First report of the plasmid-borne colistin resistance gene (mcr-1) in Proteus mirabilis isolated from a toddler in non-clinical settings

Nanoemulsion of cinnamon oil to combat colistin-resistant Klebsiella pneumoniae and cancer cells

This study aimed to investigate the potential of cinnamon oil nanoemulsion (CONE) as an antibacterial agent against clinical strains of colistin-resistant Klebsiella pneumoniae and its anticancer activity. The prepared and characterized CONE was found to have a spherical shape with an average size of 70.6 ± 28.3 nm under TEM and a PDI value of 0.076 and zeta potential value of 6.9 mV using DLS analysis. The antibacterial activity of CONE against Klebsiella pneumoniae strains was investigated, and it was found to have higher inhibitory activity (18.3 ± 1.2-30.3 ± 0.8 mm) against the tested bacteria compared to bulk cinnamon oil (14.6 ± 0.88-20.6 ± 1.2) with MIC values ranging from 0.077 to 0.31 % v/v which equivalent to 0.2-0.82 ng/ml of CONE. CONE inhibited the growth of bacteria in a dose and time-dependent manner based on the time-kill assay in which Klebsiella pneumoniae B-9 was used as a model among the bacterial strains under investigation. The study also investigated the expression of the mcr-1 gene in the Klebsiella pneumoniae strains and found that all strains were positive for the gene expression and subsequently its presence. The level of mcr-1 gene expression among the B-2, B-4, B-9, and B-11 control strains and that treated with colistin was similar, but it was different in both B-5 and B-2. However, all strains exhibited a significant downregulation in gene expression (ranging from 3.97 to 8.7-fold) after their treatment with CONE. Additionally, the CONE-treated bacterial cells appeared with a great deformation compared with control cells under TEM. Finally, CONE exhibited selective toxicity against different cancer cell lines depending on comparison with the normal cell lines.

Emergence of Extended-Spectrum Cephalosporin- and Colistin-Resistant Enterobacterales in Otherwise Healthy University Students

Resistance to last resort antibiotics has been increasing, particularly in low- and middle-income countries such as Lebanon, which has well established challenges in antimicrobial stewardship and other public health and environmental issues. However, data on the emergence of antibiotic resistance in the community in Lebanon are limited. In this study, we assessed resistance to last resort antibiotics in the fecal samples of 111 otherwise healthy university students in north Lebanon. The results showed that 47.7% of the samples harbored extended-spectrum cephalosporin-resistant isolates, while 2.7% of the samples yielded colistin-resistant isolates. Furthermore, molecular analyses showed that the β-lactamase gene group, blaCTX-M-1 group, was detected in the majority (93%) of screened extended-spectrum β-lactamase isolates. In addition, the colistin-resistant Escherichia coli isolates carried mcr-1, including the novel mcr-1.26 variant, which was previously reported in clinical samples as well as in domesticated animals and the environment in Lebanon. Taken together, these findings highlight the occurrence of resistance to important antibiotics in the community, perhaps suggesting diffuse sources, including clinical and environmental settings, and multiple factors driving the spread of multidrug-resistant bacteria and resistance determinants. There is a pressing need for comprehensive antimicrobial stewardship programs and the implementation of evidence-based practices in clinical and community settings to mitigate the increasing spread of antimicrobial resistance.

Occurrence of mcr genes and alterations in mgrB gene in intrinsic colistin- resistant Enterobacterales isolated from chicken meat samples

BACKGROUND

Tolerance of gram negative pathogens toward last resort colistin is mediated by mcr genes and alterations in chromosomal mgrB via modification of lipopolysaccharide through the PmrAB and PhoPQ component system. Proteus sp., Morganella sp., Neisseria sp., Burkholderia sp. and Providencia sp. are intrinsic resistant to colistin drug. Recent reports have shown that colistin intrinsic resistant organisms harbor and act as reservoirs for mcr genes.

AIM

To evaluate the presence of mcr-1 to mcr-5 genes and alterations in mgrB gene in intrinsic colistin-resistant gram negative bacteria isolated from chicken meat samples in Coimbatore district, Tamil Nadu, India.

METHODS

One hundred chicken meat samples were collected during 2019-20. Samples were enriched and plated on MacConkey agar supplemented with colistin (2 μg/ml). The bacterial isolates were then identified using biochemical tests. DNA were extracted from isolates using the thermal lysis method. mcr-1 to mcr-5 and mgrB genes was detected using conventional PCR and agarose gel electrophoresis methods.

RESULT AND CONCLUSION

The presence of mcr-1 to mcr-5 genes was found to be 23 % (23/100). mcr-1 and mcr-5 genes were not detected in sample isolates. 17/23 samples positive for mcr genes were also found to be carrying alterations in mgrB gene. Phenotypic characterization of these isolates revealed that these bacteria were belonging to colistin intrinsic resistant gram negative bacteria such as Proteus sp., Providencia sp., and Morganella sp. Intrinsic resistant bacteria could act as a potential reservoir and disseminate mcr genes to the colistin sensitive non-intrinsic pathogens of clinical importance in the environment.

Antibiotic Resistance in Proteus mirabilis: Mechanism, Status, and Public Health Significance

Proteus mirabilis is a specific opportunistic pathogen of many infections including urinary tract infections (UTIs). Risk factors are linked with the acquisition of multidrug-resistant (MDR) to 3 or more classes of antimicrobials) strains. The resistance in extended-spectrum alpha-lactamase is rare, but the rising resistance in extended-spectrum beta-lactamase (ESBL) producing strains is a matter of concern. β-lactamases and antibiotic modifying enzymes mainly constitute the ESBLs resistance mechanism by hydrolyzing the antibiotics. Mutation or Porin loss could lead to the reduced permeability of antibiotics, enhanced efflux pump activity hindering the antibiotic access to the target site, antibiotic failure to bind at the target site because of the target modification, and lipopolysaccharide mutation causing the resistance against polymyxin antibiotics. This review aimed to explore various antimicrobial resistance mechanisms in Proteus mirabilis and their impact on public health status.

Antibacterial activity of essential oils for combating colistin-resistant bacteria

OBJECTIVES

Colistin (polymyxin E) is a bactericidal antibiotic used to treat severe infections caused by multidrug-resistant Gram-negative bacteria. The product of the mcr1 gene generates transferrable plasmid-mediated colistin resistance, which has arisen as a worldwide healthcare problem. This study aimed to isolate, and identify colistin-resistant bacteria, and evaluate the ability of essential oils its fights.

METHODS

: Twenty-seven bacterial isolates were collected from patients who were admitted to National Cancer Institute, Cairo, Egypt, and processed by standard microbiological methods. Essential oils were purchased from AB chem company, Egypt, screened for antibacterial, cytotoxic activity, and (GC-MS) analysis.

RESULTS

A total of 5 bacterial isolates were resistant to colistin with minimum inhibitory concentration (MIC) ranging from 6.25->200µg/ml. Cinnamon oil exhibited the highest activity against colistin-resistant strains followed by thyme and eucalyptus oil. The (MIC) of cinnamon oils against resistant strains ranged from 4.88 to 312.5 µg/ml. Moreover, mcr-1 gene expression was extremely down-regulated after treatment of bacterial strains with cinnamon oil and decreased to 20-35-fold. Examination of treated bacterial cells with sub-inhibitory concentrations under transmission electron microscopy showed various abnormalities occurred in most of these cells.

CONCLUSIONS

cinnamon oil exhibits antibacterial activity against colistin-resistant strains, showing as a promising natural alternative in clinical therapy.

A sustainable and economic strategy to reduce risk antibiotic resistance genes during poultry manure bioconversion by black soldier fly Hermetia illucens larvae: Larval density adjustment

Black soldier fly (Hermetia illucens) larvae (BSFL) are common insects that are known for bioconversion of organic waste into a sustainable utilization resource. However, a strategy to increase antibiotic resistance gene (ARG) elimination in sustainable and economic ways through BSFL is lacking. In the present study, different larval densities were employed to assess the mcr-1 and tetX elimination abilities, and potential mechanisms were investigated. The application and economic value of each larval density were also analyzed. The results showed that the 100 larvae cultured in 100 g of manure group had the best density because the comprehensive disadvantage evaluation ratio was the lowest (14.97%, good bioconversion manure quality, low ARG deposition risk and reasonable larvae input cost). Further investigation showed that mcr-1 could be significantly decreased by BSFL bioconversion (4.42 ×10⁷ copies/g reduced to 4.79 ×10⁶-2.14 ×10⁵ copies/g)(P＜0.05); however, mcr-1 was increasingly deposited in the larval gut with increasing larval density. The tetX abundance was stabilized by BSFL bioconversion, except that the abundance at the lowest larval density increased (1.22 ×10¹⁰ copies/g increase, 34-fold). Escherichia was the host of mcr-1 and tetX in all samples, especially in fresh manure; Alcaligenes was the host of tetX in bioconversion manure; and the abundance of Alcaligenes was highly correlated with the pH of bioconversion manure. The pH of bioconversion manure was extremely correlated with the density of larvae. Klebsiella and Providencia were both hosts of tetX in the BSF larval gut, and Providencia was also the host of mcr-1 in the BSF larval gut. The density of larvae influenced the bioconversion manure quality and caused the ARG host abundance to change to control the abundance of ARGs, suggesting that larval density adjustment was a useful strategy to manage the ARG risk during BSFL manure bioconversion.

Knowledge, attitudes, and perceptions of dairy farmers regarding antibiotic use: Lessons from a developing country

In lower- and middle-income countries, uncontrolled use of antibiotics is causing antimicrobial resistance, affecting both animal welfare and public health. Meanwhile, studies on antibiotic use in these countries are limited. A crucial step to limit the spread of antimicrobial resistance (AMR) is to examine the use of these drugs and identify its determinants. The aim of our study, the first of its kind in Lebanon, was to assess dairy farmers' knowledge and awareness of antimicrobial use (AMU) and AMR. For this, 18 farmers from different regions, educational backgrounds, experience levels, and herd sizes were interviewed. Results showed that owners of larger farms were more aware of AMU and AMR, and trying to implement preventive actions, whereas nonsystematic antimicrobial use was prevalent among the smaller farms. Mastitis and laminitis were the most treated diseases, and antibiotics used were oxytetracycline, penicillin, streptomycin, and florfenicol. Overall, antibiotic use was found as a preventive measure and a treatment of nonbacterial diseases. Irregular uses were linked to easy access of farmers to antibiotics, interrupted relations with veterinary authorities, and lack of self-assessment and inspection. Lebanese dairy farmers and owners reported feeling disadvantaged in their local trade field, facing illegal competition and unauthorized farms and industries, and lacking support from the government. Training and awareness programs must be implemented, and policies and regulations must be set, to reduce antibiotic use and hinder the spread of AMR in Lebanon.

Virulence Determinants and Plasmid-Mediated Colistin Resistance mcr Genes in Gram-Negative Bacteria Isolated From Bovine Milk

A major increase of bacterial resistance to colistin, a last-resort treatment for severe infections, was observed globally. Using colistin in livestock rearing is believed to be the ground of mobilized colistin resistance (mcr) gene circulation and is of crucial concern to public health. This study aimed to determine the frequency and virulence characteristics of colistin-resistant Gram-negative bacteria from the milk of mastitic cows and raw unpasteurized milk in Egypt. One hundred and seventeen strains belonging to Enterobacteriaceae (n = 90), Pseudomonas aeruginosa (n = 10), and Aeromonas hydrophila (n = 17) were screened for colistin resistance by antimicrobial susceptibility testing. The genetic characteristics of colistin-resistant strains were investigated for mcr-1-9 genes, phylogenetic groups, and virulence genes. Moreover, we evaluated four commonly used biocides in dairy farms for teat disinfection toward colistin-resistant strains. Multidrug-resistant (MDR) and extensive drug-resistant (XDR) phenotypes were detected in 82.91% (97/117) and 3.42% (4/117) of the isolates, respectively. Of the 117 tested isolates, 61 (52.14%) were colistin resistant (MIC >2 mg/L), distributed as 24/70 (34.29%) from clinical mastitis, 10/11 (90.91%) from subclinical mastitis, and 27/36 (75%) from raw milk. Of these 61 colistin-resistant isolates, 47 (19 from clinical mastitis, 8 from subclinical mastitis, and 20 from raw milk) harbored plasmid-borne mcr genes. The mcr-1 gene was identified in 31.91%, mcr-2 in 29.79%, mcr-3 in 34.04%, and each of mcr-4 and mcr-7 in 2.13% of the colistin-resistant isolates. Among these isolates, 42.55% (20/47) were E. coli, 21.28% (10/47) A. hydrophila, 19.12% (9/47) K. pneumoniae, and 17.02% (8/47) P. aeruginosa. This is the first report of mcr-3 and mcr-7 in P. aeruginosa. Conjugation experiments using the broth-mating technique showed successful transfer of colistin resistance to E. coli J53-recipient strain. Different combinations of virulence genes were observed among colistin-resistant isolates with almost all isolates harboring genes. Hydrogen peroxide has the best efficiency against all bacterial isolates even at a low concentration (10%). In conclusion, the dissemination of mobile colistin resistance mcr gene and its variants between MDR- and XDR-virulent Gram-negative isolates from dairy cattle confirms the spread of mcr genes at all levels; animals, humans, and environmental, and heralds the penetration of the last-resort antimicrobial against MDR bacteria. Consequently, a decision to ban colistin in food animals is urgently required to fight XDR and MDR bacteria.

From the Urinary Catheter to the Prevalence of Three Classes of Integrons, β-Lactamase Genes, and Differences in Antimicrobial Susceptibility of Proteus mirabilis and Clonal Relatedness with Rep-PCR

Introduction

Proteus mirabilis is a biofilm-forming agent that quickly settles on the urinary catheters and causing catheter-associated urinary tract infections. Thus, the spread of multidrug-resistant P. mirabilis isolates, with the ability to form a biofilm that carries integron, extended-spectrum β-lactamases (ESBLs), and plasmid-mediated colistin resistance genes (mcr), represents a severe threat to managing nosocomial infectious diseases. This study is aimed at surveying the prevalence of ESBL, integrase, and mcr genes of P. mirabilis, isolated from the catheter, to assess the differences in their antimicrobial susceptibility and clonal dissemination.

Method

Microtiter plate assay was adopted to measure biofilm formation. The antimicrobial susceptibility was assessed by the disk diffusion method. Antimicrobial resistance genes (intI1, intI2, intI3, bla_TEM, bla_CTX-M, bla_SHV, mcr1, and mcr2) were detected by PCR. All of the isolates were characterized by repetitive sequence-based PCR.

Result

From 385 collected catheters in patients admitted to the intensive care unit (ICU), 40 P. mirabilis were isolated. All of the isolates could form a biofilm. Proteus spp. had intrinsic resistance to tetracycline (95%) and nitrofurantoin (92.5%), which explains the high resistance prevalence. The most widely resistant antibiotic was trimethoprim-sulfamethoxazole (75%). Thirty-three (82.5%) isolates were classified as multidrug resistance (MDR). The prevalence of intI1 and intI2 genes was 60% and 25%, respectively. In 6 (15%) isolates, both genes were detected. The most frequent ESBL gene detected in all of the isolates was bla_TEM. Also, no detection for mcr1 and mcr2 antibiotic resistance genes was reported. Rep-PCR identified 39(GTG)5 types (G1–G39) of 40 isolates that 38 isolates had unique patterns.

Conclusion

In this study, 82.5% of isolates were MDR with high antibiotic resistance to trimethoprim-sulfamethoxazole. The intI1 and bla_TEM were the most prevalent genes in the integrase and ESBL gene family. High diversity was seen in the isolates with Rep-PCR. The increasing rate of MDR isolates with a high prevalence of resistance genes could be alarming and demonstrate the need for hygienic procedures to prevent the increased antibiotic resistance rate in the future.

Review on the occurrence of the mcr-1 gene causing colistin resistance in cow's milk and dairy products

Both livestock farmers and the clinic use significant amount of antibiotics worldwide, in many cases the same kind. Antibiotic resistance is not a new phenomenon, however, it is a matter of concern that resistance genes (mcr - Mobilized Colistin Resistance - genes) that render last-resort drugs (Colistin) ineffective, have already evolved. Nowadays, there is a significant consumption of milk and dairy products, which, if not treated properly, can contain bacteria (mainly Gram-negative bacteria). We collected articles and reviews in which Gram-negative bacteria carrying the mcr-1 gene have been detected in milk, dairy products, or cattle. Reports have shown that although the incidence is still low, unfortunately the gene has been detected in some dairy products on almost every continent. In the interest of our health, the use of colistin in livestock farming must be banned as soon as possible, and new treatments should be applied so that we can continue to have a chance in fighting multidrug-resistant bacteria in human medicine.

First Nation-Wide Analysis of Food Safety and Acceptability Data in Lebanon

The challenges to food safety in Lebanon are numerous and have coalesced to pose a serious public health concern. This is evident in well-documented food poisoning outbreaks and adulteration cases. In response, the Lebanese government initiated an unprecedented food safety campaign (2015–2017) that aimed to test food samples that were randomly collected from foodservices and industries across the country. The data were made available publicly, but they were never analyzed to prioritize and determine high risk foods and most prevalent contaminants nationally or across governorates. To answer these questions, we performed an in-depth statistical analysis of the data, which included 11,625 individual food samples. Our analysis showed that water (55% of tested water samples), spices (49.3%), red meat (34.4%), poultry (30.9%) and dairy (28.3%) were the main foods associated with the highest rejection rates. The most common biological contaminants detected in rejected foods were sulfate-reducing bacteria (34.7%), Escherichia coli (32.1%), coliforms (19.6%), Staphylococcus aureus (12.8%), and Salmonella (11.6%). We conclude that Lebanon needs rigorous and sustainable programs to monitor the quality and safety of foods. Given the lack of resources, we recommend putting emphasis on extensive outreach programs that aim at enhancing food safety knowledge from farm to fork.

The Mobile Colistin Resistance Gene, mcr-1.1, Is Carried on IncX4 Plasmids in Multidrug Resistant E. coli Isolated from Rainbow Trout Aquaculture

Colistin, a last resort antibiotic, is important for controlling infections with carbapenem-resistant Enterobacteriaceae. The recent emergence of mobile-colistin-resistance (mcr) genes has threatened the effectiveness of colistin. Aquaculture is hypothesized to be a major contributor to the evolution and dissemination of mcr. However, data on mcr in aquaculture are limited. Here, the occurrence of mcr-1 was assessed in Rainbow Trout in Lebanon, a country with developing antimicrobial stewardship and an established use of colistin for medical and farming purposes. mcr-1 was detected in 5 Escherichia coli isolated from fish guts. The isolates were classified as multidrug-resistant and their colistin minimum inhibitory concentration ranged between 16 and 32 μg/mL. Whole genome sequencing analysis showed that mcr-1 was carried on transmissible IncX4 plasmids and that the isolates harbored more than 14 antibiotic resistance genes. The isolates belonged to ST48 and ST101, which have been associated with mcr and can occur in humans and fish. The mcr-1-positive E. coli persisted in 6-day biofilms, but there was a potential fitness cost. Given the status of infrastructure in Lebanon, there is a high potential for the dissemination of mcr via aquatic environments. Urgent actions are needed to control mcr and to enhance antimicrobial stewardship in Lebanon.

Exploring tet(X)-bearing tigecycline-resistant bacteria of swine farming environments

Emergence of high-level tigecycline resistance tet(X) variants in animal and human Enterobacterales is posing a public health concern. Recently, novel tet(X) variants including tet(X3), tet(X4), tet(X5) and tet(X6) were detected in Enterobacterales and Acinetobacter baumannii. Here, we comprehensively investigated the prevalence of tet(X) variants among different bacterial species in swine farm environment with nanopore sequencing. The tet(X6) gene was found located on both plasmids and ICEs in Proteus, but tet(X4) was in plasmids in E. coli. To our knowledge, this is the first report of the emergence of IncA/C2-type plasmid-mediated tet(X6). The bacterial host adaptation of different tet(X) variants implies they evolved in microbiota separately, but ISCR2 should be the key element facilitating horizontal transfer of various tet(X) variants through circular intermediates. Our findings further expand the knowledge about reservoirs of mobile tigecycline resistance genes and the epidemic characteristics of tet(X) variants in animals and related environments.

Audacious Hitchhikers: The Role of Travel and the International Food Trade in the Global Dissemination of Mobile Colistin-Resistance (mcr) Genes

Colistin, a last-resort antibiotic, has been used in controlling infections caused by multidrug-resistant Gram-negative bacterial pathogens. However, recent reports showed a global dissemination of mobile colistin-resistance (mcr) genes, genetic elements that encode resistance to colistin, which has raised public health concerns. These mcr genes threaten the effectiveness of colistin and could limit therapy options for complicated infections. Despite global attention, many facets of the molecular epidemiology of mcr remain poorly characterized. Here, we focus on the role of travel and the international food trade in the dissemination of mcr to countries where these genetic elements and/or colistin resistance are relatively limited in prevalence. We present evidence from the literature on the acquisition of mcr during travel, and the carriage of these genes back to travelers’ countries. We also highlight the potential transmission of mcr via imported foods. These observations emphasize the magnitude of efforts that are needed to control the spread of mcr, and further highlight the challenge of antimicrobial resistance and the urgent need for coordinated global action.

Plasmid-Determined Colistin Resistance in the North African Countries: A Systematic Review

We have conducted a systematic review to update available information on plasmid-mediated colistin resistance (mobilized colistin resistance [mcr]) genes in North African countries. We have searched the articles of PubMed, Scopus, and Web of Science databases reporting plasmid-mediated colistin resistance bacteria isolated in North African countries. After searching and selection, 30 studies that included 208 mcr-positive isolates were included. Different mcr-positive strains frequencies were recorded and ranged from 2% in clinical isolates to 12.3% in environmental samples. Escherichia coli was the predominant species recorded and these microorganisms showed high resistance to ciprofloxacin and cotrimoxazole. IncHI2 plasmids are probably the key vectors responsible for the dissemination of mcr genes in these countries. This review highlighted that the mcr-positive isolates are circulating in different ecological niches with different frequencies. Therefore, actions should be implemented to prevent the dissemination of the mcr genes within and outside of these countries, such as microbiological and molecular surveillance programs and restriction use of colistin in farming.