First Detected Human Case in Algeria of mcr-1 Plasmid-Mediated Colistin Resistance in a 2011 Escherichia coli Isolate

A Systematic Review and Comprehensive Analysis of mcr Gene Prevalence in Bacterial Isolates in Arab Countries

BACKGROUND

The resurgence of colistin has become critical in combating multidrug-resistant Gram-negative bacteria. However, the emergence of mobilized colistin resistance (mcr) genes presents a crucial global challenge, particularly in the Arab world, which includes regions with unique conditions and ongoing conflicts in some parts.

METHODS

To address this issue, a systematic review was conducted using multiple databases, including Cochrane, PubMed, Scopus, Web of Science, and Arab World Research Source.

RESULTS

A total of 153 studies were included, revealing substantial heterogeneity in the prevalence of mcr genes across 15 Arab countries, with notable findings indicating that Egypt and Lebanon reported the highest number of cases. The analysis indicated that the most prevalent sequence types were ST10, ST101, and ST1011, all of which are Escherichia coli strains linked to significant levels of colistin resistance and multiple antimicrobial resistance profiles.

CONCLUSIONS

By analyzing the diverse findings from different Arab countries, this review lays a critical foundation for future research and highlights the necessity for enhanced surveillance and targeted interventions to address the looming threat of colistin resistance in the region.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42024584379.

Molecular Characterization of Carbapenem and Colistin Resistance in Klebsiella pneumoniae Isolates Obtained from Clinical Samples at a University Hospital Center in Algeria

The current study aimed to determine the molecular mechanisms of carbapenem and colistin resistance among the clinical isolates of Klebsiella pneumoniae from hospitalized patients admitted to a university hospital in Eastern Algeria. In total, 124 non-duplicate isolates of K. pneumoniae were collected from September 2018 to April 2019. Bacterial identification was performed using MALDI-TOF MS. The presence of extended spectrum β-lactamase (ESBL) genes, carbapenemase genes, chromosomal mutation and mcr genes in colistin-resistant K. pneumoniae were evaluated by PCR. ESBLs represented a rate of 49.1% and harbored blaCTX-M, blaTEM and blaSHV genes. Concerning carbapenems, 12 strains (9.6%) were resistant to ertapenem (MIC: 1-32 μg/mL), of which one strain (0.8%) was also resistant to imipenem (MIC: 32 μg/mL). Among these strains, nine (75%) harbored blaOXA-48 gene. Seven strains (5.6%) expressed resistance to colistin (MIC: 2-32 μg/mL), of which two harbored mcr-8 and mgrB genes simultaneously. The existence of a double resistance to colistin in the same strain is new in Algeria, and this could raise concerns about the increase in levels of resistance to this antibiotic (MIC: 32 μg/mL). The mgrB gene alone was observed in five isolates (71.4%), including two strains harboring blaOXA-48. This is the first report revealing the presence of K. pneumoniae strains carrying the blaOXA-48 gene as well as a mutation in the mgrB gene. Large-scale surveillance and effective infection control measures are also urgently needed to prevent the outbreak of various carbapenem- and colistin-resistant isolates.

A review of colistin-resistant Escherichia coli isolates in the Middle East: mechanisms, epidemiology, and dissemination from different sources in humans, animals, foodand soil

Escherichia coli is a normal gut inhabitantthat can cause various diseases ,such as intestinal, urinary tract, bladder infections and systemic infections in humans and animals. The alarming increase in profiles for extended-spectrum β-lactamase-  and carbapenemase-producing Escherichia coli isolates is a serious problem throughout the world. Colistin is known as a lastresort agent for the treatment of Gram-negative bacterial infections. Inappropriate use of colistin and other classes of antibiotics combined with inadequate infection control, especially in developing countries, can lead to serious public health complications. The global increase in colistin resistance has been reported in many parts of the world, ,including the Middle East. Colistin is used to treat infections caused by extensively drug-resistant Gram-negative bacteria. There are few reliable epidemiologic data on colistin-resistant E. coli isolates, and information on colistin-resistant E. coli from Asia, the largest, most populous, and most diverse continent in the world, is generally limited compared with Europe and the United States.  The data in this review article were compiled from related articles associated with isolated colistin-resistant Escherichia coli (E. coli) isolates from humans, animals, and food-producing animals. In the Middle East, colistin-resistant E. coli isolates were reported from Turkey, Egypt, Saudi Arabia, Algeria, Iran, Iraq, Bahrain, Qatar, Oman, Kuwait, Israel, and Lebanon between 2010 and 2023. While colistin resistance is most commonly observed in E. coli isolates, data have shown that mcr genes are the most common genes associated with colistin resistance in E. coli isolatescompared to mutations in pmrAsB, phoQ, and mgrB genes.

First report of detection of mcr-1 and virulence genes in avian pathogenic Escherichia coli in the center of Algeria

Background

Antimicrobial resistance in avian pathogenic Escherichia coli (APEC) represents a major concern in the avian industry worldwide and limited studies have investigated Colistin resistance among APEC in Algeria.

Aims

Investigate antibiotic resistance, in particular, Colistin, and mediated-Colistin resistance (mcr) genes, as well as the virulence genes in APEC.

Methods

One hundred E. coli were isolated from poultry suspected of colibacillosis. Antimicrobial susceptibility testing was done on 14 antibiotics by the disk diffusion method. Colistin minimum inhibitory concentration (MIC) was assessed by the broth microdilution method. Using multiplex PCR, mcr genes (mcr-1 to 5) and 7 virulence-related genes were investigated in Colistin-resistant isolates.

Results

Results showed high resistance to Tetracycline (99%), Nalidixic acid (92%), Doxycycline (90%), Ampicillin (89%), Ofloxacin (74%), Sulfamethoxazole-Trimethoprim (72%), and Amoxicillin-Clavulanic acid (57%); in addition, 92% of isolates were multidrug resistant. The rate of resistance to Colistin was 27% (27/100) of which 96.3% (26/27) of isolates carried the mcr-1 gene. Twenty-five of the Colistin-resistant isolates (92.59%) had at least three virulence genes. The most frequently isolated virulence genes were: fim H (96.3%) followed by hlyF, iroN, and iss (77.7%, each), iutA and ompT were found in 59.25% and 55.5% of isolates, respectively. The most prevalent combination of virulence factors was hlyF-iss-iroN-iutA-ompT-fimH.

Conclusion

This is the first report which highlighted Colistin resistance with the detection of mcr-1 in APEC isolates in the area of study. Colistin resistance and carriage of mcr-1 in virulent and multidrug-resistant isolates of E. coli are alarming and a surveillance program to limit the spread of these pathogens is mandatory.

Review and analysis of the overlapping threats of carbapenem and polymyxin resistant E. coli and Klebsiella in Africa

BACKGROUND

Carbapenem-resistant Enterobacterales are among the most serious antimicrobial resistance (AMR) threats. Emerging resistance to polymyxins raises the specter of untreatable infections. These resistant organisms have spread globally but, as indicated in WHO reports, the surveillance needed to identify and track them is insufficient, particularly in less resourced countries. This study employs comprehensive search strategies with data extraction, meta-analysis and mapping to help address gaps in the understanding of the risks of carbapenem and polymyxin resistance in the nations of Africa.

METHODS

Three comprehensive Boolean searches were constructed and utilized to query scientific and medical databases as well as grey literature sources through the end of 2019. Search results were screened to exclude irrelevant results and remaining studies were examined for relevant information regarding carbapenem and/or polymyxin(s) susceptibility and/or resistance amongst E. coli and Klebsiella isolates from humans. Such data and study characteristics were extracted and coded, and the resulting data was analyzed and geographically mapped.

RESULTS

Our analysis yielded 1341 reports documenting carbapenem resistance in 40 of 54 nations. Resistance among E. coli was estimated as high (> 5%) in 3, moderate (1-5%) in 8 and low (< 1%) in 14 nations with at least 100 representative isolates from 2010 to 2019, while present in 9 others with insufficient isolates to support estimates. Carbapenem resistance was generally higher among Klebsiella: high in 10 nations, moderate in 6, low in 6, and present in 11 with insufficient isolates for estimates. While much less information was available concerning polymyxins, we found 341 reports from 33 of 54 nations, documenting resistance in 23. Resistance among E. coli was high in 2 nations, moderate in 1 and low in 6, while present in 10 with insufficient isolates for estimates. Among Klebsiella, resistance was low in 8 nations and present in 8 with insufficient isolates for estimates. The most widespread associated genotypes were, for carbapenems, blaOXA-48, blaNDM-1 and blaOXA-181 and, for polymyxins, mcr-1, mgrB, and phoPQ/pmrAB. Overlapping carbapenem and polymyxin resistance was documented in 23 nations.

CONCLUSIONS

While numerous data gaps remain, these data show that significant carbapenem resistance is widespread in Africa and polymyxin resistance is also widely distributed, indicating the need to support robust AMR surveillance, antimicrobial stewardship and infection control in a manner that also addresses broader animal and environmental health dimensions.

First Report of OXA-48 and IMP Genes Among Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Isolates from Diarrheic Calves in Tunisia

Antimicrobial resistance is one of the most serious threats to human and animal health. Evidence suggests that the overuse of antimicrobial agents in animal production has led to the emergence and dissemination of multidrug-resistant isolates. The objective of this study was to assess the rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in calf feces and to characterize their resistance genes for antibiotics like beta-lactams and colistin, but also to determine their virulence genes. Fecal samples were collected from 100 diarrheic calves in the region of Bizerte, Tunisia. After isolation, E. coli isolates were screened for antimicrobial resistance against 21 antibiotics by the disc diffusion method. Characterization of β-lactamase genes and determination of associated resistance genes were performed by polymerase chain reaction. Among 71 E. coli isolates, 26 (36.6%) strains were ESBL-producing. Most of these isolates were multidrug-resistant (92.3%) and the most prevalent beta-lactamase genes detected were bla_CTX-M (n = 26), bla_SHV (n = 11), and bla_TEM (n = 8), whereas only 1 isolate carried the bla_CMY gene. In addition, resistance to carbapenems was detected in two isolates; one of them harbored both bla_OXA-48 and bla_IMP genes and the other isolate carried only the bla_IMP gene. Several resistance genes were identified for the first time in Tunisia from cases of diarrheic calves. Furthermore, to the best of our knowledge, this is the first report of detection and identification of carbapenem resistance genes and virulence genes from calves in North Africa. A high occurrence of antimicrobial resistance of E. coli recovered from fecal samples of calves with diarrhea was observed, highlighting the need for prudent use of antimicrobial agents in veterinary medicine to decrease the incidence of multidrug-resistant bacteria for both animals and humans.

Tunisian Multicenter Study on the Prevalence of Colistin Resistance in Clinical Isolates of Gram Negative Bacilli: Emergence of Escherichia coli Harbouring the mcr-1 Gene

Background: Actually, no data on the prevalence of plasmid colistin resistance in Tunisia are available among clinical bacteria. Objectives: This study aimed to investigate the current epidemiology of colistin resistance and the spread of the mcr gene in clinical Gram-negative bacteria (GNB) isolated from six Tunisian university hospitals. Methods: A total of 836 GNB strains were inoculated on COL-R agar plates with selective screening agar for the isolation of GNB resistant to colistin. For the selected isolates, mcr genes, beta-lactamases associated-resistance genes and molecular characterisation were screened by PCRs and sequencing. Results: Colistin-resistance was detected in 5.02% (42/836) of the isolates and colistin-resistant isolates harboured an ESBL (bla_CTX-M-15) and/or a carbapenemase (bla_OXA-48, bla_VIM) encoding gene in 45.2% of the cases. The mcr-1 gene was detected in four E. coli isolates (0.59%) causing urinary tract infections and all these isolates also contained the bla_TEM-1 gene. The bla_CTX-M-15 gene was detected in three isolates that also carried the IncY and IncFIB replicons. The genetic environment surrounding the mcr-carrying plasmid indicated the presence of pap-2 gene upstream mcr-1 resistance marker with unusual missing of ISApl1 insertion sequence. The Conclusions: This study reports the first description of the mcr-1 gene among clinical E. coli isolates in Tunisia and provides an incentive to conduct routine colistin susceptibility testing in GNB clinical isolates.

Molecular mechanisms and clonal lineages of colistin-resistant bacteria across the African continent: A scoping review

Colistin (also known as Polymyxin E), a polymyxin antibiotic discovered in the late 1940s, has recently reemerged as a last-line treatment option for multidrug-resistant infections. However, in recent years, colistin-resistant pathogenic bacteria have been increasingly reported worldwide. Accordingly, the presented review was undertaken to identify, integrate and synthesize current information regarding the detection and transmission of colistin-resistant bacteria across the African continent, in addition to elucidating their molecular mechanisms of resistance. PubMed, Google Scholar, and Science Direct were employed for study identification, screening and extraction. Overall, based on the developed literature review protocol and associated inclusion/exclusion criteria, 80 studies published between 2000 and 2021 were included comprising varying bacterial species and hosts. Numerous mechanisms of colistin resistance were reported, including chromosomal mutation(s) and transferable plasmid-mediated colistin resistance (encoded by mcr genes). Perhaps unexpectedly, mcr-variants have exhibited rapid emergence and spread across most African regions. The genetic variant mcr-1 is predominant in humans, animals, and the natural environment, and is primarily carried by IncHI2- type plasmid. The highest numbers of studies reporting the dissemination of colistin-resistant Gram-negative bacteria were conducted in the North African region.

Epidemiology and Traits of Mobile Colistin Resistance (mcr) Gene-Bearing Organisms from Horses

Mobile colistin resistance (mcr) genes (mcr-1 to mcr-10) threaten the efficacy of colistin (COL), a polymyxin antibiotic that is used as a last-line agent for the treatment of deadly infections caused by multidrug-resistant and extensively drug-resistant bacteria in humans and animals. COL has been used for more than 60 years for the prophylactic control and treatment of infections in livestock husbandry but not in horses. Polymyxin B is used for the prophylactic control and empirical treatment of infections in horses without conducting sensitivity tests. The lack of sensitivity testing exerts selection pressure for the acquisition of the mcr gene. By horizontal transfer, mcr-1, mcr-5, and mcr-9 have disseminated among horse populations globally and are harbored by Escherichia coli, Klebsiella, Enterobacter, Citrobacter, and Salmonella species. Conjugative plasmids, insertion sequences, and transposons are the backbone of mcr genes in the isolates, which co-express genes conferring multi- to extensive-drug resistance, including genes encoding extended-spectrum β-lactamase, ampicillinase C, fosfomycin, and fluoroquinolone resistance, and virulence genes. The transmission of mcr genes to/among bacterial strains of equine origin is non-clonal. Contact with horses, horse manure, feed/drinking water, farmers, farmers’ clothing/farm equipment, the consumption of contaminated horse meat and its associated products, and the trading of horses, horse meat, and their associated products are routes for the transmission of mcr-gene-bearing bacteria in, to, and from the equine industry.

An Update of Mobile Colistin Resistance in Non-Fermentative Gram-Negative Bacilli

Colistin, the last resort for multidrug and extensively drug-resistant bacterial infection treatment, was reintroduced after being avoided in clinical settings from the 1970s to the 1990s because of its high toxicity. Colistin is considered a crucial treatment option for Acinetobacter baumannii and Pseudomonas aeruginosa, which are listed as critical priority pathogens for new antibiotics by the World Health Organization. The resistance mechanisms of colistin are considered to be chromosomally encoded, and no horizontal transfer has been reported. Nevertheless, in November 2015, a transmissible resistance mechanism of colistin, called mobile colistin resistance (MCR), was discovered. Up to ten families with MCR and more than 100 variants of Gram-negative bacteria have been reported worldwide. Even though few have been reported from Acinetobacter spp. and Pseudomonas spp., it is important to closely monitor the epidemiology of mcr genes in these pathogens. Therefore, this review focuses on the most recent update on colistin resistance and the epidemiology of mcr genes among non-fermentative Gram-negative bacilli, especially Acinetobacter spp. and P. aeruginosa.

Polymyxin E-Resistant Gram-Negative Bacteria in Tunisia and Neighboring Countries: Are There Commonalities?

The current global dissemination of polymyxin E resistance constitutes a real public health threat because of the restricted therapeutic options. This review provides a comprehensive assessment of the epidemiology of polymyxin E-resistant bacteria, with special reference to colistin-resistant Gram-negative bacteria in Tunisia and neighboring countries, based on available published data to January 2020. We aimed to determine their prevalence by species and origin, shedding light on the different genes involved and illustrating their genetic support, genetic environment, and geographic distribution. We found that colistin resistance varies considerably among countries. A majority of the research has focused on Algeria (13 of 32), followed by Tunisia (nine of 32), Egypt (nine of 32), and Libya (one of 32). All these reports showed that colistin-resistant Gram-negative bacteria were dramatically disseminated in these countries, as well as in African wildlife. Moreover, high prevalence of these isolates was recorded from various sources (humans, animals, food products, and natural environments). Colistin resistance was mainly reported among Enterobacteriaceae, particularly Klebsiella pneumoniae and Escherichia coli. It was associated with chromosomal mutations and plasmid-mediated genes (mcr). Four mcr variants (mcr1, mcr2, mcr3, and mcr8), mobilized by several plasmid types (IncHI2, IncP, IncFIB, and IncI2), were detected in these countries and were responsible for their rapid spread. Countrywide dissemination of high-risk clones was also observed, including E. coli ST10 and K. pneumoniae ST101 and ST11. Intensified efforts to raise awareness of antibiotic use and legalization thereon are required in order to monitor and minimize the spread of multidrug-resistant bacteria.

Global Prevalence and Molecular Epidemiology of mcr-Mediated Colistin Resistance in Escherichia coli Clinical Isolates: A Systematic Review

BACKGROUND AND AIM

The continuing rise in infections caused by multi-drug resistant (MDR) bacteria is one of the most serious public health issues in today's societies. Colistin is a last-resort antimicrobial medication used to treat infections caused by MDR gram-negative bacteria; therefore resistance to this antibiotic is extremely hazardous. The current study aimed to evaluate the global prevalence and distribution of colistin resistance genes among human clinical isolates of Escherichia coli (E. coli) as a systematic review.

METHODS

PubMed, Embase, and Web of Science databases were systematically searched. For further evaluation, all original English-language articles that demonstrated colistin resistance in E. coli clinical isolates published between 2000 and 2020 were examined.

RESULTS

Out of 4857 initial articles, after various stages of review and evaluation, 190 related articles were selected. More than 79 % of the publications selected in this research were published from 2014 to 2020. In Asia, Europe, America, Africa, and Oceania, the prevalence of mobilized colistin resistance (mcr) producing colistin-resistant E. coli was 66.72%, 25.48%, 5.19%, 2.27%, and 0.32 %, respectively.

CONCLUSION

The recent widespread spreading of E. coli strains harboring mcr conferring colistin resistance, especially in Asia and Europe, is concerning and needs more attention.

Is Africa ready for mobile colistin resistance threat?

Antimicrobial resistance is a growing public health problem and a threat to effective treatment and prevention of an array of infections caused by bacteria. Africa is already faced with many socio-economic and health crises. Many countries in Africa can seldom boast of a standardized health care facility comparable to those in developed countries. Yet, the non-therapeutic use of COL has been banned in developed countries. However, in Africa, except for South Africa, COL is an over-the-counter (OTC) medication sold and dispensed by non-professionals/without a veterinarian's supervision. The ban of non-therapeutic COL in developed countries has proven to reduce the development of mobile colistin resistance (MCR) in humans and animals. The unregulated use of COL has been proven to select pathogenic and commensal bacteria resistance. A transmissible plasmid-mediated colistin determinant, mobile COL resistance (mcr) gene, which is rapidly transferred/acquired horizontally or laterally intra/inter-species/genera, has been reported. A highly promiscuous mobile genetic element like plasmids containing transposons, insertion sequences, and integrons aid the carriage/rapid transfer and acquisition of these mcr genes. Hence, we highlight the danger posed by escalating colistin (COL) resistance in the continent and the impetus to halt the indiscriminate and non-therapeutic use of COL to protect public health.

Molecular Epidemiology of mcr-1, bla KPC-2, and bla NDM-1 Harboring Clinically Isolated Escherichia coli from Pakistan

Purpose

The multiple-drug resistant Escherichia coli are among the deadliest pathogens causing life-threatening infections. This study was planned to determine the molecular epidemiology of mcr-1, bla _KPC-2, and bla _NDM-1 harboring clinically isolated E. coli from Pakistan.

Methods

In total, 545 strains of E. coli from clinical samples were collected from June 2018 to September 2019. All the isolates were screened for colistin-resistance, extended-spectrum-β-lactamases (ESBL), and carbapenemases through the micro-dilution method, Double-Disk-Synergy-Test (DDST), and Modified-Hodge-Test (MHT). The detection, sequence-typing, conjugal transfer, S1-PFGE, plasmid-replicon-typing, and southern-blotting for mcr, ESBL, and carbapenemase-encoding genes were performed.

Findings

A total of four (0.73%) colistin-resistant strains carrying alongside mcr-1 and bla _CTX-M-15 genes, three of these strains also had the bla _TEM-1 gene. The presence of ESBL genes was detected in 139 (25.5%) isolates harboring bla _CTXM-15 (74.82%), bla _TEM (34.53%), bla _SHV (28.06%) and bla _OXA-1 (28.78%). In 129 carbapenemase-producers, 35.83% possessed bla _NDM-1, 26.67% bla _KPC-2, 8.3% bla _OXA-48, 25% bla _VIM-1, and 20.83% bla _IMP-1 genes. The sequence typing revealed that mcr-1 harboring isolates belonged to ST405, ST117, and ST156. Fifty percent of bla _KPC-2 and 48.83% of bla _NDM-1 were found on ST131 and ST1196, respectively. Two rare types of STs, ST7584, and ST8671 were also identified in this study. The mcr-1 gene was located on Incl2 (60-kb) plasmid. The bla _KPC-2 was present on (140-kb) IncH12, (100-kb) IncN, (90-kb) Incl1, while bla _NDM-1 was located on (70-kb) IncFIIK, (140-kb) IncH12, (100-kb) IncN, (60-kb) IncA/C, and (45-kb) IncFII plasmids, which were successfully trans-conjugated. Among the plasmid types, the Incl1 carrying bla _KPC-2, IncH12 harboring bla _KPC-2 and bla _NDM-1, and IncFIIK carrying bla _NDM-1 were for the first time detected in Pakistan.

Conclusion

The mcr-1, bla _KPC-2, and bla _NDM-1 genes finding in various clonal and plasmids types indicate that a substantial selection of the resistance genes had occurred in our clinical strains.

Prevalence and Traits of Mobile Colistin Resistance Gene Harbouring Isolates from Different Ecosystems in Africa

The mobile colistin resistance (mcr) gene threatens the efficacy of colistin (COL), a last-line antibiotic used in treating deadly infections. For more than six decades, COL is used in livestock around the globe, including Africa. The use of critically important antimicrobial agents, like COL, is largely unregulated in Africa, and many other factors militate against effective antimicrobial stewardship in the continent. Currently, ten mcr genes (mcr-1 to mcr-10) have been described. In Africa, mcr-1, mcr-2, mcr-3, mcr-5, mcr-8, and mcr-9 have been detected in isolates from humans, animals, foods of animal origin, and the environment. These genes are harboured by Escherichia coli, Klebsiella, Salmonella, Citrobacter, Enterobacter, Pseudomonas, Aeromonas, Alcaligenes, and Acinetobacter baumannii isolates. Different conjugative and nonconjugative plasmids form the backbone for mcr in these isolates; however, mcr-1 and mcr-3 have also been integrated into the chromosome of some African strains. Insertion sequences (ISs) (especially ISApl1), either located upstream or downstream of mcr, class 1 integrons, and transposons, are drivers of mcr in Africa. Genes coding multi/extensive drug resistance and virulence are colocated with mcr on plasmids in African strains. Transmission of mcr to/among African strains is nonclonal. Contact with mcr-habouring reservoirs, the consumption of contaminated foods of animal/plant origin or fluid, animal-/plant-based food trade and travel serve as exportation, importation, and transmission routes of mcr gene-containing bacteria in Africa. Herein, the current status of plasmid-mediated COL resistance in humans, food-producing animals, foods of animal origin, and environment in Africa is discussed.

Colistin-Resistant Enterobacterales Isolated from Chicken Meat in Western Algeria

Aim: In Algeria, colistin is used as a metaphylactic treatment in the poultry industry for the treatment of Gram-negative gastrointestinal infections and also as a feed additive to promote animal growth. The aim of this study was to investigate the importance and genetic characteristics of colistin-resistant Enterobacterales from chicken meat in Western Algeria. Results: A total of 181 samples of chicken meat were collected from three poultry farms across three provinces in Western Algeria. The presence of colistin-resistant Enterobacterales isolates was screened on selective media. Resistance and virulence profiles were characterised by PCR and sequencing. The clonal relatedness of the different mcr positive isolates was studied using repetitive sequence-based PCR (Rep-PCR) and multilocus sequence typing. Transferability and characteristics of plasmids harboring mcr-1 positive gene were performed using conjugation, PCR-based replicon typing, and whole-genome sequencing. A total of 22 isolates with acquired colistin resistance were identified giving an overall prevalence of 12.2% (22/181): 17 Escherichia coli (predominantly ST224 [n = 4, 23.5%]) and 5 Klebsiella pneumoniae (ST17 [n = 2, 40%], ST646 [n = 2, 40%], and ST944 [n = 1, 20%]). mcr-1 gene was exclusively found in 11 E. coli (prevalence of 6.1% [11/181]) and was associated with IncFV (n = 7) and IncFIIK (n = 4) plasmids. All the isolates had a commensal origin (n = 11). One isolate harbored virulence profile, a high colistin resistance (minimum inhibitory concentration = 96 mg/L), with some new mutations in the chromosomic colistin-resistant genes and different pathogenicity islands typically identified in uropathogenic E. coli. Conclusions: This study reports the diffusion of mcr-1 producing Enterobacterales from chicken meat in Western Algeria. This represents a worrisome situation needing continuous monitoring.

Molecular mechanisms of colistin resistance in Africa: A systematic review of literature

INTRODUCTION

Updated and comprehensive data on the mechanism underlying colistin resistance is lacking in Africa.

LITERATURE SEARCH

Herein, we aimed to review available literature on the molecular mechanisms of colistin resistance in Africa. PubMed, Google Scholar, and African Journal online databases were searched on the 15th of January 2020 for original research articles that reported mechanisms of colistin resistance in any of the 54 African countries.

REVIEW

Of the 1473 studies identified through initial database search, 36 met the inclusion criteria. Colistin resistance was mostly observed in Escherichia coli isolated from human clinical samples. Plasmid-mediated colistin resistance mechanism (26; 72.2%) was the most frequently reported resistance mechanism. About three-quarters (27; 75.0%) of the 36 studies were done in North Africa. In this zone, the mobilized colistin resistance (mcr) genes were mostly detected in E. coli harboring three plasmid types, IncHI2, IncI2, and IncX4, from animal samples (n=9; 42.8%). Of the six studies performed in Southern Africa, four reported mcr-1 mostly detected from human samples (n=2; 50.0%) in E. coli isolates carrying IncHI2, IncI2, and IncX4 with diverse range of STs. One hitherto unknown mutation, the mutation in the I527N gene was detected in colistin resistant isolates in this region, which was absent in colistin susceptible isolates. In West and Central Africa, two and one studies, respectively, reported mcr-1 gene exclusively in Escherichia coli isolates.

CONCLUSIONS

Transferable plasmid mediated colistin resistance is rapidly emerging in Africa with mcr-1 as the predominant genetic variant in human, animals, and environmental samples.

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.

Emergence of Escherichia coli harbouring mcr-1 and mcr-3 genes in North West Algerian farmlands

OBJECTIVES

Colistin resistance has emerged worldwide, threatening the efficacy of colistin treatment of Gram-negative bacterial infections. Farms have been recognised as an important reservoir of genes conferring resistance to colistin. This study aimed to isolate and characterise colistin-resistant bacteria in farmlands located in the region of Oran, northwest Algeria.

METHODS

Forty environmental samples were collected between May 2016 and March 2018 at eight agricultural sites in the Oran region.

RESULTS

From the 40 samples, 103 colistin-resistant isolates were isolated from agricultural soil (n = 52), irrigation water (n = 31) and manure (n = 20). Eight isolates were identified as Escherichia coli, including six and two isolates carrying the mcr-1 and mcr-3 gene, respectively. All eight E. coli isolates were non-susceptible to amoxicillin, amoxicillin/clavulanic acid, ticarcillin, nalidixic acid, ciprofloxacin, gentamicin, trimethoprim/sulfamethoxazole and rifamycin; two were also non-susceptible to cefotaxime, cefepime and aztreonam and carried the bla_TEM-12 gene in addition to mcr-1. The six mcr-1-carrying E. coli isolates (MIC ≥ 2 μg/mL) belonged to three sequences types, including ST10 (n = 3), ST405 (n = 2) and ST345 (n = 1), whereas the two mcr-3-carrying isolates were assigned to ST155. The conjugation assay was positive only for two mcr-1-positive isolates.

CONCLUSION

These results show that farms are an important reservoir of colistin-resistant E. coli as well as other antimicrobial resistance genes such as ESBL genes. Transfer of manure from animals to soil and irrigation water might be disseminating a mix of multiple resistances, posing a worrying threat to human health.

Efflux pump inhibitor CCCP to rescue colistin susceptibility in mcr-1 plasmid-mediated colistin-resistant strains and Gram-negative bacteria

Objectives

Efflux in bacteria is a ubiquitous mechanism associated with resistance to antimicrobials agents. Efflux pump inhibitors (EPIs) have been developed to inhibit efflux mechanisms and could be a good alternative to reverse colistin resistance, but only CCCP has shown good activity. The aim of our study was to identify CCCP activity in a collection of 93 Gram-negative bacteria with known and unknown colistin resistance mechanisms including isolates with mcr-1 plasmid-mediated colistin resistance.

Methods

Colistin MIC was evaluated with and without CCCP and the fold decrease of colistin MIC was calculated for each strain. In order to evaluate the effect of this combination, a time-kill study was performed on five strains carrying different colistin resistance mechanisms.

Results

Overall, CCCP was able to reverse colistin resistance for all strains tested. The effect of CCCP was significantly greater on intrinsically colistin-resistant bacteria (i.e. Proteus spp., Serratia marcescens, Morganella morganii and Providencia spp.) than on other Enterobacteriaceae (P < 0.0001). The same was true for bacteria with a heteroresistance mechanism compared to bacteria with other colistin resistance mechanisms (P < 0.0001). A time-kill study showed the combination was bacteriostatic on strains tested.

Conclusions

These results suggest an efflux mechanism, especially on intrinsically resistant bacteria and Enterobacter spp., but further analysis is needed to identify the molecular support of this mechanism. EPIs could be an alternative for restoring colistin activity in Gram-negative bacteria. Further work is necessary to identify new EPIs that could be used in humans.

Development of real-time PCR assay allowed describing the first clinical Klebsiella pneumoniae isolate harboring plasmid-mediated colistin resistance mcr-8 gene in Algeria

OBJECTIVES

We aimed to develop here a specific real-time PCR assay with TaqMan® probe to detect efficiently bacterial strains harboring the new plasmid mediated-colistin resistance mcr-8 gene.

METHODS

Specific primers and probe for mcr-8 gene were designed from sequences alignment of all mcr genes variants. Specificity of the designed primers and probe were first checked par BlastN analysis and by in silico PCR. The analytical sensitivity and specificity tests were performed in vitro on a panel of 290 genomic DNA of Gram-negative bacteria and 250 metagenomic DNA from human stool samples. Whole genome sequencing (WGS) was performed here using MiSeq technology.

RESULTS

Designed primers and probe were 100% specific tomcr-8 gene by BlastN and in silico PCR analysis. Real-time PCR screening of a collection of clinical isolates resulted to one positive Klebsiella pneumoniae isolate (KP95). WGS confirmed that this isolate harbored the mcr-8 gene and other resistance genes such as bla_OXA-48, bla_CTX-M-15 β-lactamases. Our real-time PCR was highly sensitive on a 10-fold dilution serie from a calibrated inoculum at 10⁸ CFU/mL with a limit of detection at 55 CFU/mL.

CONCLUSION

To the best of our knowledge, we propose here, the first real-time PCR assay targeting mcr-8 gene with high specificity and sensitivity, able to detect mcr-8 gene in less than 2 h from any DNA sample. This real-time PCR assay allowed the first description of a clinical K. pneumoniae strain harboring the mcr-8 gene in Algeria.

The rise and spread of mcr plasmid-mediated polymyxin resistance

Polymyxins are important lipopeptide antibiotics that serve as the last-line defense against multidrug-resistant (MDR) Gram-negative bacterial infections. Worryingly, the clinical utility of polymyxins is currently facing a serious threat with the global dissemination of mcr, plasmid-mediated polymyxin resistance. The first plasmid-mediated polymyxin resistance gene, termed as mcr-1 was identified in China in November 2015. Following its discovery, isolates carrying mcr, mainly mcr-1 and less commonly mcr-2 to -7, have been reported across Asia, Africa, Europe, North America, South America and Oceania. This review covers the epidemiological, microbiological and genomics aspects of this emerging threat to global human health. The mcr has been identified in various species of Gram-negative bacteria including Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Salmonella enterica, Cronobacter sakazakii, Kluyvera ascorbata, Shigella sonnei, Citrobacter freundii, Citrobacter braakii, Raoultella ornithinolytica, Proteus mirabilis, Aeromonas, Moraxella and Enterobacter species from animal, meat, food product, environment and human sources. More alarmingly is the detection of mcr in extended-spectrum-β-lactamases- and carbapenemases-producing bacteria. The mcr can be carried by different plasmids, demonstrating the high diversity of mcr plasmid reservoirs. Our review analyses the current knowledge on the emergence of mcr-mediated polymyxin resistance.

Rapid detection of colistin resistance protein MCR-1 by LC-MS/MS

Background

Colistin (polymyxin E) and polymixin B are important bactericidal antibiotics used in the treatment of serious infections caused by multi-drug resistant Gram-negative organisms. Transferrable plasmid-mediated colistin resistance, conferred by the product of the mcr-1 gene, has emerged as a global healthcare threat. Consequently, the rapid detection of the MCR-1 protein in clinical bacterial isolates has become increasingly important. We used a genoproteomic approach to identify unique peptides of the MCR-1 protein that could be detected rapidly by liquid chromatography tandem mass spectrometry (LC–MS/MS).

Methods

MCR-1 tryptic peptides that were efficiently ionized and readily detectable were characterized in a set of mcr-1-containing isolates with triple quadrupole LC–MS. Three optimal peptides were selected for the development of a rapid multiple reaction monitoring LC–MS/MS assay for the MCR-1 protein. To investigate the feasibility of rapid detection of the MCR-1 protein in bacterial isolates using this assay, a blinded 99-sample test set was built that included three additional mcr-1-containing clinical isolates tested in triplicate (9 samples) and 90 negative control isolates.

Results

All of the mcr-1-containing isolates in the test set were accurately identified with no false positive detections by three independent, blinded operators, yielding an overall performance of 100% sensitivity and specificity for multiple operators. Among the three peptides tested in this study, the best performing was DTFPQLAK. The isolate-to-result time for the assay as implemented is less than 90 min.

Conclusions

This work demonstrates the feasibility of rapid detection of the MCR-1 protein in bacterial isolates by LC–MS/MS.

Electronic supplementary material

The online version of this article (10.1186/s12014-019-9228-2) contains supplementary material, which is available to authorized users.

Emergence of mcr-1 plasmid-mediated colistin-resistant Escherichia coli isolates from seawater

Colistin is currently regarded as one of the 'last-resort' antibiotics used for the treatment of critical infections caused by multidrug-resistant Gram-negative pathogens. Recently, there have been numerous reports of the emergence of a transferable plasmid-mediated colistin resistance gene, mcr-1 in patients, animals, food, and environment. Here, we characterize the support of colistin resistance among environmental isolates collected from seawater of Algiers coast. Our study was carried out on 246 isolates resistant to colistin (MIC > 2 μg/L). The mcr-1 gene was identified in only two isolates; M49 and M78. The two strains were identified as Escherichia coli and were non-susceptible to amoxicillin, ticarcillin, piperacillin, gentamicin, nalidixic acid, tigecycline, tetracycline, trimethoprim-sulfamethoxazole and colistin. For the latter, isolates M49 and M78 showed MIC values of 4 μg/mL and 8 μg/mL, respectively. Only the strain M78 was intermediary resistant to tobramycin. The two E. coli strains belonged to two different sequence types (STs): ST23 for M49 and ST115 for M78. The mcr-1 gene was present on a non-conjugative plasmid in the two strains.

Role of Institut Hospitalo-Universitaire Méditerranée Infection in the surveillance of resistance to antibiotics and training of students in the Mediterranean basin and in African countries

Surveillance of antibiotic resistance has become a public global concern after the rapid worldwide dissemination of several antibiotic resistance genes. Here we report the role of the Institut Hospitalo-Universitaire Méditerranée Infection created in 2011 in the identification and description of multidrug-resistant bacteria thanks to collaborations and training of students from the Mediterranean basin and from African countries. Since the creation of the institute, 95 students and researchers have come from 19 different countries from these areas to characterize 6359 bacterial isolates from 7280 samples from humans (64%), animals (28%) and the environment (8%). Most bacterial isolates studied were Gram-negative bacteria (n = 5588; 87.9%), mostly from Algeria (n = 4190), Lebanon (n = 946), Greece (n = 610), Saudi Arabia (n = 299) and Senegal (n = 278). Antibiotic resistance was diversified with the detection and characterization of extended-spectrum β-lactamases, carbapenemases and resistance to colistin, vancomycin and methicillin. All those studies led to 97 indexed international scientific papers. Over the last 6 years, our institute has created a huge network of collaborations by training students that plays a major role in the surveillance of resistance to antibiotics in these countries.

Fitness cost of mcr-1-mediated polymyxin resistance in Klebsiella pneumoniae

Objectives

The discovery of mobile colistin resistance mcr-1, a plasmid-borne polymyxin resistance gene, highlights the potential for widespread resistance to the last-line polymyxins. In the present study, we investigated the impact of mcr-1 acquisition on polymyxin resistance and biological fitness in Klebsiella pneumoniae.

Methods

K. pneumoniae B5055 was used as the parental strain for the construction of strains carrying vector only (pBBR1MCS-5) and mcr-1 recombinant plasmids (pmcr-1). Plasmid stability was determined by serial passaging for 10 consecutive days in antibiotic-free LB broth, followed by patching on gentamicin-containing and antibiotic-free LB agar plates. Lipid A was analysed using LC-MS. The biological fitness was examined using an in vitro competition assay analysed with flow cytometry. The in vivo fitness cost of mcr-1 was evaluated in a neutropenic mouse thigh infection model.

Results

Increased polymyxin resistance was observed following acquisition of mcr-1 in K. pneumoniae B5055. The modification of lipid A with phosphoethanolamine following mcr-1 addition was demonstrated by lipid A profiling. The plasmid stability assay revealed the instability of the plasmid after acquiring mcr-1. Reduced in vitro biological fitness and in vivo growth were observed with the mcr-1-carrying K. pneumoniae strain.

Conclusions

Although mcr-1 confers a moderate level of polymyxin resistance, it is associated with a significant biological fitness cost in K. pneumoniae. This indicates that mcr-1-mediated resistance in K. pneumoniae could be attenuated by limiting the usage of polymyxins.

Towards Understanding MCR-like Colistin Resistance

Antibiotic resistance has become a global public health priority. Polymyxins, a family of cationic polypeptide antibiotics, act as a final line of refuge against severe infections by Gram-negative pathogens with pan-drug resistance. Unfortunately, this last-resort antibiotic has been challenged by the emergence and global spread of mobilized colistin resistance determinants (mcr). Given the fact that it has triggered extensive concerns worldwide, we present here an updated view of MCR-like colistin resistance. These studies provide a basic framework for understanding the molecular epidemiology and resistance mechanism of MCR-like genes. However, further large-scale epidemiology and functional studies are urgently needed to better understand the biology of this clinically important antibiotic resistance.

Study of mcr-1 Gene-Mediated Colistin Resistance in Enterobacteriaceae Isolated from Humans and Animals in Different Countries

In this study, we aim to characterize the genetic environment of the plasmid-mediated colistin resistance gene mcr-1 in 25 Escherichia coli and seven Klebsiella pneumoniae strains from different countries and continents. Multilocus sequence typing, conjugation experiments, plasmid typing, and the presence and location of the insertion sequence ISApl1 were investigated. Whole genome sequencing of four E. coli was performed to analyse the genetic environment of the mcr-1 gene. Colistin minimum inhibitory concentration of mcr-1 strains varied from 3 to 32 µg/mL. Six E. coli sequence types were detected: ST 4015, ST 3997, ST 10, ST 93, ST 48, and ST 648. IncHI2, IncI2, and IncP plasmid types were predominant and were unrelated to a specific country of origin. ISApl1 was found in 69% of analysed plasmids that were mainly around the mcr-1 gene. Analysis of four closed mcr-1 plasmids revealed the integration of mcr-1 into hotspots. We found that the spread of mcr-1 gene was due to the diffusion of a composite transposon and not to the diffusion of a specific plasmid or a specific bacterial clone. The ease with which the mcr-1 gene integrates into various regions facilitates its dissemination among bacteria and explains its large diffusion all over the world, both in animals and in humans.

First Report of the Plasmid-Mediated Colistin Resistance Gene mcr-1 in Escherichia coli ST405 Isolated from Wildlife in Bejaia, Algeria

BACKGROUND

The aim of the present study was to screen for the presence of mcr-1 gene in Enterobacteriaceae isolated from Barbary macaques (Macaca sylvanus) in Algeria.

MATERIALS AND METHODS

From January to April 2016, a total of 86 fresh stool samples from Barbary macaques were collected in the Toudja forest (Bejaia, Algeria). After isolation, the isolates were identified by matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. Antibiotic susceptibility was determined by disk diffusion method, and minimum inhibitory concentration (MIC) of colistin was determined by E-test. Polymerase chain reaction (PCR) and sequencing were used to identify mcr-1gene. The sequence type (ST) was done using multilocus sequence typing. Phylogenetic groups of Escherichia coli and the presence of virulence genes were determined by PCR. Transfer of mcr-1 and extended-spectrum β-lactamase genes was assessed by conjugation and transformation experiments.

RESULTS

E. coli M076 isolate was found resistant to colistin with a MIC of 4 mg/L and to other antibiotic families, including β-lactams, aminoglycosides, and fluoroquinolones. PCR and sequencing revealed that this isolate harbored the mcr-1, bla_CTX-M-15, bla_TEM-1, and qnrB19 genes. This isolate was assigned to ST405, belonged to phylogroup D, and contains only one virulence gene fyuA (siderophore uptake receptor). Neither transconjugants nor transformants were obtained for this isolate.

CONCLUSION

In this study, we report the detection of mcr-1 gene producing E. coli from wild animals.

LBJMR medium: a new polyvalent culture medium for isolating and selecting vancomycin and colistin-resistant bacteria

BACKGROUND

Multi-drug resistant bacteria are a phenomenon which is on the increase around the world, particularly with the emergence of colistin-resistant Enterobacteriaceae and vancomycin-resistant enterococci strains. The recent discovery of a plasmid-mediated colistin resistance with the description of the transferable mcr-1 gene raised concerns about the need for an efficient detection method for these pathogens, to isolate infected patients as early as possible. The LBJMR medium was developed to screen for all polymyxin-resistant Gram-negative bacteria, including mcr-1 positive isolates, and vancomycin-resistant Gram-positive bacteria.

RESULTS

The LBJMR medium was developed by adding colistin sulfate salt at a low concentration (4 μg/mL) and vancomycin (50 μg/mL), with glucose (7.5 g/L) as a fermentative substrate, to a Purple Agar Base (31 g/L). A total of 143 bacterial strains were used to evaluate this universal culture medium, and the sensitivity and specificity of detection were 100% for the growth of resistant strains. 68 stool samples were cultured on LBJMR, and both colistin-resistant Gram-negative and vancomycin-resistant Gram-positive strains were specifically detected.

CONCLUSIONS

The LBJMR medium is a multipurpose selective medium which makes it possible to identify bacteria of interest from clinical samples and to isolate contaminated patients in hospital settings. This is a simple medium that could be easily used for screening in clinical microbiology laboratories.