratory scale bioreactors

Carbapenems are last-resort antibiotics used to treat bacterial infections unsuccessfully treated by most common categories of antibiotics in humans. Most of their dosage is secreted unchanged as waste, thereby making its way into the urban water system. There are two major knowledge gaps addressed in this study to gain a better understanding of the effects of their residual concentrations on the environment and environmental microbiome: development of a UHPLC-MS/MS method of detection and quantification from raw domestic wastewater via direct injection and study of their stability in sewer environment during the transportation from domestic sewers to wastewater treatment plants. The UHPLC-MS/MS method was developed for four carbapenems: meropenem, doripenem, biapenem and ertapenem, and validation was performed in the range of 0.5-10 μg/L for all analytes, with limit of detection (LOD) and limit of quantification (LOQ) values ranging from 0.2-0.5 μg/L and 0.8-1.6 μg/L respectively. Laboratory scale rising main (RM) and gravity sewer (GS) bioreactors were employed to culture mature biofilms with real wastewater as the feed. Batch tests were conducted in RM and GS sewer bioreactors fed with carbapenem-spiked wastewater to evaluate the stability of carbapenems and compared against those in a control reactor (CTL) without sewer biofilms, over a duration of 12 h. Significantly higher degradation was observed for all carbapenems in RM and GS reactors (60 - 80%) as opposed to CTL reactor (5 - 15%), which indicates that sewer biofilms play a significant role in the degradation. First order kinetics model was applied to the concentration data along with Friedman's test and Dunn's multiple comparisons analysis to establish degradation patterns and differences in the degradation observed in sewer reactors. As per Friedman's test, there was a statistically significant difference in the degradation of carbapenems observed depending on the reactor type (p = 0.0017 - 0.0289). The results from Dunn's test indicate that the degradation in the CTL reactor was statistically different from that observed in either RM (p = 0.0033 - 0.1088) or GS (p = 0.0162 - 0.1088), with the latter two showing insignificant difference in the degradation rates observed (p = 0.2850 - 0.5930). The findings contribute to the understanding about the fate of carbapenems in urban wastewater and the potential application of wastewater-based epidemiology.

A systematic review of the current status of carbapenem resistance in Nigeria: Its public health implication for national intervention

Carbapenem antibiotics are considered one of the most effective and the last-resort antibiotics for the treatment of infections caused by multidrug-resistant Gram-negative bacteria. However, with the advent of carbapenem resistance, it becomes obvious that quality health-care delivery will be hampered if adequate measure is not put in place. This review assessed the prevalence of carbapenem-resistant Gram-negative bacteria (CR-GNB) and also provided an up-to-date position on carbapenem resistance (CR) in Nigeria. Three electronic databases (Google Scholar, PubMed and African Journal online) were searched for relevant literatures, and 38 articles published between January 2013 and June 2022 that met the criteria for inclusion were recruited into the study. The mean prevalence of CR in Nigeria stands at 21.3%, with the southern and northern regions documenting a mean prevalence of 22.0% and 20.9%, respectively. Most of the reviewed articles were from clinical settings (81.6%), with urine samples (38.7%) constituting the most prevalent clinical sample in which CR-GNB were detected. The preponderance of phenotypic methods (55.3%) over molecular method (44.7%), particularly the use of disk diffusion test breakpoint and Modified Hodge test was documented. The most prevalent carbapenem-resistant bacteria were Escherichia coli (50.0%) and Klebsiella pneumoniae (26.3%). The blaNDM and blaVIM were the major reported carbapenemase-encoded genes, particularly among E. coli, K. pneumoniae and Pseudomonas species. This systematic review revealed a mean prevalence of CR-GNB in Nigeria that required urgent attention. Furthermore, the detection of clinically and epidemiologically important carbapenemase coding genes is of public health importance.

Discrimination between Carbapenem-Resistant and Carbapenem-Sensitive Klebsiella pneumoniae Strains through Computational Analysis of Surface-Enhanced Raman Spectra: a Pilot Study

In clinical settings, rapid and accurate diagnosis of antibiotic resistance is essential for the efficient treatment of bacterial infections. Conventional methods for antibiotic resistance testing are time consuming, while molecular methods such as PCR-based testing might not accurately reflect phenotypic resistance. Thus, fast and accurate methods for the analysis of bacterial antibiotic resistance are in high demand for clinical applications. In this pilot study, we isolated 7 carbapenem-sensitive Klebsiella pneumoniae (CSKP) strains and 8 carbapenem-resistant Klebsiella pneumoniae (CRKP) strains from clinical samples. Surface-enhanced Raman spectroscopy (SERS) as a label-free and noninvasive method was employed for discriminating CSKP strains from CRKP strains through computational analysis. Eight supervised machine learning algorithms were applied for sample analysis. According to the results, all supervised machine learning methods could successfully predict carbapenem sensitivity and resistance in K. pneumoniae, with a convolutional neural network (CNN) algorithm on top of all other methods. Taken together, this pilot study confirmed the application potentials of surface-enhanced Raman spectroscopy in fast and accurate discrimination of Klebsiella pneumoniae strains with different antibiotic resistance profiles. IMPORTANCE With the low-cost, label-free, and nondestructive features, Raman spectroscopy is becoming an attractive technique with great potential to discriminate bacterial infections. In this pilot study, we analyzed surfaced-enhanced Raman spectroscopy (SERS) spectra via supervised machine learning algorithms, through which we confirmed the application potentials of the SERS technique in rapid and accurate discrimination of Klebsiella pneumoniae strains with different antibiotic resistance profiles.

Environmental spreading of clinically relevant carbapenem-resistant gram-negative bacilli: the occurrence of blaKPC-or-NDM strains relates to local hospital activities

Background

Aquatic matrices impacted by sewage may shelter carbapenem-resistant (CR) Gram-negative bacilli (GNB) harboring resistance genes of public health concern. In this study, sewage treatment plants (STPs) servicing well-defined catchment areas were surveyed for the presence of CR-GNB bearing carbapenemase genes (bla_KPC or bla_NDM).

Results

A total of 325 CR-GNB were recovered from raw (RS) and treated (TS) sewage samples as well as from water body spots upstream (UW) and downstream (DW) from STPs. Klebsiella-Enterobacter (KE) group amounted to 116 isolates (35.7%). CR-KE isolates were recovered from TS, DW (35.7%) and RS samples (44.2%) (p = 0.001); but not from UW samples. KE isolates represented 65.8% of all bla_KPC or bla_NDM positive strains. The frequency of bla_KPC-or-NDM strains was positively associated with the occurrence of district hospitals located near STPs, as well as with the number of hospitalizations and of sewer connections serviced by the STPs. bla_KPC-or-NDM strains were recovered from ST samples in 7 out of 14 STPs, including four tertiary-level STPs; and from 6 out of 13 DW spots whose RS samples also had bla_KPC-or-NDM strains.

Conclusions

Clinically relevant GNB bearing bla_KPC-or-NDM resist sewage treatments and spread into environmental aquatic matrices mainly from STPs impacted by hospital activities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02400-1.

Urban Aquatic Ecosystems as a Factor of the Spread of Antibiotic Resistant Microorganisms and Resistance Genes

In this work, studies have been conducted to detect antibiotic resistance microorganisms and resistance genes in the natural waters of the Uzh River, which flows in the Carpathian region (Ukraine) and flows into the Laborec River in the territory of Slovakia. Among the most common microorganisms of the Uzh River, there has been a high level of resistance to tetracyclines, β-lactams, and antibiotics of the last line of defence (carbapenems, fourth-generation fluoroquinolones). The results of molecular genetic analysis indicate the presence of resistance genes bla tet-M, bla CTX-M, bla TEM, and bla KPC in microorganisms of the Enterobacteriaceae family.

Molecular Epidemiology of Carbapenemases in Enterobacteriales from Humans, Animals, Food and the Environment

The Enterobacteriales order consists of seven families including Enterobacteriaceae, Erwiniaceae, Pectobacteriaceae, Yersiniaceae, Hafniaceae, Morganellaceae, and Budviciaceae and 60 genera encompassing over 250 species. The Enterobacteriaceae is currently considered as the most taxonomically diverse among all seven recognized families. The emergence of carbapenem resistance (CR) in Enterobacteriaceae caused by hydrolytic enzymes called carbapenemases has become a major concern worldwide. Carbapenem-resistant Enterobacteriaceae (CRE) isolates have been reported not only in nosocomial and community-acquired pathogens but also in food-producing animals, companion animals, and the environment. The reported carbapenemases in Enterobacteriaceae from different sources belong to the Ambler class A (bla_KPC), class B (bla_IMP, bla_VIM, bla_NDM), and class D (bla_OXA-48) β-lactamases. The carbapenem encoding genes are often located on plasmids or associated with various mobile genetic elements (MGEs) like transposons and integrons, which contribute significantly to their spread. These genes are most of the time associated with other antimicrobial resistance genes such as other β-lactamases, as well as aminoglycosides and fluoroquinolones resistance genes leading to multidrug resistance phenotypes. Control strategies to prevent infections due to CRE and their dissemination in human, animal and food have become necessary. Several factors involved in the emergence of CRE have been described. This review mainly focuses on the molecular epidemiology of carbapenemases in members of Enterobacteriaceae family from humans, animals, food and the environment.